Sleep apnoea in acute bronchiolitis.

Three- to 4-hour polygraphic sleep studies were carried out in 16 infants aged between 1 and 6 months during and after recovery from acute bronchiolitis. During bronchiolitis 35% of total sleep time was active sleep compared with 31% after recovery. Respiration rate was increased during bronchiolitis and was higher in active sleep and quiet sleep irrespective of the stage of the illness. Apnoeic pauses were invariably shorter than 15 seconds, the mean duration for active sleep and quiet sleep being similar during infection and after recovery. Apnoeic episodes were central in type and generally initiated by a sign or body movements. Preapnoea heart rate was significantly higher than during or after apnoea. Apnoea index (the percentage of time the baby spends apnoeic), apnoea attack rate (the number of episodes of apnoea per unit time), and apnoea percentage (the distribution of episodes of apnoea while in a given sleep state) were increased significantly in quiet sleep during the index illness. Transcutaneous oxygen tension was significantly reduced during the course of infection, but comparable values were obtained in active sleep and quiet sleep during initial and recovery periods. These results show that the main changes in respiration pattern during the course of acute bronchiolitis occur in quiet sleep.