Quantitative Assessment Of Carotid Diameter Measurements In Parallel Versus Rotated And Tilted Orientation Using Ultrasound In The Operating Room – A Comparative Analysis

Abstract

Hemodynamic monitoring is of utmost importance when treating critically ill patients, but currently used techniques are invasive and associated with catheter-related complications. Carotid artery ultrasound (US) has been investigated as a non-invasive alternative, including for cardiac output estimation, in which vessel diameter and blood flow velocity are needed to compute flow. Traditionally, carotid flow measurements are performed in the long-axis (LA) view, in which the probe should be properly positioned along the mid-axis to obtain an accurate blood flow calculation. However, obtaining and maintaining this mid-axis LA view is difficult, and operator experience may impact the reliability of the measurements. Therefore, a view that is robust to motion while providing accurate diameter and velocity estimates is clinically desirable. An alternative view is obtained by rotating and tilting the probe, which is easier to visualize and assess for sonographers, and preliminary evidence suggests it might be more robust to motion and less operator-dependent than the LA view. To evaluate these findings in a clinical setting, we performed carotid Doppler measurements in 25 adult cardiac surgery patients with a LA and RT probe orientation intending to compare diameter estimates. Short-axis (SA) measurements were used as a reference, as these represent the most truthful depiction of the vessel’s cross-sectional area. Per 30s US recording, the median and spread in diameter values were computed and differences between views were statistically compared. Preliminary results of the first 18 patients show that the median RT diameter values were comparable to those of the SA (p=0.349), whereas the median LA values were smaller (p<0.001). With respect to the SA view, the spread in diameter values during the 30s measurements was lower for the RT view (p=0.014) and comparable for the LA view (p=0.306). These preliminary findings seem promising for the usage of the RT view to enable free-hand US measurements and usage of the view in wearable US devices. Future analysis comprises expansion of the current results and investigating inter- and intra-operator reliability of the different views.