Functional magnetic resonance imaging (fMRI) is an indirect measure of neural activity with the hemodynamic response function (HRF) coupling it with unmeasured neural activity. The HRF, modulated by several non-neural factors, is variable across brain regions, individuals and populations. Yet, a majority of human resting-state fMRI connectivity studies continue to assume a non-variable HRF. In this article, with supportive prior evidence, we argue that HRF variability cannot be ignored as it substantially confounds within-subject connectivity estimates and between-subjects connectivity group differences. We also discuss its clinical relevance with connectivity impairments confounded by HRF aberrations in several disorders. We present limited data on HRF differences between women and men, which resulted in a 15.4% median error in functional connectivity estimates in a group-level comparison. We also discuss the implications of HRF variability for fMRI studies in the spinal cord. There is a need for more dialogue within the community on the HRF confound, and we hope that our article is a catalyst in the process. While nactivity , measuriactivity . The comactivity . HRF shaactivity . Represeactivity  such as activity . The HRFactivity .The current ‘perspective’ article focuses on this HRF variability (HRFv) and its impact on fMRI data processing and subsequent outcome measures within the scope of human fMRI research. This topic is important because thousands of human fMRI studies are published each year, but a significant portion of those do not account for HRFv. Resting-state fMRI (rs-fMRI) and connectivity studies dominate that list. Thus, there is a need for more dialogue within the community on HRFv. We argue that HRFv causes a measurable impact on the BOLD time series, which, if ignored, will confound fMRI outcomes such as connectivity. We substantiate our argument with prior human HRFv research, including those focusing on rs-fMRI connectivity. We also present limited new data (to substantiate our ‘perspective’) on HRFv across two important demographic variables: age and sex. Lastly, to cover structures of the central nervous system beyond the brain, we also discuss the implications of HRFv for spinal cord fMRI.2.HRFv was first demonstrated in 1998  and furt3.3dDeconvolve  and one unknown (HRF). This is possible with simultaneous fMRI and invasive recordings , which convolve ] is probconvolve . A viablconvolve  independconvolve  utilizedconvolve . MoreoveTo circumvent these concerns, an alternative is to perform blind deconvolution; that is, solve the mathematically ill-posed inverse problem of having two unknowns  and one known (fMRI). This is feasible because the natural limits and biophysics of HRF and fMRI are well understood. HRF estimation then becomes a constrained optimization exercise. Such deconvolution techniques primarily focusing on task fMRI data  are geneThis leaves us with four rs-fMRI deconvolution techniques that have been more widely adopted: (i) 4.We focus here on functional connectivity FC;  because FC studies have, however, largely ignored HRFv either with the assumption that the HRF is similar enough among brain regions and individuals or due to the unavailability of HRF estimation methods. Recent evidence suggests that these assumptions must be re-evaluated. Although researchers have been aware, since the early days of fMRI, that BOLD measures blood oxygenation and not neural activity, the magnitude of HRF confound on FC is being investigated only recently with the availability of deconvolution techniques. We take a closer look at these. It has been demonstrated that the HRF is variable  and receThe HRF is not only different across individuals, but also different across clinical populations due to impairments in various factors contributing to HRFv. Our prior work has highlighted this in autism , post-tr5.Non-invasive measurements are not as “clean” as invasive ones. There is always an effort to make fMRI data as “clean” as possible by maximizing relative variance from neural sources. Examples of such efforts include minimizing physiological/thermal noise through ultra-high-field imaging  as well as longer time for peak BOLD activity . T-test was used for RH, and Wilcoxon rank-sum test was used for discrete variables . There were no RH differences, but men had significantly longer TTP and/or FWHM in four regions , all three identified FCs were false positives . Although only four regions and three connections exhibited significant HRF and FC differences, respectively, it must not be inferred that the rest of the regions or connections were unaffected by HRFv. These HRF/FC differences were large enough to be detected for our sample size and data quality, but that does not mean that the difference can be ignored in the other connections. The testament to this fact is that HRF differences between sexes resulted in 15.4% median FC error with contribution even from a vast number of regions/FCs outside of the significant ones . Within-subjects, we found on average 14.1% RH variability, 13.5% TTP and 13.4% FWHM variability. L/R orbitofrontal had the largest HRF difference with other regions , perhaps due to susceptibility (p = 0.034), TTP (p = 0.039) and FWHM (p = 0.037). Between-lobe variability was higher than within-lobe in RH (p = 0.039), TTP (p = 0.028) and FWHM (p = 0.041) (possibly due to vastly different vasculature across lobes). Between-subjects HRFv  was larger than within-subjects. The occipital lobe varied significantly less across subjects than other lobes in RH (p = 0.048) and TTP (p = 0.045).As a secondary result not related to sex differences, we also report whole-brain-level average metrics of variability in HRF parameters within and between healthy young adult subjects, because these were not reported in our earlier publication , but thetibility  and/or vtibility  differen9.The central nervous system (CNS), which includes the brain and the spinal cord, is a single continuous entity. But prior HRF literature is exclusively focused on the brain. Spinal cord rs-fMRI studies have so far not accounted for HRFv, except for a recent study . If syst10.Herein we described prior evidence for HRFv and its confound on rs-fMRI FC and elaborated on this research’s importance and clinical relevance. Unexplained variability in BOLD is a more significant concern today than before because connectivity is used in sophisticated contexts such as dynamics , single-Taken together, measurements of FC often involve unexplained variance between 40% (ML prediction) and 70%  can be found at: The studies involving human participants were reviewed and approved by Auburn University Institutional Review Board. The patients/participants provided their written informed consent to participate in this study.DR: conceptualization, methodology, software, data analysis, investigation, visualization, writing–original draft, and reviewing and editing. RB: investigation, writing–reviewing and editing, and supervision. GD: conceptualization, methodology, data acquisition, investigation, writing–reviewing and editing, and supervision. All authors contributed to the article and approved the submitted version.This work was supported by National Institutes of Health (NIH) through grants R01EB027779 and R21EB031211 (RB) and R01EY025978 (GD). Support was also received through the Athinoula A. Martinos Center for Biomedical Imaging (RB) and the Auburn University MRI Research Center (GD). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The objective of this study is to explore patient, relative/carer and clinician perceptions of barriers to early physical rehabilitation in intensive care units (ICUs) within an associated group of hospitals in the UK and how they can be overcome.Qualitative study using semi-structured interviews and thematic framework analysis.Four ICUs over three hospital sites in London, UK.Former ICU patients or their relatives/carers with personal experience of ICU rehabilitation. ICU clinicians, including doctors, nurses, physiotherapists and occupational therapists, involved in the delivery of physical rehabilitation or decisions over its initiation.Views and experiences on the barriers and facilitators to ICU physical rehabilitation.Interviews were carried out with 11 former patients, 3 family members and 16 clinicians. The themes generated related to: safety and physiological concerns, patient participation and engagement, clinician experience and knowledge, teamwork, equipment and environment and risks and benefits of rehabilitation in intensive care. The overarching theme for overcoming barriers was a change in working model from ICU clinicians having separate responsibilities (a multidisciplinary approach) to one where all parties have a shared aim of providing patient-centred ICU physical rehabilitation (an interdisciplinary approach).The results have revealed barriers that can be modified to improve rehabilitation delivery in an ICU. Interdisciplinary working could overcome many of these barriers to optimise recovery from critical illness. This study explored a range of perspectives on the barriers to intensive care unit (ICU) rehabilitation (including clinicians and services users), thus eliciting in depth information to reveal a breadth of experiences of barriers and facilitators.Thematic framework analysis was used, which enables a systematic approach to organising data, facilitating in-depth exploration of the range of views within themes and between participant groups.Patient and family recall of their experiences may have been impacted by the time from intensive care admission to interview; however, interviews took place at the first follow-up opportunity to minimise this effect.Efforts were made to gain a range of perspectives using purposive sampling; however, fewer family members or carers took part in this study than former ICU patients.The importance of physical rehabilitation of critically ill patients has been recognised because of the prevalence of acute muscle weakness and wasting,11–17Studies have previously measured the barriers to implementing rehabilitation, the majority of which use a quantitative approach.22 28–30The objective of this study, therefore, was to explore service users (patients or their relatives/carers) and clinician perceptions of barriers to early physical rehabilitation in ICUs within an associated group of hospitals in the UK and how they can be overcome.A qualitative study using semi-structured interviews was conducted based on the approach recommended by the National Centre for Social Research. This is based on critical realism and interpretivism using the framework approach to analysis.10.1136/bmjopen-2023-073061.supp1Supplementary dataThe study was based at a UK National Health Service hospital trust in London, which has four ICUs for adult patients across three hospital sites, each of which has different referring specialities. Purposive samplingClinicians were included if they were doctors (senior trainees (registrars/fellows) or consultants), nurses, occupational therapists (OTs) or physiotherapists with at least 2 months of ICU experience and who had experience of rehabilitation treatments or deciding when they should be initiated. Clinicians were approached via adverts in meetings, posted in staff areas or via general group or more targeted emails. Former ICU patients and family members were included if they had any personal experience of physical rehabilitation while in ICU. Participants were excluded if they could not attend an in-person interview, if they felt unable to participate in English, if they were less than 18 years of age or unable to give informed consent. Patients or their relatives/carers were approached via local ICU patient support groups and follow-up clinics.a priori as when no new themes of barriers and facilitators were evident