Pattern electroretinogram (PERG) is an objective measure of the central retinal function that correlates with macular GCL thickness. The aim of this study is to determine possible relationships between the N95 amplitude of pattern electroretinogram . The best-fit model for the relationship between visual field parameters and GCIPLT was the broken stick model. During early glaucoma, macular GCIPLT was positively correlated with PERGamp, but not with visual field loss. In advanced glaucoma, macular GCIPLT was positively correlated with both PERGamp and visual field loss.This was a retrospective and comparative study including 74 glaucoma patients (44 early stage and 30 advanced stage cases) and 66 normal control subjects. Macular GCIPLT was measured using Cirrus spectral domain-optical coherence tomography. Standard automated perimetry and pattern ERGs were used in all patient examinations. Three types of regression analysis  were used to evaluate possible relationships between PERGamp was significantly correlated with macular GCIPT in early glaucoma patients, while visual field performance showed no correlation with GCIPLT. PERGamp can therefore assist clinicians in making an early decision regarding the most suitable treatment plan, especially when GCIPLT is thinning with no change in visual field performance.PERG The main characteristic of glaucoma is loss of retinal ganglion cell axons, which typically leads to optic neuropathy. Retinal ganglion cell (RGC) death is a common cause of loss of vision during glaucoma and most optic neuropathies. Stress in the cellular and molecular environment that exceeds the survival capacity of RGCs can lead to progressive damage to ganglion cells and their fibers. This damage can induce retinal dysfunction, as revealed by flash electroretinogram (FERG) or pattern electroretinogram (PERG) recordings –4.Macular ganglion cell loss has been detected during early experimental glaucoma . NagarajLoss of RGCs leads to atrophy of the ganglion cell layer (GCL). In eyes with pre-perimetric glaucoma, the macular GCL shows severe thinning . The macPERG signals are comprised of positive P50 and negative N95 components. The positive P50 component is always affected by retinal/macular dysfunction, while the late negative N95 component is mainly affected by optic nerve diseases . A previA previous study reported that PERG loss was greater than circumpapillary RNFL thinning . HoweverThis was a retrospective and comparative study, performed at Pusan National University Hospital  from July 1, 2015 to August 31, 2016. The study was performed in accordance with the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board (IRB) of Pusan National University Hospital. The institutional review board waived consent from patients because this is a retrospective, anonymous study.Participants were ≥ 18 years of age, and were either healthy or had been previously diagnosed with open-angle glaucoma. Glaucoma patients were further classified as having early [mean deviation (MD) ≥ -6 dB] or moderate/advanced (MD < -6 dB) glaucoma. Patients were excluded if they met any one of the following exclusion criteria: corneal scarring, media opacities, anterior segment dysgenesis, past chronic steroid use, history of diabetic retinopathy, previous intraocular surgery (except uncomplicated cataract surgery), a refractive error outside the -6.00 to +6.00 diopters range, and any abnormality other than glaucoma. When both eyes were involved, one eye was chosen randomly.A complete medical history was taken from the participants, all of whom underwent an ophthalmic examination by a glaucoma specialist. Clinical data included best-corrected visual acuity, and results of Goldmann applanation tonometry, slit-lamp examination, gonioscopy, pachymetry , and fundus examination with a dilated pupil. Age, sex, and spherical equivalent refractive error  were also recorded for all participants.2. The pattern ERGs were obtained as binocular recordings at a reversal rate of 2 ± 0.4 Hz, and at least 100 artifact-free sweeps were collected and averaged.The PERG measurements were recorded using a commercial ERG system  that conformed to the International Society of Clinical Electrophysiology and Vision (ISCEV) standards of 2012 . All patamp) was measured from the peak of P50 to the trough of N95. The implicit times of the P50 and N95 were also measured.The P50 amplitude was measured from the trough of N35 to the peak of P50. The N95 amplitude . Reliable visual field tests were defined as a false positive rate < 15%, false negative rate < 33%, and fixation loss < 20%. Normal control subjects had a glaucoma hemifield test (GHT) within normal limits and their MD and pattern standard deviation (PSD) were within 95% of the normal population. Glaucomatous visual fields were those that met at least one of the following criteria: a GHT outside normal limits and a PSD probability outside of 95% of the normal population.center; Visual field total deviation values were recorded at all 52 testing points, among which the 12 most central points, i.e. those corresponding to the macular area, were selected. The selected values were unlogged, averaged, and finally logged again to transform them back to a decibel scale, termed the central visual field total deviation  GCIPLT and retinal nerve fiber layer thickness (RNFLT) values were obtained, and the average values were used in the statistical analyses. All of the included SD-OCT scans had a signal strength of at least six.The Cirrus SD-OCT instrument (Carl Zeiss Meditec) (version 6.0 software) was used to measure ganglion cell/inner plexiform layer thickness (GCIPLT). After pupil dilation using 0.5% tropicamide and 0.5% phenylephrine, the Cirrus SD-OCT instrument was used to acquire a single macular scan (200 × 200 macular cube scan protocol) of each eye studied. The GCA algorithm automatically segmented the GCIPL and RNFL and calculated the thickness of the macular GCIPL and RNFL within a 14.13 mmhttp://www.R-project.org) and segmented R library were used for the Davies’ test and segmented regression analyses  according to the severity of glaucoma.Three statistical regression models, namely broken stick, linear regression, and quadratic regression models, were used to evaluate macular structure-function relationships. The broken stick model is a nonlinear statistical model consisting of two linear regression lines with tipping point. An initial estimate of the tipping point was determined using the Davies’ test ; then, sanalyses . Linear P -value < 0.05 was considered statistically significant.The normality of the data distribution was checked using the Kolmogorov-Smirnov test. To compare parameters between normal subjects and glaucoma patients, one-way analysis of variance, or the Kruskal-Wallis test, was used according to the normality of the data. The chi-squared test was used for the categorical variables. A P = 0.004 and P = 0.029, respectively).In total, data from 66 normal control subjects and 74 glaucoma patients (44 early and 30 early advanced stage) were included . The patient demographics are summarized in amp values were 7.11 ± 2.20 μV, 5.30 ± 1.72 μV, and 4.87 ± 1.78 μV  and were significantly different (P < 0.001). The mean GCIPLT values were 81.91 ± 6.12 μM, 74.59 ± 7.43 μM, and 66.33 ± 8.56 μM, and the mean RNFLTs were 33.42 ± 3.62 μM, 29.52 ± 4.90 μM, and 24.34 ± 1.62 μM . These two SD OCT parameters were significantly different between normal control subjects, early glaucoma patients, and advanced glaucoma patients .The mean PERGsamp was the linear regression model . A scatterplot of the three regression models is shown in center, with a significant tipping point  at 71.9 μM. When the GCIPLT was greater than the tipping point, the VFcenter was unrelated to the GCIPLT (P = 0.050) and the slope was nearly zero (slope = 0.06). However, as the GCIPLT became thinner than the tipping point, the VFcenter and GCIPLT became significantly correlated (P < 0.001) and the slope below the tipping point was steeper than the slope above the tipping point . The relationship between GCIPLT and VFMD was similar to that between GCIPLT and VFcenter (P < 0.001). The slopes below and above the tipping point were 0.74 and 0.13, respectively, and were significantly different from each other (P < 0.001).The results of the regression analyses are summarized in VFcenter . Among tamp, and visual field parameters (VFcenter and VFMD) are summarized in Tables amp, but not with VFcenter or VFMD Click here for additional data file.


Several diseases, such as obesity, hypertension and type 2 diabetes are frequently associated with metabolic abnormalities, high costs of healthcare and morbi-mortality; thus the aim of this study was to investigate the relationship between out-of-clinic high blood pressure and chronic disease-associated adiposity indicators in practitioners of leisure physical activity.≥140 mmHg and diastolic ≥90 mmHg blood pressures were classified as high blood pressure. All analyses were adjusted for age and sex.A cross-sectional study with 414 subjects of both genders aged 24–65 years. Data were collected by trained interviewers in five public parks. Body Mass Index (BMI), triceps skinfold and waist circumference (WC) were evaluated. Exercise training, smoking status, alcohol consumption and hypertension diagnosis were self-reported. Casual glycemia concentrations were collected and blood pressure was measured out-of-clinic once during the study. Participants with systolic n = 130), but 34 (8.3%) from patients took medication anti-hypertensive and were previously hypertension diagnosed. Participants with high blood pressure had a higher BMI , WC , and systolic and diastolic blood pressure (p <  0.0001) when compared to subjects with normal blood pressure. Logistic regression analysis revealed that overweight status assessed by BMI, triceps skinfold and WC increases the high blood pressure probability by approximately 1.61 (95 CI%: 1.06–2.45), 1.02 (95%CI: 1.01–1.05) and 1.61 (95%CI: 1.06–2.45), respectively.High-blood pressure was diagnosed in 31.4% (Adiposity indicators are associated with high out-of-clinic blood pressure measured in practitioners of leisure physical activity. The World Health Organization estimated 56 million deaths worldwide in 2012, out of which 38 million were due to chronic noncommunicable diseases (NCDs). Noncommunicable diseases are increasing and may be responsible for 52 million deaths worldwide in 2030; in Brazil, the proportion may reach 74% of all deaths. Obesity, hypertension and type 2 diabetes mellitus are factors that contribute to the high rate of NCDs’ morbidity and mortality. However, leisure physical activity helps in the prevention and treatment of hypertension, and reduces cardiovascular risk and mortality  ≥160 mmHg or diastolic blood pressure [DBP] ≥100 mmHg) were considered as diagnostic criteria, according to values of blood pressure of the European Society of Hypertension  ≥160 mmHg or diastolic blood pressure [DBP] ≥100 mmHg [n = 284, 68.6%) or high  blood pressure groups (Table n = 130) blood pressure, 34 (8.3%) patients took medication anti-hypertensive and were previously hypertension diagnosed by physician and self-reported by patients, and 96 (23.2%) had no hypertension diagnosed.A total of 414 practitioners of leisure physical activity were evaluated, comprising 195 men and 219 women, with a mean age of 45.2 years. Participants’ data were divided into normal (p = 0.012), waist circumference (p = 0.001), systolic (p <  0.0001) and diastolic (p <  0.0001) blood pressure were greater in the high than normal blood pressure group.Table 2 for adult  and ≥ 27 kg/m2 for elderly (≥60 years) [Next, we performed a logistic regression analysis Table  to disco0 years) . A raiseIn addition, smoking status was associated in 2.07 (95%CI: 1.02–4.21) times with high blood pressure in crude model, but no after adjusting for sex and age , leading us to suggest that their time, intensity and frequency of exercise were low and that the adiposity indicators, such as BMI, triceps and WC and smoke status were responsible for raising their blood pressure levels. On the other hand, we have demonstrated previously that nutritional counseling can reduce adiposity indicators and to prevent NCDs [Although the individuals carried out leisure physical activity, such as walking and jogging, and racing in the parks, they presented high out-of-clinic blood pressures (ent NCDs , 18.We can speculate that monitoring out-of-clinic blood pressure in, for example, public parks can be very important as it helps to control adiposity and prevent increased blood pressure levels. Although the exercises performed in public parks are protect to some extent against NCDs it seems that, for the control of high blood pressure, they do not. Therefore, more studies are needed to verify the appropriate physical activity in terms of its intensity and duration to prevent high blood pressure.A limitation of this study is that we evaluated only Midwestern Brazilian subjects, but though is not a representative sample of other regions of Brazil, the sample size calculus revealed that we evaluated more individuals than the sample size. Although we used only the wrist blood pressure monitor, this equipment has been validated and adequate for overweight people. And even though the blood pressure was measured only once, all individuals were asked to remain seated when completing the socioeconomic questionnaire to avoid changes in their blood pressure levels and so the blood pressure was measured after eight to 10 min at rest.In summary, we found that high out-of-clinic blood pressure is associated with chronic disease-linked adiposity indicators in leisure activity practitioners in Midwest Brazil. This information is useful for developing nutritional and physical activity interventions in primary care to attenuate co-morbidities and chronic disease-related metabolic consequences.


