Lower extremity edema and pulmonary hypertension in morbidly obese patients with obstructive sleep apnea

In 70 consecutive male patients with obstructive sleep apnea (OSA) diagnosed at the Northport VA Medical Center Sleep Disorders Center, we have characterized the association between obesity, OSA, and pulmonary hypertension (PH).

By including anthropometric, pulmonary function, and sleep study parameters in a multivariate logistic regression model, we found that a BMI of >40 kg/m(2) and the minimum oxygen saturation in non-rapid eye movement (NREM) sleep predicted the presence of pretibial edema in this sleep apnea population. We then characterized the hemodynamics of those OSA patients that had lower extremity edema. Twenty-nine of the 70 consecutive patients with sleep apnea (41%) had pretibial edema, and right heart catheterization data was obtained for 28 (97%) of these patients.

Ninety-three percent (26/28) of the patients had right heart failure (mean RAP > 5 mm Hg; RAP range = 0-32 mmHg) and PH (PA mean >or= 20 mm Hg) was present in 86% (24/28.) The OSA patients with lower extremity edema had an increased cardiac output (7.0 + 1.4 l/min) with a normal cardiac index (2.9 + 0.5 l/min/m(2)) in the setting of an elevated pulmonary capillary wedge pressure (PCWP 17 +/- 7 mmHg) and a normal pulmonary vascular resistance (122 + 70 dynes s cm(-5)). While PCWP, FEV(1)% predicted, and the minimum oxygen saturation in NREM sleep all independently predicted PH, PCWP was the most important predictor of PH.

We conclude that pulmonary hypertension is commonly seen in patients with OSA with pretibial edema and that pretibial edema is a highly specific sign of PH in OSA patients. Pulmonary hypertension appears to result from an elevated back pressure and diastolic dysfunction with contributions from lung function and nocturnal oxygen saturation.