Upper airway genioglossal activity in children with sickle cell disease

Study Objectives: The prevalence of obstructive sleep apnea syndrome (OSAS) in sickle cell disease (SCD) has been reported to be higher than that in the general pediatric population. However, not all subjects with SCD develop OSAS. We hypothesized that SCD patients with OSAS have a blunted neuromuscular response to subatmospheric pressure loads during sleep, making them more likely to develop upper airway collapse. Design: Subjects with SCD with and without OSAS underwent pressure-flow measurements during sleep using intraoral surface electrodes to measure genioglossal EMG (EMGgg). Two techniques were applied to decrease the nasal pressure (P _N) to subatmospheric levels, resulting in an activated and relatively hypotonic upper airway. The area under the curve of the inspiratory EMGgg moving time average was analyzed. EMGgg activity was expressed as a percentage of baseline. Changes in EMGgg in response to decrements in nasal pressure were expressed as the slope of the EMGgg vs. nasal pressure (slope of EMGgg-P _N). Setting: Sleep laboratory. Participants: 4 children with SCD and OSAS and 18 children with SCD but without OSAS. Results: The major findings of this study were: (1) using the activated but not the hypotonic technique, the slope of EMGgg-P _N was more negative in SCD controls than SCD OSAS; (2) the slope of EMGgg-P _N was significantly lower using the activated technique compared to the hypotonic technique in SCD controls only; (3) similarly, the critical closing pressure, Pcrit, was more negative using the activated technique than the hypotonic technique in SCD controls but not in SCD OSAS. Conclusion: This preliminary study has shown that children with SCD but without OSAS have more prominent upper airway reflexes than children with SCD and OSAS.