However, most studiesprioritize peak VO2 as the main variable, leaving aside otherimportant CPET variables that can specify the severity of the disease andguide the clinical treatment.Endomyocardial fibrosis (EMF) is a rare disease, characterized by diastolicdysfunction which leads to reduced peak oxygen consumption  were compared with 15healthy subjects (HS). Functional capacity was evaluated using CPET anddiastolic and systolic functions were evaluated by echocardiography.2, peak oxygen(O2) pulse and peak pulmonary ventilation (VE)were decreased in EMF compared to HS. Also, EMF patients showed increasedΔ heart rate /Δ oxygen uptake and Δ oxygen uptake/Δ work rate compared to HS.Age and gender were similar between EMF patients and HS. Left ventricularejection fraction was normal in EMF patients, but decreased compared to HS.Peak heart rate, peak workload, peak VODetermination of the aerobic capacity by noninvasive respiratory gas exchangeduring incremental exercise provides additional information about theexercise tolerance in patients with EMF. The analysis of different CPETvariables is necessary to help us understand more about the central andperipheral alterations cause by both diastolic dysfunction and restrictivepattern. Also, Lele et al.15 demonstrated that there is an inverse correlationof left ventricular time to peak filling at peak exercise and peak VO2with peak cardiac output. Thus, changes in left ventricular compliance andrelaxation can be more apparent and better understood when exercise isperformed.Currently, for patients with EMF with functional class (FC) III (decompensated) or IV, the most common treatment is the endocardialresection surgery.17 In this context, CPET has adefined role in the clinical diagnose of exercise intolerance.18 Peak VO2 is a fundamental variable that resultsfrom peripheral (A-VO2) and central alterations (CO). However, moststudies prioritize peak VO2 as the main variable, leaving aside otherimportant CPET variables. Workload is a CPET variable that reflexes peripherallimitations once it represents the ability of the muscles to absorb oxygen(O2) to produce adequate energy to tolerate the workload during theCPET. Therefore, the higher is the peak workload, the higher is the energy providedby the working muscle. Progressive O2 pulse response to incrementalexercise is a variable that indirectly represents left ventricular stroke volume(LV-SV) and peripheral extraction of O2 per heartbeat. A decreasedO2 pulse represents an inability to increase LV-SV and maintainCO.19 Therefore, CPETvariables can help in the identification of different mechanisms of exerciselimitation and peripheral mechanisms that can specify the severity of the diseasesand guide the clinical treatment. Taking this into consideration, the aim of thisstudy was to evaluate central and peripheral limitations caused by diastolicdysfunction in symptomatic patients with EMF after endomyocardial resection surgeryby different CPET variables.Cardiopulmonary exercise testing (CPET) has been proved to be a fundamental tool thatspecifies physical exercise intolerance and has being used as an independent markerof severity and mortality.Fifty-eight patients with EMF attending from the Clinical Unit of Cardiomyopathyat the Heart Institute (Incor), University of Sao Paulo Medical School, SaoPaulo, Brazil were screened for this study. Of those 58 patients, 26 patientsmet the inclusion criteria. Were also included 15 age-matched healthy sedentarysubjects (HS).Inclusion criteria for patients with EMF were: endocardial resection surgery morethan 1 year before the study; functional class III by the NYHA; under optimaltreatment (most appropriate medication at the maximum tolerated doses). Theinclusion criteria for the HS subjects were: a normal history and physicalexaminations and; no metabolic, cardiovascular, kidney, and liver diseases.2).EMF patients and HS were excluded if they present: regular exercise trainingactivities, history of coronary revascularization or myocardial infarction,diabetes, bi-ventricular pacemakers with or without implantable cardioverterdefibrillator and obesity  and by the Scientific ResearchCommittee of the Incor (SDC- 3151/08/067). All study participants providedwritten informed consent. This study was performed according to the declarationof Helsinki and followed the recommendations of the STROBE Statement.21 EMF assessment was performedthrough the presence of obliteration in the apex in one or both ventricles, withor without atrioventricular regurgitation.Echocardiographic parameters were determined based on the American Society ofEchocardiography recommendations as previously described.22 Thecompletion of the test occurred when, despite verbal encouragement, the subjectcould no longer maintain the exercise and maximal respiratory exchange ratio(RER)19 reached >1.10. Means of gas exchange on a breath-by-breath basis in a computerized system were used to determinedpulmonary ventilation (VE), VO2 and carbon dioxideventilation (VCO2). Anaerobic threshold was estimated as previouslydescribed.23 Oxygenpulse (O2 pulse) was calculated as the ratio between VO2and heart rate (HR) at peak exercise and during CPET.24 ΔHR/ΔVO2 was measuredas the ratio between HR (peak HR - baseline HR) and VO2 .23ΔVO2/ΔWR was evaluated as previouslydescribed.26 We used values ofVO2 and WR from the 1st minute up to the peak of theexercise.25Ventilatory response (VE/VCO2 slope) was also calculatedas previously described.25 Weused values of VE and VCO2 from the beginning of the CPETup to the peak of exercise.27All patients underwent a maximal progressive exercise test on a cycle ergometer to assess maximal oxygen consumption andother ventilatory and cardiovascular parameters, using a ramp protocol with workrate (WR) increments of 5-10 W every minute until exhaustion as describedbefore.CPET was assessed in the morning (between 8and 10 a.m.) and all participants wereinstructed to have the last meal 2 hours before CPET, and to avoid caffeine andhigh-fat food intake for 24 hours before.2 (ml/kg/min) between EMF group and healthysubjects with a 5% significance level. We calculated a total of at least 20patients with EMF and 15 HS to identify a difference in peak VO2.The sample size calculation was based on at least 80% power to detect a meandifference in peak VOP values < 0.05 were consideredstatistically significant. All calculations were performed using SPSS softwarefor Windows version 21 .The Kolmogorov-Smirnov and Levene’s tests were used to assess normality ofdistribution and homogeneity for each variable. Fisher exact test was used toanalyze the distribution of sex. For independent samples, the t-test was used tocompare parametric variables, and Mann-Whitney U test was used to comparenonparametric variables. ANOVA for repeated measures and Scheffé’sposthoc test were used to compare the effect of time during CPET on parametricvariables, and the Friedman test was used for this same situation fornonparametric variables. Parametric variables were presented as mean ± SDand nonparametric variables were presented as median and interquartile range. Echocardiographic variables are shown in 2 (PetCO2),VE/VCO2 slope and RER were similar between the groups. Peak HR,peak workload, peak VO2, peak O2 pulse, peakVCO2 and peak VE were decreased in EMF compared to HS.Also, ΔHR/ΔVO2 and ΔVO2/ΔWRwere increased in EMF patients compared to HS.CPET variables are displayed in 2 response duringexercise  in one patient withEMF and in one HS. 2 pulse response to incremental exercise in one subjectfrom each group (EMF and HS). 2 and ∆VO2/∆WR(respectively) in one patient with EMF and in one HS.2 is one of the most important variables to describeexercise tolerance in humans. However, other parameters of CPET can provideadditional information on the exercise capacity. The aim of this study was toevaluate different CPET parameters that could help us understand the physicallimitations caused by DD in symptomatic patients with EMF. We demonstrated that CPETvariables were impaired in symptomatic EMF compared to HS. These findings show thatexercise intolerance in these patients is caused by central and peripheralalterations of the restrictive cardiomyopathy condition.We know that peak VO28The fibrotic tissue in the ventricles and in the papillary muscles provokes fillingrestriction, and this alteration causes severe hemodynamic disturbances. Evenknowing that ejection fraction is normal or slightly reduced, the stroke volume inEMF patients is decreased, leading to poor peripheral perfusion.30 Reduced peak VO2 iscorrelated with increased hospitalization and mortality rate.31 In patients with EMF, peakVO2 reduction can be related to 1) a fixed LV-EDV that affects LV-SVincreases during a maximal cardiac work, and thereby affects CO increases; 2)blunted maximal workload during maximal exercise testing, showing that thesepatients cannot handle a high workload due to an inefficient cardiac work; 3) thedifficulty in increasing the CO during maximal exercise test can provoke a reductionin peripheral blood flow favoring an early fatigue. It is important to highlightthat all these patients had been submitted to endocardial resection surgery, anddespite the procedure, they still presented inefficient O2 distributionand consumption compared to HS.In patients with heart failure and systolic dysfunction, the importance of functionalcapacity is well described.2/ΔWR in patients with EMF. This variable evaluates:1) the metabolically induced vasodilation and thus the increased O2 flowto the place of demand; 2) an increased O2 uptake when transforminglactate to glycogen by tissues actively involved in gluconeogenesis; and 3) anincreased O2 demand of breathing muscle.32 Therefore, this variable represents the importanceof peripheral metabolism during incremental exercise. Knowing that VO2increases progressively and linearly to increases in workload during CPET, healthysedentary subjects consume a constant O2 amount to produce energy andfulfill the metabolic demands during a specific work. Regardless of age or physicaltraining level, the normal value for HS is 10 mL/min/watts.33 In this study, we showed