Nocturnal hypoxia in patients with idiopathic pulmonary arterial hypertension

BACKGROUND: Sleep-disordered breathing causes a variety of cardiovascular complications and increases the risk of a poor prognosis in patients. There is still some controversy regarding the clinical diagnosis and treatment of sleep-disordered breathing in patients with pulmonary hypertension. The aim of this study was to determine the incidence of desaturation in idiopathic pulmonary arterial hypertension (IPAH) patients, evaluate the effect of desaturation on the clinical status of patients with IPAH, and identify possible influencing factors. METHODS: Patients with IPAH diagnosed by right heart catheterization who underwent overnight cardiorespiratory monitoring from January 2018 to July 2019 were enrolled. Nocturnal hypoxic time was defined as the time that oxygen saturation remained below 90%. Desaturation was defined as a nocturnal oxygen saturation level less than 90% for more than 10% of the total recording time. Baseline clinical characteristics and parameters were collected to compare IPAH patients with and without desaturation. In addition, logistic regression was performed to identify possible factors associated with desaturation in IPAH patients. RESULTS: Fifty patients with IPAH were included. Among them, 17 patients presented desaturation. Patients with desaturation were older, had a shorter six-min walking distance (6MWD), had a higher mean right atrial pressure, and had a lower daytime arterial oxygen partial pressure than patients without desaturation, and there were significant differences in the VE/VCO(2) and VE/VCO(2) slope (P < 0.05). The multivariate logistic regression analysis indicated that the 6 MWD (OR = 0.971, 95% CI: 0.948–0.994, P = 0.013) and; VE/VCO(2) slope (OR = 1.095, 95% CI: 1.010–1.307, P = 0.032) were independently associated with desaturation after adjusting for age, sex, and body mass index. CONCLUSION: Nocturnal hypoxia is common in IPAH patients. Desaturation may aggravate the clinical situation of patients with IPAH. In IPAH patients, a poor exercise capacity (6 MWD) and the VE/VCO(2) slope can predict desaturation after adjusting for age, sex, and body mass index.