from interviews, as decided by the research steering group. During data collection, when the interviewer felt no new themes were being discussed, the latest version of the initial thematic framework was shown to the final clinician and patient participant as a sense check to see whether they could identify any additional themes that had been missed. Following this, the initial thematic framework was reviewed by clinical colleagues from all four professional groups included in the study, as well as the research steering group members who were former ICU patients, to discuss if any obvious themes were missing.Estimates were that 30 participants would be required to gain a sufficient range of perspectives, with sampling ending once apparent data saturation had been reached. Data saturation was defined A semi-structured interview topic guide was developed , designe10.1136/bmjopen-2023-073061.supp2Supplementary dataInterviews took place at the hospital site in person and only included the interviewer and the individual participant. Each participant took part in one semistructured interview. Before the interview began, participants were asked for demographic data then the interview proceeded. The format of the interview was a conversation, where wording was not fixed and prompts were used to gain greater depth of understanding of participant views and experiences.40All interviews were carried out by one interviewer (HRW) who is a male physiotherapist, working full time on the research study as part of work towards a doctorate, with training in qualitative research methods. The interviewer had previous clinical experience at several of the ICUs that were settings for this study, including working alongside some of the clinician participants, but not the patients or their relatives/carers. The researcher, therefore, had previous experiences of barriers and facilitators of rehabilitation in the study setting. These influences were taken into account using a reflexive diary before and after data collection, which was then considered during the analysis process.Thematic framework analysisFormer ICU patients were members of the research steering group. These patient representatives edited the wording of recruitment materials and inputted into the design of the topic guide. They also assisted the interviewer (HRW) to practise interview technique and were involved in reviewing the initial thematic framework, as part of data saturation checks. These patient representatives did not participate or contribute data to the study itself.Recruited participants included 16 clinicians, from a range of professions, with a range of experience in different settings . Eleven The study themes and subthemes are described in detail below. Clinician and patient participant concerns over the safety of rehabilitation were reported as a barrier to rehabilitation. This included the risk of dislodging lines and attachments, such as ventilator tubing and femoral lines (quote 1). However, some participants, who were mostly clinicians, did not perceive this as a barrier, if careful planning and also organisation of the bed space environment was carried out. For example, avoiding the use of femoral vascular catheters as access for haemofiltration or planning breaks in haemofiltration could enable rehabilitation. Endotracheal tubes or airways that had been difficult to insert, were also cited as barriers, with the difficulty of titrating sedation for a balance between tube tolerance and patient alertness cited as one explanation by a clinician.Clinician participants identified particular patient groups with barriers to rehabilitation because they felt they were at an increased risk or they presented additional logistical challenges, such as those with multiple traumatic injuries (quote 2). They suggested that patients admitted after surgery could have certain surgical precautions which presented logistical issues contacting different teams to gain clarity over safety of rehabilitation. Despite this, patients in ICU after elective surgery could have received preoperative education or preplanned rehabilitation programmes, both facilitating rehabilitation post-operatively.Physiological instability, such as instances of respiratory distress or cardiovascular instability, was reported as preventing rehabilitation treatments by participants who were mostly clinicians.…it’s mainly blood pressure related for me, or their resp[iratory] rate. If I don’t think they’re going to tolerate mobilising, and if it’s going to cause more harm than good. Dependence on organ support, such as the amount of respiratory support or vasoactive drugs were also identified as barriers. Clinician opinion ranged from perceiving patients receiving vasoactive drugs as a contraindication to rehabilitation (quote 4), to others who considered rehabilitation possible if a low or weaning dose was used or if the patient was less severely unwell, for example, if vasoactive drugs were being used for epidural-induced hypotension. Risk relating to hypotension during rehabilitation was suggested by a clinician to relate to anxiety from junior staff about managing vasoactive drugs during mobilisation (quote 5). Some clinician participants suggested potential organ support barriers should be discussed with the ICU doctors and also advocated actively sedating patients less.Patient participants sometimes reported feeling too unwell to actively participate in rehabilitation. Some patients reported profound feelings of weakness, making their bodies feel ‘like a lead weight’, which came as a surprise when they first tried to get up and was linked with feelings of vulnerability (quotes 6 and 7). These participants did then identify a time in their recovery where these symptoms subsided to the point where they could then participate.Additionally, level of alertness, confusion and agitation, cognitive impairments and personality disorders were all cited as barriers by clinicians (quote 8). Some patients and relatives recalled experiences of delirium and hallucinations as profound influences on their recovery in general.The difference between clinicians’ perception of safety and a patient’s readiness to begin rehabilitation was expressed as a barrier by some clinician participants (quote 9). Some explanations included clinician fear of the unwell patient and the risk of perceived harm which caused anxiety for some (quote 10).…happy to cause no harm, or kind of, and no perceived harm by not mobilising someone but actively getting up and causing harm is a, always going to be a significant anxiety for staff… This was linked to clinician need for control over the physiological numbers, potentially leading to a reluctance to reduce that control by moving a patient out of bed (quote 12). One doctor suggested that a paradigm shift was required to address this barrier (quote 13). Another doctor said they modified targets for acceptable changes in physiological observations (such as blood pressure), to reassure other clinicians that mobility was still safe (quote 14).Clinician participants reported experience of patients who may be reluctant to participate in rehabilitation. When asked about this theme, patient participant responses ranged from reporting enthusiastic engagement in rehabilitation, to not wishing to mobilise out of bed. Reasons cited for their reluctance included not wanting to do something perceived as potentially worsening their condition (quote 15). Furthermore, a lack of incentive or motivation to engage was discussed, as well as a feeling of weakness, which some found difficult to accept.…there were times when I simply didn’t want to do it… Depression, … lack of energy, lack of spirits really … Suboptimal communication between patients and clinicians was felt to be a barrier to rehabilitation by some patient and clinician participants. Suggested reasons included the little time spent by clinicians discussing rehabilitation, difficulty communicating rehabilitation goals and some sometimes showed a lack of empathy. Suggested ways of overcoming these issues included maximising a patient’s ability to communicate, giving more reassurance, building up trust, showing kindness and helping patients to feel safe (quote 17). Patients valued humour from staff and felt rapport was aided by staff continuity. Patients and relatives recommended that when a patient was reluctant to mobilise, an encouraging and diplomatic approach should be balanced with assertiveness from clinicians to ‘push’ patients (quote 18).Some patient participants recommended that strategies to improve patient engagement in rehabilitation should always be patient-specific. Other suggestions, mostly from clinicians, included promoting sleep at night, involving patients in planning a rehabilitation timetable, goal setting and using outcome measures to demonstrate progress (quote 19). Furthermore, education for patients and relatives at the appropriate time, around the importance of rehabilitation was suggested.Further facilitators suggested by patients and clinicians included the use of meaningful activities and identifying key patient motivators. The importance of tailoring rehabilitation to include activities meaningful to patients  were identified to facilitate engagement within a context more readily understood by patients.Looking at therapy in a slightly different way and finding an activity that’s meaningful to [patients], whether that’s personal care or leisure activities, and through that encouraging them to… engage in that activity and then helping them to see the therapeutic value of that. Recognising key patient motivators such as gaining independence and dignity by being able to do more for themselves was also suggested (quote 21). Patients reported being motivated through their improvement during rehabilitation sessions, almost as a proxy for improvement from critical illness. Patient qualities of resilience, determination and a positive mental attitude were reported as a facilitator by patients themselves.The role of family was discussed as both a barrier and facilitator. Instances were reported by some clinician participants where relatives could be reluctant for patient participation in rehabilitation. When this was discussed with patient and relative participants, responses ranged from an understanding of why this happens, to a strong disbelief that this could be the case. The role of family in encouraging patients was discussed, with some highlighting how they were motivated to improve mobility to help their family member feel better (quote 22).Clinician participants discussed the experience and knowledge of those carrying out rehabilitation. A lack of experience, confidence and senior support were cited as barriers (quote 23). However, some therapists also proposed those clinicians with more experience could pose a barrier. They suggested some more experienced nurses may perceive rehabilitation as outside of their role or may have spent more time in an environment where rehabilitation was not a priority. Opinions over experience as a facilitator also varied. Some emphasised that a team with the right skill mix (including adequate senior support) was important, with a nurse suggesting having more confident staff freed up time for rehabilitation. However, some therapists reported that more inexperienced nurses could be a facilitator as they have received recent training in rehabilitation. One therapist cited enthusiasm as being more important than experience to facilitate rehabilitation.A lack of training and knowledge, including about the importance of rehabilitation, organisation and planning of sessions and therapeutic manual handling were suggested as important factors by clinicians.It doesn’t happen because… we are not aware enough yet how important it is, or how much difference it could make, so it’s not embedded in our