Introduction Sleep apnea is classified as a sleep disorder characterized by a complete cessation, known as apneas, or impairment (partial cessation) of breathing, known as hypopneas. During obstructive sleep apnea (OSA), the airways become blocked, mostly due to the collapsing of the throat muscles or increased adipose tissue surrounding the airway. Apneas/hypopneas indirectly lead to the over-activity of the sympathetic nervous system. These events lead to a very interrupted sleep pattern and architecture. The most common symptoms of OSA are excessive daytime sleepiness, morning headaches and concentration problems. OSA may lead to various other disorders such as hypertension, diabetes mellitus, depression and heart failure when not treated. Limited research on OSA has been done in developing countries such as South Africa due to limited resources, funding and/or facilities. It is therefore critical that this disorder be studied in specific populations to establish more accurate parameters and normative values for clinicians to diagnose as well as treat the disorder. Methods A total of 160 patients that had suspected OSA, were referred to a private practice of clinical neurophysiology (B. Tjallinks) by their respective physicians. They were subsequently admitted at a sleep laboratory, based in Pretoria, for a single night to test for the disorder. Full polysomnography (PSG) was used to monitor the patients’ sleep. Various information such as the desaturation index, amount of obstructive sleep apneas/hypopneas, sleep architecture and baseline oxygen-haemoglobin saturation were interpreted from the test. This information was then used to assess the severity of the disorder in the patients. The PSG data were then compared with other aspects of the patient such as BMI, medical history and questionnaires. Results The oxygen deprivation state (ODS) and the apnea-hyponea index (AHI) were compared with many variables tested during the polysomnogram and it was found that ODS correlated stronger with the majority. The most important independent variables to test for hypoxia in this study was baseline SpO2, minimum SpO2, average desaturation and average duration of events. AHI was correlated (Pearson correlation coefficients) with the baseline SpO2 (-0.4463, weak), minimum SpO2 (-0.4716, weak), average desaturation (0.6701, moderate) and average duration of events (0.3262, weak). ODS was correlated (Pearson correlation coefficients) with the baseline SpO2 (-0.4524, weak), minimum SpO2 (-0.4820, weak), average desaturation (0.7524, strong) and average duration of events (0.5740, moderate). The ODS correlated stronger, even though mildly in some parameters, with all critical variables tested for the severity of hypoxic crisis in OSA. Conclusion Based on all the study objectives and results, the ODS was able to correlate stronger with the critical polysomnography variables for hypoxia and thus has proven to be a better estimate of hypoxic crisis in the severity of obstructive sleep apnea. A raw grading scale was developed based on the results of this study and are as follows: Normal (ODS ≤ 2.0%), mild (2.0% < ODS ≤ 7.7%), moderate (7.7% < ODS ≤ 17.9%) and severe (ODS > 17.9%). / Thesis (PhD (Human Physiology))--University of Pretoria, 2020. / Physiology / PhD (Human Physiology) / Restricted

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No abstract available. / Thesis (M.Sc.)-University of Durban-Westville, 1990.

This study was designed to examine two premises: that the morphological "severity" of duodenal ulcers (DU) may influence the incidence of drug mediated healing and the morphological "quality" of healing after curative therapy may influence t he duration of remission. Biopsies taken at endoscopy from five healthy volunteers and from 84 patients suffering from DU were examined by light and electron microscopy. The endoscopic and morphological appearance of the mucosa within 8mm of the DU or scar, before and up to 1 year after therapy with either sucralfate, cimetidine, pirenzipine or misoprostol are described. Irrespective of the mode of therapy or whether the biopsies were from normal, juxta-DU or scar mucosa, specimens could be divided into 2 primary morphological classes: gastric metaplastic and non-metaplastic. Based on the degree of metaplastic differentiation and nonmetaplastic degeneration, these classes were further divided into 4 sub-classes. When correlated with the incidence of healing and duration of remission, metaplasia was generally found to be a positive and degenerative nonmetaplasia a negative prognostic criterion. Scores were awarded to primary morphological criteria and weighted to give high total s to favourable (metaplastic) and low totals to non-favourable (degenerative non-metaplastic) prognostic features. The sum of scores expressed as a percentage was termed the morphological index. This proved useful as a means of correlating mucosal morphology with DU healing and duration of remission. It also facilitated comparison of morphology within and between groups of patients before and after each drug regimen. The results showed that the morphological appearance of the ulcerative mucosa influenced healing and remission outcome. Discriminant analysis was applied to the numeric data that described the juxta-DU (group 1) and scar (group 2) morphology of patients treated with cimetidine in 2 studies. Separation between healed and not healed DU was achieved in 92% of group 1 and 100% (remission - more or less than 6 months) of group 2. When applied to the juxta-DU data from patients treated with cimetidine in a third study, the formulae predicted correctly in 88% of cases. In addition to predicting outcome, the formulae were used as standards to accommodate for natural variations in the prognosis of individual DU of patients enrolled for comparative drug studies. These data show that morphological analysis may be usefully employed in duodenal ulcer therapy. / Thesis (Ph.D.)-University of Natal, Durban, 1994.

