Trajectory of Change in ENO, FEV_1,and FEV25.75 in Children with Asthma During Usual and Delayed Bedtime

摘要

Children with asthma experience sleep disruptions due to respiratory symptoms. Little is known about the relative influence of sleep versus circadian forces on broncho-constrictive and inflammatory parameters. This study examined differences in trajectory of change in eNO, FEV_1, and FEV_25-75 during a usual and 4-hour sleep delay protocol. Methods: Children were free of URI and systemic steroid use for 2 weeks. After 1 week symptom monitoring to assure asthma control/partial control, children completed 2 nights of poly-somnographic monitored-sleep with respiratory testing. Night 1, lights out began at the child's usual bedtime. Night 2, lights out was delayed 4 hours. On both nights, eNO was collected off-line and analyzed using a Seivers (Boulder, CO) chemiluminescence analyzer (ppb) and FEV^nd 25-75% predicted assessed with a portable 2170-Spirotac III, BreezeSC-TM software at the child's usual bedtime and 4 and 8 hours later. Results: A main effect by asthma status was found for eNO (F = 31.8, P < 0.001) such that children with asthma exhibited increased eNO values. The eNO pattern of change, similar for both groups, was not significant by night or session. There was a significant interaction of night by session (F = 4.3, P < 0.02). This night by session interaction reflected the sleep delay night's, eNO value pre-sleep (usual-bedtime-plus-4 h) having a level similar to the first night's pre-sleep value (usual-bedtime), both subsequently rising when the child feel asleep. Both nights there was a mono-tonic decrease in FEV_1 and FEV_25-75 that did not differ by asthma status or night. Conclusions: Rises in eNO may have a different etiology (sleep) than do falls in both FEV_1/25-75 (circadian). Higher baseline eNO of children with asthma may place them at greater risk for consequences of airway obstruction initiated after sleep. A better understanding of these differences may assist in designing effective approaches to treatment of nocturnal asthma in youth.