Sleep-related O2 desaturation and daytime pulmonary haemodynamics in COPD

ABSTRACT: It has been hypothesized but not firmly established that sleep-related hypoxaemia could favour the development of pulmonary hypertension in chronic obstructive pulmonary disease (COPD) patients without marked daytime hypox-aemia. We have investigated the relationships between pulmonary function data, sleep-related desaturation and daytime pulmonary haemodynamics in a group of 94 COPD patients not qualifying for conventional O2 therapy (daytime arterial oxy-gen tension (Pa,O2) in the range 7.4–9.2 kPa (56–69 mmHg)). Nocturnal desatura-tion was defined by spending ≥30 % of the recording time with a transcutaneous O2 saturation <90%. An obstructive sleep apnoea syndrome was excluded by polysomnography. Sixty six patients were desaturators (Group 1) and 28 were nondesaturators (Group 2). There was no significant difference between Groups 1 and 2 with regard to pulmonary volumes and Pa,O2 (8.4±0.6 vs 8.4±0.4 kPa (63±4 vs 63±3 mmHg)) but arterial carbon dioxide tension (Pa,CO2) was higher in Group 1 (6.0±0.7 v