thinking and in our behaviour… A popular strategy suggested by clinicians to address these barriers was through education and training for the ICU interdisciplinary team, such as through study days and experiential learning (quote 25). Additionally, the use of a rehabilitation policy and guidelines to drive implementation and aid less experienced clinicians know when to begin rehabilitation was discussed.Discussion of teamwork covered team culture, clinician roles, rehabilitation definitions and logistics. A lack of a rehabilitation culture leading to some staff having a less proactive attitude to rehabilitation delivery was discussed.But a lot of it’s just to do with the attitude of the individual staff member, how proactive they are and how much they believe in mobilisation as a kind of key thing One explanatory factor was a lack of medical leadership. Participants (mostly clinicians) suggested promoting a culture where an interdisciplinary team works together to promote rehabilitation as routine and important would facilitate implementation. A less hierarchical culture would encourage proactive team planning and problem solving, with medical leadership again emphasised as key (quote 27).Another key barrier to rehabilitation discussed by clinicians, was differences in opinion between professions over roles and responsibilities (quote 28). Some reported that rehabilitation was perceived as only a therapist’s job (quote 29). Therapists reported that there could be a lack of understanding of their role or their other responsibilities, for example, covering other clinical areas in addition to the ICU. To overcome this, clinicians suggested promoting teamwork where separate responsibilities were acknowledged and there was a willingness to crossover professional roles, with therapists empowering nurses to facilitate rehabilitation (quote 30).Differences in opinions over roles and responsibilities were impacted on by variation in how rehabilitation was defined and delivered. This in itself may explain some of the difficulty in promoting a proactive rehabilitation culture. Clinicians sometimes limited their definition of rehabilitation to a patient sitting out in a chair (quote 31). Conversely, OT participants widened the concept of rehabilitation to encompass a 24-hour interdisciplinary approach utilising functional tasks.…rehabilitation is not, you know, 20 minutes with the physio or the OT every day. Really good rehabilitation is a 24 hour approach, and that – part of that is positioning a patient in bed. Part of that is ensuring the patient gets the right nutrition as well as looking at the actual physical things that they’re doing. This may increase patient engagement and interdisciplinary involvement, by helping staff to incorporate more rehabilitation activities during the course of their normal duties, for example, during personal care activities (quote 33).Finally, lack of staff and logistical difficulties in implementing rehabilitation were suggested as barriers by clinicians and patients. Greater investment in staffing and utilisation of healthcare support workers was suggested to address this. Logistical concerns covered the number of staff required and the duration of a rehabilitation session in competition with other unit procedures. Logistical barriers also concerned a difficulty in timing around nurses’ rest breaks and staffing ratios (quote 34). Within the study ICUs, once a patient’s illness severity decreased to a certain level, the nursing staffing ratio fell from one nurse to one patient to one nurse to two patients, coinciding with a potential increase in readiness for rehabilitation. Potential strategies to address these concerns include proactive planning of sessions, for example during morning team briefings. Additionally, a change to working patterns to build in more time for rehabilitation to occur was suggested.A lack of working specialist rehabilitation equipment was highlighted as a barrier by clinician participants (quote 35). Clinicians advocated greater investment and suggested the whole team take ownership of ensuring equipment was fixed or find funding sources for equipment replacement. Environmental concerns raised by patients and clinicians first covered practical limitations such as space to move rehabilitation equipment around the bedspace. Furthermore, a patient highlighted the nature of the ICU environment itself did not encourage them to move out of bed (quote 36).…you can see some bright lights and monitors, you can hear monitors going off, but you don’t have the, “Crash, bang, wallops!” that you get in a general ward… but it’s a capsule and a bubble, it’s a weird feeling… “People think it’s like being in a spaceship” and I thought, “That’s such a good description” and that’s how it did feel. Opinions over risks and benefits were explored, which closely related to safety, knowledge and attitude towards rehabilitation. Clinician ideas about risks resembled the safety issues from theme one, however, this did not necessarily mean a reluctance to mobilise (quotes 38 and 39). Most patients and relatives reported they had not worried about the risks of mobilising while in an ICU (quote 40), although some had experienced things such as dizziness and one reported passing out. Considering benefits reported by clinicians and patients, physical benefits of rehabilitation focused on the acute impact of improving physical function, including in preparation for recovery on the wards (quote 41). Suggested psychological benefits for the patient included helping mood and well-being and restoring a sense of dignity.…the important thing is you sense that you’re not just lying there waiting to die. …so you are… you are… coming back to being a human being that wants to live. Finally, several clinicians reported how a benefit of patient rehabilitation was the encouragement and sense of achievement it provided for staff.The overarching theme for how to overcome barriers to physical ICU rehabilitation related to moving from a multidisciplinary approach where different professions work together but have separate responsibilities; towards a patient-centred, interdisciplinary team approach. This was where all parties have a shared aim of providing physical rehabilitation (quotes 27 and 30). This can facilitate clinicians working together to develop a shared understanding of the definition of rehabilitation, so patients can participate in activities that are more meaningful. Furthermore, an agreement can be developed among the team, about the benefits and risks, the optimum way to deliver rehabilitation and when it is safe to start. This can then help different professions to collaborate to help to overcome barriers related to team working and to improve the ICU environment.This study has provided an in-depth exploration of the views of multiprofessional ICU clinicians and was strengthened by including former ICU patients and their relatives, adding to the knowledge of overcoming barriers to ICU physical rehabilitation. Primarily, this is suggested to be through a change in approach to team working, from a multidisciplinary to an interdisciplinary and patient-centred approach. This means moving from a multidisciplinary way of working where a team is made up of different professions working on their distinct priorities,44 48 49It is interesting to see that several of the themes of barriers and facilitators to ICU rehabilitation are similar to previous qualitative studies. This includes themes of safety,et alThis study has added to previous knowledge in several ways. Interestingly and perhaps surprisingly, less clinical experience was highlighted as a potential facilitator of rehabilitation. Some therapists reported that more inexperienced nurses have received recent training in rehabilitation and one therapist cited enthusiasm as more important than experience. Additionally, perceptions of the content of rehabilitation were notable. Some viewed rehabilitation as being limited to sitting in a chair. This can contribute to a limited scope of rehabilitation practiceThe findings from this study focus us to create a patient-centred interdisciplinary approach to rehabilitation. This involves considering how clinicians communicate with patients and broadening the definition of rehabilitation to include functional tasks that are meaningful to patients. Furthermore, broadening delivery of rehabilitation to a 24-hour holistic approach that includes family members,58Limitations of this study include the potential for poor recall from patient or relative/carer participants as the time from ICU admission to interview was not recorded.In conclusion, this exploration of a range of clinician and patient perspectives suggested a patient-centred, interdisciplinary approach to implementing ICU physical rehabilitation. These findings constitute a starting point for optimising rehabilitation delivery through improvement and implementation science.


This article was migrated. The article was marked as recommended.Background - There is a demand for new and efficient tools to teach anatomical sciences. Rapid developments in virtual reality (VR) and augmented reality (AR) mean educational use of the technology is becoming increasingly viable. However, uptake of this technology in anatomy teaching is still limited. This brief review aims to examine the effectiveness of VR/AR in anatomy teaching and includes evaluation of: head mounted devices (HMDs), stereoscopic projectors and screens, AR Magic Mirrors and AR Magic Books.Methods - PubMed, Scopus and Google Scholar were searched for relevant articles from 2013 to 29th June 2018.Results - Students’ academic performance was equal to or better than control methods for all four types of technology. All studies found high levels of student satisfaction for VR/AR teaching methods.Discussion - Various confounding factors and the large heterogeneity between studies are likely to have a major impact on results. Further research into the depth and longevity of learning in the different teaching methods, as well as their cost-effectiveness, would be beneficial for prospective institutions. In recent years, there has been growing interest in the use of virtual reality (VR) and augmented reality (AR) in anatomy education. This follows a decline in overall anatomy teaching time, as well as reductions in cadaver-based teaching and available laboratory hours  are superimposed onto the user’s view of the real world. Models can be displayed on an individual basis through devices including mobiles, desktops and head-mounted devices (HMDs), and to wider audiences with stereoscopic projectors and screen-based AR systems.Several institutions have trialled and used VR/AR technology as part of a multimodal, multimedia approach to anatomy teaching and learning. However, uptake of the technology is still limited. This can be due to concerns regarding the purchase cost and software development, as well as uncertainty over usability or efficacy of the technology. This brief review aims to examine the effectiveness of VR/AR in anatomy teaching, both in terms of academic results and student perceptions.th June 2018.A literature review was conducted using PubMed, Scopus and Google Scholar. Search terms included “virtual reality”, “augmented reality”, “mixed reality”, “head mounted device”, “anatomy” and “students”. To maintain temporal validity, papers prior to 2013 were excluded. The last search was conducted on 29The characteristics of the included studies (n=9) are summarised in Appendix 1.HMDs aim to create a sense of presence by realistically immersing the user in a shifting virtual environment displayed on head-mounted screens.In this review, all three studies consulted found no significant differences in the post-test results of HMDs compared with the control alternatives: 2D images , with 3D stereoscopy