In this prospective single-arm study of 50 pediatric patients with acute lymphoblastic leukemia (ALL), we evaluated the clinical performance of a novel bioimpedance spinal needle system in 152 intrathecal treatment lumbar punctures (LP) of these patients. The system detects in real-time when the needle tip reaches the cerebrospinal fluid (CSF) in the spinal canal. The success was defined as getting a CSF sample and/or administering the intrathecal treatment with one needle insertion. Incidence of traumatic LP (TLP) was defined as ≥ 10 erythrocytes/µL of CSF. Post-procedural complications were monitored with a one-week diary and one-month register follow-up. The success of the first attempt was 79.5%, with the CSF detection sensitivity of 86.1%. The incidence of TLP was 17.3%. A successful first attempt was associated with a significantly lower incidence of TLP . During the week after the procedure, the incidence of post-dural puncture headache was 6%. During the follow-up, no major complications were observed. In conclusion, the novel bioimpedance spinal needle system achieved a high success rate and low incidence of TLP and other complications in pediatric patients with ALL in a real-world clinical setting, indicating clinical utility for this system in pediatric hemato-oncology. These reported values mostly reflect the incidence of TLPs in the patient’s first diagnostic puncture, not in intrathecal treatment punctures during the subsequent therapy period. Since blood leakage into the spinal canal not only compromises the diagnostics but also increases the risk of blasts entering CSF space and the central nervous system, a successful puncture at the first attempt together with a low incidence of TLP are of paramount importance. TLP and a high number of blasts in CSF are associated with patients’ poorer event-free survival and relapse of the disease9.Lumbar puncture (LP) is an essential clinical procedure for diagnostics of acute lymphoblastic leukemia (ALL), and intrathecal administration of chemotherapy in patients with ALL. Traumatic LP (TLP), manifesting as red blood cells in the sample of cerebrospinal fluid (CSF) above a specified criterion, is common in clinical practice. Compiling the reported data from almost 19,000 LP procedures performed in pediatric oncology patients10. In children with ALL, the incidence of PDPH is yet quite low varying from 5 to 14%15. Excellent success at the first attempt is likely to contribute to the low incidence of PDPH14.Albeit LP is a well-established and safe procedure some complications are relatively common and inconvenient to the patient. The most considerable LP-specific complication is post-dural puncture headache (PDPH)13 to 90% or more15. In adults with leukemia, the success is associated with about halved incidence of TLP16, but to our knowledge, this issue is not specifically addressed in children with ALL. Generally, in pediatric patients, a successful LP at the first attempt is associated with about 50% lower incidence of TLP as well17.Success at the first attempt cannot be taken for granted, however. In pediatric patients with ALL, the success of LP with single skin penetration is generally good varying from 7020, ultrasound guidance confers several benefits: it can at least halve the incidence of TLPs, improve the success rate of LPs, and reduce the incidence of failed procedures compared to traditional palpation-based LP. As regards the children with ALL, challenging patients with high body mass index (BMI), anatomic abnormalities, young age, or a history of several failed attempts may be referred to ultrasound imaging for guidance before or during the LP procedure21.The success of LP can be improved by employing image guidance either before inserting the needle into the body or in real-time during the procedure. Crucial to the utility of image guidance is whether the obtained information on the patient’s anatomy or the orientation and location of the advancing needle can help prevent puncture-induced trauma on tissues in contact with CSF. According to recent meta-analyses20, particularly the real-time guidance requires the physician’s one hand to use the ultrasonic probe and the other to advance the needle, let alone the need for bedside imaging equipment, and user’s adequate proficiency to use this technique. These needs may alter the performance of the proven LP the physicians are commonly used to doing. Thus, a needle guidance method that does not require specific expertise and simultaneous operation of the imaging equipment but provides real-time feedback on the needle tip location might be an option worth considering. Recently, a novel bioimpedance-based spinal needle system was found clinically feasible in LPs of both adults and infants, including neonates23. This new system provides real-time needle guidance by informing the user when the needle tip reaches CSF in the subarachnoid space of the spinal canal, and the correct location for CSF sampling or administration of intrathecal treatment. In this prospective study, we extended the use of the bioimpedance spinal needle system to LPs of pediatric patients with ALL and specifically evaluated the success rate at the first attempt, the incidence of TLP and other potential complications related to its use in a real-world clinical setting.While there is convincing evidence for the clinical utility of ultrasound imaging in performing LPAll pediatric patients aged between 18 months and 18 years treated for ALL in pediatric hemato-oncology departments of Helsinki, Turku, and Tampere university hospitals were eligible for the study. LP procedures and data collection were done between November 2019 and September 2020. Before the study, all patients and/or their parents gave informed consent, depending on the patient’s age.Exclusion criteria were refusal to participate, no informed consent from the patient and/or parents as appropriate for age, or any concurrent clinical contraindication including skin infection around the puncture site, unstable hemodynamics, bleeding tendency, or increased intracranial pressure. Also, the patient’s first diagnostic LP was excluded because of apparent ethical and practical reasons. According to the study protocol, our goal was to gather data from at least 150 procedures of at least 50 pediatric patients with ALL but not more than four procedures per patient.www.injeq.com) comprises either 40 mm, 65 mm, or 90 mm long 22G Quincke-type spinal needles , bioimpedance analyzer, and a thin, flexible coaxial cable for connecting the needle to the analyzer. The needle is practically identical to the Quincke-type spinal needle with a stylet, except the stylet is configured as a bioimpedance electrode and has a cable connector at the handle end. Basically, performing the LP either with the bioimpedance needle or conventional spinal needle is similar. Also, the removal and reinsertion of the stylet do not differ from the conventional spinal needle.The bioimpedance spinal needle system  around the needle tip is calculated by discrete Fourier-transformations of the measured voltage and current data at the specified frequencies24. These bioimpedance values are used for tissue classification 200 times per second, meaning that the tissue classification is performed virtually in real-time (at every 5th ms) with high spatial sensitivity (< 1 mm3). By design, the system gives an audio-visual alarm when the needle tip reaches CSF in the subarachnoid space.For the needle guidance, the bioimpedance spinal needle system measures continuously the bioimpedance of tissues that are in immediate contact with the needle tip. In short, the analyzer employs a 1 ms long proprietary pulse sequence as an excitation signal which is continuously transmitted to the needle electrode. This low-power signal carries most of its power at few specified frequencies within a range from 1 to 349 kHz. Simultaneously the bioimpedance of a small tissue volume  gave an overview and practical training session on the use of the bioimpedance spinal needle system to local principal investigators , other physicians, and research nurses. The attendees could try the system on a lumbar phantom . Later, the principal investigators were responsible for the training of new users at their departments.All study LP procedures were part of the patients’ scheduled intrathecal treatment protocol. The procedure was performed under general anesthesia in the lateral decubitus position. The personnel of the participating departments performed the LP procedures according to their normal treatment schedules and practices. Primarily, all study procedures were to be performed with the bioimpedance needle system. However, in case of two unsuccessful attempts with the system, the user  could, upon personal decision, use the conventional Quincke-type 22G spinal needle to complete the procedure.After perceiving the CSF detection alarm from the system and upon clinical judgment, the user could either remove the stylet and check for CSF flow through the needle or continue the puncture. Also, the user could remove the stylet and check for CSF flow solely upon the clinical judgment about the location of the needle tip before the alarm.When the needle tip was correctly in the subarachnoid space verified by CSF flow, the user took the CSF sample and delivered the intrathecal treatment according to the patient’s treatment protocol.The red blood cell count (erythrocytes/µL) was routinely determined from the second or the third vial of CSF sample by the hospital laboratories with standard cytometric methods.Immediately after the study LP, the user evaluated the system performance and recorded the data on the patient’s Case Report Form (CRF) concerning the success of LP at the first attempt, the total number of attempts needed for a successful procedure, and the accuracy of perceived alarms.The success of LP at the first attempt was defined as getting a valid CSF sample and/or delivering intrathecal treatment with single needle insertion and skin penetration. Redirections of the needle inside the body, if needed, were allowed.The