Stephen G. Guill

Altered ventilatory responses to exercise testing in young adult men with obstructive sleep apnea

BACKGROUND Obstructive sleep apnea (OSA) is a disorder characterized by repetitive obstructions of the upper airway. Individuals with OSA experience intermittent hypoxia, hypercapnia, and arousals during sleep, resulting in increased sympathetic activation. Chemoreflex activation, arising from the resultant oscillatory disturbances in blood gases from OSA, exerts control over ventilation, and may induce increases in sympathetic vasoconstriction, contributing to increased long-term risks for hypertension (HTN) and cardiovascular disease (CVD). METHODS To evaluate whether OSA elicits exaggerated ventilatory responses to exercise in young men, 14 overweight men with OSA and 16 overweight men without OSA performed maximal ramping cycle ergometer exercise tests. Oxygen consumption (VO(2)), ventilation, (V(E)), ventilatory equivalents for oxygen (V(E)/VO(2)) and carbon dioxide (V(E)/VCO(2)), and V(E)/VCO(2) slope were measured. RESULTS The VO(2) response to exercise did not differ between groups. The V(E), V(E)/VCO(2), V(E)/VO(2) were higher (p< 0.05, 0.002, and p<0.02, respectively) in the OSA group across all workloads. The V(E)/VCO(2) slope was greater in the OSA group (p<0.05). The V(E)/VCO(2) slope and AHI were significantly correlated (r=0.56, p<0.03). Thus, young, overweight men with OSA exhibit increased ventilatory responses to exercise when compared to overweight controls. This may reflect alterations in chemoreflex sensitivity, and contribute to increased sympathetic drive and HTN risk.

Early evidence of increased risk for metabolic syndrome in young men with latent obstructive sleep apnea.

BACKGROUND Obstructive sleep apnea (OSA) is characterized by a repetitive collapse of the upper airway during sleep and may affect as many as 1 in 5 adults. Although OSA appears to increase risk for metabolic syndrome in middle-aged adults, no data currently exist in a younger, preclinical cohort. METHODS Forty-five sedentary young men: 12 overweight with OSA (OSA), 18 overweight without OSA (NOSA), and 15 normal-weight without OSA (CON). Respiratory distress index (RDI) was determined using an at-home, unsupervised, portable polygraphy device. Total and subcutaneous abdominal fat (SAF) were quantified using dual-energy X-ray absorptiometry (DXA). Blood pressure was obtained manually via auscultation. Fasting triglycerides, glucose, and high-density lipoprotein cholesterol (HDL-C) concentrations were analyzed from whole blood using a commercial lipid profile kit. RESULTS The OSA group had 25% more SAF than the NOSA group (P < 0.05) and higher triglycerides (136.7 +/- 21.3 mg/dL versus 92.2 +/- 7.5, P < 0.05). RDI was directly related to fasting triglycerides (R = 0.32, P < 0.05) after controlling for SAF. The number of metabolic syndrome components was directly correlated to indices of adiposity, but not RDI. Using multiple linear regression analysis, triglycerides were the only independent predictor of RDI. CONCLUSIONS Results from this study demonstrate that unique physiologic and anthropometric abnormalities exist in young men with occult OSA, beyond those that are seen in uncomplicated obesity. These findings may indicate early pathogenesis of metabolic syndrome in these young men.

Does Progression Of Untreated Obstructive Sleep Apnea Incrementally Blunt Post-exercise Heart Rate Recovery?: 1309

heart rate recovery? Trent A. Hargens;1,4 Stephen G. Guill;1,5 Anthony S. Kaleth;1,2 Adrian Aron;1 Donald Zedalis;3,5 and William G. Herbert FACSM.1 Laboratory for Health and Exercise Sciences, Department of Human Nutrition, Foods and Exercise; Virginia Tech, Blacksburg, VA; 1 Department of Physical Education, Indiana University-Purdue University Indianapolis, IN;2 The Sleep Disorders Network of Southwest Virginia, Christiansburg, VA;3 Human Performance Laboratory, Clinical Exercise Physiology Program; Ball State University, Muncie, IN;4 Edward Via Virginia College of Osteopathic Medicine, Blacksburg, VA.5 Laboratory for Health and Exercise Science Human Performance Laboratory

Association Between Graded Exercise Test Indicators of Cardiovascular Disease Risks and Peripheral Vascular Stiffness: 2079

Exaggerated systolic blood pressure (SBP) responses to graded exercise testing in normotensive adults have been associated with risk of future hypertension. Endothelial dysfunction is one of the mechanisms that lead to functional and structural changes in resistance vessels. Venous occlusion plethysmography (VOP) non-invasively characterizes endothelium-dependent vasodilatory capacity in peripheral arteries (reactive hyperemia: RH). PURPOSE: To determine if an association exists between exaggerated SBP responses to graded exercise and peripheral vascular vasodilatory capacity. METHODS: Subjects were 50 young males (Mean ± SD: age = 22.4 ± 2.6 yr; body fat = 24.3 ± 6.1 %; BMI = 27.7 ± 5.7). Post-occlusive RH was assessed after a 5-min brachial artery occlusion using VOP and standard procedures recommended by the manufacturer (Hokanson EC-6, Bellevue, WA). Each subject performed maximal cycle ergometer exercise tests with a 15 watts/min ramping protocol. Blood pressures (BP) were measured at rest, every 2 min during, and at 15 sec intervals after exercise. RESULTS: During exercise, no relationship was found between any of the exaggerated SBP indices and the measures of peripheral artery status by VOP. Furthermore, when individual SBP responses from peak exercise at the highest vs. lowest tertiles were contrasted, no differences in the VOP measures of vascular status were found. CONCLUSION: Exaggerated SBP response to graded exercise in young adult males seems to be regulated largely by factors other than peripheral vascular status, as assessed by VOP/RH.