achieving significantly higher post-test results (p=0.0033)  and had a significantly lower score distribution .Positive student perceptions of the AR Magic Book were found in both studies . This inReported research studies suggest that VR and AR are at least as effective as traditional anatomy teaching methods. However, this generalisation may be unreliable due to the large heterogeneity between studies. As there is a limited number of studies available, this review included various teaching methods that may not be directly comparable. Another confounding factor is the control method used. Whilst there is value in comparing VR/AR to one simple teaching method like 2D diagrams or textbooks, it can be more insightful to also compare it with multiple methods, like standard 3D physical and virtual models. This is demonstrated by an included study , form of study  and study time. Differences in model quality and features (such as the level of interactivity) may have also impacted results. Furthermore, for many studies, results may be unrepresentative due to small sample sizes.The number of questions, as well as their difficulty and the presence of any repeats, could have also impacted results. Results offered restricted insight into learning as studies largely used short MCQ tests that reflect factual recall over other forms of understanding, such as that of 3D relationships. For more translatable and insightful findings, all studies would need pre-, post- and long-term recall tests.Despite the wide heterogeneity, there is a consensus between studies regarding positive student perceptions of VR/AR. In all studies, surveys revealed high levels of student satisfaction - generally higher than control alternatives - demonstrating the benefits of VR/AR for student enjoyment and engagement. It can be observed that VR/AR had a notable impact on spatial understanding, motivation and interest. Other reported areas of benefit included autonomous learning, confidence, cognitive load and overall student perceptions.These survey results may be subject to sampling bias as participants were often volunteers and so more likely to be motivated and engaged. There may also be author bias, as evaluated systems were often developed by or for the paper authors. The novelty of this new technology may also affect positive perceptions. Moreover, the five-point Likert scales generally used could produce response bias, whilst yes/no responses  are rathStudies indicate that VR and AR are effective and capable resources for anatomy teaching in terms of both academic achievement and student satisfaction, supporting the use of VR and AR as supplements to current teaching methods. However, further research into the depth and longevity of learning would aid understanding of the extent of their long-term impact on academic achievement. Future investigations into cost-effectiveness would also be helpful.•There is a potential for use of VR/AR in anatomy teaching, although uptake has been limited.•Studies found students’ academic performance was equal to or better than control methods for all four types of VR/AR technology.•All studies found high levels of student satisfaction for VR/AR teaching methods.•Minimal conclusions can be drawn on the true effectiveness of VR/AR due to limitations of studies. These include poor assessment of learning and failure to compare VR/AR against a range of other teaching resources.•Further research is required into the depth and longevity of learning and the cost-effectiveness of VR/AR.Amy Heather, 2nd Year BSc Medical Sciences Student, University of Exeter.Tudor Chinnah, PhD, MScClinEd, MSc, BMedSc, SFHEA, Senior Lecturer, Human Anatomy & Clinical Education, Academic Lead, Human Anatomy, University of Exeter Medical School.Vikram Devaraj, PGCE Clin Ed MBChB FRCS(Eng) FRCS(Plast), Senior Lecturer & Clinical Lead Anatomy, Consultant Surgeon. This review has been migrated. The reviewer awarded 3 stars out of 5 I read the manuscript with great interest and I think it is important to host discussion on a issue that is involving many academic schools, medical and not, for the preparation of innovative technological tools for the study of anatomy. Having adequate feedback on the advantages and disadvantages of this approach and, above all, on the effects on learning anatomy is necessary. As other reviewers suggested, I also encourage a revision of the manuscript that should cover aspects that have not been highlighted or deeply discussed in this version.Like other reviewers have underlined, major points are:1. Please detail the methodology used in the review to select or exclude the papers;2. Detail, whenever possible, the characteristics of study groups mentioned in the original papers;3. Describe major results achieved by the use of innovative technologies. How were advantages or disadvantages quantified in the original papers?4. I also agree that the Table should be included in the text and that more images and schemes describing better each approach should be included5. A conclusion and reflection on how further research should be planned to provide adequate insights on the benefits of advanced technologies in learning anatomy should be included.Reviewer Expertise:NANo decision status is available This review has been migrated. The reviewer awarded 3 stars out of 5 Thank you for asking me to review this paperIt seems that there is a constant flow of new and innovative technologies to enhance student learning- the teaching and learning of anatomy is frequently at the front of this rise in interest so a paper that reviews the literature surrounding the subject seems a very good paper to be included in our toolbox of relevant literature.I was rather disappointed that the authors failed to explore in greater detail their approach to their search methodology, so that we could be assured that this was really an effective review.As the authors point out, and it maybe a reflection of the papers so far, that many of the evaluations of the various technologies are based upon student satisfaction, rather than usefulness in the process of learning and long term effects. I do think that this paper would be of limited value for our anatomy teachers.Reviewer Expertise:NANo decision status is available This review has been migrated. The reviewer awarded 3 stars out of 5 The paper is indeed in sync with the need of using technology for advancing education in the field of anatomy in view of the limited availability of cadavers for teaching it. The authors have highlighted the available resources for the same and discussed how previous studies weighed the use of VR/AR. But I have a few reservations, addressing which I think will significantly improve the scope of this review of the literature:1. What age/ course students were included in the studies reviewed here? The perspective and need of a senior student, may be one pursuing a post-graduation in a surgical branch having the to revisit anatomy, will be different from a first year student, who has just entered the field. 2. Like other reviewers have mentioned, including the table in the main body of the article will be more useful.Reviewer Expertise:NANo decision status is available This review has been migrated. The reviewer awarded 3 stars out of 5 Many thanks to the authors for this brief but welcome and interesting review of VR/AR in anatomy education. I would like to have seen a more detailed introduction to the paper, perhaps describing the scholarly basis and theoretical underpinnings of visual technology-enhanced learning approaches in anatomy.Like the other reviewers, I would like to have seen a more detailed description of the methodology and perhaps a systematic review approach utilised in future, which I would read with great interest. Due to the visual nature of the subject matter I would also like to have seen further images, and in colour. I also agree that the table would be more effectively presented within the main body of the article.Reviewer Expertise:NANo decision status is available This review has been migrated. The reviewer awarded 3 stars out of 5 Thank you for the opportunity to read this manuscript titled "The Use of Virtual and Augmented Reality in Anatomy Teaching". The brief explanation of the VR/AR by the author is useful but superficial. Readers may benefit from the explanation on the Learning Objective content delivery methodology. It is an interesting review of the VR/AR teaching tool.Reviewer Expertise:NANo decision status is available This review has been migrated. The reviewer awarded 4 stars out of 5 Thank you for the invitation to review this interesting manuscript. The authors address an area of increasing importance in medical education. AR and VR technologies are widely used in Anatomy teaching-learning and have many advantages over traditional teaching-learning methods. The table provides a useful summary of the different studies included in the review. AR magic mirror and AR magic book were new concepts to me and the authors could describe these in greater detail. The authors could provide a more detailed description of the inclusion and exclusion criteria followed for the various studies included in the paper. The authors have described the limitations of their study. The paper will be of special interest to medical educators especially those teaching Anatomy.Reviewer Expertise:NANo decision status is available This review has been migrated. The reviewer awarded 3 stars out of 5 This is an interesting review dealing with a rapidly emerging topic. The small number of included studies is indicative of the novelty of the teaching methods. While later reviews are sure to introduce issues and results not foreseen in this review, this is a useful starter to the field. And, as with all reviews, the authors are constrained by the quality of the original studies, and the data they present.I would like to make two recommendations for Version 2 of this paper:• Although this paper is not billed as a systematic literature review (SLR), it does appear to have elements of it. I would strongly recommend that the authors flesh out the description of their Methods, and give the types of details that one would find in an SLR, typically a diagram showing numbers on initial search, exclusions, inclusions, etc. This would dramatically improve the quality of the paper.• Appendix 1 contains a table that is an essential part of the paper. This table should not be in the appendix, but should be placed into the body of the paper. An appendix should really only be used for material that is nice to have, in case anybody is interested, or to not interrupt the flow of the paper. In this case, however, the table in Appendix 1 is a significantly important portion of the Results, and should be inserted there.Reviewer Expertise:NANo decision status is available