accuracy of CSF detection was evaluated by counting the numbers of correct alarms , missing alarms , and false alarms .The CSF detection sensitivity and false detection rate were determined as performance outcomes. The CSF detection sensitivity was calculated by dividing the number of correct alarms by the sum of correct alarms and missing alarms. The false detection rate was calculated by dividing the number of procedures showing false alarms by the number of all procedures.After each study LP procedure, the research nurse gave the patient/parents a diary to be filled for reporting perceived symptoms or complications during the day of the procedure and seven subsequent days. These included PDPH, headache, nausea, backache, fever, leaking or inflammation of the puncture site. PDPH was defined as a severe headache that worsened in sitting or standing position, eased after lying down, and occurred within 7 days of the preceding LP. After the week, the research nurse called the patient/parents and inquired about the diary data.Concerning the four weeks after the study LP procedure, the research nurse or investigator searched the patient-specific hospital records for potential complications or issues that might have been related to the LP procedure or the use of the bioimpedance needle system. Potential causality between the found complications or symptoms and the LP procedure or the use of the bioimpedance spinal needle system was evaluated by the local principal investigator using 5-level scoring system .2.Mean, standard deviation (SD) and ranges are given as descriptive data. A cumulative distribution curve was specifically used to illustrate the incidence of TLP. The curve depicts respective proportions of CSF samples, where the erythrocyte counts did or did not indicate TLP at any given criterion. In this study, the standard criterion of ≥ 10 erythrocytes/µL of CSF used in hemato-oncology was chosen as the criterion for TLP2), normal weight (17 ≤ BMI < 25 kg/m2), overweight (25 ≤ BMI < 30 kg/m2), and obese (BMI ≥ 30 kg/m2) by applying the patients’ BMI adjusted for age25. Finally, the association of system performance with the incidence of TLP was assessed.As a primary analysis, the association of the success of LP at the first attempt with the incidence of TLP was evaluated. Then, associations of the physician’s experience and patients’ body weight with the success rate and incidence of TLP were assessed. The patient’s weight was categorized into underweight  of the success rate at the first attempt, CSF detection sensitivity, and false detection rate were calculated with the exact Clopper-Pearson method. Statistical analyses were done with IBM SPSS Statistics for Windows, version 27.0 .The statistical comparisons were done using the ΧThe study protocol was approved by the Regional Ethics Committee of the Expert Responsibility Area of Tampere University Hospital, Finland (R19050). Also, the National Competent Authority  was notified about the study before its commencement in accordance with national legislation. The study was registered in ClinicalTrials.gov  and conducted according to Helsinki Declaration and Good Clinical Practice.The study LP procedures were performed in different phases of patients’ intrathecal treatment schedules, excluding the patients’ first diagnostic punctures. In total, data from 152 procedures of 50 pediatric patients with ALL  were obtained. The present data comprised four LP procedures from 26 patients, three from 8 patients, two from 8 patients, and one from 8 patients. A valid CSF sample was obtained in 150 procedures and intrathecal treatment was delivered in 151 procedures.Patients’ age ranged from 1.8 to 16.0 years with a mean of 7.1 (SD 3.9) years. Their body height ranged from 85 to 178 cm with a mean of 123 (24.3) cm, and weight from 13 to 71 kg with a mean of 29 (16.0) kg. At the time of their study LP procedures, 4% of patients were underweight, 66% normal weight, 23% overweight, and 7% obese.Of the 151 LP procedures, 120 were successful at the first attempt and the respective success rate was 79.5% (95% CI from 72.1 to 85.6%). One procedure was excluded from this analysis, because the physician accidentally chose too short a needle for the first attempt. Two attempts were required in 20 procedures, three attempts in five procedures, and at least four attempts in six procedures. One procedure could not be completed even after several attempts by three different physicians.The incidence of TLP was 17.3% (95% CI 11.7–24.4%). The red blood cell count in the CSF sample was at least 10 erythrocytes/µL in 26 samples out of 150 samples. The incidence of erythrocyte-free samples was 55.3%.2 test, p = 0.0015).The success rate at the first attempt was associated with a significantly lower incidence of TLP Fig. . When th2 test, p = 0.91). The respective incidences of TLP were 18.7% and 13.3% .The success rate at the first attempt was similar when the normal and underweight patients were compared to overweight and obese patients . The incidence of TLP was 13.2% in LPs performed by the experienced physicians and 20.7% in LPs performed by less experienced physicians .Twenty-six different physicians performed at least one study LP procedure. The median number of procedures per physician was 4, ranging from one to 16. Physicians with previous experience of more than 100 LPs performed 45% of the study procedures. The success rate at the first attempt did not differ between the more experienced physicians and less experienced physicians . The system detected CSF correctly in 118 out of these 137 procedures , whereas there was no CSF alarm in 19 procedures.False CSF alarms occurred in 14 out of 152 procedures . In six out of these 14 procedures, the system detected CSF correctly after preceding false alarms. Seven procedures were eventually completed with a conventional spinal needle.2 test, p = 0.11).Correct performance of the system seemed to be associated with a lower incidence of TLP Fig. . The incThe 7-day diary data were received after 140 study LP procedures (92%). During the 7-day period, PDPH was observed after 9 procedures (6%), three times in the same patient. Other complications during the first week included nausea after 22 procedures (15%), headache after 20 procedures (14%), backache after 20 procedures (14%), and fever after 10 procedures (7%).Patients’ four-week register data were accessed for all 152 procedures (100%). During the four-week follow-up, 17 complications with at least a possible link to the preceding LP procedure with the bioimpedance needle system were reported. The most common complications were various aches  that were reported after seven procedures, vomiting/nausea after five procedures, PDPH after four procedures (linked to the same patient’s coincident LP procedures during the follow-up), and neutropenic infection after one procedure.Traumatic lumbar puncture and leakage of blood into the spinal canal compromise the diagnostics of CNS involvement of acute leukemia and may have a negative impact on the patient survival. The present prospective study, conducted in the pediatric hemato-oncology departments of three university hospitals in Finland, demonstrated good clinical performance and safety of the novel bioimpedance system in a real-world setting. This pivotal study suggests clinical utility for the novel bioimpedance spinal needle system in the diagnostics and treatment of pediatric leukemia.26, the patient material represents well the entire target population. Further, 26 pediatric oncologists, including both novice and highly experienced providers of LP, used the bioimpedance needle system, but only a few of them knew or had seen the device before the study. These physicians received a brief overview of the system and could try it with a lumbar phantom. Given the good results of the present study, the physicians seemed to adopt well the clinical use of the system with limited training. It is also notable that neither the physician’s experience in performing LPs nor the patient’s weight did essentially affect the success of the first attempt or incidence of TLP.The study material comprised 152 intrathecal treatment procedures in 50 unselected pediatric patients with ALL who were recruited during their scheduled appointments to the hemato-oncology department; we omitted only the first diagnostic punctures because of ethical reasons. As around 50 Finnish children are annually diagnosed with ALL13, the 90% success rate achieved by three pediatric oncologists with ultrasound guidance after specific training for its use15 and the 95% success rate without image guidance achieved by a single, highly experienced pediatric oncologist14. Clinically, the most relevant result of the present study is that the success of LP at the first attempt was significantly associated with almost four times lower incidence of TLP compared to LP procedures where two or more attempts were required. This finding not only underlines the importance of the first attempt in getting a high-quality CSF sample but also compares well to halved incidences of TLPs reported after successful first attempts in adults with leukemia or neurologic problems27, and children in general17. The present 10% incidence of TLP associated with the successful first attempts agrees well with the 16% incidence observed in a recent study where the overall success rate at the first attempt was 90%15. Sedation most likely accounts for the low incidence of TLP among the pediatric patients with ALL, but acceptable results may also be obtained in intrathecal treatment LPs without sedation28. In further considering the incidence of TLP, the present study did not include the diagnostic LPs, which may show a substantially lower incidence of TLP than later intrathecal treatment punctures (19% vs 32%)2, but not necessarily (20% vs. 18%)9. This issue warrants further studies.The success of LP at the first attempt achieved with the novel bioimpedance needle system was about 80%. Comparing this value to previous studies of pediatric patients with ALL is congruent with the 70% success rate