title: The respiratory pressure-abdominal volume curve in a porcine model.
abstract: BACKGROUND
  Increasing intra-abdominal volume (IAV) can lead to intra-abdominal hypertension (IAH) or abdominal compartment syndrome. Both are associated with raised morbidity and mortality. IAH can increase airway pressures and impair ventilation. The relationship between increasing IAV and airway pressures is not known. We therefore assessed the effect of increasing IAV on airway and intra-abdominal pressures (IAP).
  
  
  METHODS
  Seven pigs (41.4 +/-8.5 kg) received standardized anesthesia and mechanical ventilation. A latex balloon inserted in the peritoneal cavity was inflated in 1-L increments until IAP exceeded 40 cmH2O. Peak airway pressure (pPAW), respiratory compliance, and IAP (bladder pressure) were measured. Abdominal compliance was calculated. Different equations were tested that best described the measured pressure-volume curves.
  
  
  RESULTS
  An exponential equation best described the measured pressure-volume curves. Raising IAV increased pPAWand IAP in an exponential manner. Increases in IAP were associated with parallel increases in pPAWwith an approximate 40% transmission of IAP to pPAW. The higher the IAP, the greater IAV effected pPAWand IAP.
  
  
  CONCLUSIONS
  The exponential nature of the effect of IAV on pPAWand IAP implies that, in the presence of high grades of IAH, small reductions in IAV can lead to significant reductions in airway and abdominal pressures. Conversely, in the presence of normal IAP levels, large increases in IAV may not affect airway and abdominal pressures.
authors.affiliation: Intensive Care Unit, Fiona Stanley Hospital, 102-118 Murdoch Drive, Murdoch (Perth), WA, 6150, Australia. adrian.regli@gmail.com.|Intensive Care Unit, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands (Perth), WA, 6009, Australia. adrian.regli@gmail.com.|School of Medicine and Pharmacology, The University of Western Australia, Sterling Highway, Crawley (Perth), WA, 6009, Australia. adrian.regli@gmail.com.|Medical School, The Notre Dame University, Henry Road, Fremantle (Perth), WA, 6959, Australia. adrian.regli@gmail.com.
authors.forename: Adrian
authors.identifier: http://orcid.org/0000-0002-3960-6013
authors.initials: A
authors.lastname: Regli
authors.affiliation: Intensive Care Unit, Fiona Stanley Hospital, 102-118 Murdoch Drive, Murdoch (Perth), WA, 6150, Australia.|School of Medicine and Pharmacology, The University of Western Australia, Sterling Highway, Crawley (Perth), WA, 6009, Australia.
authors.forename: Bart Leon
authors.initials: BL
authors.lastname: De Keulenaer
authors.affiliation: Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands (Perth), WA, 6009, Australia.|Faculty of Science, The University of Western Australia, Sterling Highway, Crawley (Perth), WA, 6009, Australia.|West Australian Sleep Disorders Research Institute, QE II Medical Centre, Nedlands (Perth), WA, 6009, Australia.
authors.forename: Bhajan
authors.initials: B
authors.lastname: Singh
authors.affiliation: Intensive Care Unit, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands (Perth), WA, 6009, Australia.|Department of Anaesthesia and Perioperative Medicine, The Alfred Hospital, Commercial Road, Prahran (Melbourne), VIC, 3181, Australia.
authors.forename: Lisen Emma
authors.initials: LE
authors.lastname: Hockings
authors.affiliation: Department of Pulmonary Physiology and Sleep Medicine, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands (Perth), WA, 6009, Australia.|West Australian Sleep Disorders Research Institute, QE II Medical Centre, Nedlands (Perth), WA, 6009, Australia.
authors.forename: Bill
authors.initials: B
authors.lastname: Noffsinger
authors.affiliation: Intensive Care Unit, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands (Perth), WA, 6009, Australia.|School of Medicine and Pharmacology, The University of Western Australia, Sterling Highway, Crawley (Perth), WA, 6009, Australia.|General Intensive Care Unit, Hadassah University Hospital, Kiryat Hadassah, Jerusalem, 91120, Israel.
authors.forename: Peter Vernon
authors.initials: PV
authors.lastname: van Heerden
keywords: Abdominal compliance; Abdominal volume; Airway pressures; Intra-abdominal hypertension; Intra-abdominal pressure; Respiratory compliance