No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Obstructive sleep apnea syndrome (OSAS) is a serious disorder that affects an estimated 24% of middle-age males, and 9% of middle-aged females. In addition, a large portion of individuals with OSAS go undiagnosed. OSAS is associated with several adverse health problems, including the metabolic syndrome. Therefore, there is a clear need to identify new methods for assessing OSAS risk. The exercise test has been used effectively as a diagnostic and prognostic tool for those at high risk for cardiovascular disease and hypertension. Research into the cardiopulmonary responses to exercise testing in young adult men with OSAS has not been examined. Objectives: The objectives of this study were to: 1) evaluate whether OSAS is characterized by exaggerated ventilatory responses to ramp exercise testing, with a secondary aim to evaluate if variations in serum leptin concentration might exert a regulatory in ventilatory responses during exercise; 2) To evaluate whether autonomic control of the cardiovascular response during exercise is distorted by OSAS in young overweight men, as manifested by a blunting of heart rate and exaggeration of blood pressure responses.; 3) To explore whether various simple clinical measures and response patterns from graded exercise testing might serve to discriminate between young men with and without OSAS. Methods: For objectives one and two, 14 obese men with OSAS [age = 22.4 ± 2.8; body mass index (BMI) = 32.0 ± 3.7; apnea-hypopnea index (AHI) = 22.7 ± 18.5], 16 obese men without OSAS (age = 21.4 ± 2.6; BMI = 31.4 ± 3.7), and 14 normal weight subjects (objective 2) (age = 21.4 ± 2.1; BMI = 22.0 ± 1.3) were recruited. For objective three, 91 men (age = 21.6 ± 2.8; AHI range = 0.6 – 60.5; BMI range = 19.0 – 43.9) were recruited. Subjects completed a ramp cycle ergometer exercise test, and a fasting blood sample was obtained to measure plasma leptin and blood lipid levels. Repeated measures ANOVA and stepwise linear regression was used to examine objectives 1 and 2. For objective 3, stepwise linear regression and receiver operator curve (ROC) analysis was utilized. Results: Ventilation (VE), the ventilatory equivalents for oxygen (VE/VO₂) and carbon dioxide (VE/VCO₂) were greater in the OSAS subjects vs. the overweight subjects without OSAS (P = 0.05, P < 0.05 and P < 0.005, respectively) at all exercise intensities. Heart rate (HR) recovery was attenuated in the overweight OSAS subjects compared to the No-OSAS and Control groups throughout 5 minutes of active recovery (P = 0.009). Oxygen uptake, HR, and blood pressure did not differ throughout exercise. Leptin was not associated with ventilatory responses at any exercise intensity. Linear regression analysis revealed hip-to-height ratio (HHR), hip circumference (HC), triglyceride levels, and recovery systolic blood pressure ratio (SBPR) at 2 and 4 minutes were independent predictors of AHI (model fit: R² = 0.68, p <0.0001). ROC analysis determined that percent body fat, HHR, and recovery HR at 2 minutes and 4 minutes were the best single predictors of OSAS risk (AUC = 0.77 for each measure, p = 0.003). Conclusions: Unique ventilatory and hemodynamic characteristics to maximal exercise testing are exhibited in young men with OSAS. These characteristics may be related to alterations in the sympathetic nervous system and chemoreceptor activation, and may be early clinical signs in the progression of OSAS. These exercise characteristics, along with anthropometric and body composition measures may provide useful information in identifying young men at risk for OSAS. / Ph. D.

Obstructive sleep apnea (OSA) is a serious disorder that affects up to 24% of middle-aged males. The substantial cost and inconvenience associated with polysomnography limits the number of people who seek treatment. Therefore, information concerning exercise tolerance and hemodynamic function in obstructive sleep apnea (OSA) patients may add new and clinically meaningful information to the process of grading disease severity and/or assessing treatment outcomes. Objectives: The primary objective of this study was to explore relationships between polysomnography (PSG) markers of sleep function and resting and exercise measures of hemodynamic function in patients diagnosed with mild-to-severe OSA. A family of clinical markers including heart rate (HR), blood pressure (BP), cardiac index (CI), stroke volume index (SVI), total peripheral resistance (TPR), and oxygen uptake (VO2) were assessed in this study. A second objective was to explore differences in hemodynamic function at rest and during graded exercise in OSA patients versus control subjects matched for age and body mass index (BMI). A final objective was to evaluate the extent that treatment with nCPAP alone, or combined with a moderate aerobic exercise training program impacted markers of hemodynamic function (results not reported here). Methods: Eleven newly diagnosed OSA patients [5 male, 6 female; age: 46.5 + 12.0 yrs; respiratory disturbance index (RDI) = 30.2 + 15.0] and 10 apparently healthy control subjects (4 male, 6 female; age: 39.8 + 6.9 yrs) completed daytime resting measurements of heart rate variability (HRV) and blood pressure (BP); and underwent a maximal cycle ergometer exercise test at baseline and 6 wk post-treatment initiation. Pearson product moment correlations were calculated between PSG markers of sleep function and: (1) daytime measures of HRV; (2) BP; and (3) submaximal and peak exercise measures of hemodynamic function. Independent t tests were used to explore differences between OSA patients and controls. Results: Stage 1 sleep duration was significantly related to daytime SBP (r = 0.69; P < 0.05) and MAP (r = 0.72; P < 0.05). Daytime MAP (P = 0.01) and DBP (P = 0.02) were significantly different between groups. Exercise testing yielded the following results: RDI was significantly related to HR at 60 watts (r = -0.70; P = 0.02) and 100 watts (r = -0.69; P = 02); stage 2 sleep duration was inversely related to CI at 60 (r = -0.76; P = 0.03) and 100 watts. In addition, stage 1 sleep duration was significantly correlated with TPR at 60 watts (r = 0.70; P = 0.06) and 100 watts (r = 0.71; P = 0.05). At peak exercise, a significant relationship was noted between peak HR and stage 2 sleep duration (r = -0.73; P = 0.02); and RDI (r = -0.66; P = 0.03). Furthermore, relative VO2pk was positively correlated to REM sleep duration (r = 0.62; P = 0.04). Conclusions: Distinct patterns exist in measures of daytime HRV and BP may provide physicians unique and clinically useful information. In addition, peak exercise capacity is reduced in the OSA patient and may be related to a blunted HR response to graded exercise. / Ph. D.