Evaluation of automated finger compression for capillary refill time measurement in pediatrics

Introduction: Early shock reversal is crucial to improve patient outcomes. Capillary refill time (CRT) is important to identify and monitor shock state in children but has issues with inconsistency among clinicians. To minimize inconsistency, we tested a monitoring system for serial CRT measurement using an automated compression device. Our objective was to determine the proper compression pressure. We hypothesize a difference between compression pressures to eliminate pulsatile blood flow. Methods: Clinician force data was collected during manual CRT as a reference for automated compression. Measurement from clinician CRT identified a force of 12.9N (95% CI: 12.5-13.4) from 454 measurements. An automated compression device with a soft inflation bladder was fitted with a force sensor. A bench comparison of pressures from 300-500mmHg on a simulated finger yielded a force of 8-12N, equivalent to clinician CRT force. Once we identified a range of optimal pressure, we evaluated the effectiveness of pressure to eliminate pulsatile blood flow from the distal phalange in children. We also assessed the variance of the device measured CRT using waveform analysis at each inflation pressure. Difference in variance was assessed by Levene’s test. Results: Automated compression was tested in 44 subjects (median age 33mo, IQR 14-56). At interim quality analysis of 17 subjects, there was a significant difference in the waveform with residual pulsatile blood flow (18% at 300mmHg, 10% at 400mmHg, 0% at 500mmHg, Chi-squared, p=0.008), and pressure at 300mmHg was determined not adequate for automated CRT measures. With subsequent enrollment of 27 subjects with analyzable device measured CRTs, none at 400mmHg and 500mmHg had residual pulsatile blood flow. There was no difference in variance of device measured CRT (2.99 in 400mmHg vs. 1.35 in 500mmHg, p=0.093). Conclusions: Using clinician performed CRT measurement data, we identified a reliable automated compression system to replicate manual CRT for children. We determined either 400mmHg or 500mmHg is an appropriate inflation pressure for automated compression to measure CRT. Future study will determine the clinical value of serial measurement of device measured CRT.