title: Changes in upper airway size during tidal breathing in children with obstructive sleep apnea syndrome.
abstract: We performed respiratory-gated magnetic resonance imaging to evaluate airway dynamics during tidal breathing in 10 children with obstructive sleep apnea syndrome (OSAS; age, 4.3 +/- 2.3 years) and 10 matched control subjects (age, 5.0 +/- 2.0 years). We hypothesized that respiratory cycle fluctuations in upper airway cross-sectional area would be larger in children with OSAS.
  
  
  METHODS
  Studies were performed under sedation. Respiratory gating was performed automatically at 10, 30, 50, 70, and 90% of inspiratory and expiratory volume. Airway cross-sectional area was measured at four ascending oropharyngeal levels at each increment of the respiratory cycle.
  
  
  RESULTS
  We noted the following in subjects with OSAS compared with control subjects: (1) a smaller upper airway cross-sectional area, particularly during inspiration; (2) airway narrowing occurred during inspiration without evidence of complete airway collapse; (3) airway dilatation occurred during expiration, particularly early in the phase; and (4) magnitude of cross-sectional areas fluctuations during tidal breathing noted in OSAS at levels 1 through 4 were 317, 422, 785, and 922%, compared with 19, 15 17, and 24% in control subjects (p < 0.001, p < 0.005, p < 0.001, and p < 0.001, respectively).
  
  
  CONCLUSIONS
  Fluctuations in airway area during tidal breathing are significantly greater in subjects with OSAS compared with control subjects. Resistive pressure loading is a probable explanation, although increased airway compliance may be a contributing factor.
authors.affiliation: Division of Pulmonary Medicine, The Children's Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104-4399, USA. arens@email.chop.edu
authors.forename: Raanan
authors.initials: R
authors.lastname: Arens
authors.forename: Sanghun
authors.initials: S
authors.lastname: Sin
authors.forename: Joseph M
authors.initials: JM
authors.lastname: McDonough
authors.forename: John M
authors.initials: JM
authors.lastname: Palmer
authors.forename: Troy
authors.initials: T
authors.lastname: Dominguez
authors.forename: Heiko
authors.initials: H
authors.lastname: Meyer
authors.forename: David M
authors.initials: DM
authors.lastname: Wootton
authors.forename: Allan I
authors.initials: AI
authors.lastname: Pack
mesh_terms: D019412:Anatomy, Cross-Sectional; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009929:Organ Size; D017286:Polysomnography; D015656:Respiratory Mechanics / Q000502:physiology; D012137:Respiratory System / Q000473:pathology* / Q000503:physiopathology*; D020181:Sleep Apnea, Obstructive / Q000473:pathology* / Q000503:physiopathology*; D013990:Tidal Volume