OXYGEN-SATURATION DURING DAILY ACTIVITIES IN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Patients with chronic obstructive pulmonary disease (COPD) frequently develop nocturnal oxygen desaturation because of alveolar hypoventilat ion, worsening of ventilation-perfusion mismatch, and sometimes obstru ctive sleep apnoeas, In contrast, little is known about their oxygen s tatus during the various activities of daily life, The aim of this stu dy was to compare the oxygen saturation profile during day and night, and to assess the influence of different daily activities in COPD. Dur ing a rehabilitation programme, we studied 30 patients with moderate-t o-severe COPD (median forced expiratory volume in one second (FEV1) 37 % of predicted), without marked hypoxaemia (median arterial oxygen ten sion (Pa,O-2) 9.1 kPa), Arterial oxygen saturation (SaO(2)) was assess ed by pulse oximetry during night (8 h) and day (10.5 h), The mean and minimal Sa,O-2 were calculated, and desaturations were defined as Sa, O-2 falls >4%. h(-1). Daily activities were identified by the patients as resting, eating, washing, nebulization therapy and walking. Mean S a,O-2 was lower during the night (88%) than during the day (89%). In c ontrast, minimal Sa,O-2 was lower during the day (69%) than during the night (72%), and the number of desaturations was higher during the da y (8.6 desaturations . h(-1) than during the night (6.8 desaturations . h(-1)). Mean Sa,O-2 was 88% during walking, which was lower than dur ing resting (90%), nebulization (90%), and meals (89%). The number of desaturations was higher during walking (13.1 desaturations h(-1)), wa shing (12.6 desaturations . h(-1)), and eating (9.2 desaturations . h( -1)) than during resting (5.3 desaturations . h(-1)). We conclude that daily activities, such as walking, washing and eating, are associated with transient oxygen desaturation in patients with moderate-to-sever e chronic obstructive pulmonary disease, even without marked resting h ypoxaemia.