Objectives: In septic patients, reliable non-invasive predictors of fluid responsiveness are needed. We hypothesised that the respiratory changes in the amplitude of the plethysmographic pulse wave (ΔPPLET) would allow the prediction of changes in cardiac index following volume administration in mechanically ventilated septic patients. Design: Prospective clinical investigation. Setting: An 11-bed hospital medical intensive care unit. Patients: Twenty-three deeply sedated septic patients mechanically ventilated with tidal volume ≥ 8 ml/kg and equipped with an arterial catheter and apulse oximetry plethysmographic sensor. Interventions: Respiratory changes in pulse pressure (ΔPP), ΔPPLET and cardiac index (transthoracic Doppler echocardiography) were determined before and after volume infusion of colloids (8 ml/kg). Measurements and main results: Twenty-eight volume challenges were performed in 23 patients. Before volume expansion, ΔPP correlated with ΔPPLET (r 2 = 0.71, p < 0.001). Changes in cardiac index after volume expansion significantly (p < 0.001) correlated with baseline ΔPP (r 2 = 0.76) and ΔPPLET (r 2 = 0.50). The patients were defined as responders to fluid challenge when cardiac index increased by at least 15% after the fluid challenge. Such an event occurred 18 times. Before volume challenge, aΔPP value of 12% and aΔPPLET value of 14% allowed discrimination between responders and non-responders with sensitivity of 100% and 94% respectively and specificity of 70% and 80% respectively. Comparison of areas under the receiver operator characteristic curves showed that ΔPP and ΔPPLET predicted similarly fluid responsiveness. Conclusion: The present study found ΔPPLET to be as accurate as ΔPP for predicting fluid responsiveness in mechanically ventilated septic patient
