Carotid Doppler Measurement Variability in Functional Hemodynamic Monitoring: An Analysis of 17,822 Cardiac Cycles

Abstract

OBJECTIVES: Carotid Doppler ultrasound is used as a measure of fluid responsiveness, however, assessing change with statistical confidence requires an adequate beat sample size. The coefficient of variation helps quantify the number of cardiac cycles needed to adequately detect change during functional hemodynamic monitoring. DESIGN: Prospective, observational, human model of hemorrhage and resuscitation. SETTING: Human physiology laboratory at Mayo Clinic. SUBJECTS: Healthy volunteers. INTERVENTIONS: Lower body negative pressure. MEASUREMENTS AND MAIN RESULTS: We measured the coefficient of variation of the carotid artery velocity time integral and corrected flow time during significant cardiac preload changes. Seventeen-thousand eight-hundred twenty-two cardiac cycles were analyzed. The median coefficient of variation of the carotid velocity time integral was 8.7% at baseline and 11.9% during lowest-tolerated lower body negative pressure stage. These values were 3.6% and 4.6%, respectively, for the corrected flow time. CONCLUSIONS: The median coefficient of variation values measured in this large dataset indicates that at least 6 cardiac cycles should be averaged before and after an intervention when using the carotid artery as a functional hemodynamic measure.

Carotid artery velocity time integral and corrected flow time measured by a wearable Doppler ultrasound detect stroke volume rise from simulated hemorrhage to transfusion

“…The U.S. Food and Drug Administration (FDA) cleared, 4 MHz Doppler ultrasound (Fig. 1 ) (Flosonics Medical, Sudbury, Canada) was placed and the ccFT, maximum and power-weighted, i.e., centroid, VTIs were captured [ 6 , 8 – 10 ].

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“…Yet measuring SV change (SV ∆ ) is clinically challenging, so surrogates like the common carotid artery Doppler pulse have been proposed [ 3 , 4 ] with some conflicting data [ 5 ]. We contend that statistically-inadequate beat sampling coupled with variation introduced by the respiratory cycle are important arbiters of inconsistent clinical research [ 6 ]. To rectify the shortcomings of handheld examinations, we developed a wireless, wearable Doppler ultrasound [ 7 , 8 ].…”

“…To rectify the shortcomings of handheld examinations, we developed a wireless, wearable Doppler ultrasound [ 7 , 8 ]. This device adheres to the neck, maintains a constant insonation angle and accurately measures beat-to-beat changes across multiple cardiorespiratory cycles [ 6 , 7 ].…”

A Wireless Wearable Doppler Ultrasound Detects Changing Stroke Volume: Proof-of-Principle Comparison with Trans-Esophageal Echocardiography during Coronary Bypass Surgery

“…Second, we believe that the described experimental paradigm is promising because it illustrates that averaging more beats in the carotid artery improves its relationship with the LVOT VTI. We have previously shown that the inherent physiological variation in the ccVTI that is induced by the respiratory cycle increases the sample size of cardiac cycles required to detect change with statistical confidence [ 15 ]. Thus, analyzing the relationship between the carotid artery and left ventricle with varying degrees of granularity may explain discordant clinical data [ 22 , 23 ].…”

“…Therefore, peripheral arteries have been exploited as surrogates of SV ∆ [ 10 ] as peripheral arteries, like the common carotid [ 11 , 12 ], are typically easier to insonate. Nevertheless, key drawbacks to hand-held Doppler measurements are human error [ 13 , 14 ] and relatively little guidance on the number of cardiac cycles to measure [ 15 ].…”