Background: Obstructive sleep apnea (OSA) is characterized by repetitive nighttime obstructions of the upper airway that induce hypoxemia, hypercapnia, sympathetic activation, and arousals. This disorder induces cardiovascular autonomic imbalance and contributes to the development of hypertension. While the diagnostic and prognostic utility of exercise testing is well established in cardiology, the clinical utility of the exercise test in screening for OSA has not been carefully explored. To explore this potential application, we contrasted cardiopulmonary responses to exercise testing in patients recently diagnosed with OSA with apparently healthy counterparts of similar physical inactivity history, age, and body habitus.
Methods: Twenty-three normotensive overweight adults with OSA [apnea-hypopnea index (AHI)=24.7+/-13.5 events h(-1); body mass index (BMI)=33.1+/-5.5 kg m(-2); age=45.6+/-10.7 years] and nine apparently healthy controls of similar age and morphology (BMI=29.5+/-5.5 kg m(-2); age=40.2+/-8.1 years; AHI=4.9+/-0.1) completed a maximal ramping cardiopulmonary exercise tolerance test on a cycle ergometer. Measures included oxygen consumption (VO(2)pk), ventilation (V(E)), heart rate (HR), blood pressure (BP), cardiac output (Qc), and stroke volume (SV).
Results: Age, BMI, rest HR, rest BP, rest and exercise cardiac index (QI), rest and exercise stroke volume index (SVI), and V O(2)pk were not different between OSA patients and controls (p>0.05). Exercise heart rate was significantly lower and diastolic BP higher in the OSA group (p<0.05). In the physically active recovery (low-load pedaling), systolic BP recovery was delayed (p<0.05) in the OSA group while diastolic BP tended to remain higher (p=0.056).
Conclusion: Patients with OSA have a distinctive response to graded exercise, characterized by a blunted HR response, markedly delayed systolic BP response in early recovery, and elevated diastolic BP in both exercise and early recovery. Clinical trials are justified to determine the clinical utility of graded exercise testing to independently inform clinical decision-making for triaging patients to diagnostic polysomnography.