Respiratory Variability of Pulmonary Velocity-Time Integral As a New Gauge of Fluid Responsiveness For Mechanically Ventilated Patients in the ICU*

To evaluate reliability and feasibility of the respiratory variability of pulmonary velocity-time integral as a new dynamic marker of fluid responsiveness in mechanically ventilated patients.Prospective observational study.Medical-surgical ICU of a general hospital.Fifty mechanically ventilated patients with acute circulatory failure.Transthoracic echocardiography was performed at inclusion (transthoracic echocardiography baseline). Fluid therapy was prescribed to patients exhibiting one value greater than or equal to 13% among commonly used variables of fluid responsiveness: respiratory variability of aortic velocity-time integral, respiratory variability of inferior vena cava diameter, or pulse pressure variation.Respiratory variability of pulmonary velocity-time integral was assessed at baseline. Respiratory variability of pulmonary velocity-time integral was significantly greater in patients who received fluid therapy (26.9 ± 12.5% vs 6.2 ± 4.3%; p < 0.0001). Respiratory variability of pulmonary velocity-time integral was correlated with respiratory variability of aortic velocity-time integral (r = 0.75; p < 0.0001), respiratory variability of inferior vena cava diameter (r = 0.42; p < 0.01), and pulse pressure variation (r = 0.87; p < 0.0001) at baseline and with the relative increase in cardiac output after fluid therapy (r = 0.44; p = 0.019). Fluid responsiveness was defined as a 10% increase in cardiac output after fluid therapy, assessed by a second transthoracic echocardiography. Respiratory variability of pulmonary velocity-time integral was associated with fluid responsiveness (adjusted odds ratio, 1.58; 95% CI, 1.08-2.32; p = 0.002). Area under the receiver operating characteristics curve was 0.972, and a value of respiratory variability of pulmonary velocity-time integral greater than or equal to 14% yielded a sensitivity of 92% and specificity of 87% to predict fluid responsiveness. Interobserver reproducibility was excellent (intraclass correlation coefficient = 0.94).Respiratory variability of pulmonary velocity-time integral is a simple and reliable marker of fluid responsiveness for ventilated patients in ICU.