Pulse-wave transit time with ventilator-induced variation for the prediction of fluid responsiveness

Abstract

Aim: Although pulse pressure variation is a good predictor of fluid responsiveness, its measurement is invasive. Therefore, a technically simple, non-invasive method is needed for evaluating circulatory status to prevent fluid loading and optimize hemodynamic status. We focused in the pulse-wave transit time (PWTT) defined as the time interval between electrocardiogram R wave to plethysmograph upstroke, which has been recently introduced to non-invasively assess cardiovascular response. In the present study, we evaluated the efficacy of pulse-wave transit time (PWTT) with ventilator-induced variation (PWTTV) in predicting fluid responsiveness.

Methods: We evaluated six domestic pigs weighing 46.0 ± 3.5 kg. After anesthesia induction, electrocardiogram, femoral arterial blood pressure, plethysmograph on the tail, and carotid artery blood flow were monitored and hemorrhage was induced by withdrawing 20 mL/kg blood over 20 min; 5 mL/kg blood volume was then autotransfused over 10 min. Then PWTTV and pulse pressure variation were measured at tidal volumes of 6 and 12 mL/kg.

Results: Area under the receiver operating curve values for the prediction of a >10% change in carotid artery blood flow were 0.979 for pulse pressure variation and 0.993 for PWTTV at a tidal volume of 6 mL/kg and 0.979 and 0.979, respectively, at a tidal volume of 12 mL/kg (all P < 0.0001).

Conclusions: Measured non-invasively, PWTTV showed similar utility to pulse pressure variation in predicting >10% changes in carotid artery blood flow induced by autotransfusion.

Keywords: Autotransfusion; blood volume; hemodynamic; non‐invasive; pulse pressure.

Figure 1

Outline of the present study. ART, arterial pressure waveform; avg, average; BV, blood volume; CO, cardiac output; max, maximum; min, minimum; Pleth, photoplethysmography; PP, pulse pressure; PPV, pulse pressure variation; Ptrach, tracheal pressure; PWTT, pulse‐wave transit time; PWTTV, pulse‐wave transit time with ventilator‐induced variation; TV, tidal volume.

Figure 2

Study protocol. PEEP, positive end‐expiratory pressure; TV, tidal volume.

Figure 3

A, Receiver operating characteristic (ROC) curve of hemodynamic variables in hypovolemia secondary to hemorrhage under a tidal volume of 6 mL/kg. B, ROC curve of hemodynamic variables in hypovolemia secondary to hemorrhage under a tidal volume of 12 mL/kg. Solid line indicates pulse‐wave transit time with ventilator‐induced variation (PWTTV). Dashed line indicates pulse pressure variation (PPV).