title: Abdominal compression increases upper airway collapsibility during sleep in obese male obstructive sleep apnea patients.
abstract: OBJECTIVE
  Abdominal obesity, particularly common in centrally obese males, may have a negative impact on upper airway (UA) function during sleep. For example, cranial displacement of the diaphragm with raised intra-abdominal pressure may reduce axial tension exerted on the UA by intrathoracic structures and increase UA collapsibility during sleep.
  
  
  METHODS
  This study aimed to examine the effect of abdominal compression on UA function during sleep in obese male obstructive sleep apnea patients.
  
  
  METHODS
  Participants slept in a sound-insulated room with physiologic measurements controlled from an adjacent room.
  
  
  METHODS
  Fifteen obese (body mass index: 34.5 +/- 1.1 kg/m2) male obstructive sleep apnea patients (apnea-hypopnea index: 58.1 +/- 6.8 events/h) aged 50 +/- 2.6 years participated.
  
  
  METHODS
  Gastric (PGA) and transdiaphragmatic pressures (P(DI)), UA closing pressure (UACP), UA airflow resistance (R(UA)), and changes in end-expiratory lung volume (EELV) were determined during stable stage 2 sleep with and without abdominal compression, achieved via inflation of a pneumatic cuff placed around the abdomen. UACP was assessed during brief mask occlusions.
  
  
  RESULTS
  Abdominal compression significantly decreased EELV by 0.53 +/- 0.24 L (P=0.045) and increased PGA (16.2 +/- 0.8 versus 10.8 +/- 0.7 cm H2O, P < 0.001), P(DI) (11.7 +/- 0.9 versus 7.6 +/- 1.2 cm H2O, P < 0.001) and UACP (1.4 +/- 0.8 versus 0.9 +/- 0.9 cm H2O, P = 0.039) but not R(UA)(6.5 +/- 1.4 versus 6.9 +/- 1.4 cm H2O x L/s, P=0.585).
  
  
  CONCLUSIONS
  Abdominal compression negatively impacts on UA collapsibility during sleep and this effect may help explain strong associations between central obesity and obstructive sleep apnea.
authors.affiliation: Adelaide Institute for Sleep Health, The Repatriation General Hospital, Daw Park, South Australia 5041, Australia. daniel.stadler@health.sa.gov.au
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Stadler
authors.forename: R Doug
authors.initials: RD
authors.lastname: McEvoy
authors.forename: Kate E
authors.initials: KE
authors.lastname: Sprecher
authors.forename: Kieron J
authors.initials: KJ
authors.lastname: Thomson
authors.forename: Melissa K
authors.initials: MK
authors.lastname: Ryan
authors.forename: Courtney C
authors.initials: CC
authors.lastname: Thompson
authors.forename: Peter G
authors.initials: PG
authors.lastname: Catcheside
mesh_terms: D000005:Abdomen / Q000503:physiopathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000403:Airway Resistance; D006801:Humans; D008176:Lung Volume Measurements / Q000379:methods; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D056128:Obesity, Abdominal / Q000150:complications; D011312:Pressure; D015656:Respiratory Mechanics; D012137:Respiratory System / Q000503:physiopathology*; D012890:Sleep; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000503:physiopathology*; D055815:Young Adult