title: New acoustic method for detecting upper airway obstruction in patients with sleep apnoea.
abstract: This article investigates a new acoustic device to assess the behaviour of the upper airway in patients with OSA. Currently there is no simple non-invasive method to perform such measurements. As such this paper describes the device in probing the patency of the airway during sleep and increasing the efficiency of diagnosing OSA.
  
  
  OBJECTIVE
  OSA is a common disorder resulting in health and economic burdens. Currently identifying OSA in patients involves expensive techniques that require overnight studies in a laboratory setting with qualified staff. This paper tests a new acoustic device (AirwayClear (AC)) for assessing upper airway patency in human subjects with OSA. We hypothesize that obstructive apnoeas would be detected equally well with AC and polysomnography (PSG).
  
  
  METHODS
  Twenty-three patients with severe OSA underwent an overnight CPAP titration study. We introduced pseudorandom noise (600-1200 Hz) using AC to the patient's nasal mask during 1 h of subtherapeutic CPAP. AC determined a measure of airway patency based on the level of pseudorandom noise reaching a sternal notch sensor. The ability of AC to detect obstructive respiratory events was compared with standard PSG.
  
  
  RESULTS
  Three hundred and twenty-two obstructive events (obstructive and mixed apnoeas) were identified by PSG. AC scored 80% as complete obstructions and 16% as partial obstructions. Conversely, AC detected 281 complete obstructions. PSG recognized 84% as apnoeas and scored 11% as hypopnoeas. Of the 204 hypopnoeas identified with PSG, AC indicated the airway was partially or completely obstructed in 69% of patients. A Bland-Altman analysis for the apnoeas from the two measures showed a mean difference of 2.3 events/h and 95% confidence intervals of +/-15.5 events/h.
  
  
  CONCLUSIONS
  We conclude that AC is able to track airway patency and to identify airway closure in patients with OSA.
authors.affiliation: Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, Clayton, Victoria, Australia. elaine.stockx@med.monash.edu.au
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Stockx
authors.forename: Peter
authors.initials: P
authors.lastname: Camilleri
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Skuza
authors.forename: Thomas
authors.initials: T
authors.lastname: Churchward
authors.forename: Julie M
authors.initials: JM
authors.lastname: Howes
authors.forename: Michael
authors.initials: M
authors.lastname: Ho
authors.forename: Timothy
authors.initials: T
authors.lastname: McDonald
authors.forename: Nicholas
authors.initials: N
authors.lastname: Freezer
authors.forename: Garun
authors.initials: G
authors.lastname: Hamilton
authors.forename: Malcolm H
authors.initials: MH
authors.lastname: Wilkinson
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Berger
mesh_terms: D000162:Acoustics; D000328:Adult; D000402:Airway Obstruction / Q000175:diagnosis* / Q000209:etiology* / Q000503:physiopathology; D045422:Continuous Positive Airway Pressure; D003955:Diagnostic Tests, Routine / Q000295:instrumentation*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012891:Sleep Apnea Syndromes / Q000150:complications* / Q000503:physiopathology; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology