title: Respiratory variation of intra-abdominal pressure: indirect indicator of abdominal compliance?
abstract: OBJECTIVE
  To assess if the observed respiratory cycle-related variation in intra-abdominal pressure is reliably quantifiable and a possible indirect indicator of abdominal compliance. Secondary issues were to assess the roles played by respiratory parameters in determining this oscillation and by patients' position in increasing their intra-abdominal pressure.
  
  
  METHODS
  Prospective observational study in a 26-bed medical-surgical intensive care unit.
  
  
  METHODS
  Sixteen consecutive patients admitted to intensive care for at least 24 h, requiring mechanical ventilation and intra-abdominal pressure monitoring.
  
  
  RESULTS
  Intra-abdominal pressure was measured with a modified Kron technique; its waveform was recorded and inspiratory and expiratory values were measured during five consecutive respiratory cycles for 5 days, both in the supine and the 30 degrees head-up position. Inspiratory values were significantly higher than expiratory values (p = 0.001) and a correlation was found between their difference and intra-abdominal pressure basal values (p = 0.025). A positive linear relationship was shown between intra-abdominal pressure and the amplitude of its oscillation (r = 0.4), particularly in the subgroup of patients with intra-abdominal hypertension (r = 0.9). Intra-abdominal pressure was lower in patients supine than in the 30 degrees head-up position (p = 0.001).
  
  
  CONCLUSIONS
  Respiratory cycle-related variations in intra-abdominal pressure were specifically investigated, quantified and shown as linearly increasing with end-expiratory intra-abdominal pressure; this phenomenon could be explained by patients' abdominal compliance status. Supine posture should be an important consideration in specific patients affected by intra-abdominal hypertension.
authors.affiliation: Intensive Care Unit, Liverpool Hospital, University of New South Wales, Elizabeth St, Liverpool, Sydney, NSW, 1871, Australia. e.sturini@libero.it
authors.forename: Evelina
authors.initials: E
authors.lastname: Sturini
authors.forename: Andrea
authors.initials: A
authors.lastname: Saporito
authors.forename: Michael
authors.initials: M
authors.lastname: Sugrue
authors.forename: Michael J A
authors.initials: MJ
authors.lastname: Parr
authors.forename: Gillian
authors.initials: G
authors.lastname: Bishop
authors.forename: Antonio
authors.initials: A
authors.lastname: Braschi
mesh_terms: D000005:Abdomen / Q000503:physiopathology*; D003161:Compartment Syndromes / Q000503:physiopathology*; D006801:Humans; D006973:Hypertension; D007362:Intensive Care Units; D008875:Middle Aged; D011446:Prospective Studies; D012119:Respiration; D012121:Respiration, Artificial; D016683:Supine Position