Abstract
STUDY OBJECTIVES: Upper airway (UA) collapsibility is a major pathophysiologic feature of the obstructive sleep apnea syndrome (OSAS). In adolescents, it is measured by obtaining the slope of pressure-flow relationship (SPF) while applying negative nasal pressure during sleep. An easier technique to assess UA collapsibility, consisting of application of negative expiratory pressure (NEP) during wakefulness, has demonstrated differences between control and OSAS subjects. We hypothesized that the NEP technique would correlate with SPF as a measurement of UA collapsibility in adolescents. DESIGN: During wakefulness, NEP of -5 cm H2O in the seated and supine position was applied during the first second of expiration. The area under the expiratory flow-volume curve during NEP was compared to tidal breathing (RatioNEP). In addition, adolescents underwent SPF measurements during sleep. Two SPF techniques were performed to measure the activated and relatively hypotonic UA. SETTING: Pediatric sleep laboratory. PARTICIPANTS: Seven adolescents with OSAS and 20 controls. RESULTS: In the seated position, there was a correlation between RatioNEP and both hypotonic SPF (r = -0.39, P = 0.04) and activated SPF (r = -0.62, P = 0.001). In the supine position, there was a correlation between RatioNEP and activated SPF (r = -0.43, P = 0.03) and a trend for hypotonic SPF (r = -0.38, P = 0.06). CONCLUSIONS: The negative expiratory pressure (NEP) technique correlates with the hypotonic and activated slope of pressure-flow relationship measurements. The seated position showed the strongest correlation. The NEP technique can be used as an alternative method to evaluate upper airway collapsibility in adolescents.