Arterial oxygen desaturation during sleep in children with asthma and its relation to airway obstruction and ventilatory drive.

The possibility that arterial oxygen saturation (SaO2) decreases during sleep in children with chronic bronchial asthma was investigated. The relationship between decreases in sleep SaO2 and airflow obstruction and ventilatory drives, as characterized by ventilatory and inspiratory muscle activity responses to hypoxia and hypercapnia was also examined. Sixteen asthmatics on suboptimal bronchodilator therapy and ten healthy children were studied. Both maximum decrease in SaO2 and number of desaturations (decrease in SaO2 greater than or equal to 4%) per hour during sleep were greater in the asthmatics than in the control subjects. Both maximum decrease in SaO2 and number of desaturations per hour asleep were correlated with change in FEV1 and FEF25%-75% over the sleep period. Changes in SaO2 were not related to awake measurements of ventilatory drive. Eight of the asthmatics also were studied when on a more optimal medication regimen. On this program they had less airflow obstruction before and after sleep, and the number and extent of decreases in SaO2 were not different from those of the control subjects. We conclude: (1) decreases in SaO2 occurred during sleep in suboptimally treated asthmatic children; (2) SaO2 changes during sleep were related to the amount of air-flow obstruction that developed during sleep; (3) SaO2 changes during sleep were not related to ventilatory drive measured during wakefulness; and (4) a good therapeutic regimen eliminated abnormal amounts of sleep hypoxemia by improving airflow limitation. However, as the results of this study indicate, when their pulmonary status is unstable, asthmatic children may develop clinically significant hypoxemia during sleep.