Upper airway collapsibility and genioglossus activity in adolescents during sleep

Study objectives: Obese patients develop obstructive sleep apnea syndrome (OSAS), at least in part because of a narrowed upper airway. However, many obese adolescents do not develop OSAS, despite having a presumably narrower airway. The reasons for this phenomenon are unclear. The authors hypothesized that obese controls have a compensatory neuromuscular response to subatmospheric pressure loads during sleep, making them less likely to develop upper airway collapse.

Design: Patients underwent pressure-flow measurements during sleep while wearing intraoral electrodes to measure genioglossal electromyography (EMGgg). Two techniques were applied to decrease nasal pressure (P(N)) to subatmospheric levels, resulting in an activated and relatively hypotonic upper airway.

Setting: Sleep laboratory.

Participants: There were 35 obese patients with OSAS, 28 obese controls, and 43 lean controls.

Results: In the activated state, the two control groups had a flatter slope of the pressure-flow relationship and a more negative critical closing pressure (less collapsible) than the OSAS group. In the hypotonic state, the lean controls had a flatter slope of the pressure-flow relationship than the OSAS and obese control groups. In the activated state, the slope of EMGgg versus P(N) was greater in the obese control group than in the OSAS or lean control groups (P = 0.002 and P = 0.028, respectively); there were no differences in the hypotonic state.

Conclusions: Obese controls have vigorous upper airway neuromuscular responses during sleep. Upper airway reflexes normally decline during adolescent development. It is speculated that obese adolescents without OSAS maintain protective upper airway reflexes during adolescent development, whereas those who go on to develop OSAS do not.