Mechanically ventilated patients with low tidal volume in the intensive care unit whom clinician decided to provide fluid for correction of hypovolemia

Corrected carotid artery flow time is measured using 6-13 MHz linear probe on a portable ultrasound machine. On the two-dimensional image, the optimal image of the long-axis view is obtained at the left common carotid artery. The sample volume is placed on the center of the lumen, 2 cm proximal to the bulb, and a pulsed wave Doppler examination was performed while the Doppler beams were adjusted to ensure < 60° of angle for the best signal. Then, cardiac cycle time and carotid flow time is measured. Carotid flow time is measured between the upstroke of the flow tracing and the dicrotic notch, and it is corrected for pulse rate by dividing flow time by the square root of the cardiac cycle time to calculate corrected carotid artery flow time (flow time/√cycle time).

Area under the receiver operating curve of Corrected carotid artery flow time for fluid responsiveness in low tidal volume ventilator setting before fluid resuscitation

Area under the receiver operating curve of pulse pressure variation for fluid responsiveness in low tidal volume ventilator setting before fluid resuscitation