achieved by seven experienced pediatricians with a conventional spinal needle14. In the present study, the incidence of PDPH was low, about 6%. Since the Quincke-type needle is associated with a higher incidence of PDPH compared to pencil-point spinal needles30, we compared the present incidence of PDPH only to studies of pediatric patients with ALL that were done with the 22G Quincke-type needle. Our finding is fully in line with the reported incidences of 7%14, 8%11, 11%13, and 14%15. The other post-procedural complications observed in this study were expected consequences of LP procedure or intrathecal treatment. Altogether, we found no indication that the use of the bioimpedance needle system would increase the patient risks.Success at the first attempt is also likely to reduce the risk of PDPH23. Of the procedures completed with the system, the CSF detection sensitivity was 86%, being fully in line with the previously reported 82% in neonates and infants23 and 100% in adults22.The technical performance of the bioimpedance needle system was not perfect. Whereas the system can instantly detect the contact of the needle tip with CSF and provide the user with opportune audio-visual feedback to avoid too deep needle insertion, the user may unintentionally withdraw the needle slightly along with the stylet removal. If so, the initial contact between the needle lumen and CSF may vanish and explain the false CSF alarms, which took place in 9% of all study procedures. This value compares well with 11% and 19% incidences observed in previous clinical feasibility studies of the systemThe bioimpedance needle system detects CSF when the continuously measured impedance stays sufficiently long time within the frequency-specific ranges of impedance classified as CSF. However, if some extrinsic  or intrinsic factors  of the system disturbs the impedance measurement of the needle, the detection of CSF may be missed. According to the post-hoc analysis of recorded raw bioimpedance data and users’ comments on CRFs, about half of the missed CSF detections were attributable to soft tissue remnants that likely masked the needle tip electrode and altered the impedance values. The rest of the missed CSF detections were mostly due to deficiencies in the electrical contact. Despite the missed CSF detections, the success rate at the first attempt was high, and the LP procedure per se was not compromised. This finding pinpoints the intended purpose of the bioimpedance needle system as a guidance method providing supplemental information on the needle tip location while the final decision remains up to the physician.32. However, there is not yet strong evidence that the early stylet removal technique would improve the success rate of LP but is under rigorous investigation33. Nevertheless, this technique seems to be frequently used at present: e.g., in a recent survey34, graduating residents utilized early stylet removal in more than 60% of their LP procedures in infants. This observation implies the novice physicians’ desire for objective information on the needle tip location when performing the LP procedure. The early stylet removal technique offers a direct way to see when CSF starts flowing through the needle whereas the bioimpedance needle system detects in real-time when the needle tip reaches contact with CSF without the stylet removal.Besides the bioimpedance needle system, another simple guidance method not requiring simultaneous imaging  is the early stylet removal from the spinal needle before penetrating the dura. In previous observational studies, the use of this technique has been associated with a higher success rate in pediatric patientsSingle-arm design and observational nature are the main limitations of our study. Therefore, we cannot conclude that the novel bioimpedance needle system improved the success rate, reduced the incidences of TLP, PDPH or other complications, or was of added clinical benefit compared to the conventional spinal needle in the intrathecal treatment LPs of children with ALL. A randomized controlled trial would be the appropriate design to demonstrate the anticipated benefits. However, before conducting a demanding clinical trial with the system, we considered it essential to get first relevant information on the clinical performance and safety of the system in a sufficiently large and representative target group. Also, the prospective design is a strength in increasing the reliability of data collection and related findings.Pediatric oncologists adopted well the use of the novel bioimpedance spinal needle system in a real-world clinical setting. The system achieved a high success rate at the first attempt and a low incidence of TLP in a representative sample of pediatric patients with ALL. Also, the incidence of PDPH was particularly low, while the other complications were in line with the results reported in the literature. All these promising performance and safety results indicate clinical utility for the system in pediatric hemato-oncology. These results need to be confirmed in adequately powered randomized clinical trials where the bioimpedance spinal needle system is compared to a conventional spinal needle or other relevant comparators.


Capturing changes in health and wellbeing within randomised controlled trials (RCTs) can be complex. The precision and accuracy of outcome scales to measure change is crucial, and therefore, consideration needs to be given to potential measurement errors when collecting these outcomes.Many RCTs use multiple researchers to collect data, which has the potential to introduce variation in measurements. This study aimed to identify if there was a measurable effect of using different researchers to collect repeated assessments of quality of life (QoL) at different time points.A previously conducted study assessing the impact of reminiscence therapy on participants with dementia and carer (PwD-carer) dyads, ‘REMCARE’ (Reminiscence groups for people with dementia and their family caregivers), provided the platform for this exploratory secondary analysis. Data was categorised into two broad groups: those where the same researcher attended all assessments and those where different researchers undertook the assessments. ANCOVA  models used in the original REMCARE analysis with the addition of the ‘researcher-continuity’ variable were run on two QoL measures, the QoL-AD  and QCPR .Three hundred thirty PwD-carer dyads were included in the analysis. For the PwD, a statistically significant effect was found on the researcher continuity variable for the QoL-AD and QCPR outcome measures at follow-up 1 but not at follow-up 2 signifying an impact of researcher attendance at the first follow-up but not follow-up 2. For the carer data, analyses revealed no statistically significant effects at follow-up 1; however, the QoL-AD measure at follow-up 2 was found to be statistically significant.These exploratory results indicate the possible impact of researcher continuity on QoL outcomes in dementia studies. Further research is required to explore this further and establish causality. If demonstrated, this would have implications for the planning of future empirical studies in dementia, in order to reduce this potential source of bias.The online version contains supplementary material available at 10.1186/s13063-022-07064-4. There is potential to introduce bias when collecting and evaluating outcomes for randomised controlled trials (RCTs) , 27. DemSeveral studies have demonstrated that dementia-specific QoL measures appear to be reliable , 24. HowThe impact of using multiple raters across multiple time points has received limited attention and is influenced by the prevailing philosophical stance of some trialists, based on positivism and empiricism, where there is an assumption that a measure remains reliable over time , 12, 22.Data from a previously conducted RCT—the REMCARE study ‘Reminiscence groups for people with dementia and their family caregivers – effectiveness and cost-effectiveness pragmatic multi centre randomised trial’—was used . This waThis study focuses on two REMCARE outcome measures that were completed by both the PwD and the carer: the Quality of the Caregiving Relationship (QCPR) , a validA third QoL measure, the EQ5D was also considered however is a relatively short and generic measure, which can be independently completed by the participants with little interaction from the researcher; thus, the measure is unlikely to be susceptible to a researcher effect and therefore is not included for this analysis. The QCPR was collected from both the PwD and carer based on their own perceptions of the caregiving relationship. The participant QoL-AD was collected from the PwD based on their perception of their own QoL, and the carer QoL-AD proxy version was collected from the carer regarding their view of the QoL of the PwD they care for. It follows that an effect, if there is one, would be apparent within the PwD responses but not the carer responses.In total, the REMCARE study recruited 488 dyads (participant-carer), and data was collected at baseline, 3 months after baseline (follow-up 1) and 10 months after baseline (follow-up 2). As this analysis is exploring a researcher effect across the time points, based on a relationship building hypothesis, only PwD that completed all three visits were used; this resulted in a dataset containing 336 participants (69% of the REMCARE sample). A further six participants were removed due to the carers not completing all three follow-ups. Therefore, the final data sets contained 330 participants in each totalling 660 .one researcher attending all three visits to collect data (i.e. “same researcher”), two visits with the same researcher but one of the visits was completed with a different researcher to the other two visits (i.e. “one same and two different researchers”) or lastly, three different researchers attending the visits therefore had all different researchers collecting outcome data (i.e. “different researchers”).A ‘researcher attendance’ variable was created for inclusion in the models to