Annual decline in arterial blood oxygen predicts development of chronic respiratory failure in COPD with mild hypoxaemia: A 6‐year follow‐up study

ABSTRACT Background and objective Chronic respiratory failure (CRF) with hypoxaemia is an important pathophysiology in patients with chronic obstructive pulmonary disease (COPD), and existing mild hypoxaemia may be a sign of future CRF development. However, little is known about the trajectory of partial arterial pressure of oxygen (PaO2) decline in patients with COPD. We assessed decline in PaO2 and the impact of short‐term reductions in PaO2 to predict future decline in PaO2. Methods A total of 172 outpatients with COPD from a prospective cohort study were enrolled. Pulmonary function tests and arterial blood gas (ABG) analyses were conducted at baseline and 1 year after enrolment and changes in PaO2 (ΔPaO2) and other parameters were calculated. Survival and incidence of CRF (as assessed by prescription of long‐term home oxygen therapy) were monitored for 6 years. Results A total of 164 patients completed the observation period and 101 patients had mild hypoxaemia (PaO2