Response to inspiratory resistive loading during sleep in normal children and children with obstructive apnea

The response to inspiratory resistance loading (IRL) of the upper airway du ring sleep in children is not known. We, therefore, evaluated the arousal r esponses to IRL during sleep in children with the obstructive sleep apnea s yndrome (OSAS) compared with controls. Children with OSAS aroused at a high er load than did controls (23 +/- 8 vs. 15 +/- 7 cmH(2)O.l(-1).s; P < 0.05) . Patients with OSAS had higher arousal thresholds during rapid eye movemen t (REM) vs, non-REM sleep (P < 0.001), whereas normal subjects had lower ar ousal thresholds during REM (P < 0.005). Ventilatory responses to IRL were evaluated in the controls. There was a marked decrease in tidal volume both immediately (56 +/- 17% of baseline at an IRL of 15 cmH(2)O. I-1.min; P < 0.001) and after 3 min of IRL (67 +/- 23%, P < 0.005). The duty cycle incre ased. We conclude that children with OSAS have impaired arousal responses t o IRL. Despite compensatory changes in respiratory timing, normal children have a decrease in minute ventilation in response to IRL during sleep. Howe ver, arousal occurs before gas-exchange abnormalities.