Adrian Aron

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.

Potential clinical use of cardiopulmonary exercise testing in obstructive sleep apnea hypopnea syndrome

There is growing evidence linking obstructive sleep apnea hypopnea syndrome (OSAHS) with multiple cardiovascular and metabolic diseases. Exercise testing is generally available and routinely used to provide valuable information on cardiopulmonary function in healthy and diseased populations. This review summarizes and integrates recent findings on exercise testing in OSAHS and discusses the potential mechanisms that may contribute to the responses that seem to differentiate these patients from apparently healthy subjects and patients with other cardiopulmonary diseases. Although exercise testing is widely used in the evaluation and diagnosis of coronary artery disease patients, recent studies showed distinctive cardiopulmonary responses in OSAHS that raise the possibility of similar applications in this disorder, as well. Several studies illustrated in this review found that OSAHS patients have a reduced exercise capacity, as shown by low peak oxygen uptake achieved. Also, their exercise HR response was reported as significantly lower than in healthy peers, suggesting chronotropic incompetence. Exercise blood pressure response were atypical as well. OSAHS patients had increased systolic and diastolic BP during exercise and a persistently elevated systolic BP during the early post-exercise recovery period. Possible explanations for these responses include cardiac dysfunction, impaired muscle metabolism, chronic sympathetic over-activation, and endothelial dysfunction. Early identification of OSAHS using cardiopulmonary exercise testing (CPXT) shows promise for selecting patients at risk for this disorder in the clinical setting. A uniform definition and measurement of OSAHS together with more rigorous trials are necessary to establish the utility of exercise responses in clinical settings.

Effects of obstructive sleep apnea on hemodynamic parameters in patients entering cardiac rehabilitation.

PURPOSE: Obstructive sleep apnea (OSA) is a prevalent form of sleep-disordered breathing. Evidence suggests that OSA may lead to cardiac remodeling, although the literature is equivocal. Previous literature suggests a high percentage of individuals entering a cardiac rehabilitation (CR) program also have OSA. The objective of this study was to determine whether resting hemodynamic variables were altered in OSA subjects entering CR compared with those without OSA, as determined by impedance cardiography. METHODS: Subjects entering an early outpatient CR program were screened for OSA using an at-home screening device and verified by a sleep physician. Subjects were divided into an OSA group (n = 48) or a control group (n = 25) on the basis of the screening results. Hemodynamic variables were measured during supine rest using impedance cardiography. A 6-minute walk test was performed to assess functional capacity. RESULTS: The proportion of cardiac diagnoses was similar between groups. Overall, 66% of the subjects were positive for OSA. Subject groups did not differ by age, body mass index, heart rate, diastolic blood pressure, or functional capacity. Cardiac output, cardiac index, stroke volume, contractility index, and left cardiac work index were all significantly decreased in the OSA group compared with the control group (P < .05). CONCLUSIONS: Findings suggest that OSA results in decreased cardiac function in patients entering CR, likely because of pressure and volume changes associated with apneic events. This may place those individuals at a disadvantage in recovering from their cardiac event, and place them at increased risk for secondary complications.

The Effect of Localized Upper Body Fatigue on Static and Dynamic Balance: 1294 Board #6 June 2, 8: 00 AM - 10: 00 AM.

Fatigue is one of the mechanisms with a great impact on the neuromuscular motor control. Lower extremity fatigue has been shown to alter static and dynamic balance through the effects on the lower muscles involved in balance control. Upper body exercises that lead to localized fatigue are commonly utilized in physical therapy clinics. PURPOSE: The aim of this study was to determine the effects of upper body muscle fatigue on dynamic and static balance in young and old populations. METHODS: Static and dynamic balance assessments were performed on 17 males (age 36.6 ± 15.6 years) before and after an upper body fatigue protocol. Static balance was assessed on the NeuroCom Equitest system using the Sensory Organization Test protocol, while dynamic balance was evaluated using the Lower Quarter Y-Balance Test normalized to leg length. Fatigue was induced through arm ergometry testing consisted of 25 watt/minute (70-80 rpm) incremental exercise protocol until exhaustion. Lactate was measured before and after the fatigue protocol in order to provide an objective measure of the participant’s fatigue level. RESULTS: There was a significant difference between young and old groups when comparing dynamic balance performance on the right leg (92.4 ± 6.4 vs 81.2 ± 10.3, p<0.001). Similar results were found for the left leg (91.6 ± 6.3 vs 83.5 ± 9.6, p<0.001). No significant differences were found within each of the age groups when comparing pre- and post-fatigue for dynamic balance on the right leg (p=0.70) and left leg (p=0.49). Static balance performance was not different between young and old groups pre fatigue (81.2 ± 10.2 vs 82.2 ± 3.5, p=0.31) or post fatigue (79.8 ± 9.4 vs 83.3 ± 3.8, p=0.46). The same not significant trend for static balance was demonstrated within groups pre and post fatigue (p=0.38). CONCLUSIONS: A single high intensity session of localized upper body fatigue did not significantly impact static or dynamic balance. It appears that core and upper extremity musculature is not recruited intense enough to alter the sensory and motor function. Age did not have an effect on the efficient use of strategies for postural control. These results suggest that clinicians may be able to safely implement intense upper body exercises without significantly increasing fall risk.

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.