This study aimed to explore the utilization of rehabilitation services and associated socioeconomic position (SEP) factors among Chinese older adults disabled by injury.Data from the second China National Sample Survey on Disability (CSSD) were used in this study. Chi-square test was used to analyze the significant differences between groups, and binary logistic regression model was used to calculate the odds ratios and 95% confidence intervals for socioeconomic factors associated with utilization of rehabilitation services among Chinese older adults disabled by injury.Among the older adults disabled by injury in the CSSD, the gap between demand and utilization of medical treatment, assistive devices and rehabilitation training were around 38, 75, and 64%, respectively. This study revealed two relationship patterns (“high-low-high” and “low-high-low”) among SEP, prevalence of injury-caused disability and odds of utilization of rehabilitation services among the Chinese older adults disabled by injury, that is, the older adult with higher SEP have a lower prevalence of injury-caused disability, but a higher odds of utilization of rehabilitation services; conversely, the older adults with lower SEP have a relatively higher prevalence but a lower odds of utilization of rehabilitation services.There is a large gap between the high demand and low utilization of rehabilitation services among the Chinese older adults disabled by injury, especially for those living in the central or western regions or rural areas, without insurance or disability certificate, having the annual household per capita income lower than the national average or lower educational level. Strategies to improve the disability manage system, to strengthen the chain of “information discovery-information transmission-rehabilitation services supply-continuous health monitoring and management” for the older adults disabled by injury are warranted. In view of the poor and illiterate groups among the disabled older adults, to enhance medical aids and popularize the scientific information to compensate for the lack of affordability and awareness of rehabilitation services utilization is essential. In addition, it is necessary to further expand the coverage and improve the payment system of medical insurance for rehabilitation services. Injury has become the main cause of death and disability in most countries , accountRehabilitation service needs are universal, a conclusion confirmed by a study based on the Global Burden of Disease (GBD) 2019, which estimates that in 2019, 2.41 billion individuals had conditions that would benefit from rehabilitation, that is, at least one in every three people in the world needs rehabilitation at some point in the course of their illness or injury . HoweverBased on this, some studies have explored more possible strategies to remove the barriers to the utilization of rehabilitation services for the disabled from the perspective of the socioeconomic position (SEP). And yet, to the best of our knowledge, there may be few studies on rehabilitation services and associated SEP factors for the Chinese older adults disabled by injury. Taken all these into consideration, this article analyzes the utilization of rehabilitation services and related SEP factors for the Chinese older adults with injury-caused disability. In this way, it aims to supplement the research in this field and provide empirical data in making rehabilitation policies for the older adults disabled by injury in China.In this study, the Second National Sampling Survey on Disability in China in 2006 (CSSD) database was used to extract samples of the older adults aged 60 and above who were disabled by injury. It adopts the stratified, multi-stage and cluster probability proportional sampling method. It covers a total of 2,526,145 people from 771,797 households in 31 provinces, autonomous regions, and cities, with a sampling ratio of 1.93‰. The survey data is authentic .Disability refers to the abnormality or the loss of anatomical structure and physiological function caused by various physical and mental diseases, or injuries, or congenital abnormalities, which results in long-term, continuous or permanent dysfunction of the body that cannot be cured .Injury is defined as tissue damage or hypoxia by asphyxia that affect individual activities and need treatment or rehabilitation, resulting from energy transfer or interference exceeding the limits of biological endurance .Injury-caused disability is defined as a person who completely or partially loses the ability to engage in certain activities normally due to the loss or abnormality of certain organization or function in physiology and psychology caused by injury .As an important part of rehabilitation, medical rehabilitation is the application of rehabilitation concept in the medical field. It refers to healing the dysfunction of the sick, the injured, and the disabled through medical means . The rehSocioeconomic position (SEP) is an economic and sociological combined total measure of an individual's or family's economic access to resources and social position in relation to others , 16. WheThis research aims to study the demand and utilization of rehabilitation services in the Chinese older adults aged 60 and above who are disabled by injury, and the correlation between the utilization of rehabilitation services and individual's SEP. In the CSSD, it lists only organic and non-organic mental disorders as the causes of mental disability based on ICD-10 diagnostic criteria, failing to examine the injury-related causes , 19. TheIn this study, the dependent variable is “the usage of rehabilitation services”, that is, as long as any one of “medical services and assistance, assistive devices, rehabilitation training and services” is used, the participant is considered to have used rehabilitation services. Since the older adult/adults are less affected by occupation, the explanatory variables of SEP include annual household per capita income and educational level. The higher the annual household per capita income or educational level, the higher the SEP. In the descriptive analysis, the annual disposable per capita income of urban residents in China in 2006 was 11,759 yuan, and the per capita net income of rural residents was 3,587 yuan, according to the data of the National Bureau of Statistics. In this study, the annual per capita income of urban households that is higher than 11,759 yuan and the per capita net income of rural households that is higher 3,587 yuan are defined as higher than the annual per capita income of national residents . In addiThese surveys were approved by the State Council  and the survey plan was formulated in accordance with the Statistics Law of the People's Republic of China and the Law of the People's Republic of China on the Protection of Disabled Persons. During the surveys, all respondents provided informed consent to participate in the surveys and clinical diagnosis.Stata 16.0 was used for data analysis. Chi square test was employed for univariate analysis, and binary logistic regression was adopted for multivariate analysis. Hosmer-Lemeshow test was used for the test of goodness of fit of the model. The significance level was 0.05.A total of 354,859 elders were surveyed in CSSD, including 85,260 disabled elders. Among them, 10,314 older adults people were disabled by injury, with the prevalence of 291/10,000 , accounting for 12.1% of all older adults disabled people. The prevalence of physical disability by injury is the highest in this group  , followed by hearing disability . On the contrary, the prevalence is relatively low for the visual , intellectual , and speech  disabilities caused by injury in the older adults. As for the disability grading, most injury-caused disability in the older adult is mild (grade IV), accounting for nearly 57% of the total, followed by moderate . Severe (grade II) and extremely severe (grade I) disabled elders account for only 15%.In terms of SEP factors, the injury-caused disability in the older adults shows a higher prevalence in the groups of those with the annual household per capita income lower than the national average , the illiteracy/with no schooling  .There is a large gap between the high demand and low utilization of rehabilitation services among the Chinese older adults disabled by injury (hereinafter referred to as the “rehabilitation gap”). Thirty-eight percentage of demand for medical treatment, 75% for assistive devices and 64% for rehabilitation training are left unsatisfied. Based on social and demographic factors, there is little difference in the rehabilitation gap among different disability grades, gender, age groups, and marital status. However, the rehabilitation gap is relatively larger among the older adults with injury-related disability who (1) live in the central or western regions, (2) are rural residents, (3) without insurance, (4) without disability certificate, (5) have the annual household per capita income lower than the national average, and (6) are illiterate or with no schooling .2 = 12.77, P = 0.12 > 0.05, which means that the model fits better.Binary logistic regression analysis was carried out with “the usage of rehabilitation services” as the dependent variable; and disability grade, gender, age, marital status, region, residence , insurance status, and disability certificate status as the control variables; and annual household per capita income, educational level as the explanatory variables. The assignment of independent variables is shown in The results show that after controlling the variables of disability grade, gender, age, marital status, region, residence , insurance status, and disability certificate status, the odds of utilization of rehabilitation services is much higher in the groups of participants that (1) with higher annual household per capita income , (2) have been to primary school or above  .The gap between the utilization of rehabilitation services and the demand is large for the older adults disabled by injury. Rehabilitation services needs are universal . As for Existing research showed a “inverse combination” pattern between individual health status and SEP , that isHowever, there are some limitations that require consideration. First, It fails to distinguish mentally disabled persons due to injury in the CSSD database. Therefore, this study lacks the situation of mentally disabled people. Second, The CSSD database is relatively old and has limited practical guidance. Nonetheless, it is still the latest national sampling survey on disability in China.Facing the current situation of limited rehabilitation services in China, it is an essential means to improve the efficiency of rehabilitation services by clarifying the vulnerable groups of people with injury-caused disability and taking precise assistance measures. To be more specific, according to the distribution of the prevalence of injury-related disability and the utilization rate of rehabilitation services among different older adults groups, targeted measures should be taken based on their specific characteristics, especially the rural residents or people living in the central or western regions, poverty-stricken people, people with low educational level, or without insurance and disability certificate among the older adults. Strategies to improve the disability manage system, to strengthen the chain of “information discovery-information transmission-rehabilitation services supply-continuous health monitoring and management” for the older adults with injury-caused disability are warranted, especially for the vulnerable groups aforementioned. In view of the poor and illiterate groups, to enhance medical aids and popularize the scientific information to compensate for the lack of affordability and awareness of rehabilitation services utilization is essential. In addition, it is necessary to further expand the coverage and improve the payment system of medical insurance for rehabilitation services.The data that support the findings of this study are available from the Institute of Population Research of Peking University (IPR). Restrictions apply to the availability of these data, which were used under license for this study. Data are available with the permission of IPR. Requests to access these datasets should be directed to 00-86-010-62751974.Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.Y-RW is responsible for conceptualizing, data analysis, formal interpretation of results, and writing the manuscript. Y-NL is responsible for conceptualizing, critical revision of article for important intellectual content, and writing—review and editing. Y-LF and Y-YF are responsibility for revision of article. X-YZ is responsible for conceptualizing the study, methodology, and supervision. All authors have read and agreed to the published version of the manuscript.


