title: Use of flow-volume curves to predict oral appliance treatment outcome in obstructive sleep apnea.
abstract: BACKGROUND
  It has been recognized that mandibular advancement splint (MAS) treatment is effective in some, but not all, patients with obstructive sleep apnea (OSA). Hence there is a need for a simple and reliable clinical tool to assist in the differentiation of treatment responses. We hypothesized that abnormalities of flow-volume curves, together with other clinical variables, may have clinical utility in the prediction of MAS treatment outcome.
  
  
  METHODS
  Fifty-four patients with known OSA underwent MAS treatment. Expiratory and inspiratory flow-volume curves were measured in the erect and supine positions to derive midinspiratory flow (MIF(50)) and the ratio of expiratory to inspiratory flow at 50% of vital capacity (MEF(50):MIF(50)). Multivariable logistic regression was performed to identify additional significant clinical variables in the prediction of treatment outcome.
  
  
  RESULTS
  The mean (+/- SD) apnea-hypopnea index (AHI) in 35 responders was significantly reduced from 28.9 +/- 13.7 to 6.7 +/- 5.8/hour (p<0.001). In 19 nonresponders there was no significant change in AHI. MIF(50) was lower (6.04 +/- 1.80 vs. 6.88 +/- 1.08 L/second; p=0.035) and the MEF(50):MIF(50) ratio was higher (0.82 +/- 0.23 vs. 0.61 +/- 0.15; p=0.001) in responders than nonresponders. Logistic regression analysis revealed that the MEF(50):MIF(50) ratio was the most important predictive factor for MAS treatment outcome, but that body mass index, age, and baseline AHI were also contributory.
  
  
  CONCLUSIONS
  These data suggest that flow-volume curves, in combination with other factors such as body mass index, age, and baseline AHI, may have a useful clinical role in the prediction of treatment outcome with MAS.
authors.affiliation: Centre for Sleep Health and Research, Department of Respiratory Medicine, Royal North Shore Hospital, University of Sydney, Sydney, Australia.
authors.forename: Biao
authors.initials: B
authors.lastname: Zeng
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Ng
authors.forename: M Ali
authors.initials: MA
authors.lastname: Darendeliler
authors.forename: Peter
authors.initials: P
authors.lastname: Petocz
authors.forename: Peter A
authors.initials: PA
authors.lastname: Cistulli
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D019186:Mandibular Advancement / Q000295:instrumentation*; D008875:Middle Aged; D009968:Orthodontic Appliances, Removable; D011237:Predictive Value of Tests; D012123:Pulmonary Ventilation / Q000502:physiology*; D012372:ROC Curve; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology / Q000628:therapy*; D013147:Spirometry; D014109:Total Lung Capacity / Q000502:physiology*; D016896:Treatment Outcome