title: Relative occurrence of flow limitation and snoring during continuous positive airway pressure titration.
abstract: OBJECTIVE
  To examine the relative temporal appearance of flow limitation and snoring during continuous positive airway pressure (CPAP) titration, compare their sensitivity as indicators of airway obstruction, and assess their relative utility as feedback variables for automatic titration of CPAP.
  
  
  METHODS
  Retrospective review of data.
  
  
  METHODS
  University teaching hospital.
  
  
  METHODS
  Fifty-three patients diagnosed as having obstructive sleep apnea or upper airway resistance syndrome undergoing CPAP titration.
  
  
  RESULTS
  We used a prototype automatic CPAP device that adjusts pressure in response to apnea, snoring, and/or flow limitation. The present study takes advantage of the frequent automatic decreases in pressure from a therapeutic level, as well as any technician-initiated decreases in pressure. We tabulated, for each pressure decrease of >0.4 cm H2O, the occurrences of snoring alone, flow limitation alone, or simultaneous appearance of both. Of 2,177 automatic pressure decreases, 64% resulted in flow limitation alone, 8% in snoring alone, and 22% in the simultaneous occurrence of both. Overall, 86% of decreases resulted in flow limitation alone or were simultaneous with snoring, whereas 30% of decreases resulted in snoring alone or were simultaneous with flow limitation. In 10 of 35 patients, snoring alone occurred in > 10% of the pressure decreases. In all but 5 of 133 manual pressure decreases, flow limitation developed at or above the pressure at which snoring developed.
  
  
  CONCLUSIONS
  While detection of snoring occasionally provided additional information, overall flow limitation was the earliest indicator of obstruction during decreases in CPAP.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, New York University Medical Center, NY 10016, USA.
authors.forename: I
authors.initials: I
authors.lastname: Ayappa
authors.forename: R G
authors.initials: RG
authors.lastname: Norman
authors.forename: J J
authors.initials: JJ
authors.lastname: Hosselet
authors.forename: R A
authors.initials: RA
authors.lastname: Gruenke
authors.forename: J A
authors.initials: JA
authors.lastname: Walsleben
authors.forename: D M
authors.initials: DM
authors.lastname: Rapoport
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000403:Airway Resistance; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D012123:Pulmonary Ventilation; D012189:Retrospective Studies; D012891:Sleep Apnea Syndromes / Q000503:physiopathology / Q000628:therapy; D012913:Snoring / Q000503:physiopathology*