The adequacy of oxygenation in COPD patients undergoing long-term oxygen therapy assessed by pulse oximetry at home.

It is probable that some daily activities may cause marked falls in arterial oxygen saturation (SaO2) in patients undergoing long-term oxygen therapy (LTOT), despite good oxygenation at rest. We estimated the adequacy of LTOT in 34 randomly selected chronic obstructive pulmonary disease (COPD) patients at home by monitoring SaO2 continuously over 24 h. The subjects were also asked to complete a questionnaire listing frequent daily activities. Despite almost normal mean SaO2 (94%) at the beginning of recording (O2 2 l.min-1, at rest) the subjects studied spent 6.9 h below an SaO2 of 90%, with minimum SaO2 of 61%. On average we observed 10 episodes of desaturation in each patient over 24 h, both while breathing air and oxygen. The comparison of SaO2 recordings and questionnaires revealed the highest number of desaturations during sleep, followed by naps, watching the television, eating, washing and talking. The oxygen flow rate prescribed, based on blood gas measurements at rest, did not protect 85% of the patients studied from deep falls in SaO2 during daily life. An increase oxygen flow during some activities and during sleep is suggested.