The influence of the airway driving pressure on pulsed pressure variation as a predictor of fluid responsiveness.

Abstract

Assessing pulse pressure variation (PPV) to predict fluid responsiveness in mechanically ventilated patients with tidal volume (VT) and the impact of VT and airway driving pressure (P(plat) - PEEP) on the ability of PPV for predicting fluid responsiveness. Prospective interventional study. ICU of a university hospital. Fifty-seven mechanically ventilated and sedated patients with acute circulatory failure requiring cardiac output (CO) measurement. Fluid challenge was given in patients with signs of hypoperfusion (oliguria <0.5 ml kg(-1) h(-1), attempt to decrease vasopressor infusion rate). Fluid responsiveness was defined as an increase in the stroke index (SI) >or=15%. Receiver-operating characteristic (ROC) curves were generated for PPV and central venous pressure (CVP). The stroke index was increased >or=15% in 41 patients (71%). At baseline, CVP was lower and PPV was higher in responders. The areas under the ROC curves of PPV and CVP were 0.77 (95% CI 0.65-0.90) and 0.76 (95% CI 0.64-0.89), respectively (P = 0.93). The best cutoff values of PPV and CVP were 7% and 9 mmHg, respectively. In 30 out of 41 responders, PPV was <13%. Using a polytomic logistic regression (P(plat)--PEEP) was the sole independent factor associated with a PPV value <13% in responders. In these responders, (P(plat)--PEEP) was <or=20 cmH(2)O. In patients mechanically ventilated with low VT, PPV values <13% do not rule out fluid responsiveness, especially when (P(plat)--PEEP) is <or=20 cmH(2)O.