Abstract 276: Impact of Skin Color on Accuracy of Capillary Refill Time Measurement by Pulse Oximeter

Abstract

Capillary refill time(CRT) is a non-invasive method to assess tissue perfusion, routinely performed in pediatric practice. Current methods to measure CRT have limitations in objectivity and reproducibility. The measurement depends on clinician’s assessment. New analytic approach using pulse oximeter waveform has been developed. Hypothesis: CRT measured by pulse oximeter device and clinicians(critical care/anesthesiologist attending physicians) were different across skin color and finger thickness. Method: Children(1-12 yr) with different skin color tones (Fitzpatrick scale 1-2:fair, 3-4:medium, 5-6:dark) were recruited. Subjects were randomized to a pulse oximeter either on index/middle finger, and had a total 10 CRT measurements (5 with device, 5 with clinician’s visual assessment, alternating). Waveform analysis was performed with quick compression and release on the pulse oximetry device by clinician. The difference between device and clinician measured CRT was calculated. ANOVA for difference in CRT across 3 skin color categories and across 4 finger thickness. Result: 64 subjects(skin color fair 33, medium 16, dark 15) were recruited (median age 72 m, IQR 42-123m). Out of 640 CRT measurements, 300 pairs had measurable CRTs in both device and clinician. Based on clinician’s measurement, 114 CRTs were >2s and 26 CRTs > 4s. The overall CRT difference was mean 0.97±1.32s. The CRT difference by skin color was fair 0.86±1.35s, medium 0.90±1.31s, dark 1.26±1.22s, p=0.095. Pearson correlation coefficient was all 0.49 (fair 0.31, medium 0.67, and dark 0.41, all p<0.001). There was no significant difference in CRT difference among 4 finger thickness categories(thin to thick); 1.21±1.48s, 0.94±1.48s, 1.12±1.20s, 0.75±1.20s, p=0.108. Conclusion: The difference between device and clinician measured CRT did not vary across the different patient skin color or finger thickness. Device measured CRT may be a helpful indicator for peripheral perfusion.