represent researcher continuity. PwD’s were categorised into ‘researcher attendance’ groups based on whether they had the same researcher for all visits, different researchers or a combination. At follow-up 1, only two visits had been completed therefore participants were dichotomised into either the “same researcher” or “different researcher” collecting baseline data to the follow-up 1 data. At follow-up 2, three visits had been completed; therefore, participants were put into one of three categories: Analysis of covariance (ANCOVA) models were used at follow-up 1 (3 months) and follow-up 2 (10 months) to evaluate the impact of the researcher attendance variable, using the corresponding analysis models used in REMCARE, which accommodated for Age, Gender, Marital Status, Centre (study site), Wave (recruitment phase within centre) and Allocation. The carer model also included PwD Age and PwD Gender. In total, eight separate models were run, across the two outcomes, QoL-AD and QCPR, at the two follow-up time points for both PwD and carer data.Sensitivity analysis was also conducted on assumptions about the consistency of researcher attendance for the second follow-up. The theory was that consistency in attendance of the researcher may build-up rapport with the PwD, potentially impacting the outcome scores. In the scenario where there were three visits by two researchers, this was either achieved with consistency for two visits with either the first or third conducted by another researcher, or, the first and third visit conducted by the same researcher and another researcher attending the ‘middle’ second visit. The consistency of visiting was broken up within the second scenario here and so could be considered as three different researchers given the timespan covered. Therefore, these visits where re-categorised as ‘three different researchers’ for the sensitivity analysis.All data extraction, merging and subsequent analysis was conducted using SPSS IBM version 25 .Table Descriptive statistics of the outcome measures at each time point are displayed in Table Complete case analysis was conducted with no methods of missing data imputation adopted. Methods of dealing with missing data in RCTs is debated amongst researchers, although it is acknowledged that methods of dealing with missing data for analysis should be based on how much data is missing, the kind of missing data  and what type of missing data exists within the dataset (missing completely at random (MCAR), missing at random (MAR) or missing not at random (MNAR)). The REMCARE study adopted multiple imputation techniques for analysis. Since the completion rates of the outcomes to be used for the current analysis are high  = 10.24, p < 0.01  = 5.65, p = 0.02   = 1.14, p = 0.32, nor on the QCPR, F = 2.93, p = 0.06  = 3.32, p = 0.04 and on the PwD QCPR F = 4.02, p = 0.02  = 0.03, p = 0.86, on the QCPR at follow-up 1 F = 0.70, p = 0.40 nor on the QCPR at follow-up 2, F = 0.46, p = 0.63  = 4.15, p = 0.02 . ThThe effect seen on the carer QoL-AD at follow-up 2 was unexpected in relation to the hypothesis. This suggests that although the carer completed the measure independently, they may still have been influenced by researcher continuity. However, several elements could have contributed to this result which cannot be measured here and the impact of researcher consistency on carer data should be further explored.The impact of researcher continuity has received little attention in the context of trial-based research in dementia studies examining QoL. Kobak  hypothesn = 43), and the variability between these researchers was not calculated or accounted for. Equally, the reliability of researchers’ scores is not known, and individual researcher characteristics, such as age, training, experience, warmth and ability to establish rapport, were not taken into account (given the lack of data). There was no allocation concealment for participants in REMCARE. As a result, researchers may have become accidentally unblinded during the follow-up assessments. Post hoc assessment in the original study found that researchers ‘were indeed more likely to be correct than incorrect in the direction of their prediction’ [The current research has several limitations. The analyses presented here were explorative in nature and the data collected was not designed to test the hypotheses, i.e. it was a post hoc analysis and was not conceptualised or conducted a priori. As a result, the study was not powered to detect the effect of researcher continuity. Although the splits between researcher attendance groups are relatively similar Table , allocatdiction’ . FurtherThis explorative study indicates a possible researcher continuity effect on the outcome measure scores of participants in one dementia QoL trial. This effect may be relevant to all clinical trials and settings or may only reflect an issue within dementia research, further investigation would be required in other trial settings to establish this. Whilst the results imply that there is a possible effect present, they are not definitive and subject to the limitations outlined above. It should be noted that this study was not designed nor powered to detect this signal and all results and findings should be interpreted with this knowledge. To definitively address this question, future research should be conducted with the research hypotheses framed and powered a priori. This could be undertaken as a Study Within A Trial (SWAT), which is a “self-contained research study that has been embedded within a host trial with the aim of evaluating or exploring alternative ways of delivering or organising a particular trial process” .Furthermore, dementia studies may not be the most appropriate disease area to evaluate researcher continuity, given the inter-relationship between rapport and memory, which is more difficult to establish in dementia trials , 33. If Dementia trials with QoL end-points may be influenced by researcher continuity. However, further empirical research is needed to explore this possible relationship definitely.Additional file 1: Table S5. ANCOVA Model Results for PwD Data. Table S6: ANCOVA Model Results for Carer Data. Table S7. ANCOVA Model Sensitivity Analysis Results at Follow-up 2. Table S8. Adjusted Means for Researcher Attendance Groups from PwD ANCOVA Model.


This paper aims to solve the problems of the low quality and shallow depth of the traditional straw return method. According to the requirements of the new furrow burial and return agronomic model, a corn straw ditch-buried returning machine was designed that could simultaneously complete the processes of picking, conveying, ditching, soil-covering and pressing. Key components were theoretically analyzed and designed, such as the pickup device, ditching device and straw-guiding soil-covering and pressing device. Based on a field experiment, the main factors influencing the effects of straw picking, soil ditching and straw return were studied. Both forward speed and pickup device speed significantly affected the straw picking rate. The ditching area, ditching width consistency factor and ditching depth stability factor gradually decreased with increasing forward speed and gradually increased with increasing trenching device speed. There was a significant interaction among the forward speed, pickup device speed and ditching device speed. At a forward speed of 1.68 m/s, the picking device speed was 330 r/min, the ditching device speed was 290 r/min, and the highest straw return rate was 93.65%. Then, the conditions for straw not to be ejected into the carrying area are as follows:In summary, 15.71 rad/sThe chain ditching device can stably and efficiently open the ditch and discharge soil onto both sides of the ditch. The quality of ditching directly impacts the quality of straw covering. A design diagram of the chain ditching device is shown in The efficiency of the chain ditching device can be determined as:3/h; where where The angle between the absolute speed of the chain ditching device and the horizontal plane is °.and ch = 220 mm.According to the requirements of the actual working conditions, if the height of the ditching knife increases the load, the body of the ditching knife can be deformed or broken. This paper designed the height of the ditching knife as The width of the ditching knife and thickness of the cut soil can be calculated with a is the thickness of the soil cut by a set of ditching knives, mm, and initially set to 9 mm; b is the width of the ditching knife, mm, and set to 125 mm.where When the preliminary design of the ditching knife was finished, the transportation capacity of the chain ditching device and soil clearing capacity were evaluated. The productivity of the chain ditching device was calculated based on the discharge capacity  follows :where 3/h was obtained.It was determined whether substituting each parameter into After calculation, where kF is calculated with The chain ditching device is mainly affected by the cutting resistance during operation. Then, the total cutting resistance jk is the coefficient of the difficulty in soil processing, selected as 4.3 × 104 Pa; sk is the proportion coefficient of the side knife cutting soil, selected as 1.8 × 103 N/m; cz is the cutting coefficient of the closed side tool, selected as 2; yk is the influence coefficient of the cutting angle, selected as 0.9; tF is the resistance of each ditching knife to soil cutting, N; tz is the total number of ditching knives in the chain ditching device, selected as 38; kF is the total cutting resistance of the chain ditching device, N.where via gravity. The soil-covering mechanism pushes soil on both sides of the ditch toward the top of the straw occurring in the ditch, and the pressing device subsequently compacts the soil. A structure diagram is shown in The straw-guiding soil-covering and pressing device is located behind the chain ditching device. The straw-guiding soil-covering and pressing device mainly consists of a straw-guiding mechanism, a soil-covering mechanism and a pressing mechanism. The straw-guiding mechanism