Sleep-Disordered Breathing and Nocturnal Hypoxemia in Precapillary Pulmonary Hypertension: Prevalence, Pathophysiological Determinants, and Clinical Consequences

Abstract

<b><i>Background and objective:</i></b> The clinical relevance and interrelation of sleep-disordered breathing and nocturnal hypoxemia in patients with precapillary pulmonary hypertension (PH) is not fully understood. <b><i>Methods:</i></b> Seventy-one patients with PH (age 63 ± 15 years, 41% male) and 35 matched controls were enrolled. Patients with PH underwent clinical examination with assessment of sleep quality, daytime sleepiness, 6-minute walk distance (6MWD), overnight cardiorespiratory polygraphy, lung function, hypercapnic ventilatory response (HCVR; by rebreathing technique), amino-terminal pro-brain natriuretic peptide (NT-proBNP) levels, and cardiac MRI (<i>n</i> = 34). <b><i>Results:</i></b> Prevalence of obstructive sleep apnea (OSA) was 68% in patients with PH (34% mild, apnea-hypopnea index [AHI] ≥5 to &#x3c;15/h; 34% moderate to severe, AHI ≥15/h) versus 5% in controls (<i>p</i> &#x3c; 0.01). Only 1 patient with PH showed predominant central sleep apnea (CSA). Nocturnal hypoxemia (mean oxygen saturation [SpO₂] &#x3c;90%) was present in 48% of patients with PH, independent of the presence of OSA. There were no significant differences in mean nocturnal SpO₂, self-reported sleep quality, 6MWD, HCVR, and lung and cardiac function between patients with moderate to severe OSA and those with mild or no OSA (all <i>p</i> &#x3e; 0.05). Right ventricular (RV) end-diastolic (<i>r</i> = −0.39; <i>p</i> = 0.03) and end-systolic (<i>r</i> = −0.36; <i>p</i> = 0.04) volumes were inversely correlated with mean nocturnal SpO₂ but not with measures of OSA severity or daytime clinical variables. <b><i>Conclusion:</i></b> OSA, but not CSA, is highly prevalent in patients with PH, and OSA severity is not associated with nighttime SpO₂, clinical and functional status. Nocturnal hypoxemia is a frequent finding and (in contrast to OSA) relates to structural RV remodeling in PH.