The effect of positive end-expiratory pressure on pulse pressure variation

Abstract

Objectives: To determine the effect of different levels of positive end-expiratory pressure (PEEP) on pulse pressure variation (PPV).
Design: An observational study. Setting: Operating theatres of a tertiary training hospital.
Subjects: Ventilated patients who required intra-arterial blood pressure monitoring.
Outcome measures: PPV during different levels of PEEP.
Method: Patients were anaesthetised by means of a standard technique and ventilated with a tidal volume of 9 ml/kg ideal body mass. The PPV was calculated at PEEP levels of 2, 5, 8 and 10 cmH₂O. PPV was compared at the various PEEP levels.
Results: PPV at a PEEP of 8 cmH₂O and 10 cmH₂O was significantly larger than that at 2 cmH₂O (p-value < 0.001). PPV at a PEEP of 10 cmH₂O was significantly larger than that at 8 cmH2O (p-value < 0.001). PPV at a PEEP of 8 cmH₂O was larger than that at 5 cmH₂O (p-value = 0.002). PPV at a PEEP of 2 and 5 cmH₂O did not differ significantly (p-value = 0.194).
Conclusion: We have demonstrated that, in patients with normal lungs, PEEP has a significant influence on PPV. PPV may be overestimated if PEEP ≥ 8 cmH₂O is applied in patients who are ventilated with a tidal volume of 9 ml/kg. It is recommended that in patients with healthy lungs PPV should be measured at a standardised PEEP of ≤ 5 cmH₂O.

Keywords: blood volume, monitoring, pulse pressure, blood pressure determination, positive-pressure respiration, positive end-expiratory pressure

South Afr J Anaesth Analg 2012;18(6):333-338