The Correlation between Carotid Artery Corrected Flow Time and Velocity Time Integral during Central Blood Volume Loss and Resuscitation

Abstract

Background: Doppler ultrasound of the common carotid artery is used to infer central hemodynamics. For example, change in the common carotid artery corrected flow time (ccFT) and velocity time integral (VTI) are proposed surrogates of changing stroke volume. However, conflicting data exist which may be due to inadequate beat sample size and measurement variability – both intrinsic to handheld systems. In this brief communication, we determined the correlation between changing ccFT and carotid VTI during progressively severe central blood volume loss and resuscitation. Methods: Measurements were obtained through a novel, wireless, wearable Doppler ultrasound system. Sixteen participants (ages of 18–40 years with no previous medical history) were studied across 25 lower body-negative pressure protocols. Relationships were assessed using repeated-measures correlation regression models. Results: In total, 33,110 cardiac cycles comprise this analysis; repeated-measures correlation showed a strong, linear relationship between ccFT and VTI. The strength of the ccFT-VTI relationship was dependent on the number of consecutively averaged cardiac cycles (R1 cycle = 0.70, R2 cycles = 0.74, and R10 cycles = 0.81). Conclusions: These results positively support future clinical investigations employing common carotid artery Doppler as a surrogate for central hemodynamics.

The left ventricular outflow tract and carotid artery velocity time integrals

“…Again, these authors found a strong, linear correlation between carotid Doppler measures and ascending aortic VTI as measured by the USCOM device. This group has also observed a strong, linear correlation between changing ccFT cand VTI CA , thus these measures are likely physiologically-linked ( 23 ). As mentioned by Cheong and colleagues, composite measures integrating both ccFT and VTI CA are of great interest.…”