Stadler, D.McEvoy, R.Sprecher, K.Thomson, K.Ryan, M.Thompson, C.Catcheside, P.2010-04-292010-04-292009Sleep, 2009; 32(12):1579-15870161-81051550-9109http://hdl.handle.net/2440/57960<h4>Study objectives</h4>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.<h4>Design</h4>This study aimed to examine the effect of abdominal compression on UA function during sleep in obese male obstructive sleep apnea patients.<h4>Setting</h4>Participants slept in a sound-insulated room with physiologic measurements controlled from an adjacent room.<h4>Participants</h4>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.<h4>Interventions</h4>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.<h4>Measurements and results</h4>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).<h4>Conclusions</h4>Abdominal compression negatively impacts on UA collapsibility during sleep and this effect may help explain strong associations between central obesity and obstructive sleep apnea.enCopyright © 2009 by the Associated Professional Sleep Societies, LLCObstructive sleep apneaabdominal loadinglung volumecaudal tractionJournal article002009408710.1093/sleep/32.12.15790002723763000092-s2.0-7324912148636553McEvoy, R. [0000-0002-5759-0094]Catcheside, P. [0000-0002-9372-6788]