Nocturnal hypoxemia is common in primary pulmonary hypertension

Study objective: Unsuspected sleep-related respiratory events are common in patients with severe pulmonary disease. Sleep in patients with primary pulmonary hypertension (PPH) has not been studied (to our knowledge). The purpose of this study was to measure the prevalence of respiratory disturbances and nocturnal hypoxemia during the sleep of patients with PPH. Setting: Tertiary-care referral hospital. Design: Retrospective review. Patients: Thirteen patients with PPH. Measurements: All patients underwent a single-night comprehensive polysomnogram study. Patients who spent > 10% of the total sleep time with oxygen saturation by pulse oximetry (Spo(2)) at < 90% or who needed oxygen to maintain their Spo(2) level at > 90% were classified as nocturnal desaturators. Analysis was performed to determine which clinical variables (ie, demographics, body mass index, spirometry, diffusion capacity, right heart catheterization pressures, 6-min walk test, arterial blood gas levels, resting and walking Spot levels, and polysomnogram variables) would predict nocturnal desaturation. Statistical significance was considered when p values were < 0.05. Results: Of the 13 patients in the study, 10 (77%) were nocturnal desaturators. All patients had normal apnea indexes, but two had mild elevations of the hypopnea index (< 15 episodes per hour). Nocturnal desaturations occurred independently of apneas or hypopneas. Six patients who did not have O-2 titration during sleep spent > 25% of sleep time with Spo(2) < 90%. The mean ( SD) variables that were significantly different between desaturators (10 patients) and nondesaturators (3 patients) were FEV1 (70.1 +/- 9.1% predicted vs 98.1 +/- 15.1% predicted, respectively; p = 0.002), resting Pao(2) (61.8 +/- 16.1 vs 90.3 +/- 2.3 inm Hg, respectively; p = 0.001), alveolar-arterial oxygen pressure difference (P[A-a]O-2) (40.5 +/- 20.5 vs 12.2 +/- 7.2 mm Hg, respectively; p = 0.048), resting Spo(2) (91.6 +/- 5.4% vs 98.7 +/- 2.3%, respectively; p = 0.038), and walking Spo(2) (83.8 +/- 9.3% vs 95.3 +/- 1.2%, respectively; p = 0.002). The mean hemoglobin level was higher in the group of nocturnal desaturators than in the group of nondesaturators (10.43 +/- 0.31 vs 13.95 +/- 0.98 g/dL, respectively; p < 0.0001). Conclusion: Seventy-seven percent of patients with PPH have significant nocturnal hypoxeinia that is unrelated to apneas and hypopneas. Nocturnal desaturation occurs more frequently in patients with higher P(A-a)O-2 values and lower FEV1 values, resting arterial Pao(2) and Spot values, and walking Spo(2) values.