title: Influence of intra-abdominal pressure on the specificity of pulse pressure variations to predict fluid responsiveness.
abstract: BACKGROUND
  The positive predictive value of pulse pressure variations (ΔPP) to discriminate patients who should respond to volume expansion (VE) may be altered in mechanically ventilated patients. Our goal was to determine whether intra-abdominal pressure (IAP) measurements could discriminate patients with true-positive ΔPP values versus patients with false-positive ΔPP values.
  
  
  METHODS
  We designed a prospective pathophysiologic study in a mixed intensive care unit of a university hospital. Sixteen mechanically ventilated patients with hypotension (SAP, <90 mm Hg) and with ΔPP of 13% or more were included. Cardiac output was assessed using Doppler echocardiography before and after VE; IAP was measured using the bladder pressure method. Patients were classified into two groups according to their response to a standardized VE (500 mL of NaCl 0.9%): responders (≥15% increase in cardiac output) and nonresponders.
  
  
  RESULTS
  Nine patients (57%) were responders, and seven patients (43%) were nonresponders. Before VE, IAP was statistically higher in nonresponders (15 [11-22] mm Hg vs. 9 [6.5-11] mm Hg; p = 0.008). The area under the curve of the receiver operating characteristic curve was 0.9 ± 0.08. In patients with ΔPP of 13% or more, an IAP cutoff value of 10.5 mm Hg discriminated between responders and nonresponders with a sensitivity of 100% (59-100%) and a specificity of 78% (40-97%).
  
  
  CONCLUSIONS
  An increase in IAP of more than 10.5 mm Hg can decrease the positive predictive value of ΔPP. Hence, in patients prone to present abnormal IAP values, IAP should be measured before performing VE directed by the ΔPP marker.
  
  
  METHODS
  Diagnostic study, level II.
authors.affiliation: From the Medical and Surgical Intensive Care Unit (P.R., R.V., D.R., C.C., H.M.), Fort de France University Hospital, Martinique, French West Indies, France; Intensive Care Service (K.B.), Geneva University Hospitals, Geneva, Switzerland; and Medical Intensive Care Unit (P.R.), Cochin Hospital, Assistance Publique des Hôpitaux de Paris, Groupe Hospitalier Universitaire Cochin Broca Hôtel-Dieu, Paris, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Royer
authors.forename: Karim
authors.initials: K
authors.lastname: Bendjelid
authors.forename: Ruddy
authors.initials: R
authors.lastname: Valentino
authors.forename: Dabor
authors.initials: D
authors.lastname: Résière
authors.forename: Cyrille
authors.initials: C
authors.lastname: Chabartier
authors.forename: Hossein
authors.initials: H
authors.lastname: Mehdaoui
mesh_terms: D034841:Abdominal Cavity / Q000503:physiopathology*; D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D016638:Critical Illness / Q000628:therapy*; D015150:Echocardiography, Doppler; D005260:Female; D005440:Fluid Therapy / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012121:Respiration, Artificial / Q000379:methods*; D012151:Resuscitation / Q000379:methods*; D013318:Stroke Volume / Q000502:physiology