that EMFpatients have a ΔVO2/ΔWR of 12.5 ml/min/watts. Change in∆VO2/∆WR reflects a low A-VO2difference34 that maycontribute significantly to exercise limitation in EMF patients. Also, the∆VO2/∆WR impairment may be explained by abnormalitiesof oxygen extraction in skeletal muscle or conditions causing reduced blood flow toexercising muscle. Abnormal skeletal muscle fibers with low mitochondrial densityare associated with reduced oxidative capacity due to reduced oxygen use andinappropriate vascular responses to exercise.Other interesting CPET variable explored in this study was the increasedΔVO2 pulse. This variable is calculated by the ratio betweenVO2 and HR,24 andconsequently, it can be used as a noninvasive indicator of stroke volume.35 It normally rises progressivelythroughout exercise; however, a decreased value suggests decreasing stroke volumeduring exercise.36 EMF patientsshow a reduced O2 pulse which could be explained, at least in part, by adifficulty in increasing CO via systolic volume caused by fixed diastolic volume. Inconsequence, the increase in CO during CPET is highly dependent on increases in HR,limiting the increase in O2 pulse.On the other hand, to evaluate central limitations during CPET, we analyzedO2 ratio. It indicates the necessary cardiac workto provide 1 liter of O2 to fulfill metabolic demands, such as muscleenergy for a specific workload.23Reduced values of ΔHR/ΔVO2 in EMF patients, even afterendocardium resection, demonstrate that these patients have an increased cardiacwork to consume the same amount of O2 compared to HS. As previouslystated by Ramos et al.,23 areduced stroke volume and/or diminished A-VO2 difference would lead to asteeper ΔHR/ΔVO2, whereas cardiac dysfunction, decreasedarterial O2, and impaired muscle aerobic capacity can increaseΔHR/ΔVO2.Another important variable that can be used to evaluate central alterations is theΔHR/ΔVOFinally, this study demonstrated that patients with EMF have an impaired cardiacfunction and peripheral alterations that influence the exercise intolerance. Takingall into consideration, we demonstrated the importance of the combined evaluation ofdifferent CPET variables. All these variables together may be an important key toevaluate patients with restrictive cardiomyopathy due to EMF.2 differencein a direct way.There are limitations in this study. EMF is a rare and neglected disease, and forthis reason we studied a small sample size. We only studied patients with EMF,which is the most common etiology of restrictive cardiomyopathy in tropicalcountries. Therefore, we cannot assume that these results will be found in otherforms of restrictive cardiomyopathy or diastolic dysfunction. All patients fromthis study had been submitted to resectional surgical for fibrosis; therefore,we do not know whether similar results would be found in patients before thesurgical procedure. Lastly, central and peripheral CPET variables were evaluatednoninvasively, and thereby in an indirect way. It would be of great interest toreproduce this study evaluating cardiac output and A-VODetermination of patient’s aerobic capacity by noninvasive respiratory gas exchangeduring incremental exercise provides additional information about the exercisetolerance in patients with EMF. The analysis of different CPET variables isnecessary to help us understand more about the central and peripheral alterationscaused by both diastolic dysfunction and restrictive pattern.


The causal interaction between cardio-postural-musculoskeletal systems is critical in maintaining postural stability under orthostatic challenge. The absence or reduction of such interactions could lead to fainting and falls often experienced by elderly individuals. The causal relationship between systolic blood pressure (SBP), calf electromyography (EMG), and resultant center of pressure (COPr) can quantify the behavior of cardio-postural control loop. Convergent cross mapping (CCM) is a non-linear approach to establish causality, thus, expected to decipher nonlinear causal cardio-postural-musculoskeletal interactions. Data were acquired simultaneously from young participants  during a 10-minute sit-to-stand test. In the young population, skeletal muscle pump was found to drive blood pressure control (EMG → SBP) as well as control the postural sway (EMG → COPr) through the significantly higher causal drive in the direction towards SBP and COPr. Furthermore, the effect of aging on muscle pump activation associated with blood pressure regulation was explored. Simultaneous EMG and SBP were acquired from elderly group . A significant (p = 0.002) decline in EMG → SBP causality was observed in the elderly group, compared to the young group. The results highlight the potential of causality to detect alteration in blood pressure regulation with age, thus, a potential clinical utility towards detection of fall proneness. Stable upright posture is achieved through numerous complex physiological interactions567891011Postural stability is dependent on input from visual, cognitive, somatosensory, and vestibular systems111315161819Causality describes the directional relationship between cause and its effect. The human body as a highly integrated group of dynamic and adaptive systems often shows cause and effect relationships, such relationship has been studied in neural2122242628213031Convergent cross mapping (CCM), a nonlinear approach for estimating causality between two time series is based on the state space reconstruction of a time series called ‘shadow-manifold’3535On the other hand, CCM infers causality in terms of strength of coupling, thus, revealing vital information regarding the degree to which the interacting variables are coupled. The quantified knowledge of the strength of directional interaction can have a clinical relevance; as aging or pathology may cause an alteration in the strength of such interaction. The strength of the CCM method has been demonstrated in physiological applications to understand blood pressure and cerebral blood flow velocity interactionTo the best of our knowledge, our preliminary study is the only effort so far in the direction of establishing causality in the cardio-postural control loop40414215Data was acquired from 18 healthy young  and 14 healthy elderly  participants during a 10-minute sit-to-stand test. Participants under medication that could alter cardiovascular and postural stability along with those with any history of cardiovascular, respiratory, neurological, and major musculoskeletal injuries or hormone imbalance were screened out from the experimentation. The sit-to-stand test required participants to be seated for 5 minutes, after this, participants were passively assisted to standing phase to maintain a quiet stance for additional 5 minutes. During a 10-minute period electrocardiogram (ECG), blood pressure, calf EMG and COP signals were simultaneously acquired at a sampling rate of 1000 Hz using National Instruments  data acquisition system. For the elderly group, COP signal was not a part of the ethics, hence, it was not acquired.ECG was acquired in a standard lead II electrode configuration using LifePak 8 . Continuous blood pressure was recorded non-invasively using finger photoplethysmograph cuff from Finometer model 1 . Medio-lateral (COPx) and anterior-posterior (COPy) center of pressure signals were derived from force and moment data obtained using force platform . Calf EMG was acquired from four different leg muscles namely tibialis anterior, lateral gastrocnemius, medial gastrocnemius, and medial soleus using the 8 channel EMG acquisition system Bangoli-8  in the form of transdermal differential recordings.The study was approved to be of minimal risk by the research ethics board of Simon Fraser University (SFU). Data acquisition protocols were performed according to relevant guidelines and regulations set by research ethics board of SFU. Participants had the option to terminate experiment any time. Written informed consent was obtained from each participant before experimentation. All participants were required to abstain from alcohol, exercise, and ingesting caffeine 24 hours before the experiment. The data acquisition was performed at the Aerospace Physiology Laboratory, Department of Biomedical Physiology and Kinesiology, SFU.Y) and X(MX) are constructed using lagged coordinates of variables Y and X, respectively34X are used to find the neighbors on MY to estimate Y. More detailed algorithmic explanation of the steps to perform a CCM causality is explained in the supplementary material of Sugihara et al.’s workX is denoted as Using the CCM method, for Y having a causal influence on X (Y → X), causality is inferred by quantifying the degree to which historical records of X can be used to accurately estimate the states of Y. In order to do so, first, the shadow (reconstructed) manifold of Y could be represented as; Y can be used to estimate X and historical record from MX can be used to estimate Y. In this case, both the correlation of X and estimated X as well as the correlation of Y and estimated Y will vary between 0 and 1. Mathematically, Using CCM method unidirectional and bidirectional causality can be detected. In the case of a unidirectional causality (X → Y), the driver X can be estimated using a historical record from MAll acquired signals were low-pass filtered at a cutoff frequency of 20 Hz. Only standing data was used for studying causality between variables in cardio-postural-musculoskeletal systems. The first minute of data was discarded to eliminate possible motion artifact incorporated in the signals during the sit-to-stand transition. The QRS complex was detected from ECG using the Pan-Tompkins algorithmThe resampled signals (2 at a time) were input to the CCM algorithm. The correlation coefficient value (magnitude) at which each causal event converged were taken into account as a marker degree of causal information flowing from one variable to another and vice-versa. The statistical significance of correlation was set at α = 0.05. For each analysis, depending upon convergence of causality of the signal pair under analysis, three scenarios were possible: (1) unidirectional (X → Y or Y → X), (2) bidirectional (X → Y and Y → X i.e. X ↔ Y), and (3) no causality. The data analyses were performed in MATLAB .The Arterial baroreflex sensitivity (BRS), a marker of autonomic blood pressure regulation, was calculated using the sequence methodThe normality of the distribution was checked using Shapiro-Wilk test of normality . Statistical test for significance was conducted using a 2-tailed student t-test for normally distributed data otherwise, Wilcoxon rank sum test was performed, both in MATLAB . A significance level of 1%, 5%, or 10% was considered and it will be mentioned appropriately throughout the text. All results are presented as mean ± standard deviation (SD) unless mentioned otherwise.The performance of CCM in effectively revealing causality between two time series data is dependent on the optimal choice of E and τ. The optimal value of E was determined to be 4 using false nearest neighbor (FNN) algorithmAs per our hypothesis, the outcome of causality analysis between cardio-postural-musculoskeletal variables resulted in the existence of bidirectional causality. The population-wide behavior of CCM causality between respective signals is summarized in The dominant causal interaction (X → Y or Y → X) was determined by performing a test of significance between forward (X → Y) and reverse (Y → X) causal activities for different interactions . If there existed a significant difference between the two, the difference was considered as an indicator of one system being a dominant driver of the other. To this end, the non-baroreflex events (EMG → SBP and COPr → SBP) were found to be significantly higher (p < 0.001) than the baroreflex events (SBP → EMG and SBP → COPr). The EMG ↔ COPr interaction revealed muscle pump driven (EMG → COPr) posture control to be more dominant (p = 0.06) than the reverse case (COPr → EMG). In order to validate the potential of CCM methodology to differentiate causality with age, causality (EMG ↔ SBP) for the elderly group was calculated  and compAlthough the role of the interaction between physiological systems is well-known for the maintenance of stable upright posture, the directional information flow between such systems, in order to compensate for external perturbation to achieve postural stability is not generalized. The current work investigated the existence of bidirectional (feedback) causality in cardio-postural-musculoskeletal systems in young, healthy population.Further differentiation in the strength of muscle pump-baroreflex (EMG ↔ SBP) directional interaction due to aging was explored. The external perturbation to evoke physiological alteration was applied via a controlled sit-to-stand test. The novel insights unearthed by a thoroughly validated causality methodology confirmed previously speculated, yet unclear, directional information flow in the cardio-postural control loop. The advantages of CCM methodology was exploited to quantify the role of the individual physiological link of the cardio-postural control loop  towards maintaining postural stability. The key finding of the current work was the central role of skeletal muscle pump in facilitating increase in the venous return to the heart and simultaneously controlling the postural sway.The causal information flow from one physiological system to the other and vice-versa was of variable strength, suggesting one system to be the dominant driver of another system. In general, causal information flow of significantly greater strength (p < 0.001) from skeletal muscle pump to SBP was observed, indicating stronger mechanical skeletal muscle pump effect on blood pressure  compared to the baroreflex mediated skeletal muscle activation . Similarly, postural sway driven control of SBP  was significantly stronger (p < 0.001) than the baroreflex mediated control of postural sway  and the muscle pump mediated control of postural sway was stronger (p = 0.06) than the reverse, postural sway mediated skeletal muscle activation.This behavior of causality in the cardio-postural control loop highlighted the two-fold role of the skeletal muscle pump; a) driving control of the cardiovascular system by increasing venous return and b) driving control of postural system by controlling postural sway through skeletal muscle activation. There were two primary pathways of causal information flow observed in the cardio-postural control loop, a) stronger non-baroreflex driven control of SBP through postural sway and b) weaker baroreflex mediated activation of skeletal muscles through postural sway. These two pathways manifest the bidirectional transitive behavior  of the cardio-postural control loop towards the regulation of blood pressure. The two pathways are shown in To ascertain the potential of CCM causality in differentiating the alterations in the strength of directional information flow between physiological systems due to aging; the established baseline causal behavior of EMG ↔ SBP interaction obtained from the young group was compared with the elderly group. The comparison result highlighted a significant decline from young to elderly group  in the strength of skeletal muscle pump driven control of blood pressure (EMG → SBP), while the reverse causality signifying baroreflex mediated skeletal muscle pump activation (SBP → EMG) did not achieve statistical significance , Since baroreflex mediated muscle pump activation (SBP → EMG) did not alter significantly with age, it suggests that blood pressure homeostasis is mainly achieved through mechanical muscle pump and baroreflex mediated control has a limited role in driving skeletal muscle activation, this could be further emphasized, by an observation of significant decline (p < 0.001) in the arterial baroreflex sensitivity in the elderly (3.63 ± 2.54 ms/mmHg) compared to young (9.00 ± 3.58 ms/mmHg) group. The findings of this comparison open further avenues regarding the importance of muscle pump in blood pressure regulation. Clinically, this finding can be exploited towards early diagnosis of syncope prone individuals to limit falling incidents. Additionally, it is known that pathologies such as stroke, concussion, and Parkinson’s disease impair skeletal muscle functionality as well as alter postural stability4950The current study has following conclusions. First, an establishment of directional information flow in the cardio-postural control loop, based on data from the young and healthy population. The establishment of causality was achieved by quantifying causality between cardiovascular-postural-musculoskeletal systems by a nonlinear CCM methodology. Second, the non-baroreflex events (EMG → SBP and COPr → SBP) of the cardio-postural control loop have a significantly higher causal drive towards SBP and COPr in comparison to the baroreflex events (SBP → EMG and SBP → COPr) . We did The limitation of the current study was the unavailability of the center of pressure data (COPr) in the elderly group, as a result, the effect of aging on cardio-postural control loop was not generalized, however, this shall be explored in the future work. Additionally, both population group studied in this research were healthy, therefore, the alteration in causality observed was solely due to aging. The role of skeletal muscles towards blood pressure regulation and the behavior of baroreflex mediated skeletal muscle activation under pathological conditions is still an open field. Future comparison of the cardio-postural control loop generalized in the current research with cardio-postural control loop established under more challenging physiological condition  and post pathological events  will further our understanding regarding the behavior of complex directional interaction between physiological systems forming the cardio-postural control loop. Such findings will be a step forward towards clinical applicability of causality established in physiological systems, towards diagnosis and prevention of fall proneness, as well as monitoring the rehabilitation efficacy post pathology.How to cite this article: Verma, A. K. et al. Skeletal Muscle Pump Drives Control of Cardiovascular and Postural Systems. Sci. Rep.7, 45301; doi: 10.1038/srep45301 (2017).Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


Hypertension and dyssomnia are increasing significantly in Mongolians, and the related factors of ethnic differences in hypertension and dyssomnia between Mongolians and Han Chinese are unclear. This study examined the relationship of morning surge in blood pressure (MBP) with ethnicity, sleep situation, and sympathetic activity throughout the day.n = 87) and Han (n = 115) groups. The differences in dyssomnia, 24-h blood pressure, and urinary catecholamine were analyzed in all subjects; they were then further divided according to the degree of dyssomnia  to determine the differences in blood pressure and catecholamine.Of 692 hypertensive patients screened, 202 subjects with dyssomnia were selected. They were then divided into Mongolian (p < 0.05). D-DA was entered into the MSBP regression model of Mongolians , whereas D-DA and D-NE were entered into the MSBP regression model of Han Chinese .Mongolians had a lower history of smoking, daytime dysfunction, nocturnal heart rates, and dopamine levels, but their body mass index, triglyceride, fasting glucose, morning surge in systolic blood pressure (MSBP), nocturnal systolic blood pressure (NSBP), nocturnal diastolic blood pressure, daytime systolic blood pressure, daytime heart rates, and dopamine level (D-DA) were higher than those of Han Chinese. With the aggravation of dyssomnia, MSBP, NSBP, D-NE, daytime epinephrine, and D-DA of Mongolians and Han Chinese increased gradually, but the rate of increase was faster in the latter (Worsened dyssomnia induces higher MSBP and augments sympathetic excitability in Mongolians and Han Chinese. Mongolians with hypertension and dyssomnia had higher MSBP baseline and D-DA but lower N-DA. With an increase in D-DA, MSBP in Han and Mongolian patients increased gradually. Evidence from previous studies suggests that dyssomnia can increase the incidence of high blood pressure, even if it is a single factor