The mechanisms which cause post exercise hypotension (a phenomenon of prolonged, decreased resting blood pressure following physical exertion) are unknown. Atrial natriuretic peptide (ANP) is known to exert potent natriuretic and vasodilatory properties which play an integral role in fluid regulation and blood pressure control. Elevations in plasma ANP concentration have been shown to occur during dynamic endurance exercise, and to a lesser extent during heavy resistance exercise. The purposes of this investigation were to 1) examine the effects of resistance and endurance exercise on the release of ANP, 2) examine the effects of resistance and endurance exercise on post exercise blood pressure and 3) evaluate the potential correlations of ANP release with any observed changes. Thirteen males (24.3±2.4yrs.) performed 15 min of unilateral leg press (65% 1 RM) and, one week later ~15 min (based on summed cardiac cycles of the resistance trial) of cycle ergometry (65% V0₂ ₚₑₐₖ). Blood pressure was measured using an intra-arterial catheter during exercise and for 1 h post exercise. Arterial blood was drawn at rest, 5, 10 and 15 min of exercise and 1 1/2, 3, 5, 10, 15, 30, 45 and 60 min post exercise for subsequent analysis of hematocrit and αANP. No differences occurred in blood pressure responses between trials, but significant decrements in blood pressure occurred post exercise compared to pre exercise. Systolic pressure was ~20mmHg lower from 10 min post exercise until measurements terminated at 60 min post exercise. Mean pressure was also significantly attenuated by ~7 mmHg from 30 min post exercise onwards. Only slight (non significant) elevations in αANP concentration were detected immediately following exercise with no elevation present by 5 min post exercise. It was concluded that post exercise hypotension occurs with acute bouts of either resistance or endurance exercise and that αANP does not appear to be directly related to this hypotensive effect. This study was supported by the Natural Sciences and Engineering Research Council of Canada / Thesis / Master of Science (MSc)

Reproduction de : Thèse d'exercice : Médecine : Nancy 1 : 2006. / Titre provenant de l'écran-titre.

published_or_final_version / Dentistry / Master / Master of Dental Surgery

A growing literature suggests that training in relaxation or meditation results in significant reductions in blood pressure in hypertensive patients. The present study was designed to assess the efficacy of a combination relaxation and meditation training program structured by the author and previously used in treatment of a broad spectrum of anxiety-related clinical problems of either a medical (somatic) or a psychological (cognitive and emotional) nature. The 20 subjects were a heterogeneous clinical group of veterans with mild hypertension who were seen at the Tucson Veterans Administration Medical Center. Volunteers were randomly assigned to either (I) an education/cognition group, (II) a three-treatment relaxation/meditation group, or (III) a six-treatment relaxation/meditation group. Blood pressure, anxiety, and stress were measured at regular intervals during training and follow up. All groups were trained over a six-week period. Both relaxation/meditation groups were taught the same skills; only the schedules for training were varied. The educational group, conceived as a control for therapist attention, was, in fact, a cognitive treatment group. Statistically significant reductions in both systolic and diastolic blood pressure were found over time in all groups, while no difference in blood pressure reductions was found among the groups. Anxiety scores increased over time, and no correlation was found between subjective anxiety and objective blood pressure measures. Means of both systolic and diastolic blood pressure were lower at times when subjects reported no stress. Results of this study tend to support those of previous studies, finding statistically significant reductions in systolic and diastolic blood pressure over time in two groups of hypertensive subjects trained in relaxation and meditation techniques. No difference was found, moreover, between these groups and an education/cognition group, suggesting that group techniques, in either significant lowering of blood pressure. This finding lends support to a multiprocess theory which suggests that all treatments have multiple effects.

No description available.

A research report submitted to the Faculty of Medicine, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Medicine in Applied Physiology. Johannesburg, 1997. / A post-exercise reduction in blood pressure (BP) may be the primary reason that athletes suffer from exerclse-assoclated collapse (EAC) at the end ot ultra-endurance running ever.s. Plasma volume decreases, possibly caused by dehydration, may be the cause of the decrease til blood pressure, In order to determine whether there is a correlation between plasma volume changes and the post-exercise BP drop, this study evaluated alterations in pre- and post-race blood pressures and changes in blood and plasma volumes, It found that compared to resting values, systolic, dlastollc and mean arterial blood pressures (mmHg) fell significantly from 119 ± 4, mean ± standard deviation, 74 ± 8, and 88 ± 5 respectively to '106 ± 14, 62 ± 12 and 77 ± 10 (ps 0,05), whereas pulse pressure failed to change, Compared to pre-race values, plasma and blood volume were found not to have changed significantly, During the race plasma urea (U) and creatinine (C) concentrations increased significantly, whereas body mass and body mass index both fell significantly. Haernatocrlt, haemoglobin, mean cell volume, red blood cell number, mean cell haemoglobin concentration, the mean cell haemoglobin, plasma sodium, potassium, chloride and protein concentrations, the U:C ratio and osmolality remained constant. There were no significClnt correlations between changes in plasma or blood volume and changes in blood pressure, These data support the Idea that a post-race decrease in blood pressure does not result primarily from an intravascular fluid loss, It is likely therefore that athletes who collapse at the end of ultraendurance races due to EAC do so as a result of 'post-exercise hypotension' secondary to venous pooling, and not as a result of a reduction in plasma volume, / MT2017

