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Response to inspiratory resistive loading during sleep in normal children and children with obstructive apnea
C L Marcus1, G A Moreira, O Bamford
1The Eudowood Division of Pediatric Respiratory Sciences, Johns Hopkins University, Baltimore, Maryland 21287-2533, USA. cmarcus@welchlink.welch.jhu.edu
Insights
Children with obstructive sleep apnea syndrome (OSAS) show impaired arousal responses to inspiratory resistance loading (IRL) during sleep. They require higher resistance to arouse compared to controls, indicating a significant difference in sleep arousal mechanisms.
Area of Science:
- Pediatric Pulmonology
- Sleep Medicine
- Respiratory Physiology
Background:
- The upper airway's response to inspiratory resistance loading (IRL) during sleep in children remains largely uncharacterized.
- Obstructive sleep apnea syndrome (OSAS) is a common pediatric condition affecting sleep and respiratory function.
Purpose of the Study:
- To investigate and compare arousal responses to IRL during sleep in children diagnosed with OSAS versus healthy controls.
- To evaluate ventilatory responses to IRL in healthy children during sleep.
Main Methods:
- Children with OSAS and control subjects underwent polysomnography with the application of controlled inspiratory resistance loading (IRL).
- Arousal thresholds to IRL were measured in both groups, differentiating between REM and non-REM sleep stages.
- Ventilatory parameters, including tidal volume and duty cycle, were assessed in controls during IRL exposure.
Main Results:
- Children with OSAS exhibited significantly higher arousal thresholds to IRL compared to controls (23 cmH2O.L-1.s vs. 15 cmH2O.L-1.s).
- OSAS patients demonstrated higher arousal thresholds during REM sleep compared to non-REM sleep, while controls showed the opposite pattern.
- In controls, IRL led to a marked decrease in tidal volume and an increase in the duty cycle, with arousal preceding gas-exchange abnormalities.
Conclusions:
- Children with OSAS possess impaired arousal responses to inspiratory resistance loading during sleep.
- Healthy children exhibit compensatory respiratory timing adjustments to IRL but experience a reduction in minute ventilation, with arousal occurring before significant gas exchange impairment.
Abstract:
The response to inspiratory resistance loading (IRL) of the upper airway during sleep in children is not known. We, therefore, evaluated the arousal responses to IRL during sleep in children with the obstructive sleep apnea syndrome (OSAS) compared with controls. Children with OSAS aroused at a higher 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 movement (REM) vs. non-REM sleep (P < 0.001), whereas normal subjects had lower arousal 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. l(-1). min; P < 0.001) and after 3 min of IRL (67 +/- 23%, P < 0.005). The duty cycle increased. We conclude that children with OSAS have impaired arousal responses to IRL. Despite compensatory changes in respiratory timing, normal children have a decrease in minute ventilation in response to IRL during sleep. However, arousal occurs before gas-exchange abnormalities.