can accurately guide straw on the conveyor into the ditch q is the depth of ditching, mm, chosen as 300 mm; t is the width of ditching, chosen as 250 mm; h1 is the distance between the top of the soil on both sides of the ditch and the bottom of the ditch after ditching, mm; e is the distance between the soil edges on both sides of the ditch , mm.where To ensure the burying effect of straw, the amount of soil covered by the soil-covering mechanism should be larger than the amount of soil required to cover the straw layer.f is the width of the soil-covering mechanism operation , mm, and H1 is the distance from the top of the soil-covering mechanism to the bottom of the ditch, mm. According to the overall configuration requirements, H1 was 500 mm. The solution was f > 215 mm, and the design value was 240 mm.where Then, the angle l0 is the top distance of the soil-covering mechanism, mm, chosen as 40 mm . Then, the angle between the soil-covering and forward directions was designed as 45°.where 2, and the moisture content in straw was 18.30%. The soil type was black loam, and the soil moisture content was 22.71, 19.83 and 18.97% measured at depths of 0–10 cm, 10–20 cm and 20–30 cm, respectively. The soil compactness was 0.88, 2.67 and 3.73 MPa, respectively. The ditching depth was 300 mm. Supporting power was provided by a Leimu 1304 tractor.A field experiment was conducted in September 2021 at the experimental site of the Northeast Agricultural University in Acheng District, Harbin city, Heilongjiang Province, as shown in The test method referred to national standards GB/T24675.62009 (conservation tillage machinery straw crushing and returning machine), NY/T740 2003  and JB/T5160 2010 (forage picker).In this study, a field performance experiment of the developed corn straw ditch-buried returning machine was conducted in terms of the straw picking rate, furrow opening stability and furrow burial return rate. In the experiment, each group was selected with a 20-m working stroke, each group of indicators was measured three times, and the results were averaged.The straw picking rate and furrow opening stability constitute intermediate indicators, and the quality of both operations can impact the furrow burial return rate. Therefore, single-factor experiments were separately conducted to study the effect pattern of each factor on these indicators. In the experiments, forward speeds of 0.50, 0.80, 1.10, 1.40, 1.70, and 2.00 m/s at a pickup device rotational speed of 270 r/min and pickup device rotational speeds of 150, 190, 230, 270, 310, and 350 r/min at a forward speed of 1.40 m/s were employed as experimental factors to explore the effect on the straw picking rate. The influence on the stability of ditching was studied considering forward speeds of 0.50, 0.80, 1.10, 1.40, 1.70, and 2.00 m/s at a ditching device rotational speed of 320 r/min and ditching device rotational speeds of 200, 240, 280, 320, 360, and 400 r/min at a forward speed of 1.40 m/s as experimental factors.The straw return rate was the final indicator. A three-factor and five-level orthogonal rotational combination test design was realized with the forward speed, rotational speed of the pickup device and rotational speed of the ditching device as the experimental factors to study the interaction effects among these factors and the best combination of parameters. The experimental factor level coding is summarized in To further verify and analyze the operation effect of the optimized straw returning machine, the optimized forward speed, rotation speed of the pickup device and rotation speed of the chain ditching device were taken as the test factor level, and the straw returning rate was taken as the test index to perform the field verification test. The test was repeated three times, and the results were averaged and compared with the software optimization results.A collection device was installed behind the pickup device. The weight of straw collected within each set of strokes and the weight of residual straw within this set of strokes were measured. The calculation method is expressed as P is the straw picking rate, %; M0 is the weight of the straw collected, g; M1 is the weight of the residual straw, g.where The stability of ditching was measured based on the amount of soil disturbance, ditching width consistency factor and ditching depth stability factor. In each group of trips, three positions were chosen on average to measure the ditch size. The soil disturbance was calculated using a previously reported method in the literature based on the area of the ditch boundary . The ditn is the number of measurement positions, chosen as 3 (repeat the measurement three times); where The ditching depth stability factor can be determined with where In each group of trips, the weight of straw in the soil surface layer before ditch burial and the weight of straw in the soil surface layer after ditch burial were separately measured. The straw return rate can be calculated with where via Duncan’s multiple comparison testing with an assessment threshold of p < 0.05. The results are expressed as the mean ± standard error. Each repetition was treated as a random effect in the statistical model.The data obtained in this study were evaluated using the SPSS 22.0  statistical software. Analysis of variance was performed p < 0.001). The straw picking rate gradually decreased with increasing forward speed. The main reason was that under the condition of a certain rotational speed of the pickup device, a higher forward speed corresponds to a larger missing picking area formed by the cycloidal motion trajectory interactions between the pickup device and the forward speed and ground. Moreover, the pile phenomenon occurred, so a large amount of straw was missing in the field, which reduced the straw picking rate. The straw picking rate first increased and subsequently decreased with increasing rotational speed of the pickup device. The main reason was that under the condition of a certain forward speed, a higher speed of the pickup device corresponded to more frequently movement trajectory to collect straw per unit time. This effectively reduced the area of the missing picking area. When the speed of the pickup device exceeded 270 r/min, straw was ejected into the carrying area, which made the previously collected straw fall back to the ground and reduced the straw picking rate.p < 0.001). The ditching area, ditching width consistency factor and ditching depth stability factor gradually decreased with increasing forward speed. The main reason was that a higher forward speed corresponds to a shorter time for the ditching device to impact the soil per unit area, which results in a smaller amount of soil disturbance, a larger difference between opened and ideal ditches, and lower stability of the ditch width and depth.If the rotational speed of the ditching device remained constant, the ditching area, ditching width consistency factor and ditching depth stability factor were not significant within the range of 0.4–1.0 m/s but were significant within the range of 1.0–2.0 m/s . The consistency factor of the ditching area, ditching width and stability factor of the ditching depth gradually increased with increasing speed of the ditching device. This phenomenon largely occurred because a higher rotational speed of the ditching device corresponds to a stronger effect of soil cutting and discharge. As a result, the opened ditch was highly consistent with the contour of the motion track of the ditching knife. The overall structure was relatively flat and closely resembled the ideal ditch type, and the stability of the ditching width and depth was satisfactory.Orthogonal rotation combination experiments considering three factors and five levels were conducted with the forward speed, rotational speed of the pickup device and speed of the ditching device as the experimental factors and the straw return rate as the experimental index. The experimental results are summarized in The experimental results were analyzed in the ANOVA module based on the Design-Expert 8.0.6 software . The results are provided in F value of each experimental factor in the analysis of variance, the primary and secondary factors that affect the straw return rate were X1 > X12 > X22 > X32 > X1X2 > X3 > X2 > X1X3 > X2X3. Within the range of the experimental parameters, the experimental factors that affect the straw return rate significantly differed. To visually describe the effects of the experimental factors and their interactions on the experimental index, response surface and contour plots were generated, as shown in According to the There was a significant interaction among the forward speed, rotational speed of the pickup device and rotational speed of the ditching device. Under the interaction between forward speed and rotational speed of the pickup device, the straw return rate gradually decreased with increasing forward speed. The straw return rate increased and subsequently decreased with increasing pickup device rotational speed. Under the interaction between forward speed and rotational speed of the ditching device, the straw return rate gradually decreased with increasing forward speed. At a low forward speed, the straw return rate first increased and subsequently decreased with increasing rotational speed of the ditching device. At a high forward speed, the straw return rate gradually decreased with increasing rotational speed of the ditching device. Under the interaction between the rotational speeds of the pickup device and ditching device, the straw return rate gradually increased with increasing rotational speed of the pickup device. The straw return rate first increased and thereafter decreased with increasing rotational speed of the ditching device.To explore the best parameter combination of various experimental factors and maximize the work efficiency, solution optimization was performed under the condition of maximizing both forward speed and straw return rate. The constraint range of the objective function and working parameters is defined by The Design Expert 