The influence of the airway driving pressure on pulsed pressure variation as a predictor of fluid responsiveness
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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 (Pplat − 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) ≥15%. Receiver-operating characteristic (ROC) curves were generated for PPV and central venous pressure (CVP).
The stroke index was increased ≥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 (Pplat − PEEP) was the sole independent factor associated with a PPV value <13% in responders. In these responders, (Pplat − PEEP) was ≤20 cmH2O.
In patients mechanically ventilated with low VT, PPV values <13% do not rule out fluid responsiveness, especially when (Pplat − PEEP) is ≤20 cmH2O.