Epidemiology of supplemental oxygen in patients with pulmonary hypertension.

Background and objective: Patients with pulmonary hypertension (PH) may present with hypoxaemia at rest or during daily activities. There is no epidemiological data on the prescription of long-term oxygen therapy (LTOT) in patients with PH. The study sought to analyse the prevalence and incidence of LTOT prescription among patients with pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH) in Spain and to determine predictors for this prescription.

Methods: A retrospective analysis was performed from the Spanish Registry of Pulmonary Arterial Hypertension (REHAP). Collected data included demographics and anthropometric measurements, functional class (FC), arterial blood gases, pulmonary function tests, haemodynamic measurements, six-minute walking distance (6MWD) and LTOT prescription. In addition, we assessed the prevalence and incidence of LTOT prescription by PH group and subtype and potential predictors for LTOT initiation in the first 5 years after diagnosis.

Results: We analysed 4533 patients (69.9% PAH and 30.1% CTEPH), mostly female (64.5%), with a mean age of 53.0 ± 18.3 years. The prevalence of LTOT was 19.3% for all patients. The incidence of LTOT prescriptions decreased from 5.6% to 1.6% between 2010 and 2019, respectively. Predictors for LTOT prescription, excluding those that represent the indication for oxygen therapy were: FC (HR: 1.813), 6MWD (HR: 1.002), mean pulmonary arterial pressure (mPAP) (HR: 1.014), cardiac index (CI) (HR: 1.253), pulmonary vascular resistance (PVR) (HR: 1.023) and diffusing capacity of carbon monoxide (DL_CO) (HR: 1.294).

Conclusion: The prevalence of LTOT in PAH and CTEPH patients is close to 20%. FC, 6MWD, mPAP, CI, PVR and DL_CO were predictors for LTOT prescription.