OBSTRUCTIVE APNEAS IN DUCHENNE MUSCULAR-DYSTROPHY

Background - In order to clarify the treatment of sleep hypoxaemias in Duchenne muscular dystrophy polysomnographic studies were performed on patients at home with the purpose of recruiting them into two clinical therapeutic trials. Observations concerning the nature of sleep hypoxaemia in these patients are presented. Methods - Twenty one non-ambulant patients with Duchenne muscular dystrophy aged 13-23 years with no symptoms of sleep hypoventilation or apnoea were studied for two consecutive nights with eight channel polysomnography. A comparative study was performed in 12 age matched normal male subjects. The evolution of sleep hypoxaemia with age was studied in 14 patients with Duchenne muscular dystrophy. Results - Thirteen of the 21 patients had hypoxaemia below 90% during sleep, and 12 of the 13 had discrete hypoxaemic dips in association with apnoeas; 60% of all apnoeas were obstructive in nature. The hypoxaemic periods became more frequent with increasing age and, in two patient at three year follow up, were more frequently associated with central or possibly ''pseudocentral'' apnoeas. Although the normal subjects had a few apnoeic episodes, none had sleep hypoxaemia below 90% saturation. Conclusion - The sleep related breathing abnormality in Duchenne muscular dystrophy is initially obstructive and this has implications for management.