Background: Sex-specific differences in heart disease outcomes are influenced by the levels of the steroid hormones, estrogen and testosterone. While the roles of estrogen receptors in cardiac disease are well-studied in animals and humans, respective research on androgen receptors (AR) is limited. Here we investigate AR protein and mRNA expression in human myocardium of various cardiac diseases. Methods: AR expression was analyzed by western blotting in myocardium from human non-failing hearts  and patients with aortic stenosis , hypertrophic cardiomyopathy , dilated cardiomyopathy , and ischemic cardiomyopathy . Using an AR45-specific antibody, a subsequent western blot assessed samples from male and female patients with HCM (n = 10) and DCM (n = 10). The same sample set was probed for full-length AR and AR45 mRNA expression. Immunohistochemistry (IHC) localized AR in myocardium from HCM and AS hearts. Results: Full-length AR was notably enriched in AS and HCM hearts compared to ICM, DCM, and NF. Similarly, AR45 was more abundant in HCM than in DCM. In contrast to the pattern observed for AR protein, full-length AR mRNA levels were lower in HCM compared to DCM, with no discernible difference for the AR45 isoform. Although gender differences in AR expression were not detected in western blots or qRT-PCR, IHC showed stronger nuclear AR signals in males than in females. Conclusions: Our findings indicate disease-specific regulation of AR mRNA and/or AR protein in cardiac hypertrophy, underscoring a potential role in this cardiac pathology. Sex-specific differences have been identified in adult patients with valvular aortic stenosis (AS) and left ventricular hypertrophic cardiomyopathy (HCM). Men, in comparison to age-matched women, appear to be more susceptible to HCM, with distinct variations in heart size ,2.The gender-related disparities in disease outcomes are hypothesized to arise from the differential levels of sexual steroids, notably estrogen and testosterone ,4. WhileWhile estrogen predominantly interacts with estrogen receptors α and β , testosterone associates with the androgen receptor (AR) . SteroidIn contrast, the cardiac role of AR is relatively understudied. Yet, its presence in cardiac myocytes across different species, including humans, is well-documented . An AR-dInterestingly, the heart not only expresses full-length AR but also a heart specific AR isoform called AR45 . AR45 isAR and AR45 mRNA expression. Lastly, we study AR protein localization in HCM and AS myocardium using immunohistochemistry.In this study, we assess AR protein expression in various cardiac diseases using western blotting. We analyze myocardial samples from HCM and DCM patients, focusing on gender-specific differences in AR45 protein and full-length Procedures for obtaining human tissue were in accordance with the principles outlined in the Declaration of Helsinki. The respective local Ethics Committees of the University of Hamburg and the University of Goettingen in Germany granted permission for the use of this human material (Az. 532/116/9.7.1991).To analyze full length AR protein expression by Western blotting we used six nonfailing (NF) human hearts  that were obtained from prospective organ donors that could not be transplanted due to technical reasons. Seven DCM samples  and seven ICM samples  were taken from patients undergoing heart transplantation due to end-stage heart failure. NF, DCM, and ICM samples have already been described in studies published by Stein et al. and El-Armouche et al. ,12 and wFor AR45 Western blot and qRT-PCR analysis of AR45 and full-length AR, a second set of tissue was implemented consisting of 10 HCM samples  and 10 DCM samples . For IHC, we used 10 HCM samples  and 10 AS samples .Freshly taken tissue samples were snap-frozen in liquid nitrogen and then stored at −80 °C or fixed in Formalin.v/v), complete protease inhibitors and PhosSTOPTM phosphatase inhibitors ) and further processed by sonication. A total of 35 µg tissue protein extract per lane was subjected to SDS-PAGE . From a second set of samples, our objective was to extract both protein and mRNA. We used frozen tissue powder from the myocardium of twenty patients: ten with HCM  and ten with DCM . This powder was dissolved in Trizol® reagent . Following the manufacturer’s instructions, we isolated protein alongside mRNA. The resultant pellets were dissolved in lysis buffer and processed further by sonication. We subjected 15 µg of the tissue protein extract per lane to SDS-PAGE. Size-separated protein was transferred from the SDS-PAGE into a nitrocellulose membrane  by wet blotting. The membrane was then blocked in TBS buffer pH 7.6 containing 5% milk powder for 2 h at room temperature. Incubation with the primary antibody was performed overnight at 4 °C in TBS buffer containing 1% Tween and 5% milk powder. Monoclonal rabbit anti-androgen receptor  was used at a dilution of 1:1000 to detect full-length AR at 110 kDa. EPR1535 detects an N-terminal epitope on Exon 1. The monoclonal rabbit anti-androgen receptor  was used at a dilution of 1:300 to detect AR isoform 45 at 45 kDa. SP242 detects a c-terminal epitope. AR receptor signals were normalized to GAPDH expression, that was determined using the monoclonal rabbit anti-GAPDH antibody, clone 14C10  at a dilution of 1:20,000. HRP-conjugated secondary antibodies were diluted in TBS buffer containing 1% Tween and 5% milk powder for 1 h at room temperature. Chemiluminescence was detected using SuperSignalTM West Femto reagent  and an LAS-3000 Imaging System .Frozen tissue powder from tissue samples of NF, DCM, ICM, AS, and HCM patients, which were used for full-length AR western blotting was dissolved in lysis buffer  lysate as we did for protein isolation. We extracted the total RNA following the manufacturer’s instructions. Subsequently, we purified the resulting RNA using the RNeasy® Mini Kit . Reverse transcription was carried out with 1 µg total RNA, the Superscript II Reverse Transcriptase , and random hexamer primers . For mRNA isolation from HCM and DCM, we utilized the same TrizolTo distinguish between full-length AR and AR45, we designed isoform-specific primers. For both PCRs, we utilized the same reverse primer that binds to AR exon 3: 5′-GAAGACCTTGCAGCTTCCAC-3′. However, the forward primers were tailored to specifically target each isoform. For the detection of full-length AR, we employed a forward primer that binds to AR exon 1A: 5′-GGTGAGCAGAGTGCCCTATC-3′. This exon is present in full-length AR but absent in AR45. Conversely, to detect the AR45 isoform, we utilized a forward primer that targets the AR45-specific exon 1B: 5′-GGTGAGCAGAGTGCCCTATC-3′. This primer does not bind to full-length AR. We normalized AR expression to GAPDH, using the forward primer 5′-GAGTCAACGGATTTGGTCGT-3′ and the reverse primer 5′-GACAAGCTTCCCGTTCTCAG-3′. The qPCR was executed using the iQ SYBR® Green Supermix  on the MyiQTM RT-PCR Detection System . For data evaluation, we utilized the iQTM5 software from BioRad (Version 2.1).Formalin-fixed myocardial tissue from AS , and HCM  hearts were embedded in paraffin and then sectioned into 5 µm thick slices, ready for immunohistological staining following standard protocols. The tissue slices underwent deparaffinization, and antigens were retrieved using a high pH target retrieval buffer (GV804) from DAKO , with a 20-min incubation at high pressure and 90 °C. Subsequently, the primary antibodies were incubated overnight. To detect AR in cardiac tissue, we utilized two antibodies: A rabbit polyclonal Anti-AR antibody that targets the N-terminus of the AR protein  sourced from Santa Cruz , used at a 1:300 dilution and a monoclonal rabbit anti-androgen receptor (clone SP242) from Spring Bioscience  that targets the C-terminus of AR, used at a 1:40 dilution. To enhance the AR signals, we employed the Zytochem Plus HRP Polymer anti-rabbit System (ZUC032-006) from Zytomed , which was visualized using DAB . To clearly show the identity of the AR positive cells, we employed a double-staining procedure using the monoclonal rabbit anti-androgen receptor (clone EPR1535) from Epitomics  at a 1:50 dilution with either Vimentin or Desmin as a second primary antibody. Vimentin was detected using a monoclonal mouse anti-Vimentin antibody  from DAKO  at a 1:1000 dilution. Desmin detection used the monoclonal mouse anti-Desmin antibody  from Progen Biotechnik GmbH  at a 1:1500 dilution. These signals were amplified using the Histofine Simple Stain AP (Multi) Anti-Mouse and Anti-Rabbit from Medac  and visualized with permanent red.All immunohistochemical stainings were further processed with Hemalaun to visualize the nuclei in lilac. Controls were implemented using the appropriate IgGs at the relevant concentrations in place of the primary antibody.AR was detected by western blotting using the antibody clone EPR1535, which binds to the N-terminal region of AR. This enables the detection of the full-length AR at 110 kDa, but not the heart-specific isoform AR45. Total protein from NF (n = 6), DCM (n = 7), ICM (n = 7), AS (n = 6), HCM (n = 7) heart tissues was analyzed. For normalization, a consistent reference sample set was used to bracket the test samples, and AR signal intensity was normalized against GAPDH. An exemplary western blot is depicted in Distinct variations in AR protein levels were observed across various cardiac disorders. DCM (0.62 ± 0.12) and ICM (0.54 ± 0.07) samples demonstrated average AR protein levels similar to the control group (NF: 0.79 ± 0.18). In contrast, AS (1.82 ± 0.44) and HCM (2.45 ± 0.23) samples exhibited a significant increase, approximately three to four-fold, compared to NF, DCM and ICM hearts.The heart-specific AR isoform, AR45, was detected at 45kDa using the antibody clone SP242. This clone binds to the C-terminal region of AR, allowing for the detection of both the full-length AR and AR45. Total protein from HCM and DCM myocardium, comprising n = 5 female and n = 5 male samples, was analyzed. For normalization, a consistent reference sample set bracketed the test samples, and AR signal intensity was normalized against GAPDH. AR signal intensities for each condition and gender are presented as a box and whiskers plot in To distinguish between full-length AR and AR45, we used isoform-specific primers on HCM and DCM myocardium, comprising n = 5 female and n = 5 male samples. QRT-PCR analysis showed an increase in full-length AR mRNA in DCM samples compared to HCM samples. Expression levels of AR45 mRNA were similar. No gender-specific differences were detected Refer to B,C.Immunohistochemical single stainings were performed using antibodies sc-816, directed to the N-terminus, and SP242, directed to the C-terminus. These were applied to myocardium from AS  and HCM  hearts. AR signals were observed in the nucleus of cardiomyocytes A–D. SomeContrary to the western blot results, nuclear staining was more pronounced in the myocardium of males compared to females in both HCM and AS specimens. Specifically, only 3 out of 5 female HCM and 1 out of 5 AS patients displayed weak nuclear signals. Conversely, 5 out of 5 male HCM and 3 out of 5 male AS patients showed intense nuclear signals. One male AS patient had a weak signal. Specimens not mentioned did not exhibit any nuclear signal. The results were consistent across both antibodies. The identity of the AR-expressing cells was affirmed by their distinct morphological characteristics. This was further validated by the absence of Vimentin and the presence of Desmin, as identified by double staining E–H.Information on AR in human cardiac tissue  is limitIn our study, both full-length AR and AR isoform 45 were expressed in human myocardium at mRNA and protein levels. AR protein was enriched by 3 to 4-fold in hypertrophied myocardium from AS and HCM patients, compared to NF myocardium or myocardium diagnosed with DCM or ICM. Likewise, the heart-specific isoform AR45 was enriched in HCM compared to DCM, with no significant differences between males and females. Contrarily, AR mRNA levels were reduced in myocardium from HCM patients when compared to that of DCM patients, with no statistically significant difference between males and females and with no difference in the expression of AR45. Our study also described the localization of AR in the nucleus of cardiomyocytes, and in contrast to the western blot results, observed a differential nuclear abundance between male and female hypertrophied cardiomyocytes.Cardiac hypertrophy acts as a compensatory mechanism in response to increased pressure overload. Myocardial hypertrophy can be triggered by AS  due to tSex-specific differences have been identified in adult patients with valvular aortic stenosis (AS) and left ventricular hypertrophic cardiomyopathy (HCM) ,2. The cOur findings on AR protein expression in the myocardium of AS patients parallel those of Nordmeyer et al., who reported an upregulation of ERα in samples from both female and male AS patients . ContrarWhile no gender-related difference in AR was detected by western blot, IHC showed a differential nuclear abundance in male vs. female hypertrophied myocardium. The findings were consistent with both C- and N-terminal antibodies, indicating that the detected signal stems from full-length AR, or potentially from both isoforms, AR and AR45. Elevated testosterone levels in men  might reNext to the full-length androgen receptor, there exists the variant AR45 that utilizes Exon 1B instead of exon 1A . AR45, pAR mRNA expression was down-regulated by its ligand, DHT, while the protein levels appeared to be up-regulated under certain conditions [An intriguing aspect of AR regulation is the contrasting findings of AR mRNA and protein levels in HCM and DCM samples. While protein levels were elevated in HCM, mRNA levels were lower compared to DCM. Similar findings have been observed for vas deferens epithelial cells where nditions . This diLimitations of the Study and Future Directions: A significant limitation of our research was the small sample size, especially in sex-specific analyses , leading to reduced statistical power. Another constraint was that the DCM and ICM patients in our study were in the end-stage of heart failure. Future research should delve deeper into the mechanisms behind AR's role in cardiac hypertrophy, especially focusing on the functional implications of AR45 and the gender-specific effects of AR.In conclusion, our study marks the first-time demonstration of AR expression at the protein level in a sizable human myocardium cohort. The elevated AR and AR45 protein levels in hypertrophic conditions, coupled with the observed gender differences, highlight the intricate roles of androgen receptors in cardiac diseases. Further research is essential to fully understand these roles and their therapeutic implications.