that can lead to high blood pressure in a given environment for quite a time . HoweverElevated morning surge in blood pressure (MBP) is undoubtedly a major sign of these two diseases, which could increase damage to organs affected by cardiovascular and cerebrovascular diseases and increase morbidity and mortality . MeanwhiIn China, different ethnic groups have different levels of blood pressure, and the prevalence of hypertension is also different. Mongolians are the ninth largest minority in China, and their incidence of hypertension is higher than that of Han Chinese . At presThus, we conducted a prospective cross-sectional study to confirm the hypothesis that Mongolian patients with hypertension and dyssomnia have more obvious increase in sympathetic excitability, higher MBP, and closer correlation between sympathetic activity and MBP, compared with Han patients.Participants were recruited from the Second Affiliated Hospital of Baotou Medical College in the city of Baotou, Inner Mongolia, by posting study flyers in cardiovascular clinics and wards. Study samples who met eligibility criteria were screened from a total of 692 participants . The proHypertensive Mongolian and Han patients ≥ 18 years or older with systolic blood pressure (SBP) ≥ 140 mmHg and/or diastolic blood pressure (DBP) ≥ 90 mmHg and blood pressure < 180/110 mmHg measured three times or more on different days and have not taken any medicines during the week were included.Patients with secondary hypertension, stroke, coronary heart disease, diabetes mellitus, severe arrhythmia, heart failure, valvular disease, liver and kidney dysfunction, mental disorders, tumor, respiratory diseases, hyperthyroidism, connective tissue disease, or infection; those who had surgery in the past three months; those who were pregnant or breastfeeding; those who cannot independently complete the questionnaire independently; and those who were unwilling to participate in the clinical study were excluded.To avoid interference factors as much as possible, patients taking any medicines within a week, including antihypertensive drugs and drugs for the treatment of dyssomnia, were excluded. Patients with SBP ≥ 180 mmHg or DBP ≥ 110 mmHg were also excluded to ensure their safety during examination.All subjects answered the Pittsburgh sleep quality index (PSQI) questionnaire, with PSQI ≥ 7 points being enrolled in this study. Selected subjects supplied their demographic characteristics, and underwent blood biochemistry analysis, 24-h urinary catecholamine detection, and 24-h ambulatory blood pressure monitoring (ABPM). Blood biochemical analysis, 24-h urine catecholamine detection, and ABPM were performed on the same day. Fasting blood was drawn from the subjects before 07:00. The subjects proceeded to the laboratory to get containers and preservatives for collection of 24-h urine catecholamines and then underwent ABPM. The next day, at the appointed time, subjects returned for another ABPM and submission of urine specimens.All subjects were investigated by PSQI, which is a standardized subjective questionnaire used to retrospectively rate sleep quality during the past four weeks . This in2 (kg/m2).The demographic characteristics of all selected subjects were collected . The body mass index (BMI) was computed as weight/heightMorning fasting blood was used for the biochemical examination of fasting glucose (FG), triglyceride (TG), total cholesterol (CHO), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), aspartate alanine transaminase (AST), alanine transaminase (ALT), and creatinine (Cr).A noninvasive blood pressure monitor  that can record the corresponding blood pressure and heart rate was used for the ABPM of subjects every 30 min during daytime (06:00–22:00) and every 60 min during nighttime (22:00–06:00). Daytime systolic and diastolic, nocturnal systolic and diastolic, morning surge in systolic and diastolic blood pressure  and the daytime and nocturnal mean heart rates  were recorded. Effective blood pressure and heart rate data should be greater than 85% of the set number; otherwise, they were retested.Subjects collected 24-h urine samples during two periods (day and night) of the ABPM session. Each urine sample container had a preservative to prevent deterioration of urine and was stored in portable coolers. Urinary norepinephrine, epinephrine, and dopamine were tested by high-pressure liquid chromatography with electrochemical detection.2 test was used for categorical variables. Kruskal-Wallis H-test was used to compare blood pressure and catecholamine in the PSQI groups. Spearman’s correlations were used to assess the relationships between MSBP and catecholamine. Multiple linear regression analysis was used to determine the regression equation of MSBP and catecholamine in the Mongolian and Han groups. The SPSS 22.0 system  was used for the statistical analysis, and significance was set at p < 0.05.Data were expressed as mean ± standard deviation (SD) for continuous variables and as number (percentage) for categorical variables. To assess ethnic differences, Mann–Whitney U-test was used for continuous non-normally distributed variables and χn = 115, 56.93%; Mongolians, n = 87, 43.07%) (p < 0.05), but their smoking history, DDBP, N-HR, and N-DA were lower than those of the Han group (p < 0.05)  had dyssomnia. Because of incomplete registration of subjects, liver and kidney dysfunctions, nonstandardized ABPM data, and failed urine catecholamine specimens, 69 patients were excluded, and finally, 202 complete data of hypertensive patients with dyssomnia were included in the study  . The Mon < 0.05) . The chaThere was no statistical difference in the three PSQI degrees between the Mongolian and Han groups in the following aspects: sex, age, residence, nature of work, and movement condition. However, an incidence rate of hypertension of approximately 50% complicated by dyssomnia was found in patients younger than 50 years in these two groups .p < 0.01)  .p < 0.01). Meanwhile, DDBP and MDBP also increased gradually, but there was no statistical difference .In the Han group, with gradual aggravation of dyssomnia, D-NE, D-E, D-DA, N-NE, and N-DA were also increasing and had statistically significant differences among the three PSQI groups   in the Mongolian group, which indicated that when 1 µmol/L D-DA was added, MSBP increased by an average of 5.554 mmHg. In the Han group, the regression equation was y = 141.730 + 8.108x1 + 16.984x2 , which suggested that when 1 μmol/L D-DA was added, MSBP increased by an average of 8.108 mmHg, and when 1 µmol/L D-NE was added, MSBP increased by 16.984 mmHg.Spearman’s correlation of MSBP and D-NE, D-E, D-DA, N-NE, N-E, and N-DA showed that MSBP and D-DA were correlated (Mongolians mainly live in the Inner Mongolia Autonomous Region in China, where Han Chinese and Mongolians account for about 96% of the total population, and these two ethnic groups have different customs and lifestyle . There iAs can be seen in our study, Mongolians had higher BMI, FG, and TG levels than Han Chinese, but a lower history of smoking, which can probably be attributed to their carnivorous diet and low preference for smoking. In our opinion, elevated BMI, FG, and TG levels depend on dietary history to a great extent and on some habits, such as high-salt diets and alcohol consumption, which are both closely associated with dietary history. Smoking, a commonly accepted hypertension-related factor , was lowIn addition, this study showed that even with the same degree of dyssomnia at night, the Mongolian group had lower daytime dysfunction and physical discomfort. We also found that regardless of the level of sleep disorder, the highest incidence of hypertension complicated with dyssomnia was found in patients younger than 50 years in these two groups, which accounted for half of the subjects. Consistent with previous reports, middle-aged, rather than elderly, Chinese with sleep disorder were more likely to be hypertensive than healthy people . SimilarSleep has been recognized as an essential element of cardiovascular control, because sleep disorders are interrelated with increased risk of hypertension, cardiac disease, and stroke . Sleep-rIn our study, with the aggravation of sleep disorder, whether in the Mongolian or Han group, DSBP, DDBP, NSBP, NDBP, MSBP, and MDBP gradually increased as well, which was in agreement with previous studies . FurtherThe sympathetic nervous system is thought to play a crucial role in the regulation of blood pressure during daytime and nighttime. During sleep, the baroreceptor reflex is lower, which reduces the sympathetic activity of the heart and blood vessels, eventually leading to a drop in blood pressure . HoweverPrevious research indicated that the sympathetic nervous system had a significant influence on MSBP . OtherwiOur study has limitations, such as its small sample size. Additionally, we did not use polysomnography to assess sleep architecture. Furthermore, the Mongolian patients in our study may have changed their habits and customs to a certain extent when they lived in the same area as the Han Chinese, and high blood pressure therapy may have been underestimated due to inclusion criteria of the study.Worsened dyssomnia induces higher MSBP and augments sympathetic excitability in Mongolians and Han Chinese. However, Mongolian patients have higher baseline of MSBP but lower daytime dysfunction. They also have higher D-DA but lower N-DA. With the increase in D-DA, the MSBP in Mongolian patients also gradually increased, but their rate of increase is lower than that in Han patients. These ethnic characteristics might provide information when deciding on clinical medication. Further studies on the mechanism of underlying genetic factors and pathological routines in the two ethnicities are needed.10.7717/peerj.3758/supp-1Supplemental Information 1Click here for additional data file.10.7717/peerj.3758/supp-2Supplemental Information 2Click here for additional data file.10.7717/peerj.3758/supp-3Supplemental Information 3Click here for additional data file.10.7717/peerj.3758/supp-4Supplemental Information 4Click here for additional data file.


