Abstract 20606: Persistent Low Oxygen Saturation During Sleep Predicts Impaired Pulmonary Vascular Response to Exercise in Patients With Sleep Disordered Breathing

Introduction: Sleep disordered breathing (SDB) is common among patients with cardiovascular disease, but its impact on physiologic responses to exercise remains unclear. Hypothesis: We sought to determine the functional significance of SDB and low nocturnal oxygen saturation (SaO2) on hemodynamic responses to exercise. Methods: We investigated subjects who underwent invasive cardiopulmonary exercise tests (iCPET) to evaluate dyspnea of unclear etiology who had evidence of SDB defined as an apnea hypopnea index (AHI) > 5 events/hour during a formal sleep study done within 3 years of the iCPET. Mean pulmonary artery pressure (mPAP) and mean wedge pressure (mPW) were indexed to cardiac output (CO) during exercise, with a mPAP-CO slope > 3 mmHg·min·L(-1) and a mPW-CO slope > 2 mmHg·min·L(-1) indicating an abnormal pulmonary vascular (PV) response to exercise. Results: A total of 120 patients (mean±SD age 58.2 ± 12.6 years, body mass index 31.6 ± 7.5) with SDB (mean AHI 18.9 ± 21.3) and reduced SaO2 during the sleep study (minimal SaO2: 83± 7%, percentage of sleep-time with SaO2 Conclusions: The magnitude and duration of reduced SaO2 during sleep is related to degree of impairment in exercise capacity and pulmonary hemodynamic responses to exercise among patients with dyspnea on exertion. Persistent low nocturnal SaO2 correlates better than AHI with impaired PV response to exercise.