Am. J. Respir. Crit. Care Med., Volume 165, Number 2, January 2002, 152-158

Continuous Positive Airway Pressure Treatment Improves Pulmonary Hemodynamics in Patients with Obstructive Sleep Apnea

DIMITAR SAJKOV, TINGTING WANG, NICHOLAS A. SAUNDERS, ALEXANDRA J. BUNE, and R. DOUGLAS MCEVOY

Sleep Disorders Unit and Department of Cardiology, Repatriation General Hospital, Daw Park, Australia; and School of Medicine, Flinders University, Bedford Park, Adelaide, Australia

Daytime pulmonary hypertension (PH) is relatively common in obstructive sleep apnea (OSA) and is thought to be associated with pulmonary vascular remodeling (PRm). The extent to which PH is reversible with treatment is uncertain. To study this, we measured pulmonary hemodynamics (Doppler echocardiography) in 20 patients with OSA (apnea-hypopnea index [AHI] 48.6 ± 5.2/h, mean ± SEM) before and after 1 and 4 mo of CPAP treatment (compliance 4.7 ± 0.5 h/night). Patients had normal lung function, and no cardiac disease or systemic hypertension. Doppler studies were performed at three levels of inspired oxygen concentration (11%, 21%, and 50%) and during incremental increases in pulmonary blood flow (10, 20, and 30 µg/kg/min dobutamine infusions). Treatment resulted in a decrease in pulmonary artery pressure (Ppa, 16.8 ± 1.2 mm Hg before CPAP versus 13.9 ± 0.6 mm Hg after 4 mo CPAP, p < 0.05) and total pulmonary vascular resistance (231.1 ± 19.6 versus 186.4 ± 12.3 dyn · s · cm⁵, p < 0.05). The greatest treatment effects occurred in the five patients who were pulmonary hypertensive at baseline. The pulmonary vascular response to hypoxia decreased after CPAP (Ppa/Sa_O2 10.0 ± 1.6 mm Hg before versus 6.3 ± 0.8 mm Hg after 4 mo CPAP, p < 0.05). The curve of Ppa versus cardiac output (), derived from the incremental dobutamine infusion, shifted downward in a parallel fashion during treatment. Systemic diastolic blood pressure also fell significantly. Improvements in pulmonary hemodynamics were not attributable to changes in left ventricular diastolic function or Pa _O2. We conclude that CPAP treatment reduces Ppa and hypoxic pulmonary vascular reactivity in OSA and speculate that this may be due to improved pulmonary endothelial function.

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