Following evaluation in a larger population, our approach may be useful in predictive monitoring to identify infants at high risk of developing IVH, offering caregivers more time to adjust intensive care treatment.Despite the decline in mortality rates of extremely preterm infants, intraventricular haemorrhage (IVH) remains common in survivors. The need for resuscitation and cardiorespiratory management, particularly within the first 24 hours of life, are important factors in the incidence and timing of IVH. Variability analyses of heart rate and blood pressure data has demonstrated potential approaches to predictive monitoring. In this study, we investigated the early identification of infants at a high risk of developing IVH, using time series analysis of blood pressure and respiratory data. We also explore approaches to improving model performance, such as the inclusion of multiple variables and signal pre-processing to enhance the results from detrended fluctuation analysis. Of the models we evaluated, the highest area under receiver-operator characteristic curve  achieved was 0.921  by mean diastolic blood pressure and the long-term scaling exponent of pulse interval (PI  Intraventricular Haemorrhage (IVH) remains a serious threat to survival for preterm infants and neurodevelopmental outcomes3α) which can be calculated over different time scales and indicates the corresponding degree of correlation10Retrospective studies of premature infants after the diagnosis of IVH have highlighted altered autonomic functions which are reflected by heart rate variability analysis6et al. has demonstrated associations between a heart rate characteristic index and adverse neurodevelopmental outcomes or white matter damageet al.et al. who reported a sensitivity of 70% and specificity of 79% for their model using heart rate variabilityMore recent work in this area by Fairchild μ) as well as short- and long-term scaling exponents derived from DFA , extracted from five different time series. These were: mean arterial pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP) and pulse interval (PI) series as derived from the arterial blood pressure data, as well as the interbreath intervals (IBI) from the respiratory air flow data.The objective of this study was twofold; firstly, to explore means of improving prediction of IVH from DFA through pre-processing, and secondly, to evaluate the potential of multivariable or multimodal models in the prediction of IVH. The latter objective focused specifically on combinations of blood pressure and respiratory features and inherently involved an evaluation of robustness as applied in a clinical context. The features evaluated comprised of the mean (p < 0.05). This established a foundation for fitting the univariate logistic regression models, though evaluation of their overall performance requires reference to leave-one-out cross-validation (LOOCV) results.The study cohort consisted of 27 low birth-weight (<1500 g) infants, 8 of which subsequently developed IVH. We examined the differences in physiological characteristics and other metadata between the two groups, as summarised in α1 and α2, the short- and long-term scaling exponents, respectively). The Mann-Whitney U-test comparisons of the non-detrended features are shown in p values from the two-sided Mann-Whitney U-test. For example, the AUC scores of the mean DBP model improved from 0.757 to 0.807 subsequent to detrending. A similar increase from 0.757 to 0.771 was also observed for the univariate model of the long-term scaling exponent of DBP (DBP α2), motivating the inclusion of this pre-processing step for the subsequent analyses. The histograms of mean DBP and DBP α1 are also shown in In the initial stages of model fitting, we observed that in certain instances, the arterial blood pressure was subject to non-linear drift. We examined the effect of detrending the arterial blood pressure signal and noted that prediction performance of the fitted logistic regression models could be improved. This detrending affected the linear blood pressure features in particular, which also propagated to the beat-to-beat blood pressure values and thus the scaling exponents derived from DFA (α1) derived from the MAP, SBP and DBP signals as well as the mean DBP yielded the highest AUCs. Respiratory variables were not found to be strongly predictive.We fitted univariate logistic regression models using various linear and DFA features, taking the mean across all qualifying time windows of data for each subject. We evaluated the AUC, the 95% confidence interval  according to the Delong method for determining standard errorα2.It was also observed that model performance could also be improved through combination of the predictors extracted for the univariate models, as shown in p > 0.05) due to high degree of overlap. The ROC curves for a number of these models are displayed in cμ feature is illustrated in Similar results were obtained when evaluating all qualifying windows and with the inclusion of gestational age. Note however that the comparisons with the best performing univariate model , with the exception of the mean DBP and SBP α1 combination.The models were further evaluated using LOOCV, where the probability estimates of each testing sample were used to construct a receiver-operator characteristic (ROC) curve15α2 remained the most predictive combination for IVH  calculated from all qualifying 10 min windows for each subject, with a 30 sec overlap. To evaluate how robust these results were, we examined the effect of including all individual windows rather than the mean feature per subject, of using non-overlapping windows and of including gestational age. The first two cases involved use of a mixed-model allowing for repeated measures while the latter involved the addition of gestational age as a predictor in the existing multivariable models. In all three cases, we found that mean DBP and PI α2 and mean DBP. The results of cross-validation also supported this, with an AUCLOOCV of 0.821 . This model exhibited a sensitivity of >90% at a specificity of 75% which is greater than that reported for the heart rate variability-based model from Tuzcu et al. This study evaluated the blood pressure and respiratory features in discerning infants with IVH from those without. The highest AUC achieved was 0.921 95% CI 0.82, 1.00) by the model fitted with PI 2, 1.00 bα2 significantly different (p < 0.05) between the IVH and non-IVH groups, where the AUC scores for two univariate models fitted with these features increased from 0.757 to 0.807 and 0.771, respectively , breathing termination was not employed and so the potential for adverse patient ventilator interaction was possible. Previous work examining the impact of patient-ventilator asynchrony indicates the significant potential for IVH with this phenomenon18LOOCV of 0.821 , though it did not exhibit a statistically significant improvement on the univariate reference model (mean DBP)21Subsequent to detrending, a further increase in AUC achieved through fitting of bivariate models, where the combination of mean DBP with MAP p > 0.05), despite the relevance of respiration mechanics in the development of IVHIn this study, we found that the addition of respiratory signals did not considerably improve model performance. The fractal dynamics of respiration have been applied in the context of preterm infants23α2 (p < 0.05) across the entire recording in this study. Recent studies have reported a range of observations pertaining to blood pressure and IVH, with the main focus on characterising cerebral perfusion. These include reports of IVH being associated with the elevated diastolic closing marginHypercarbia, high ventilator pressure and patency of the ductus arteriosus are among the factors and events that may influence the fluctuation of blood pressure of preterm infants in the neonatal intensive care unitThis approach may be applied to a clinical context in a manner similar to that shown in We acknowledge that this study was limited by the size of the dataset n = 27) as well as representation of IVH (29.6%), slightly lower than the referenced 35–45% of incidence reported in neonatal care facilities as well α1) of MAP was able to improve model performance. Of the models evaluated, the one that performed consistently in both the initial analysis and cross-validation was fitted with mean DBP and PI α2. In a clinical context, such an approach to signal processing and predictive monitoring could be applied, where a running 10 min window could continuously evaluate the relevant features from qualifying segments of data. Following evaluation in a larger population, these features may be helpful in identifying infants at high-risk of developing IVH, offering caregivers more time to adjust intensive care treatment.In conclusion, this study found mean DBP and short-term scaling exponents from beat-to-beat MAP, DBP and SBP to be useful markers in the prediction of IVH in preterm infants. Non-linear trend removal and the inclusion of additional features such as the short-term scaling exponent , gestational age (<30 weeks) and an absence of significant congenital anomalies. Of the 46 infants enrolled, 27 infants had arterial blood pressure and air flow wave recordings with sufficiently long, artefact-free segments. The average (SD) length of recording was 156 (34) mins. Intra-arterial blood pressure was measured using an umbilical or peripheral arterial catheter, following single-point calibration to atmospheric pressure, collected using a bedside patient monitor , while the raw air flow wave was acquired from a ventilator . Both signals were sampled at 1 kHz and recorded by an analog data acquisition system . Cranial ultrasounds were performed at 2, 12, 24 and 36 hours then daily for the first week. The presence and grade of IVH was determined according to the Papile systemhttps://www.python.org/). Each of the arterial blood pressure and air flow signals were down-sampled to 125 Hz prior to analysis for computational efficiency. This frequency was sufficient for peak detection in both respiratory and blood pressure signals. From the downsampled signals, the following time series were extracted; the beat-to-beat MAP, SBP, DBP and PI, as derived from arterial blood pressure, as well as IBIs derived from air flow data. The signal quality constraints of the air flow data limited extraction of other respiratory features such as peak flow.Signal processing and feature extraction was completed in Python , short- and long-term scaling exponents  from DFA of the five time series  were subsequently extracted.The features used in IVH prediction were extracted from a running 10 min window of arterial blood pressure and air flow data, shifted in 30 sec increments across the total recording length. This approach was adopted to simulate the application of these techniques in a clinical setting, where windows which fulfilled the quality criteria were included for feature extraction. This criteria comprised defined ranges for the allowable number of beats and breaths in a given window (40–250 beats per minute and >20 breaths per minute), a maximum limit for an absence of detected beats (15 sec) as well as an absence of large spikes in the arterial blood pressure signal (range of beat-to-beat SBP <30 mmHg). For each respective time series, outliers were removed by imposing a maximum change of 150% from the previous data point and also a maximum loss of 30% for each window. Features including the mean (Developed by Peng and co-workersy(k) is any given time series, yn(k) the local linear trend for a given segment, and N the number of data points in the series for a given round of analysis. The application of DFA is further explained by Thamrin et al.where α is calculated from the gradient of the line fitted to the Log-Log relationship between n and F(n). In this case, the short-term scaling exponent was defined over 4–15 beats, as aligned with similar observations of this dataThe scaling exponent Statistical analysis was completed using R 3.3.1 softwareHow to cite this article: Huvanandana, J. et al. Prediction of intraventricular haemorrhage in preterm infants using time series analysis of blood pressure and respiratory signals. Sci. Rep.7, 46538; doi: 10.1038/srep46538 (2017).Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


