Oxygen desaturation during sleep and exercise in patients with severe chronic obstructive pulmonary disease

Abstract Patients with chronic obstructive pulmonary disease (COPD) have varying degrees of arterial oxyhaemoglobin desaturation during sleep, which have been shown to correlate with awake oxygen levels. We wished to ascertain if exercise desaturation was a better predictor of nocturnal oxygen desaturation than daytime blood gases. We studied 25 COPD patients with P aO 2 P aCO 2 ≤ 6 kPa, Group A), and 13 of whom were hypercapnic ( P aCO 2 >6 kPa, Group B), by means of overnight oximetry and maximum treadmill exercise testing. The overall group desaturated significantly more during sleep than exercise [12·9 ± 10·5 fall in nocturnal oxygen saturation ( S aO 2 ) vs. 4·5 ± 3·7, P S aO 2 during sleep than Group A (74·3 ± 13·4 vs. 84·6 ± 5·8, P S aO 2 (91·9 ± 3·2 vs. 92·8 ± 2·9, P =n.s.). Awake S aO 2 correlated well with both mean values ( r =0·7, P S aO 2 ( r =0·44, P S aO 2 ( r =0·21, P =n.s.). Minimum sleep and exercise S aO 2 were also significantly correlated ( r =0·44, P S aO 2 during sleep and exercise was not ( P =n.s.). We conclude that exercise studies add no extra information to awake blood gas analysis in predicting the likelihood of nocturnal oxygen desaturation in patients with COPD.