Many scientific studies have considered physiological aspects of swimming, but largely in the areas of endurance or strength and power. This thesis includes six studies that attempt to provide more information about the metabolic responses to single and repeated sprint swimming and the physiological mechanisms behind the limitation to sprint swimming performance. The first experimental chapter describes the metabolic responses to single and repeated sprinting in male and female swimmers. Peak blood lactate (male 18.7 and female 14.4 mmol 1-1;P <0.01) and ammonia (male 232.0 and female 154.3 ýtmol 1-1;P <0.05) values following repeated swimming (8 x 50 yards) were almost double those measured during a single 50 yards sprint and were significantly higher in males than females. It is likely that differences in body dimensions and composition between male and female swimmers account for the majority of the -12% performance differences and higher metabolic response in males than females. Energy contribution to single and repeated tethered swimming sprints was examined in chapter V. Determination of energy contribution by an accumulated oxygen deficit test found estimated anaerobic contribution of -67% in 30 s sprinting and -74%, -53%, -51% and -47% during four 30 s sprint bouts. These were much lower than values estimated previously and recommended to coaches and swimmers in popular swimming texts. Energy contribution to 55 s maximal tethered swimming in chapter VI found anaerobic contributions of -30-40%. Metabolic responses to Controlled frequency breathing (CFB) have been studied previously in endurance swimming, but not in splint swimming (chapter VI). There was increased hypercapnia, but no significant reduction in performance during 55 s maximal sprint tethered swimming between self-selected breathing and breathing every 10 strokes. Differences in metabolic responses (higher extraction of oxygen from inspired air and lower ventilation, oxygen consumption, carbon dioxide production and respiratory exchange ratio) suggest a greater efficiency during swimming with CFB. Swimmers who can train to overcome the urge to breath should not compromise performance, but benefit from avoiding an increase in drag resistance while turning the head to breath. Active recovery following intense swimming has been suggested to increase the speed of recovery and improve subsequent performance. Chapter VII illustrates that the timing and intensity of active recovery is crucial when prescribing repeated sets of repeated sprint training. Lower blood lactate was matched by a tendency for poorer performance in the trial using active recovery between repetitions. This demonstrates that the blood lactate concentration does not reflect the metabolic state of the muscle and therefore the ability to perform subsequent sprint swims. Chapters VIII and IX consider the effects of creatine supplementation on sprint swimming. No differences in single sprint swimming performance were found, but creatine supplementation improve times in a typical training set of 8x 50 yards by -4 s. Faster times recorded in the creatine group support the hypothesis that increasing resting levels of creatine and phosphocreatine will enhance recovery during repeated sprints. Supplementing with 3g creatine day-' for 22-27 weeks had no additional benefit to race performance than just 'loading' before the training period and immediately prior to the major swimming race of the year. It is likely that any enhanced training adaptation would have to be from creatine supplementation allowing swimmers to perform more training rather than just supplementation per se. The studies in this thesis describe the physiological and metabolic responses of elite male and female swimmers to single and repeated sprint swimming in detail for the first time. By manipulating breathing frequency during sprinting, metabolism altered but without compromising performance. Active recovery was successful in reducing blood lactate concentration, but performance was poorer. The blood metabolite and respiratory response to sprint training following interventions of this type allow us to determine the mechanisms behind the limitation to swimming performance. Creatine supplementation enhances repeated sprint swimming performance, but not training for success in competition. Results of this thesis suggest that phosphocreatine availability or energy supply are not limitations to sprint swimming training performance.

Dissertation (Ph.D. in Modeling, Virtual Environments, and Simulation)--Naval Postgraduate School, June 2009. / Dissertation supervisor: McCauley, Michael E. "June 2009." Description based on title screen as viewed on July 14, 2009. DTIC Identifiers: Flight simulator, virtual environment, human physiology, transfer of training, human performance, stress coping, stress exposure training. Author(s) subject terms: Stress, training, transfer of training, flight simulator, virtual environment, human physiology, human performance, strain, stress coping, stress exposure training. Includes bibliographical references (p. 163-170). Also available in print.

Thesis (Ph.D.)--Brown University, 2005. / Vita. Thesis advisor: Michael Paradiso. Includes bibliographical references (leaves 40-50, 135-140, 198-201, 258-160, 274-275). Also available online.

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