Utility of monitoring breathing during night hours in COPD patients undergoing long-term oxygen therapy

We investigated the occurrence of nocturnal respiratory disorders during air and supplemental oxygen breathing in 16 patients with chronic obstructive pulmonary disease (COPD) undergoing long-term home oxygen therapy (LTOT). Following a first night of acclimatization, non-attended continuous nocturnal monitoring was performed for two successive nights in a randomized order. During one night patients breathed room air ("Air night"), and during the other they underwent LTOT ("O2 night") at the same protective O2 nasal flow rate set during waking hours in a resting state. O2 was administered from liquid reservoirs. On both occasions, the patients were monitored during the night for oxygen saturation by pulse finger oximetry (Sp,O2), chest-abdomen impedance, mouth-nasal thermistor flow rate, electrocardiogram (ECG), body position, eye movements, and leg movements. During the O2 night, compared to the Air night, mean (+/- SD) desaturation time decreased from 46 +/- 29 to 13 +/- 25%, while obstructive apnoea-hypopnoea duration increased from 6 +/- 8 to 9 +/- 7%, both expressed as percentage of total sleep time. The sleep apnoea/hypopnoea syndrome (SAHS) rate during the Air-night was 2 out of 16, both SAHS patients showing a reduction of apnoea-hypopnoea number.h-1 during the O2 night; whilst SAHS was noted in a further two patients during the O2 night. We conclude that Sp,O2 together with monitoring of breathing during the night, is potentially useful in patients with chronic obstructive pulmonary disease undergoing long-term oxygen therapy, not only when evaluating the O2 flow rate to be used during the night, but also for an understanding of the pathogenesis of nocturnal arterial oxyhaemoglobin desaturations, which may or may not be related to respiratory events.