MS(Med), Child Health: Neurodevelopment, Faculty of Health Sciences, University of the Witwatersrand / Background: ELBW preterm infants are at extremely high risk for adverse neurodevelopmental (ND) outcome. Systemic hypotension is an important peri-natal risk factor in neurodevelopmental outcome. Numerous other risk factors exist for adverse neurodevelopmental outcome. Aim: To assess whether early mean systemic blood pressure and other risk factors contribute to poor ND outcome in ELBW preterm infants managed at Panorama Medi-Clinic. Methods: A retrospective, analytical study using data obtained from 2003 to 2008. Data from the Vermont Oxford Network database of which Panorama Medi-Clinic is a member was used to select a cohort of inborn, surviving infants weighing ≤ 1000g or ≤ 30 weeks gestational age. Early mean systemic BP records were obtained from nursing records. ND data was obtained from the neurodevelopmental clinic or routine follow up clinics notes. Infants with major defects at birth were excluded. The cohort was classified according to their general developmental quotient and whether or not they had signs of cerebral palsy into a normal or abnormal neurodevelopmental group. All patients remained completely anonymous and ethical clearance was obtained from the ethics committee at Panorama Medi- Clinic. P a g e | VII Results: 82 infants were eligible. 78 were entered the study. 4 were lost to follow up. Average birth weight was 782.1g ± 148.23. Average gestational age was 27.06w ± 1.32. Normal neurodevelopmental outcome was found in 64(82%). An abnormal neurodevelopmental outcome was found in 14(18%). No statistically significant difference was found by logistical regression when mean systemic blood was compared between normal and abnormal neurodevelopmental groups. If a cut off BP of <30 mm Hg, or inotropic agents were administered, no statistical difference was found between the normal and abnormal groups. Severe grades of IVH, ROP, post-natal steroids, and chronic lung disease, and gastro-intestinal perforation, were identified as risk factor of adverse outcome

by Chun Yiu-to. / Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 72-79.

Thesis (M. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Orthostatic vasovagal syncope is the sudden loss of consciousness resulting from a temporary impairment of cerebral blood flow, within approximately an hour of standing. Patients who suffer from this problem have "vasovagal syndrome". The purpose of this thesis was to devise a method to detect the syndrome following the assumption of upright position. Data from 106 syncopal patients undergoing head-up tilt table testing (HUT) were acquired, including electrical activity of the heart (electrocardiogram), blood pressure, oxygen saturation, and cerebral perfusion parameters from near-infrared spectroscopy (NIRS). The data set was examined with the aim of generating automatic diagnoses. Comparison of the rate-pressure product (blood pressure multiplied by heart rate) during the time of syncope with a recommended threshold, in addition to comparison with monitoring the fall of systolic blood pressure during prolonged tilt, yielded an 84% accuracy rate for vasovagal syndrome. The thesis reviewed the techniques used on the aforementioned time series by previous researchers, emphasising the concepts underlying "time-frequency analysis", a method for analysing nonstationary signals. Since even healthy patients experience time-varying frequency information in their haemodynamics, a transform known as the Smoothed Pseudo-Wigner Ville Distribution (SPWVD) is well suited to their analysis. This distribution was applied to RR tachograms, plots of heart period against time. After the smoothing parameters of the SPWVD were chosen based on artificial data, the optimised transform was then applied to a second artificial tachogram to calculate the LF/HF (low- to high-frequency) ratio, an indicator of heart rate variability. The computed LF/HF ratio tracked the expected value within an error margin of 3.6%. Finally, by applying the same transform to clinical data, it was proved to offer better resolution than an alternative known as the Lomb periodogram. Classical techniques from the literature predicting vasovagal syncope were found to fail on the current data set: out of 29 tests, only two yielded statistically significant differences between the two patient groups. These were compared with the author's time-frequency analysis of RR tachograms, linear regression of heart rate, and examination of NIRS oscillations and changes on tilt. Of these, the ICFV during time period P3 was found to perform best (negative predictive value: 0.86). A linear classifier was used to combine the best four predictors; it achieved an overall accuracy of 0.88. Following the data-driven approach, an analytical modelling approach was undertaken. In order to define an appropriate model that traded off simplicity with comprehensiveness, the mechanisms of vasovagal syncope were reviewed. A model of orthostasis was developed, validated, and used toward parameter estimation from patient data. Three parameters (baroreceptor operating point, cardiac effectiveness, and baroreflex gain) were gleaned from the supine baseline recording to "normalise" the model for a given patient, before four new parameters (sympathetic and parasympathetic gains at the sino-atrial node, peripheral vasoconstriction gain, and total blood volume) were estimated from the data collected in the upright position. The expectation was that this approach would improve feature extraction (and hence prediction accuracy) as well as the clinical interpretation of the results. However, the modelling approach was found to offer no significant improvement upon the data-driven signal processing results: a linear classifier on the four post-tilt parameters yielded a negative predictive value of just 0.69. This result may have been due to inaccuracies in the time series data owing to instrumentation error. It is also possible that the modelling approach was not able to provide the quality of feature extraction necessary for predicting vasovagal syncope in the elderly. Finally, methods to predict syncope during mid- to late HUT were examined. Using information derived from heart rate and baroreflex sensitivity, a technique was developed to ease patient comfort by terminating the test approximately 2 minutes before syncope was expected to occur.