Pulmonary hypertension in obesity-hypoventilation syndrome.

BACKGROUND: Pulmonary hypertension (PH) is considered a clinically important feature of Obesity-Hypoventilation Syndrome (OHS). We aimed to determine prevalence, characteristics and severity of PH including associations with clinical outcomes after established non-invasive positive pressure ventilation (NPPV).
METHODS: In a prospective cross-sectional study, clinically stable OHS-patients (NPPV duration ≥ 3 months) were consecutively assessed using echocardiography, serum markers and right-heart catheterization (RHC). NPPV use was quantified via ventilator counters. Blood gases, lung function, Epworth-Sleepiness Scale (ESS), sleep-quality, WHO-functional class (WHO-FC), 6-min walk distance, and health-related quality of life (HRQL) via Severe Respiratory Insufficiency (SRI) questionnaire were assessed.
RESULTS: Of 177 patients considered, 64 fulfilled inclusion criteria. Among these, 21 patients (10 female/11 male; BMI 45 [40; 53] kg/m(2), PaCO2 39.6 [37.8; 45.5] mmHg (median [quartiles])) gave consent for RHC. Four patients (19%) had normal mean pulmonary artery pressure (mPAP < 20 mmHg), 8 (38.1%) mPAP 20-24 mmHg and 9 (42.9%) manifest PH (mPAP ≥ 25 mmHg), 3 of them with combined pre- and/or postcapillary PH. mPAP was negatively correlated to NPPV use, vital capacity and lung diffusing capacity (p < 0.01 each), and positively to BMI (p < 0.05). NPPV use and vital capacity independently predicted mPAP. In patients with PH, ESS, WHO-FC, and some SRI-items were worse (p < 0.05 each) compared to patients without PH. Multivariate analyses revealed mPAP as the only independent predictor of the SRI-physical functioning domain.
CONCLUSIONS: Mild to moderate PH is frequent in patients with OHS despite NPPV, mPAP being inversely related to NPPV adherence. PH is associated with impairments in daytime-sleepiness, WHO-FC, HRQL and physical functioning.