Overnight prescription of oxygen in long term oxygen therapy: time to reconsider the guidelines?

Guidelines for long term oxygen therapy (LTOT) recommend increasing oxygen flow by 1 l/min overnight. A study was undertaken in patients with COPD on LTOT to determine the prevalence of overnight desaturation if the usual oxygen flow rate is not increased at night, whether resting oxygen saturation predicts overnight desaturation, and whether overnight desaturation correlates with health related quality of life (HRQL) and sleep quality.

A cross sectional prospective study was performed on consecutive patients with COPD on LTOT attending our regional outpatient oxygen service. All patients fulfilled standard criteria for LTOT, had been established on LTOT at a flow to achieve resting oxygen saturations >90%, but had not been instructed to increase oxygen flow overnight. Overnight desaturation was defined as <90% for > or =30% of the night on either of two consecutive nights. HRQL was evaluated with the SF-36 Health Survey Questionnaire, Chronic Respiratory Questionnaire, and the Pittsburgh Sleep Quality Index.

Thirty eight patients (63% men) of mean (SD) age 73.5 (8.04) years and mean (SD) forced expiratory volume in 1 second 0.77 (0.35) l were evaluated. Overnight desaturation occurred in six (16%; 95% CI 4 to 27). Desaturators had mean (SD) resting oxygen saturation on room air of 88 (4.2)% compared with 90 (4.1)% in non-desaturators (p = 0.15), and corrected saturations of 93 (2.0)% versus 94 (2.0)% (p = 0.18). HRQL and sleep quality were poor but did not differ between desaturators and non-desaturators.

Most patients did not exhibit overnight desaturation despite not increasing their LTOT prescription overnight. These results challenge the recommendation of routinely increasing overnight oxygen flow in patients receiving LTOT.