title: Comparison of limited monitoring using a nasal-cannula flow signal to full polysomnography in sleep-disordered breathing.
abstract: OBJECTIVE
  Evaluate the utility of overnight monitoring limited to nasal cannula airflow and oximetry in the diagnosis of obstructive sleep apnea-hypopnea syndrome (OSAHS).
  
  
  METHODS
  Prospective randomized study, blinded analysis.
  
  
  METHODS
  Sleep disorder center, academic institution.
  
  
  METHODS
  56 patients with suspected OSAHS, 10 normal volunteers.
  
  
  RESULTS
  In-laboratory full nocturnal polysomnography (NPSG) and unattended ambulatory study with monitoring of only airflow and oximetry performed in randomized order. Obstructive respiratory events were scored on the full NPSG while visualizing all signals and then rescored on the full NPSG and on the ambulatory study while visualizing only airflow and oximetry signals. Respiratory disturbance indexes (RDI) for the limited studies (RDIFlowNPSG and RDIFlowAmbulatory) were calculated as the sum of the apneas and hypopneas (defined using airflow amplitude and O2 desaturation) divided by the valid flow-signal time. The reference RDIFullNPSG was calculated from the sum of the apneas and hypopneas (defined using flow amplitude, O2 desaturation and electroencephalographic arousal) identified on the full NPSG divided by the total sleep time. RDIFullNPSG was greater than RDIFlowNPSG (bias = 5.6 events per hour) and RDIFlowAmbulatory (bias = 10.9 events per hour), but the differences were mainly in subjects with an RDI > 40 events per hour. The diagnostic sensitivity and specificity for the diagnosis of OSAHS using a cutoff of 18 events per hour were 96% and 93% using the flow signal from the NPSG and 88% and 92% using the flow signal from the ambulatory study performed on a separate night.
  
  
  CONCLUSIONS
  In subjects with OSAHS, analysis of the flow signal from a nasal cannula can provide an RDI similar to that obtained in a full NPSG.
authors.affiliation: NYU School of Medicine, New York 10016, USA.
authors.forename: Indu
authors.initials: I
authors.lastname: Ayappa
authors.forename: Robert G
authors.initials: RG
authors.lastname: Norman
authors.forename: Madhu
authors.initials: M
authors.lastname: Suryadevara
authors.forename: David M
authors.initials: DM
authors.lastname: Rapoport
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D002404:Catheterization / Q000295:instrumentation; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis / Q000453:epidemiology; D004569:Electroencephalography; D004585:Electrooculography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009296:Nasal Cavity; D010092:Oximetry; D017286:Polysomnography / Q000379:methods*; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000175:diagnosis* / Q000453:epidemiology; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology