Pulse pressure variation as a predictor of fluid responsiveness in mechanically ventilated patients with spontaneous breathing activity: a pragmatic observational study

Introduction: Pulse pressure variation predicts fluid responsiveness in mechanically ventilated patients passively adapted to the ventilator. Its usefulness in actively breathing ventilated patients was examined only by few studies with potential methodological shortcomings. This study sought to describe the performance of pulse pressure variation as a predictor of fluid responsiveness in hypotensive critically ill patients who trigger the ventilator. Methods: We studied forty two hypotensive, mechanically ventilated patients with documented spontaneous breathing activity in whom a fluid challenge was deemed necessary by the attending physician. All patients were ventilated with a Maquet Servo-i Ventilator in different ventilatory modes with a flow-regulated inspiratory trigger set on position 4. Pulse pressure variation, mean and systolic arterial pressure were observed before and after the fluid challenge, which consisted in the intravenous administration of a 250 ml bolus of 6% hetastarch. Fluid responsiveness was defined as a more than 15% increase in arterial pressure after volume expansion. Results: The area under the receiver operator characteristic curve for pulse pressure variation was 0.87 (95% CI 0.74-0.99; p<0.0001) and the grey zone limits were 10% and 15%. Pulse pressure variation was correlated with increase in systolic arterial pressure (r2= 0.32; p<0.001) and mean arterial pressure (r2= 0.10; p= 0.037). Conclusions: Pulse pressure variation predicts fluid responsiveness in patients who actively interact with a Servo-i ventilator with a flow-regulated inspiratory trigger set on position 4.