8.0.6 software was employed for optimization. The optimization results were as follows: at a forward speed of 1.68 m/s, the rotational speed of the pickup device was 330 r/min, the rotational speed of the ditching device was 290 r/min, and the straw return rate was 92.82%.To verify the reliability of the regression model and optimization results, a field verification experiment was conducted considering the best parameter combination . The experiment was repeated three times, and the results were averaged. The field experimental results revealed that the straw return rate reached 93.65%. The results of the field validation experiment were consistent with the predicted values of the regression model. The straw return rate satisfies the agronomic requirements under the optimal combination of working parameters.In this study, the key components of a corn straw ditch-buried returning machine were theoretically analyzed. Through field experiments, the main factors and interactions that affect the rates of picking, ditching and straw return were explored. Traditional straw return is typically accomplished by covering and mixing-based farming. The straw return machine developed in China now achieves a return rate of over 90% . This meThe straw ditch-buried returning technology breaks the disadvantages of traditional straw returning to the field, which buries all soil in the field. After the crops are mature, only part of the soil is ditched, and the straw is buried. It is the category of less tillage in conservation tillage. This study experimentally examined the effect of straw mulching but did not compare and analyze the changes in organic matter in the soil under the conditions of different straw returning machines, the effects of different straw lengths and different burial depths on the soil. In addition, we did not continue to track the impact on sowing, fertilization, intertillage and harvesting with this background. According to the agronomic requirements of corn straw ditch burial and return, a corn straw ditch-buried returning machine that can simultaneously complete the processes of picking, conveying, ditching, covering soil and pressing was designed. Key components were designed, such as the pickup device, chain ditching device and straw-guiding soil-covering and pressing device.The straw picking rate gradually decreased with increasing forward speed and first increased and subsequently decreased with increasing rotational speed of the pickup device. The ditching stability decreased with increasing forward speed and increased with increasing rotational speed of the ditching device. The forward and rotational speeds of the pickup and ditching devices significantly affected the straw return rate. At a forward speed of 1.68 m/s, the rotational speed of the pickup device was 330 r/min, the rotational speed of the ditching device was 290 r/min, and the straw return rate was 93.65%.This study combined theory and experiments to effectively improve the rate of corn straw return. This study provides references for the innovative design of straw returning equipment and continued exploration of ideas of conservation tillage modes.The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.HT, CX, WX, YX, and JW designed and performed the experiments and analyzed the data. HT, CX, and YSX wrote the manuscript. All authors contributed to the article and approved the submitted version.This work was supported by the National Natural Science Foundation of China (NSFC), grant number: 32071910; the Program on Industrial Technology System of National Rice (CN), grant number: CARS-01-48.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 aim of this study was to investigate whether neurofilament light (NfL) and phosphorylated neurofilament heavy (pNfH) in cerebrospinal fluid (CSF), sampled prior to referral to a neuromuscular reference center (NMRC), shorten the diagnostic delay in patients with amyotrophic lateral sclerosis.n = 58), (ii) determination of Nfs at the NMRC  or (iii) with no determination of Nfs . Fifty‐six disease controls were included.In this retrospective study, patients with ALS were included with (i) determination of neurofilaments (Nfs) before referral to the NMRC . pNfH and NfL levels in the preC‐Nfs cohort were significantly higher than in disease controls (p < 0.0001). Both Nfs showed a similar discriminating performance.The preC‐Nfs cohort had CSF sampled 2.2 months (range: 0.6–12.0 months) before referral to the NMRC. In this cohort, the diagnostic delay was significantly shorter [median (range): 8.24 (2.37–49.7) months] than in the C‐Nfs cases [median (range): 11.4 (2.93–86.5) months; CSF Nfs assessed before the diagnosis of ALS at a NMRC decreased the diagnostic delay in specific cases by 3 months and only when other covariates were not taken into account. Neurofilaments assessed in cerebrospinal fluid before diagnosis of ALS at the neuromuscular reference center decreased the diagnostic delay by 3 months only when other covariates like disease progression rate and the presence of a genetic mutation were not considered. Fluid biomarkers can be useful tools for clinicians in the diagnostic work‐up of patients with ALS. Neurofilaments have shown great potential as biomarkers in many neurodegenerative diseases including ALS.In this study, we now explore as primary objective if neurofilaments in CSF sampled before referral for diagnosis to a NMRC affect the diagnostic delay in ALS, and as a secondary objective whether early stage determined neurofilaments have a similar diagnostic performance as compared to CSF sampled at a NMRC.2C9orf72, SOD1, TARDBP, and FUS was proposed for patients with ALS using TP‐PCR (C9orf72) or direct sequencing .In total, 292 patients with ALS, all diagnosed at the NMRC of the University Hospitals Leuven according to the revised El Escorial and Awaji criteria, were included between March 2017 and June 2021 in this observational retrospective study.A disease control cohort of 56 patients was consecutively included between February 2017 and December 2020 by local neurologists at regional hospitals. Neurofilaments were requested by the local neurologist for diagnostic purposes, mainly when there was a suspicion of a motor neuron disease. The final diagnoses of the control cohort were obtained through review of the patient's electronic medical records by a neurologist (PM) affiliated to the NMRC of the University Hospitals Leuven Table . Five coAll CSF samples collected by local neurologists were transferred at room temperature to the laboratory medicine department at the University Hospitals Leuven within 5 days after lumbar puncture. Subsequently, samples were divided into aliquots of 1 ml and stored at −80°C until analysis. CSF samples collected at the NMRC were divided into aliquots of 1 ml and stored at −80°C within 24 h after sampling. All CSF samples were consecutively collected and were not included in any previous publications. Commercially available IVD‐labeled ELISAs were used according to the manufacturer's protocol for measuring NfL  and pNfH . All assays were then performed at the laboratory of molecular neurobiomarker research (KU Leuven) by the same operator (MDS). A low and high internal quality control sample was measured in each and every run for pNfH and NfL. The intra‐assay variability and inter‐assay variability were <6% and <11% for both biomarkers, respectively. The study was approved by the ethical committee of the University Hospitals Leuven (S50354 and S60768), and written informed consent was waived.U‐test or a Kruskal–Wallis test corrected for multiple comparison with Dunn's post hoc test. Correlations between continuous variables were tested with Spearman's rank test. The disease progression rate was calculated by the difference between the ALSFRS‐R score at time of diagnosis and 48, divided by the number of months between onset and time of ALSFRS‐R assessment. The diagnostic delay and the disease progression rate were log‐transformed to achieve a normal distribution before entering the parameters in an ANCOVA model. Receiver operating characteristic curve analysis was performed to establish the diagnostic accuracy, sensitivity, and specificity of each biomarker. The cutoff corresponding to the highest Youden index was selected. A logistic regression was used to calculate odds ratios providing a relationship between the neurofilament levels and the probability of the disease. GraphPad Prism , MedCalc , and SPSS  were used.Shapiro–Wilk test was used for assessing normality of data. Group comparisons were performed with a Mann–Whitney 33.1χ2 = 28.8, p < 0.0001, Table Patient demographics of the three ALS cohorts and disease control cohort are presented in Table p < 0.0001). The samples of the preC‐Nfs cohort were collected with a median of 2.2 months (range: 0.6–12.0 months) before diagnosis at the NMRC. The diagnostic delay in the preC‐Nfs cohort was significantly shorter  in comparison with the C‐Nfs cohort , but not when compared to the C‐No Nfs cohort  , but not with CSF pNfH levels  was significantly shorter than in the C‐Nfs cohort . Yet, patients carrying a genetic mutation had a significantly shorter diagnostic delay  as compared to patients with sporadic ALS . The median disease progression rate was equal in all three ALS cohorts  and in the C‐Nfs cohort   and in the C‐Nfs cohort   Figure .p = 0.14). Furthermore, the median time between the first appointment at the NMRC and the final diagnosis was significantly longer for the C‐Nfs cohort  as compared to the preC‐No Nfs cohort  and the C‐No Nfs cohort .When the disease progression rate and the presence of a genetic mutation were included as covariates to evaluate the diagnostic delay between the preC‐Nfs cohort and the C‐Nfs cohort, the diagnostic delay was not significantly different anymore between the preC‐Nfs cohort and the C‐Nfs cohort  and NfL (p = 0.61) determined between preC‐Nfs and disease controls. The sensitivity and specificity of pNfH and NfL levels in CSF to discriminate between C‐Nfs and disease controls were similar to those determined between