Abstract
STUDY OBJECTIVES: Upper airway (UA) collapsibility is a major factor in the pathophysiology of sleep disordered breathing (SDB). We hypothesized that the negative expiratory pressure (NEP) technique could distinguish between normal children and children with SDB even during wakefulness. DESIGN: During wakefulness, NEP of -5 and -10 cm H(2)O was applied during expiration in seated and supine positions. UA muscle activity (EMG) was measured using intra-oral electrodes. SETTING: Sleep laboratory. PARTICIPANTS: Twenty children with snoring, 20 with obstructive sleep apnea syndrome (OSAS), and 20 controls. MEASUREMENTS AND RESULTS: The ratio of the area under the expiratory flow-volume curve during NEP compared to tidal breathing (RatioNEP) was calculated. Similarly, EMG area under the curve during NEP as a ratio of baseline was measured (RatioEMG). There were significant differences in RatioNEP between controls and snorers and controls and OSAS, at both pressures, in both the seated and supine positions; P < 0.0001 for all (e.g., RatioNEP at -5 cm H(2)O, seated: 1.8 ± 0.5, 2.1 ± 0.4, and 3.0 ± 0.6 for OSAS, snorers, and controls, respectively). However, no significant differences were found between snorers and OSAS. For RatioEMG, no significant differences were found between groups. CONCLUSIONS: RatioNEP distinguishes between normal children and children with SDB, be it snoring or OSAS, indicating that these children have a more collapsible UA even during wakefulness. However, it does not differentiate between snorers and OSAS, highlighting the important role of UA muscle activity during sleep. NEP technique does not elicit a different UA muscle activity response between controls and children with SDB.