Optical Fibre Sensor for Simultaneous Measurement of Capillary Refill Time and Contact Pressure

Liu, Chong; Correia, Ricardo; Ballaji, Hattan Khaled; Korposh, Sergiy; Hayes-Gill, Barrie; Morgan, Stephen P.

doi:10.3390/s20051388

Cited by 7 publications

(13 citation statements)

References 37 publications

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“…CRT is typically defined as the time taken for the intensity signal to change from 90% to 10% of its maximum level [ 2 ]. Calculating the CRT directly from the complete refilling signal (i.e., Stage 3, in Figure 6 ) has some limitations, as the DC baseline varies due to respiration, vasoconstrictor waves and Mayer waves [ 28 ] and motion artefacts can distort the signal.…”

Section: Methodsmentioning

confidence: 99%

“…Calculating the CRT directly from the complete refilling signal (i.e., Stage 3, in Figure 6 ) has some limitations, as the DC baseline varies due to respiration, vasoconstrictor waves and Mayer waves [ 28 ] and motion artefacts can distort the signal. To reduce the impact of these issues on the CRT measurements, a normalising and fitting process was applied on the refill signal [ 2 , 14 ].…”

Section: Methodsmentioning

confidence: 99%

“…Liu et al [ 2 ] and Kviesis-Kipge et al [ 30 ] applied a fitting process that depended on splitting the refilling signal into the blood refilling period and the baseline period. The blood refilling period was when the light intensity decreased significantly at the beginning of blood returning to the capillaries.…”

Section: Methodsmentioning

confidence: 99%

“…Capillary refill time (CRT) is the time it takes for a distal capillary bed to regain its colour after blanching caused by an applied pressure [ 1 , 2 ]. Manual application of pressure on the forearm, finger, sole, toes and sternum is most commonly employed in conjunction with mental counting [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

“…Optical fibre sensors are a highly versatile platform for tissue measurements due to their small footprint, their ability to measure a wide range of physical and physiological parameters and their immunity to electromagnetic interference [ 17 ]. Our group previously demonstrated an integrated optical fibre sensor simultaneously measuring the CRT and applied pressure [ 2 ]. This design consisted of a photoplethysmography (PPG) sensor that measured CRT and a fibre Bragg grating (FBG) that measured contact pressure.…”

Section: Introductionmentioning

confidence: 99%

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Optical Fibre Sensor for Capillary Refill Time and Contact Pressure Measurements under the Foot

Ballaji

Correia

Liu

et al. 2021

Sensors

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Capillary refill time (CRT) refers to the time taken for body tissue to regain its colour after an applied blanching pressure is released. Usually, pressure is manually applied and not measured. Upon release of pressure, simple mental counting is typically used to estimate how long it takes for the skin to regain its colour. However, this method is subjective and can provide inaccurate readings due to human error. CRT is often used to assess shock and hydration but also has the potential to assess peripheral arterial disease which can result in tissue breakdown, foot ulcers and ultimately amputation, especially in people with diabetes. The aim of this study was to design an optical fibre sensor to simultaneously detect blood volume changes and the contact pressure applied to the foot. The CRT probe combines two sensors: a plastic optical fibre (POF) based on photoplethysmography (PPG) to measure blood volume changes and a fibre Bragg grating to measure skin contact pressure. The results from 10 healthy volunteers demonstrate that the blanching pressure on the subject’s first metatarsal head of the foot was 100.8 ± 4.8 kPa (mean and standard deviation), the average CRT was 1.37 ± 0.46 s and the time to achieve a stable blood volume was 4.77 ± 1.57 s. For individual volunteers, the fastest CRT measured was 0.82 ± 0.11 and the slowest 1.94 ± 0.49 s. The combined sensor and curve fitting process has the potential to provide increased reliability and accuracy for CRT measurement of the foot in diabetic foot ulcer clinics and in the community.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical Fibre Sensor for Capillary Refill Time and Contact Pressure Measurements under the Foot

Ballaji

Correia

Liu

et al. 2021

Sensors

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Skin‐color‐independent robust assessment of capillary refill time

Souza

Dias

Cardoso

2023

Journal of Biophotonics

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Capillary Refill Time (CRT) assesses peripheral perfusion in resource‐limited settings. However, the repeatability and reproducibility of CRT measurements are limited for individuals with darker skin. This paper presents quantitative CRT measurements demonstrating good performance and repeatability across all Fitzpatrick skin phototypes. The study involved 22 volunteers and utilized controlled compression at 7 kPa, an RGB video camera, and cocircular polarized white LED light. CRT was determined by calculating the time constant of an exponential regression applied to the mean pixel intensity of the green (G) channel. An adaptive algorithm identifies the optimal regression region for noise reduction, and flags inappropriate readings. The results indicate that 80% of the CRT readings fell within a 20% range of the expected CRT value. The repetition standard deviation was 17%. These findings suggest the potential for developing reliable and reproducible quantitative CRT methods for robust measurements in patient triage, monitoring, and telehealth applications.

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