Daytime pulmonary hypertension in patients with obstructive sleep apnea: the effect of continuous positive airway pressure on pulmonary hemodynamics

Background: Limited information exists regarding the development of pulmonary hypertension in patients with obstructive sleep apnea (OSA) in the absence of lung and heart comorbidity.

Objectives: The aims of this study were to investigate whether OSA patients without any other cardiac or lung disease develop pulmonary hypertension, and to assess the effect of continuous positive airway pressure (CPAP) treatment on pulmonary artery pressure (P(PA)).

Methods: Twenty-nine patients aged 51 +/- 10 years with OSA and 12 control subjects were studied with pulsed-wave Doppler echocardiography for estimation of P(PA) before and after 6-month effective treatment with CPAP.

Results: A significantly higher mean P(PA) was found in OSA patients as compared to control subjects (17.2 +/- 5.2 vs. 12.1 +/- 1.9 mm Hg, p < 0.001). Six out of the 29 OSA patients had mild pulmonary hypertension (P(PA) > or = 20 mm Hg). Significant differences were observed between pulmonary hypertensive and normotensive OSA patients with respect to age (62 +/- 4 vs. 48 +/- 15 years, respectively, p < 0.05), body mass index (41 +/- 7 vs. 32 +/- 4 kg/m(2), p < 0.02) and daytime P(a)O(2) (81 +/- 9 vs. 92 +/- 9 mm Hg, p < 0.05). CPAP treatment was effective in reducing mean P(PA) in both groups of pulmonary hypertensive and normotensive OSA patients (decreases in P(PA) from 25.6 +/- 4.0 to 19.5 +/- 1.5 mm Hg, p < 0.001; from 14.9 +/- 2.2 to 11.5 +/- 2.0 mm Hg, respectively, p < 0.001).

Conclusions: A proportion (20.7%) of OSA patients without any other lung or heart disease and characterized by older age, greater obesity and lower daytime oxygenation develop mild pulmonary hypertension which has been partially or completely reversed after 6-month CPAP treatment. In conclusion, OSA alone constitutes an independent risk factor for the development of pulmonary hypertension.