title: Heart-lung interactions with different ventilatory settings during acute lung injury and hypovolaemia: an experimental study.
abstract: BACKGROUND
  The functional haemodynamic variables pulse pressure variation (PPV), stroke volume variation (SVV), and systolic pressure variation (SPV) are widely used to assess haemodynamic status. However, it is not known how these perform during acute lung injury (ALI). This study evaluated the effects of different ventilatory strategies on haemodynamic parameters in pigs with ALI during normovolaemia and hypovolaemia.
  
  
  METHODS
  Eight anaesthetized Agroceres pigs [40 (1.9) kg] were instrumented with pulmonary artery, PiCCO, and arterial catheters and ventilated. Three ventilatory settings were randomly assigned for 10 min each: tidal volume (VT) 15 ml kg(-1) and PEEP 5 cm H(2)O, VT 8 ml kg(-1) and PEEP 13 cm H(2)O, or VT 6 ml kg(-1) and PEEP 13 cm H(2)O. Data were collected at each setting at baseline, after ALI (lung lavage+Tween 1.5%), and ALI with hypovolaemia (haemorrhage to 30% of estimated blood volume).
  
  
  RESULTS
  At baseline, high VT increased PPV, SVV, and SPV (P<0.05 for all). During ALI, high VT significantly increased PPV and SVV [(P = 0.002 and P = 0.008) respectively.]. After ALI with hypovolaemia, ventilation at VT 6 ml kg(-1) and PEEP 13 cm H(2)O decreased the accuracy of functional haemodynamic variables to predict hypovolaemia, with the exception of PPV (area under the curve 0.875). The parameters obtained by PiCCO were less influenced by ventilatory changes.
  
  
  CONCLUSIONS
  VT is the ventilatory parameter which influences functional haemodynamics the most. During ventilation with low VT and high PEEP, most functional variables are less able to accurately predict hypovolaemia secondary to haemorrhage, with the exception of PPV.
authors.affiliation: Intensive Care and Anaesthesiology Research Laboratory, Research and Education Institute, Hospital Sírio-Libanês, São Paulo, Brazil.
authors.forename: F J
authors.initials: FJ
authors.lastname: da Silva Ramos
authors.forename: E M
authors.initials: EM
authors.lastname: de Oliveira
authors.forename: M
authors.initials: M
authors.lastname: Park
authors.forename: G P P
authors.initials: GP
authors.lastname: Schettino
authors.forename: L C P
authors.initials: LC
authors.lastname: Azevedo
mesh_terms: D055371:Acute Lung Injury / Q000503:physiopathology*; D000818:Animals; D004195:Disease Models, Animal; D006439:Hemodynamics / Q000502:physiology; D006470:Hemorrhage / Q000150:complications; D020896:Hypovolemia / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D008991:Monitoring, Physiologic / Q000379:methods; D011175:Positive-Pressure Respiration / Q000379:methods*; D034421:Sus scrofa; D013990:Tidal Volume / Q000502:physiology