ONH and MTPRR. The relative increase in OPP (78.5 ± 19.8%) was more pronounced than the increase in BF parameters  indicating for an autoregulatory response of the vasculature. The pressure/flow curves show that MTONH, MTPRR, RFVART, RFVVEIN started to increase at OPP levels of 51.2 ± 2.0%, 58.1 ± 2.4%, 45.6 ± 1.9% and 45.6 ± 1.9% above baseline. These data indicate that ONHBF starts to increase at levels of approx. 50% increase in OPP: This is slightly lower than the values we previously reported from LDF data. Signals from the PPR may have input from both, the retina and the choroid, but the relative contribution is unknown. In addition, retinal BF appears to increase at slightly lower OPP values of approximately 45%. LSFG may be used to study ONH autoregulation in diseases such as glaucoma.The aim of the present study was to investigate regulation of blood flow (BF) in the optic nerve head (ONH) and a peripapillary region (PPR) during an isometric exercise-induced increase in ocular perfusion pressure (OPP) using laser speckle flowgraphy (LSFG) in healthy subjects. For this purpose, a total of 27 subjects was included in this study. Mean blur rate in tissue (MT) was measured in the ONH and in a PPR as well as relative flow volume (RFV) in retinal arteries (ART) and veins (VEIN) using LSFG. All participants performed isometric exercise for 6 minutes during which MT and mean arterial pressure were measured every minute. From these data OPP and pressure/flow curves were calculated. Isometric exercise increased OPP, MTTrial Registration: ClinicalTrials.gov NCT02102880 The human optic nerve is a structure with vascular supply from different sources., 2 The nAlterations in optic nerve head (ONH) blood flow have been implicated in the pathogenesis of glaucoma. More specifically ONH ischemia and altered ONH blood flow autoregulation may play a role in the processes that lead to axon damage and subsequent loss of retinal ganglion cells.–5 IndeedDue to the complexity of optic nerve blood supply relatively little is known about regulation of blood flow in this region. To date no technique is capable of measuring all aspects of ONH autoregulation. Most datThe protocol of this prospective study was approved by the Ethics Committee of the Medical University of Vienna and the study was conducted at the Department of Clinical Pharmacology of the Medical University of Vienna. All 27 participating subjects gave written informed consent after the nature and possible consequences of the study had been explained in detail. All subjects finished the study according to the protocol and no dropouts occurred. Study procedures adhered to the guidelines outlined in the Declaration of Helsinki. Subjects were recruited and completed the study between December 2015 and June 2016.All subjects underwent a screening examination during the two weeks prior to the study day that consisted of medical history, physical examination, and a full ophthalmologic examination including best-corrected visual acuity testing with standard Early Treatment of Diabetic Retinopathy Study (ETDRS) charts, slit-lamp examination including indirect funduscopy and measurement of intraocular pressure (IOP) using Goldmann applanation tonometry. In addition, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured with automated oscillometry and a urine pregnancy test was performed in women. According to the study protocol the following exclusion criteria were defined: smoking, ametropia ≥ 6 diopters, contact lens wear, any ocular surgery, and opacities of the optical media  potentially interfering with the measurement procedures. In addition, any other relevant ocular disease or abnormality as well as any clinically relevant illness as judged by the investigators were considered as exclusion. Further exclusion criteria were systemic hypertension, pregnancy or lactation, intake of any medication in the three weeks preceding the study as well as a blood donation in the three weeks prior to the study. In all subjects one eye was randomly selected as the study eye. All subjects abstained from alcohol and stimulating beverages containing xanthine derivatives  for at least 12 hours before the measurements were performed.All measurements were performed after a resting period of at least 20 minutes during which subjects remained in a sitting position. Stability of systemic blood pressure and pulse rate was verified by repeated measurements before the actual study procedures were started.Before isometric exercise was started a baseline measurement using LSFG was performed and systemic blood pressure, pulse rate (PR) and IOP were recorded while subjects were comfortably sitting in a chair. Thereafter, isometric exercise was started and maintained for 6 minutes. This period of isometric exercise consisted of squatting in a position where the upper and the lower legs formed almost a right angle. When the squatting period was started the chair was carefully removed and the subjects were asked to remain in their position, which ensures that the position between the head of the subject and the LSFG instrument does not change. This type of exercise is associated with a pronounced increase in mean arterial blood pressure. Measurement of ONH blood flow, systemic blood pressure and pulse rate was performed every minute throughout these experiments.Systemic blood pressure and pulse rate: Systolic, diastolic and mean arterial pressures  were measured on the upper arm using an automated oscillometric device. PR was automatically recorded from a finger pulse-oxymetric device.Intraocular pressure and ocular perfusion pressure: IOP was measured with a Goldmann applanation tonometer mounted on a slit lamp. Oxybuprocainhydrochloride was used for local anesthesia. OPP in the sitting position was calculated as OPP = 2/3*MAP-IOP , 21 accoLaser Speckle Flowgraphy: In the present study, a commercially available LSFG system  was used. The principles of LSFG were described in detail in recent review papers. , 23 BrieONH, MTPPR). For measurements in retinal vessels an approach to quantify blood flow was used.[Areas of larger vessels and tissue areas containing microvessels are automatically detected using the LSFG software applying a pre-defined threshold for MBR (vessel extraction function). Thus, MBR can be either determined separately for microvascular areas  or for larger vessel . In the present study only MT data were analyzed .For data description %-changes from baseline were calculated. A one-way ANOVA model was used to study the time effect of MT and OPP during squatting. In addition, pressure-flow relationships were calculated as described in more details previously.–33 BriefONH, MTPPR and OPP was highly significant (p < 0.001 each). The % change in MTONH, and MTPPR was, however, small as compared to the % change in OPP, which is indicative for blood flow autoregulation. After 6 minutes the relative increase in OPP was 78.5 ± 19.8%, whereas it was only 18.1 ± 7.7% and 21.1 ± 8.3% for MTONH and MTPPR, respectively. The squatting-induced increase in MTONH and MTPPR was, however, comparable. The change in RFV during isometric exercise is presented in ONH: p = 0.542, MTPPR,: p = 0.617, RFVART: p = 0.788, RFVVEIN, p = 0.424). The magnitude of blood flow change in response to the OPP increase had no association with baseline OPP 27 subjects aged between 18 and 34 years participated in the present study. The baseline data of the participating subjects are presented in ONH a significant increase was seen when OPP levels reached a value of 51.2 ± 2.0% above baseline. For MTPPR the OPP level at which an increase was seen was slightly higher (58.1 ± 2.4%) and this effect was statistically different between the two measurement sites (p = 0.017). Pressure-flow relationship for RFV is presented in Pressure-flow relationship as calculated from OPP and MT data are presented in In the present study we observed that blood flow is autoregulated during isometric exercise both in the ONH and PPR as well as in the retina. Values for upper limit of autoregulation as obtained in the ONH with LSFG are slightly lower than with those obtained using LDF in healthy subjects., 15–17 UThe principle of LSFG is to image the speckle pattern with an exposure time longer than the shortest speckle fluctuation time. With theONH and/or MTPPR show a zero-setoff although we deem this unlikely based on the measurement principle. All these effects may explain to a certain degree the small differences as observed between LSFG and LDF values during isometric exercise.Whereas most papers dealing with LSFG in the eye claim that the velocity is measured comparison has been done mainly with technology that measures perfusion. Indeed, LSFG has been validated for measurement of ONH blood flow using hydrogen clearance, 42, 43 Measurement of RFV to quantify blood flow in the retinal vasculature based on LSFG is a relatively new approach. Previous2 levels.[Only few studies have so far used LSFG to study autoregulation of ocular blood flow during a change in blood pressure in humans. In response to changes in posture differences between choroidal and ONH blood flow were reported. During b2 levels.–58 The t2 levels. Generall2 levels.–62LSFG was previously employed to study autoregulation in several animal studies. ONH blood flow autoregulation was investigated in rabbits, 64 duriThe data of the present study may also be relevant for validation of blood flow measurements based on either Doppler optical coherence tomography (OCT) or OCT angiography. In larger vessels techniques have been developed to study retinal blood flow based on either double circular scans around the ONH,, 72 multSome limitations of the present study need to be considered. Human validation experiments using LSFG were so far only done in Japanese populations. As such experience with the system in subjects of European descent is very limited to date., 84 InteIn conclusion we present data on the response of MT signal in the ONH and PPR during isometric exercise using LSFG. Data in the ONH resemble what has previously been shown using LDF, although values obtained for upper limit of autoregulation are slightly lower. In the PPR both retinal and choroidal circulation may contribute to the signal, but the relative ratio is unknown. LSFG is a clinically applicable tool to study ONH autoregulation in humans.S1 Data Set(XLSX)Click here for additional data file.


It is well known that atrophic renal changes are associated with chronic kidney disease (CKD) progression, but conventional diagnostic imaging methods such as noncontrast-enhanced computed tomography and magnetic resonance imaging (MRI) have been insufficient for precisely assessing kidney function because they cannot clearly distinguish between the medulla and cortex. Hence, here we used noncontrast-enhanced steady-state free precession (SSFP) MRI with a spatially selective inversion recovery (IR) pulse to improve visibility for renal corticomedullary differentiation and evaluated the association between morphological parameters and kidney function in patients with CKD.Kidney corticomedullary contrast ratio, cortical and medullary areas, and minimal cortical thickness of 107 patients with CKD G1–G5 were measured using SSFP MRI with a spatially selective IR pulse and the association between these morphological parameters and kidney function were evaluated.Corticomedullary contrast ratio was significantly improved on SSFP MRI compared with conventional in-phase T1-weighted gradient-echo MRI and positively correlated with estimated glomerular filtration ratio (eGFR), raw eGFR, and 24-h creatinine clearance. The medullary and cortical areas and minimal cortical thickness also positively correlated with those of kidney functional markers and the age. In patients with CKD and diabetes mellitus (DM), the correlation coefficients between raw eGFR and morphological parameters were higher than those in patients without DM, while minimal cortical thickness was larger in CKD patients with DM with a raw eGFR ≥ 45 mL/min.Kidney morphological parameters measured with SSFP MRI were clearly correlated with kidney function in patients with CKD, including those with advanced kidney dysfunction. In chronic kidney disease (CKD), kidney dysfunction progression correlates with reduced bipolar kidney length, kidney volume, and cortical thickness . Kidney Among these diagnostic imaging methods, US has often been used in the initial evaluation of CKD patients for its convenience. Measurement of the renal cortical thickness using US was reported to be valuable for estimating residual kidney function in CKD patients and predicting their prognosis . However2 (range 36.1–125.9 mL/min/1.73 m2), while only 16 of 65 participants had an eGFR < 60.0 mL/min/1.73 m2 −1.094 × [age (years)]−0.287 × 0.739  [CKD was defined as an eGFR < 60 mL/min/1.73 midelines , 10. The female) . Body su female)  or on thAll MRI examinations for SSFP images were performed with a 1.5-T