title: Effect of using the flow or the volume signals on the measurement of nonapneic respiratory events.
abstract: OBJECTIVE
  To assess whether the measurement of breathing reduction during obstructive sleep events depends on using the flow or the volume signals recorded with a pneumotachograph.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Sleep laboratory in a University Hospital.
  
  
  METHODS
  Data from 10 male patients with sleep apnea (54 +/- 11 years, apnea-hypopnea index: 43 +/- 21 events/hour, body mass index: 30 +/- 2 kg/m2).
  
  
  METHODS
  Slow modification of continuous positive airway pressure was performed during full-polysomnography continuous positive airway pressure titration.
  
  
  RESULTS
  Air flow was measured by a pneumotachograph, and volume was computed by numerical integration. Obstructive events of different magnitude were selected. In 500 breathing cycles analyzed, the reduction in tidal volume was greater than the reduction in the flow amplitude: mean difference of 0.091 (i.e., 9.1% amplitude) and limits of agreement of 0.095 and -0.277 (i.e., 9.5% and -27.7% amplitude). In 14% of the cycles, the reduction in flow was < 50%, whereas the reduction in volume was > 50%, resulting in discordant event classification.
  
  
  CONCLUSIONS
  The quantification of breathing reduction depends on whether the flow or the volume signal is used to assess breathing during sleep.
authors.affiliation: Sleep Laboratory Servei de Pneumologia i Allèrgia Respiratòria, Hospital Clinic, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Montserrat
authors.forename: Jordi
authors.initials: J
authors.lastname: Rigau
authors.forename: Daniel
authors.initials: D
authors.lastname: Navajas
authors.forename: Eugeni
authors.initials: E
authors.lastname: Ballester
authors.forename: Ramon
authors.initials: R
authors.lastname: Farré
mesh_terms: D000328:Adult; D015992:Body Mass Index; D045422:Continuous Positive Airway Pressure / Q000379:methods; D006801:Humans; D008875:Middle Aged; D019370:Observation; D017286:Polysomnography; D011446:Prospective Studies; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000175:diagnosis* / Q000453:epidemiology* / Q000628:therapy; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000453:epidemiology* / Q000628:therapy