Patients with Duchenne muscular dystrophy develop progressive ventilatory muscle weakness and often die of respiratory complications. Recurrent, often profound, hypoxaemia has been shown in a previous study by this group to occur during rapid eye movement (REM) sleep in these patients before they develop sleep symptoms. In this study the efficacy and physiological effects of nocturnal oxygen in such patients have been assessed. Seven patients with Duchenne muscular dystrophy (age range 16-22 years; mean vital capacity 1.37 litres) with normal arterial blood gas tensions when awake were investigated by standard overnight polysomnography on an acclimatization night followed by two successive nights on which they received room air and nasal oxygen (2 litres/min) respectively in random order. Total sleep time, proportion of REM and non-REM sleep, and frequency and duration of arousals were similar on the two nights. When breathing air six of the seven subjects developed oxygen desaturation of more than 5% during REM sleep. With oxygen only one subject showed any oxygen desaturation exceeding 2.5%. Oxygen desaturation was associated with periods of hypopnoea or cessation of respiratory effort. The mean duration of episodes of hypopnoea and apnoea was prolonged during oxygen breathing by 19% and the mean duration of episodes during REM sleep by 33% (the proportion of REM sleep associated with hypopnoea and apnoea increased in all subjects). Heart rate in non-REM sleep fell by 9.3%; heart rate variation in REM and non-REM sleep was unchanged. These acute studies show that oxygen reduces the sleep hypoxaemia associated with respiratory muscle weakness; whether long term treatment will be possible or desirable is not clear as oxygen potentiates the underlying ventilatory disturbance.
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