title: Oral airway resistance during wakefulness in patients with obstructive sleep apnoea.
abstract: BACKGROUND
  Patients with obstructive sleep apnoea (OSA) have a number of upper airway structural abnormalities which may influence the resistance of the oral airway to airflow. There have been no systematic studies of the flow dynamics of the oral cavity in such patients.
  
  
  METHODS
  Inspiratory oral airway resistance to airflow (RO) was measured in 13 awake patients with OSA in both the upright and supine positions (neck position constant). Each subject breathed via a mouthpiece while the nasal airway was occluded with a nasal mask.
  
  
  RESULTS
  In the upright position the mean (SE) RO was 1.26 (0. 19) cm H2O/l/s (at 0.4 l/s) which increased to 2.01 (0.43) cm H2O/l/s when supine (p<0.05, paired t test). The magnitude of this change correlated negatively with the respiratory disturbance index (r = -0.60, p = 0.03).
  
  
  CONCLUSIONS
  In awake patients with OSA RO is normal when upright but abnormally raised when in the supine position.
authors.affiliation: Department of Respiratory Medicine, Westmead Hospital, and University of Sydney, NSW 2145, Australia.
authors.forename: T C
authors.initials: TC
authors.lastname: Amis
authors.forename: N
authors.initials: N
authors.lastname: O'Neill
authors.forename: J R
authors.initials: JR
authors.lastname: Wheatley
mesh_terms: D000403:Airway Resistance / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009058:Mouth Breathing / Q000503:physiopathology*; D017286:Polysomnography; D011187:Posture; D012044:Regression Analysis; D012891:Sleep Apnea Syndromes / Q000175:diagnosis / Q000503:physiopathology*; D014851:Wakefulness