preC‐Nfs and disease controls (Table The AUC of CSF pNfH and NfL was 0.84 (95% CI: 0.75–0.90) and 0.85 (95% CI: 0.77–0.91), respectively, to discriminate C‐Nfs from disease controls, and were both not significantly different from the AUC of CSF pNfH  in comparison with patients whose neurofilament levels were only assessed at time of visiting the NMRC (C‐Nfs). No significant difference in diagnostic delay was observed between the preC‐Nfs cohort and patients with ALS who were diagnosed at the NMRC without neurofilament assessment (C‐No Nfs). In the latter group, neurofilament levels were not analyzed probably due to the fact that clinical and electrophysiological examination was sufficient for experienced neurologists to diagnose a patients with ALS. The significantly longer delay between first appointment and final diagnosis observed in the C‐Nfs cohort might indicate that Nfs in CSF are requested by an experienced neurologist in those patients where the diagnosis of ALS is highly uncertain, as reflected by the fact only in 5% of cases riluzole therapy was initiated prior to referral. One could speculate if Nfs had been determined prior to referral in those cases with an uncertain clinical diagnosis at first visit at a NMRC, the delay between first visit at NMRC and final diagnosis might have been shorter.Local neurologists might be reluctant to diagnose a patient who might have a slow progressive form of ALS as they are not often confronted with such a rare disease.In line with previous findings from our group and others, we strengthened the evidence that levels of pNfH and NfL are significantly increased in CSF of patients with ALS at time of diagnosis in comparison with disease controls.The highest specificity toward motor neuron degeneration was observed for CSF pNfH levels, whereas CSF NfL levels yielded the highest sensitivity. This specific pattern fits into the findings that NfL is rather a global early marker of neurodegeneration, while pNfH is more specific to motor neuron impairment as found previously in CSF sampled at a NMRC.In summary, CSF Nfs assessed before the conventional diagnosis of ALS at a NMRC did not decrease the diagnostic delay when other covariates were taken into account. Given the good discriminating power of Nfs before referral, the added value of Nfs in shortening the diagnostic delay should be further explored prospectively.M.D.S., P.V.D., and K.P. developed the concept and design of the study. M.D.S., P.M., P.V.D., and K.P. drafted the manuscript and figures. M.D.S., P.M., P.V.D., and K.P. were involved in the acquisition, analysis, and interpretation of data. Critical revision of the manuscript for important intellectual content was done by all authors.M.D.S. has a PhD Fellowship from the Research Foundation—Flanders (11E6319N) and received a grant from the Rotary's “Espoir en Tête – Hoofdzaak er is Hoop.” P.M. has a Research Fellowship from the European Academy of Neurology. K.P. received a Clinical Research fund from the University Hospitals Leuven and is a senior clinical investigator of Research Foundation—Flanders . This work was supported by a TBM grant from FWO‐Vlaanderen (no T003519N). P.V.D. is a senior clinical investigator of the Research Foundation—Flanders  and is supported through the E. von Behring Chair for Neuromuscular and Neurodegenerative Disorders, the Belgian ALS Liga, and the KU Leuven funds “Een Hart voor ALS,” “Laeversfonds voor ALS Onderzoek,” and the “Valéry Perrier Race against ALS Fund.”M.D.S. and P.M. have nothing to report. P.V.D. received a grant from CSL Behring—E. von Behring Chair for Neuromuscular and Neurodegenerative Disorders. P.V.D. participated in advisory board meetings for Biogen, UCB, Cytokinetics, Ferrer, Alexion Pharmaceuticals, Muna Therapeutics, Alector, Argenx, Augustine Therapeutics, QurAlis. P.V.D received honoraria for lectures/presentations from Biogen. K.P. is supported by a grant of the Research Foundation—Flanders .Table S1Click here for additional data file.


Bronchoscopy can be a distress for the patient. There have been few studies on the combination of sedatives and opioids. The aim of this study was to demonstrate the usefulness and safety of administration of the combination of midazolam and pethidine during bronchoscopy.P-values were two-sided, and values < 0.05 were considered statistically significant.In this prospective randomized single (patient)-blind study, we randomly assigned 100 patients who were scheduled to undergo bronchoscopy biopsy to receive treatment with either the midazolam/pethidine combination (combination group) or midazolam alone (midazolam group) during examinations. After the end of bronchoscopy, patients completed a questionnaire and the visual analogue scale was measured. The primary outcome was the patients’ acceptance of re-examination assessed by visual analogue scale. We also assessed pain levels, vital signs, midazolam use, xylocaine use, and adverse events. Univariate analyses were performed using Fisher’s exact test for categorical data, and the t-test or Mann-Whitney test was carried out for analysis of numeric data. All P = 0.400). In the combination group, the visual analog scale score for pain during bronchoscopy was significantly lower , and the sedation level score per the modified observer’s assessment of alertness/sedation scale was significantly deeper . Maximal systolic blood pressure during testing was significantly lower , and the number of additional administrations of midazolam was significantly lower . There were also significantly fewer adverse events .We analyzed 47 patients in the combination group and 49 patients in the midazolam group. The primary outcome was a good trend in the combination group, but not significantly different .This study was registered in the University Medical Hospital Information Network in Japan (UMINCTR Registration number: The online version contains supplementary material available at 10.1186/s12885-022-09640-y. Lung cancer has a high prevalence and is one of the leading causes of cancer death worldwide . In the Flexible bronchoscopy is one of the most common lung cancer tissue sampling methods. To examine acquired resistance genes, repeated bronchoscopy is also necessary. However, the bronchoscopy itself is very distressful for the patient. So, the reduction of distress is very important. The British Thoracic Society guideline recommend the use of a combination of opioids and midazolam . AccordiThere have been few studies on the combination of sedatives and opioids. The best sedative and opioid combinations are unknown and there have been no randomized reports on the usefulness of midazolam plus pethidine in bronchoscopy. The aim of this study was to demonstrate the usefulness and safety of administration of the combination of midazolam and pethidine during bronchoscopy.In this prospective single-center, randomized, single (patient)-blind study, we compared midazolam alone and the midazolam/pethidine combination during bronchoscopy. The aim of this study was to demonstrate the usefulness and safety of administration of the combination of midazolam and pethidine during bronchoscopy.Patients between 20 and 79 years of age were eligible for enrollment if they were scheduled to undergo bronchoscopy for biopsy of lung tumors or mediastinal tumors at Kobe University Hospital. Patients with any one of the following criteria were excluded: a) allergy to the drugs used in this study and drug hypersensitivity, b) acute narrow angle glaucoma, c) myasthenia gravis, d) uncontrollable bronchial asthma, e) severe respiratory depression confirmed before the examination, f) heart failure secondary to chronic lung disease, h) convulsive state, i) severe liver functional failure, j) pregnancy, potential pregnancy or lactation, k) taking HIV protease inhibitors or monoamine inhibitors, l) use of orally administered opioids when performing bronchoscopy, and m) judgment of being inappropriate for inclusion by the staff in charge of this examination.This study used block randomization to evenly allocate the midazolam/pethidine combination (combination group) or midazolam alone (midazolam group). Randomization was not stratified. Patients undergoing bronchoscopy first took 5 mL of 2% xylocaine syrup by mouth and lay in a supine position for 5 minutes. After the patient spat out the syrup, 5 mL of 2% xylocaine liquid was sprayed into the patient’s throat. The patient lay on the examination table and was attached to a vital sign mechanical monitor, including an electrocardiogram waveform monitor, a pulse oximeter and a blood pressure monitor. The combination group received 2 mg/2 mL midazolam  and 17.5 mg/5 mL pethidine  intravenously. The midazolam group received 2 mg/2 mL midazolam and 5 mL saline as a placebo intravenously. Patients aged 75 to 79 years or weighing less than 45 kg were given half the dose of midazolam and pethidine. Oral bronchoscopy intubation was started 3 minutes after the intravenous injection. When the sedation level was considered shallow, an additional 1 mg/1 mL of midazolam could be administered intravenously at an interval of more than 4 minutes per the preference of the operator. When the patient’s cough was severe, 1 mL of 2% xylocaine was administered into the trachea via a bronchoscopic approach. Vital sign monitoring and depth of sedation were checked by the assisting doctor every 2.5 minutes. The types of bronchoscopes were 1TQ290, 1 T260, F260, P290, P260, and MP290  for peripheral and central lesions, and were UC290F and UC260FW  for endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). If the patient was over sedated at the end of bronchoscopy, 0.25 mg/2.5 mL flumazenil was administered intravenously, and 0.25 mg was mixed with saline infusion and administered in drops. When patients were aware and conscious 1 hour after the end of the bronchoscopy, they filled out a questionnaire about their level of pain. We defined adverse events related to bronchoscopy as any adverse event that occurred up to 1 week after bronchoscopy. This study was approved by the ethics committee of Kobe University (300023) and was conducted in accordance with the Helsinki declaration. Written informed consent was provided voluntarily by the patient before enrollment. This study was registered in the University Medical Hospital Information Network in Japan .https://upload.umin.ac.jp/cgi-bin/icdr/ctr_view_reg.cgi?recptno=R000036694The questionnaire on patient distress during bronchoscopy consisted of ten questions: i) Did you have any concerns before the test? ii) Was the throat anesthesia you had before the bronchoscopy painful? iii) Do you remember what happened during the bronchoscopy? iv) Did you feel distressed during the bronchoscopy? v) Did you experience any pain during bronchoscopy? vi) Did you have difficulty breathing during the bronchoscopy? vii) Did you have a cough during the bronchoscopy? viii) Did you feel like the examination took a long time? ix) How are you feeling after the test? and x) Do you think you could have another bronchoscopy if necessary? Questions 1 to 10 were rated on a continuous scale from 0 (good) to 10 (bad) by means of the visual analog scale (VAS). We also included a yes or no answer to question 10   Additio. The tar2)), targeted tumor size , examination time, the types of bronchoscopes, the type of technique, diagnosis, and adverse events. Systolic hypertension was defined as over 180 mmHg, and hypoxemia was defined as SpO2 under 90%. Tachycardia was defined as over 130 beats per minute.In addition to the above items, we assessed the following: sex, age, body weight, height, the amount of 2% xylocaine administered into the trachea through a bronchoscope, total midazolam dosage, vital signs (heart rate (HR), blood pressure (BP), oxygen saturation -blind study. The study used block randomization to evenly allocate the intervention and control groups. Block sizes of 2 or 4 were randomly created. An allocation physician who was not involved in the bronchoscopy created a random function in Microsoft Excel software, assigned a block size of 2 or 4 to each random function, and created an allocation form. The allocation sheets were maintained in a password-protected file that could not be viewed by any other researcher. The researcher sent the ID of the patient undergoing bronchoscopy to the allocation manager. The allocation manager typed the patient IDs into a randomized allocation form in the order in which they were sent and communicated to the bronchoscopist whether the patient was in the intervention or control group. During the examination, pethidine was administered as CodeA and placebo  as CodeB, so that the patients did not know which pethidine or placebo they were receiving.Since the effect of the midazolam plus pethidine combination therapy is unknown, the estimated number of patients was calculated based on previous single group comparative studies of sedative drugs and single group comparative studies of opioids , 12 and P-values were two-sided, and values < 0.05 were considered statistically significant. All statistical analyses were performed with EZR version 1.51 , a graphical user interface for R  [Categorical data are reported as numbers (percentages), and numeric data are reported as means ± standard deviations. Univariate analyses were performed using Fisher’s exact test for categorical data, and the t-test or Mann-Whitney test was carried out for analysis of numeric data. All  3.6.3 ) .A total of 100 patients were enrolled between June 4, 2019, and July 31, 2020. In the combination group, 2 patients did not answer the question about the primary outcome, and 1 patient did not undergo bronchoscopy. In the midazolam group, 1 patient did not undergo bronchoscopy. We analyzed 47 patients in the combination group and 49 patients in the midazolam group , EBUS-GS-TBB, conventional transbronchial needle biopsy (TBNA), and EBUS-TBNA. Between the two groups, there were no significant differences in the types of bronchoscopic procedures Table .Table 2TP = 0.400).There was no significant difference regarding the primary outcome (VAS for question 10: patients’ acceptance of re-examination) . The VAS for question 4 (patients’ distress during the bronchoscopy) tended to be better in the combination group . The VAS was significantly better  in the combination group for question 5 (patients’ pain during bronchoscopy) (Table The VAS was highest for question 1 (patients’ concerns before the test) in both groups , and the additional number of midazolam administrations was significantly lower . Total amount of midazolam  and the amount of 2% xylocaine treatments also tended to be lower in the combination group . Maximal systolic blood pressure during testing was significantly lower , and hypoxemia tended to be better in the combination group . The lowest sedation score, MOAA/S, was significantly deeper  in the combination group . Hypertension was significantly more frequent in the midazolam group . Hypoxemia was not different in both group  (Fig. All adverse events were significantly more frequent in the midazolam group (30 in the combination group vs. 41 in the midazolam group, This study is the first randomized comparative study on the benefit of sedation during bronchoscopy in combination with pethidine and midazolam.In previous trials that compared placebo versus sedatives, the benefit was greater in the group that received diazepam , 15. In In a comparative study of sedatives versus opioids during bronchoscopy, alfentanil and midazolam were compared. Alfentanil reduced cough, but patients’ distress was lower with midazolam . This st2 under supplemental oxygen was similar in both groups [2 and heart rate [About the study comparing sedation and sedative/opioid combinations during bronchoscopy, there was one randomized, double blind, placebo-controlled study of midazolam only and midazolam/hydrocodone combination. This study showed that patients’ cough and discomfort scores were better in the combination group and that the mean lowest SpOh groups . Anotherart rate . They arIn a single-arm study of bronchoscopy with midazolam and fentanyl, patients’ VAS scores for consent to retest were reported to be significantly improved. The procedures in this study were TBB, bronchial brushing, bronchial washing, and EBUS-TBNA . This stThere are several randomized studies reporting on the use of pethidine or fentanyl in combination with sedatives in gastrointestinal endoscopy. In endoscopic retrograde cholangiopancreatography, a randomized comparative trial of propofol plus pethidine versus propofol plus fentanyl was conducted. In this trial, completion rates, time to procedure completion, length of stay in the recovery room, respiratory and cardiovascular complications, and patient satisfaction and operator satisfaction were similar . In uppeIn our study, there was a significant improvement in subjective symptoms of pain during testing in the midazolam-pethidine combination group. There was a tendency for the midazolam pethidine combination group to be better in VAS for patient distress and coughing, but there was no significant difference. There was no significant difference in the percentage of patients willing to be retested. The reason for the lack of difference in the patient’s subjective symptoms is the possibility that the patient’s memory during the examination might have been blurred due to midazolam and that the patient may have been prepared to undergo the examination with some patience if necessary. Therefore, considering the retrograde amnesia associated with midazolam, it is possible that the endpoint of “Do you think you could have another bronchoscopy if necessary?” was inappropriately set.We found that the combination with pethidine resulted in a deeper sedation, a significant reduction in examination time, and a significant reduction in the number of midazolam additions. Given that a MOAA/S score of 3 to 4 has been studied as an appropriate sedative score for the MOAA/S score , it is lThere are several limitations in this study. The first is that it was a single-blind study. To assess patients’ subjective symptoms, patients were not told whether they were in the combination or midazolam group. Thus, the primary endpoint was assessed by patient questionnaire responses, so bias mediation is unlikely, but it is possible that midazolam-induced retrograde biogenic amnesia could have influenced the study results. We believe that the universality of this study is assured, as objective indicators such as vital signs, test time and adverse events have improved. The second point is that the MOAA/S score was used in the assessment of depth of sedation. Although the MOAA/S score is neatly scored, the MOAA/S score is assessed by the assistant doctor and may be subjectively biased by the doctor. It would have been better if we could have conducted a double-blinded study to evaluate the ease of examination for the operator, assistants, and nurses. The use of bispectral index monitoring may also be useful in future studies, as it is a more objective assessment of sedation. The third point is that this study was a single-center study, and the number of patients was relatively small. The reason for choosing a single-center study was to prevent variability in assessment by limiting the number of evaluators and to allow for rapid response to emergencies by experiencing a large number of cases. We believe it is necessary to conduct this multicenter study because this single-center study has shown the benefit of the combination of midazolam and pethidine. The fourth point is that we do not know if midazolam and pethidine are the best combination. The combination of pethidine and midazolam has been shown to be useful in endoscopic pharyngeal observation . HoweverIn bronchoscopic sedation, the combination of midazolam and pethidine attenuated pain and showed significant improvements in objective indicators such as vital signs and adverse events during the examination.Additional file 1. Questionnaire.Additional file 2. Modified Observer’s Assessment of Alertness/Sedation Scale.Additional file 3. Adverse events during and after bronchoscopy.Additional file 4. Diagnosis of biopsy.