unit  using the Atlas SPEEDER™ body coil. The procedure for the MRI imaging was described in the previous study by Kanki et al. . Imagingcortex) and renal medulla (SImedulla) as (SIcortex/SImedulla). Additionally, the physicians measured and recorded the minimal cortical thicknesses and coronal sectional areas of the cortex and medulla as shown in Fig. All images were reviewed on a clinical picture archiving and communication system workstation monitor  by two physicians blinded to the subjects’ clinical information. The physicians selected the larger of the right or left kidney as the measuring object and drew operator-defined regions of interest (ROI) within the cortex and medulla in the target kidney to measure the signal intensity (SI) values of each segment by consensus. ROI measurements were also performed on the IP images. The corticomedullary contrast ratio was calculated from SI values of the renal cortex . Value of P < 0.05 was considered statistically significant.Corticomedullary contrast ratios between SSFP and IP images were compared using the Wilcoxon signed-rank test. The Pearson product-moment correlation coefficient was used to investigate the correlation between two parameters in each case. Simple associations were performed using unpaired 2 (range 8.4–130.2), 53.7 ± 25.4 mL/min (range 7.6–118.6), and 67.6 ± 31.7 mL/min (range 4.0–179.0), respectively. The numbers and percentages of patients with each CKD stage were as follows: CKD G1, four (3.7%); G2, 35 (32.7%); G3, 48 (44.9%); G4, 13 (12.1%); G5, seven (6.5%). Anti-hypertensive agents were used in 93 (86.9%) patients, and 73 patients (68.2%) were treated with renin–angiotensin system (RAS) inhibitors, whereas 14 patients (13.1%) were treated with diuretics. Renal corticomedullary differentiation was clearly depicted in SSFP images using standard TI, but not in conventional IP images at even 3.0-T unit MRI  and non-DM (n = 89) groups to evaluate the association between CKD etiology and kidney morphological parameters. Table Finally, we divided the CKD patients into DM n = 1 and non-Our study revealed that renal corticomedullary differentiation was more clearly depicted in SSFP MRI with a spatially selective IR pulse than in conventional IP images, even in patients with CKD G4 and G5. This new imaging technique enabled us to measure the thickness or area of the each renal segment without contrast agents in patients with CKD and evaluate renal cortex atrophy.It has been reported that minimal renal cortical thickness has a positive correlation with renal function because nephrons are mainly located in the renal cortex , but theWe also confirmed that morphological parameters demonstrated negative correlation with age Fig. . In a prOn the contrary, the measured morphological parameters had no significant correlations with the urine protein level. This fact may indicate that decreased morphological values reflect chronic atrophic changes but not ongoing glomerular or tubular damage expressed as elevated urine protein level. Morphological changes caused by tubular atrophy and following tubulointerstitial fibrosis would have been valuable indicators for the assessment of residual kidney function and reversibility in progressive chronic kidney disease . We are We also compared the morphological parameters of CKD patients with and without DM and demonstrated that kidney morphological parameters correlated with raw eGFR better in the CKD patients with DM than in those without DM Fig. . We surmIn the present study, raw eGFR demonstrated the highest correlation coefficient with each of the three kidney functional parameters evaluated in the study. Twenty-four-hour Ccr usually overestimates kidney function due to the tubular secretion of creatinine, especially in patients with advanced CKD and decreased glomerular filtration . The eGFThe limitation of this study was that the categorization of patients with CKD with or without DM was not based on the definite diagnosis by kidney biopsy but was clinically different by the presence of DM. The definite histopathological diagnosis by kidney biopsy would be essential to reliably utilize these kidney morphological parameters for the differential diagnosis of the CKD origin using non-invasive SSFP MRI. Another limitation of this study was that this study was performed with 1.5-T unit MRI. Even though 1.5-T unit MRI is mainly used in Japan, 3.0-T unit MRI would be becoming standard. SSFP MRI examination with 3.0-T unit should be conducted in the future study.In conclusion, noncontrast-enhanced SSFP MRI with a spatially selective IR pulse can improve the visibility of renal corticomedullary differentiation even in patients with advanced CKD patients. This new MRI method could detect early morphological changes in patients with CKD and would be useful for differentiating CKD etiologies in the future.


Tacrolimus is the main immunosuppressive agent in many kidney transplant protocols with an initial recommended daily dose of 0.2 mg/kg of ideal body weight (IBW). However, due to the high inter- and intra-patient variability in its pharmacokinetics, the required tacrolimus doses may differ markedly from patient to patient.To assess the required tacrolimus dose to achieve the desired whole blood concentration within the first three weeks after kidney transplantation among Iranian patients.This cross-sectional study was performed at kidney transplantation ward of Imam Khomeini Hospital Complex where almost all patients receive thymoglobulin induction therapy and a calcineurin inhibitor, mainly tacrolimus, plus mycophenolate, and prednisolone as maintenance immnosuppressive drugs with the target tacrolimus whole blood concentration of 8–12 ng/mL for the first month after transplantation.The mean±SD administered daily dose of tacrolimus during the first three weeks after transplantation was 0.085±0.024 mg/kg of IBW that resulted in a mean±SD whole blood concentration of 10.34±5.44 ng/mL. The required mean±SD dose of the drug to achieve the desired whole blood level of 8–10 ng/mL was 0.08±0.02 mg/kg. Only 27.4% of the assessed tacrolimus blood levels were within the desired range. Compared with males, females needed 19% more daily dose of tacrolimus to reach similar whole blood levels. Tacrolimus blood levels were significantly correlated with daily tacrolimus doses  and patients’ age .It seems that Iranian kidney transplant recipients need lower daily doses of tacrolimus to achieve the desired whole blood levels; compared with males, females need a higher dose.  Calcineurin inhibitors, cyclosporine and tacrolimus, are the cornerstones of immunosuppressive therapy in kidney transplant recipients, especially within the first three months after transplantation. Compared to cyclosporine-based immunosuppressive regimens, tacrolimus-containing regimens accompany less acute rejection episodes . Due to Variability in tacrolimus exposure is a known contributing factor to long-term graft loss . TacroliThe objective of this study was to assess the required tacrolimus doses to achieve the desired whole blood concentration within the first three weeks after kidney transplantation among Iranian patients.SettingThis cross-sectional study was conducted from September 2013 to December 2014 at Kidney Transplant Ward of Imam Khomeini Hospital Complex affiliated to Tehran University of Medical Sciences, Tehran, Iran. Immunosuppressive Regimen and Sampling® . In our center, the target tacrolimus whole blood concentration is 8–12 ng/mL within the first month after transplantation. All patients receive gancicloir/valganciclovir, cotrimoxazole, and clotrimazole as their routine prophylaxis against viral infections, Pneumocystis jiroveci pneumonia, and fungal infections. Patients are advised to receive their tacrolimus doses 2 hours after breakfast and dinner at 9:00 am and 9:00 pm. Consumption of foods and fruits that have considerable interactions with tacrolimus  are prohibited. Tacrolimus whole trough blood concentrations are assessed using monoclonal radioimmunoassay on samples taken before morning tacrolimus doses in a steady state.In our center almost all patients receive thymoglobulin induction therapy starting one hour before transplantation. Intravenous methyl-prednisolone is administered at doses of 500 mg, 250 mg, and 125 mg, respectively for day 1, 2, and 3 of transplantation; it is followed by 1 mg/kg/day oral prednisolone with rapid taper down to 5 mg/day after one month of kidney transplantation. A calcineurin inhibitor, mainly tacrolimus, plus mycophenolate and prednisolone are maintenance immunosuppressive drugs in this center. Tacrolimus is usually started with half needed daily dose during thymoglobulin induction and increased to a full dose 24 hours before suspected thymoglobulin termination time. All patients received PrografThe study protocol was approved by Local Ethics Committee of Tehran University of Medical Sciences. All patients signed informed consent forms. Data Analysis® for Windows® ver 18. Normal distribution of data was assessed using one-sample Kolmogorov-Smirnov test. The required tacrolimus doses to achieve the desired whole blood concentration in patients were assessed using descriptive analysis and compared between males and females by Student’s t test for independent samples. Pearson’s or Spearman’s correlation coefficients were used to assess correlations between quantitative variables. A p value <0.05 was considered statistically significant.Data were analyzed by SPSSi.e., almost two tacrolimus blood level per patient. The mean±SD administered tacrolimus daily dose during the first three weeks after transplantation was 0.085±0.024 (range 0.024–0.154) mg/kg of IBW that resulted in a mean±SD whole blood concentration of 10.34±5.44 (range 2–30) ng/mL. Compared with males, females needed 19% more daily doses of tacrolimus to reach similar whole blood levels  with a mean±SD age of 40.0±13.8 years received tacrolimus as their maintenance immunosuppressant and were included in this analysis. One-hundred and six whole blood concentrations were obtained during patients’ hospitalization after operation up to three weeks after transplantation, d levels .Considering whole blood tacrolimus concentrations of 8 to 12 ng/mL as the target blood level within the first month after kidney transplantation in this center, only 29 assessed tacrolimus blood levels (27.4% of tacrolimus blood levels) were within the desired range while 44 levels (41.5%) were lower and 33 (31.1%) were higher than the desired values. Daily tacrolimus doses that resulted in lower than the desired, and higher than the desired tacrolimus blood concentrations are shown in During this survey, the only concomitant administered drug with reported drug interaction with tacrolimus was diltiazem that is an inhibitor for CYP 450-3A4/3A5 and P-glycoprotein , 8. EighTacrolimus blood level was significantly correlated with the daily tacrolimus dose based on mg/kg of IBW  and patients’ age . Tacrolimus daily dose had a significant (p=0.037) negative correlation (r=0.203) with diltiazem daily dose.This study assessed the required maintenance dose of tacrolimus among Iranian kidney transplant recipients. The results showed that the mean tacrolimus daily dose to achieve the desired whole blood concentrations of 8–12 ng/mL within the first three weeks after kidney transplantation among Iranian patients was about 0.08 mg/kg of IBW that is lower than that recommended by the manufacturer and international references . A recenAbout one-third 31%) of our patients had higher than desired tacrolimus whole blood levels. These patients were administered significantly higher doses of tacrolimus compared with patients who achieved the desired or lower than the desired tacrolimus blood levels . The mai1% of ourThis study suffers some limitations. The main limitation is the single-center nature of this study. Because different kidney transplant centers use different immunosuppression protocols that may interact with tacrolimus pharmacokinetics, data from other Iranian kidney transplant centers are required to confirm the proposed required daily dose of tacrolimus in these patients. Additionally, due to limited sample size, we were unable to compare different Iranian ethnicities  in terms of the required doses of tacrolimus. Larger studies are needed to distinguish possible differences between these ethnicities. It seems that to achieve the desired whole blood concentrations, Iranian kidney transplant recipients need a lower daily dose of tacrolimus compared to those recommended by manufacturer and international references. Compared with males, females need a higher tacrolimus dose.