title: Negative Expiratory Pressure Technique: An Awake Test to Measure Upper Airway Collapsibility in Adolescents.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  METHODS
  Pediatric sleep laboratory.
  
  
  METHODS
  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.
authors.affiliation: Corporacio Sanitaria Parc Taulí, Fundacio Parc Tauli, Sabadell, Spain.|Sleep Center, The Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA.
authors.forename: Helena Larramona
authors.initials: HL
authors.lastname: Carrera
authors.affiliation: Sleep Center, The Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA.
authors.forename: Carole L
authors.initials: CL
authors.lastname: Marcus
authors.affiliation: Sleep Center, The Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: McDonough
authors.affiliation: Corporacio Sanitaria Parc Taulí, Fundacio Parc Tauli, Sabadell, Spain.
authors.forename: Joan C
authors.initials: JC
authors.lastname: Oliva Morera
authors.affiliation: Sleep Center, The Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA.
authors.forename: Jingtao
authors.initials: J
authors.lastname: Huang
authors.affiliation: Unitat de Biofisica i Bioenginyeria, Facultat de Medicina, Universitat de Barcelona-IDIBAPS, Barcelona, Spain.|CIBER de Enfermedades Respiratorias, Madrid, Spain.
authors.forename: Ramon
authors.initials: R
authors.lastname: Farre
authors.affiliation: CIBER de Enfermedades Respiratorias, Madrid, Spain.|Laboratori de la Son, Pneumologia, Hospital Clínic-IDIBAPS, Barcelona, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Montserrat
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011312:Pressure; D011897:Random Allocation; D012119:Respiration; D012137:Respiratory System / Q000503:physiopathology*; D012890:Sleep; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D014851:Wakefulness / Q000502:physiology*
keywords: adolescents; negative expiratory pressure technique; obstructive sleep apnea syndrome; upper airway collapsibility