Research Progress on the Measurement Methods and Clinical Significance of Capillary Refill Time

Abstract

The monitoring of peripheral circulation, as indicated by the capillary refill time, is a sensitive and accurate method of assessing the microcirculatory status of the body. It is a widely used tool for the evaluation of critically ill patients, the guidance of therapeutic interventions, and the assessment of prognosis. In recent years, there has been a growing emphasis on microcirculation monitoring which has led to an increased focus on capillary refill time. The International Sepsis Guidelines, the American Academy of Pediatrics, the World Health Organization, and the American Heart Association all recommend its inclusion in the evaluation of the system in question. Furthermore, the methodology for its measurement has evolved from a traditional manual approach to semiautomatic and fully automatic techniques. This article presents a comprehensive overview of the current research on the measurement of capillary refill time, with a particular focus on its clinical significance. The aim is to provide a valuable reference for clinicians and researchers and further advance the development and application of microcirculation monitoring technology.

Keywords: CRT measurement methods; capillary refill time; microcirculation; non-invasive monitoring; peripheral circulation; sepsis.

Figure 1

Wearable CRT measuring instrument based on visual feedback technology [39].

Figure 2

CRT measuring instrument test machine based on pressure sensing technology and photoelectric capacitance wave technology: (a) schematic diagram of a plane view of the probe. The red frame represents the POF connected to an infrared LED (center wavelength λ = 850 nm). The yellow frame represents the POF connected to a photodiode. As the sensor had been adapted from a pulse oximeter described previously, there was an additional channel (orange frame) that existed which was not used in this investigation. The blue frame represents the stainless steel tube. (b) Schematic diagram of a side view of the probe. The two sensors were encased in epoxy. The POFs transferred light from/to the skin, whilst the FBGs monitored the applied pressure. POF—polymer optical fiber; FBG—fiber Bragg grating; LED—light emitting diode [44].

Figure 3

Wearable CRT measuring instrument based on visual feedback technology [47].

Figure 4

Actual test image of the pneumatic CRT measuring instrument test machine: typical raw optical intensity data from the base unit, prior to any processing [47].