This study used an epidural anesthesia practice kit (model) to evaluate the accuracy of epidural anesthesia using standard techniques (blind) and augmented/mixed reality technology and whether visualization using augmented/mixed reality technology would facilitate epidural anesthesia.This study was conducted at the Yamagata University Hospital  between February and June 2022. Thirty medical students with no experience in epidural anesthesia were randomly divided into augmented reality (-), augmented reality (+), and semi-augmented reality groups, with 10 students in each group. Epidural anesthesia was performed using the paramedian approach with an epidural anesthesia practice kit. The augmented reality (-) group performed epidural anesthesia without HoloLens2Ⓡ and the augmented reality (+) group with HoloLens2Ⓡ. The semi-augmented reality group performed epidural anesthesia without HoloLens2Ⓡ after 30 s of image construction of the spine using HoloLens2Ⓡ. The epidural space puncture point distance between the ideal insertion needle and participant’s insertion needle was compared.Four medical students in the augmented reality (-), zero in the augmented reality (+), and one in the semi-augmented reality groups failed to insert the needle into the epidural space. The epidural space puncture point distance for the augmented reality (-), augmented reality (+), and semi-augmented reality groups were 8.7 (5.7–14.3) mm, 3.5 (1.8–8.0) mm (P = 0.017), and 4.9 (3.2–5.9) mm (P = 0.027), respectively; a significant difference was observed between the two groups.Augmented/mixed reality technology has the potential to contribute significantly to the improvement of epidural anesthesia techniques.The online version contains supplementary material available at 10.1186/s12871-023-02133-w. Epidural anesthesia, the gold standard for postoperative analgesia, is used with general anesthesia in thoracic, abdominal, pelvic, and lower extremity surgery. The analgesic effect of epidural anesthesia is superior to that of paravertebral nerve block, and it may be effective in reducing postoperative cognitive dysfunction and stress response –3. HowevThe incidence of insertion failure and epidural anesthesia difficulty is approximately 7% and as high as 26% among anesthesia residents , 5. ThesRecent developments in augmented reality/mixed reality (AR/MR) technology have facilitated the visualization of the invisible and have been utilized in various fields. In medicine, they are used as educational tools for ventricular drainage and extracorporeal membrane oxygenation cannulation –24. SpecThe blind technique is the gold standard for epidural anesthesia. Since the practice process is often performed blind, it is important to understand the anatomy of the patient’s spine. We hypothesized that the use of AR/MR technology to visualize internal structures using spine images constructed from the patient’s own CT images and projected onto the patient’s back would help facilitate a smooth and accurate epidural anesthesia procedure. Since the current epidural anesthesia practice method is only a blinded method using an epidural anesthesia practice kit, the blinded technique (standard technique) was used as a control group, and this study aimed to examine the usefulness of using a tool (AR/MR technology) for visualization during the procedure. In addition, the purpose of this study was to examine the usefulness of using AR/MR technology as a tool for constructing images to improve the accuracy of the procedure. This study examined the possibility of using AR/MR for epidural needle placement in epidural anesthesia in accordance with textbooks and whether AR/MR technology can be used as a training tool for medical students (MSs) in epidural anesthesia techniques.If the feasibility of epidural anesthesia using AR/MR is proven, difficulties during epidural catheter insertion can be avoided, and patient pain and anesthesia induction time can be reduced. Improved epidural anesthesia techniques may resolve issues with epidural anesthesia in obese patients and patients with atypical spinal anatomy or supraspinous ligament ossification.This study was approved by the Ethics Committee of Yamagata University and conducted in accordance with the Declaration of Helsinki . Written informed consent was obtained from all participants.We used a commercially available phantom epidural anesthesia practice kit for the lumbar spine  equipped with silicone skin and air-filled epidural space, and an 18G Tuohy needle  Fig. .This study included 30 MSs with no previous experience performing epidural anesthesia undergoing bedside training at the Yamagata University Hospital between February and June 2022. In this study, MSs over the age of 30 years were excluded from the study because of the possibility that they might have had previous experience in other medical work and to avoid allowing this experience to influence the results of the study. MSs who were unable to perform the procedure according to the video lectures and procedures described below were also excluded. MSs were randomly divided into AR(-), AR(+), and semi-augmented reality (SemiAR) groups, with 10 MSs in each group  group performed epidural anesthesia according to the procedure manual and was designated AR(-)_test1.In the AR(+) group, participants used HoloLens2Ⓡ after confirming its activation and observed a hologram of the ideal insertion model for 30 s. Epidural anesthesia was performed according to the procedure manual while using HoloLens2Ⓡ. This group was designated AR(+)_test1.In the SemiAR group, after confirming its activation, HoloLens2Ⓡ was worn, and a hologram of the ideal insertion model was observed for 30 s. HoloLens2Ⓡ was then removed, and epidural anesthesia was performed according to the procedure manual without using HoloLens2Ⓡ. This group was designated as SemiAR_test1.Epidural anesthesia was performed using the loss of resistance method . The proFor the second epidural puncture, all groups (AR(-), AR(+), and SemiAR) performed epidural anesthesia via the paramedian approach without HoloLens2Ⓡ using the epidural anesthesia practice kit. Written instructions were provided and placed in a position visible to the operator during the procedure.The AR(-) group performed the epidural anesthesia again after being instructed that the puncture should be more precise than the previous one. This group was designated AR(-)_test2.The AR(+) group retained the image of the hologram of the ideal insertion model at Test 1, and epidural anesthesia was performed without HoloLens2Ⓡ. This group was designated AR(+)_test2.The SemiAR group retained the image of the hologram of the ideal insertion model at Test 1, and epidural anesthesia was performed without HoloLens2Ⓡ. This group was designated SemiAR_test2.Data acquisition and measurements were performed as in Test 1.The user experience questionnaire (UEQ) was administered to all MSs  and analyzed with the Mann–Whitney U test. As we believe that administering epidural anesthesia with visualization is superior to administering it blindly, a one-tailed test was used to examine the SPPD, PA, and ESPPD of the model with MS insertion and model with the needle inserted according to the textbook. One-tailed tests were also performed for the comparison of the epidural anesthesia procedure time and UEQ. Tests 1 and 2 were compared using the one-tailed Wilcoxon signed-rank sum test. P-values < 0.05 were considered statistically significant.The mean age of the MSs was 24.0 (23.0–25.0) years  (Supplementary Table Four MSs in AR(-)_test1, zero in AR(+)_test1, and one in SemiAR_test1 were unable to puncture the epidural space. Table In AR(-)_test1 and SemiAR_test1, the SPPD was 11.2 ± 4.8 and 7.5 ± 4.2 mm, respectively (P = 0.04); the PA was 15.5 ± 3.6 and 8.0 ± 4.4 degrees, respectively (P < 0.01); and the ESPPD in AR(-)_test1 and SemiAR_test1 was 8.7 (5.7–14.3) and 4.9 (3.2–5.9) mm (P = 0.027), respectively. Significant differences were observed for SPPD, PA, and ESPPD  s, 148.0 (139.0–164.8) s, and 122.0 (95.5–136.3) s for the AR(-)_test1, AR(+)_test1, and SemiAR_test1, respectively. _test2, zero in AR(+)_test2, and zero in SemiAR_test2 could not puncture the epidural space. When comparing Tests 1 and 2, there was a tendency for the ESPPD to approach the ideal insertion model in the AR(-) and SemiAR groups. However, the difference was not statistically significant (Supplementary Table The execution time for Test 2 was 100.0 79.5–128.5) s, 115.0 97.3–143.0) s, and 93.0 (79.8-159.5) s for AR(-)_test2, AR(+)_test2, and SemiAR_test2, respectively  group had significantly more positive answers to questions in the perspicuity, novelty, stimulation, dependability, and efficiency categories of the UEQ than the AR(-) group. The SemiAR group also provided significantly more positive responses in all items of the UEQ than the AR(-) group _test1 MSs were able to place the epidural needle close to the ideal locations for the PA and ESPPD. In SemiAR_test1, the epidural needle was placed close to the ideal needle in all cases .These results indicate that epidural anesthesia with AR may be more appropriate for epidural needle placement than epidural anesthesia with textbook or video learning alone. The large variance in the SPPD for the AR(+)_test1 MSs may be attributed to none of the participants having experience using mixed reality head-mounted smart glasses; thus, the MSs may have misidentified the surface puncture point because they had not mastered AR sensation. Alternatively, the registration accuracy, and inherent overlay accuracy and stability could have also had some impact on the variance in the SPPD .Test 2 resulted in the SemiAR_test2 group placing the epidural needle closer to the ideal needle model at the epidural space puncture point compared to AR(-)_test2. The SemiAR group performed image training using a HoloLens2Ⓡ and performed epidural anesthesia without AR in both Tests 1 and 2. This tended to improve epidural anesthesia technique.However, a comparison of AR(+)_test1 and AR(+)_test2 showed no trend toward successful epidural anesthesia. This could be attributed to the fact that the AR(+) group used HoloLens2Ⓡ in Test 1 and did not use it in Test 2, resulting in a significantly different environment between the first and second sessions.The UEQ results indicate that many students had a positive perception of AR. We believe that AR is a useful learning tool in terms of attracting students’ interest. In terms of time, the results of Tests 1 and 2 showed that the use of AR/MR technology did not contribute to a reduction in procedure time.A previous study has examined the possibility of epidural anesthesia using AR . HoweverThere is no practice in clinical practice, it is always an actual procedure, which in the case of this study is the Test 1 situation. In Test 1, the SemiAR group had the best procedure accuracy, suggesting that epidural anesthesia using AR/MR technology may be effective for image training before the actual surgery. For residents inexperienced in epidural anesthesia, AR/MR technology appears to be a sufficient tool to learn the optimal insertion angle technique when “walking” the needle tip. Since most patients undergoing thoracic and abdominal surgery undergo CT, we believe that AR/MR technology can be applied clinically and that previewing epidural approaches with actual patient CT images before performing epidural anesthesia promotes safety. Furthermore, epidural anesthesia AR/MR is expected to be used by experienced anesthesiologists as a technical learning tool to perform epidural anesthesia more accurately and safely.Some HoloLens2Ⓡ medical applications have been approved by the US Food and Drug Administration. In the future, epidural anesthesia may be performed with HoloLens2Ⓡ, thereby improving the understanding of the anatomy and safety of epidural anesthesia. This will facilitate epidural anesthesia in patients with obesity and spinal stenosis, for whom locating the epidural space is difficult, and avoid unintentional dural and vascular puncture by the epidural needle.There are eight limitations of this study. First, the commercially available phantoms are practice kits for epidural anesthesia and have a larger gap than the actual vertebral arch, which can cause the epidural needle to accidentally penetrate the epidural space puncture point. Future research should be conducted using epidural anesthesia practice kits with smaller gaps or epidural anesthesia AR/MR in actual clinical practice. Second, blinding was impossible for MSs. Third, the sample size was determined with reference to previous similar studies. Increasing the sample size in future studies may provide more reliable results. Fourth, the AR markers were used to visualize the virtual spine, and the epidural anesthesia practice kit was held in place to prevent misalignment; however, the pressure applied by the participant during the puncture may have caused some movement, resulting in misalignment of the virtual spine. Fifth, we did not consider the possibility that the needle could successfully approach the epidural space even when the surface puncture point was located far from the ideal surface puncture point in this study. In clinical practice, the needle can approach the epidural space by changing the angle of the needle, even when the insertion point is located far from the ideal point. This study determined how close the epidural needle can be inserted to the model entry point described in Miller’s Anesthesiology (textbook), which is currently considered ideal. Therefore, there may be differences in clinical situations. We believe it is important to continue our research to further improve the practicality of applying AR/MR technology while validating it in clinical situations. Sixth, it may be necessary to consider the time factor in the data acquisition process. In the AR(-) group, there was a period of time between the video lecture and start of epidural anesthesia. In the AR(+) and SemiAR groups, there was a period of time between the video lecture and start of hologram observation, and a period of time between the end of hologram observation and start of epidural anesthesia. Thus, there were different gaps in time periods in each group. In addition, although we took care to avoid time gaps in timing, such as the replacement of the epidural puncture pad in all groups, there could have been a difference of a few seconds in each group. Seventh is an examination of the time factor when AR/MR technology is applied in actual clinical practice. Although AR/MR data acquisition, processing, and registration are likely to be required in actual clinical settings, these times were not measured in this study. We have confirmed that it takes approximately 1 min from the time the HoloLens2Ⓡ is turned on to the time the application is launched, although it is necessary to examine the exact time required in actual clinical settings. Eighth, we have not examined the comparison between the administration of epidural anesthesia using AR/MR technology and other technologies. In future studies, it would be appropriate to consider comparisons with other techniques such as Fiducial Registered CT imaging and ultrasound-guided access in future studies.These findings suggest that AR/MR technology is a useful tool to construct an image of epidural anesthesia and can significantly contribute to improved epidural anesthesia skills, potentially stabilizing patient conditions, and solving medically important epidural anesthesia problems.Below is the link to the electronic supplementary material.Supplementary Table 1: Contents of the user experience questionnaire (UEQ)Supplementary Table 2: Characteristics of each group of medical students with no experience with epidural anesthesiaSupplementary Table 3: Comparison of the ESPPD between Tests 1 and 2 in all groupsSupplementary Figure 1: CT scanner image of the ideal insertion model:  CT scanner images of the ideal insertion model from the side, top, and front viewsSupplementary Figure 2: Posture of epidural anesthesia operator (without and with HoloLens2Ⓡ) : The epidural anesthesia operator wearing HoloLens2Ⓡ can observe the hologram of the ideal insertion model projected on the back of the epidural anesthesia practice kitSupplementary Figure 3: Formula for the inner product of vectors:  The epidural needle puncture angle of the ideal insertion model and the participants’ epidural needle puncture angle were calculated using the inner product of vectorsSupplementary Figure 4: Evaluation of dural puncture and internal structure of epidural anesthesia practice kit: Dural punctures were excluded from the evaluation of the epidural anesthesia practice kit because of the possibility of anatomically improbable puncture situations, as indicated by the arrowsSupplementary Figure 5: Comparison of the SPPD, PA, and ESPPD in AR(+)_test1 and SemiAR_test1, with AR(-)_test1 as the control group:  Regarding the SPPD, SemiAR_test1 had a surface puncture point closer to the ideal needle model (A2). Regarding the PA, both AR(+)_test1 and SemiAR_test1 had a puncture angle close to the ideal needle model . Regarding the ESPPD, both the AR(+)_test1 and SemiAR_test1 groups had epidural space puncture points closer to the ideal needle model . Note: * indicates significant between-group difference (P<0.05)Supplementary Figure 6: UEQ results for the AR(-) group as the control group:  The AR(+) group had significantly more positive answers to questions in the perspicuity, novelty, stimulation, dependability, and efficiency categories of the UEQ than the AR(-) group. The SemiAR group also obtained significantly more positive responses in all items of the UEQ than the AR(-) group. Note: * indicates a significant between-group difference (P<0.05)


Technical innovations increasingly affect various areas of everyday life. A field that has come into focus in recent years, especially in lifestyle applications, is augmented reality (AR). AR claims to combine real-life with virtual content for an immersive experience known as “mixed reality”.Besides entertainment, the AR approach is also being evaluated in various medical specialties to explore its potential as an assist device in patient treatment . The claBesides surgery and medical education, AR tools have also been developed for interventional radiology . The mosThe main task for us as interventionalists is to scientifically evaluate the applicability and accuracy of those novel AR applications. And this is precisely where the greatest challenges lie. Anyone who performs CT-guided punctures knows that the main task of the interventionalist is to adjust for deviations from the originally planned puncture tract. This particularly affects organ systems that move in a respiratory-dependent manner, such as the liver and lungs. Preclinical studies on immobile phantoms cannot adequately represent this real-life scenario and simplify the technical challenges of image registration in patients. Thus, comparability usually exists only to immobile puncture targets, which also pose little challenge in routine clinical practice. Therefore, the main advantage of AR applications here would be to reduce radiation exposure, which would be straightforward and inexpensive with applications such as the one presented in this manuscript. On the other hand, the wider availability of the required hardware tends to give rise to “third-party” software solutions, which are usually only evaluated on a small scale. However, it is essential to evaluate the applications on a larger scale to provide recommendations and enable their translation into clinical routine. For this, we need extensive exchange within the IR community, which could be accomplished through our international societies, to enable further distribution and technical developments. Even though experienced interventionalists are critical of such applications, which in their view are not necessary, it is essential to investigate their potential. It is our task to transfer modern technologies into our clinical routine by evaluating them in a scientifically adequate way, and thus to further develop our field of expertise. Being open-minded to innovations moves our specialty forward and makes it even more attractive to future generations of interventionalists.