© 2026 Optics and Photonics at Nottingham
Publications
in Top 10% Journal Percentiles
43%
Global
Partnerships
56.3%
Corporate
Collaboration
8.8%
Annual research
funding
£5m+
Data for 2020-2025 from SciVal
Selected Publications
2024
3.
Ma, Zi-Yu; Sun, Shen; Wu, Shui-Cai; Lin, Lan; Chen, Yi-Xiong; Zhao, Dong; Morgan, Stephen P
Pilot study on optimizing pressure for standardized capillary refill time measurement Journal Article
In: Heliyon, vol. 10, no. 15, pp. e35716, 2024.
Abstract | Links | Altmetric | Tags: Capillary refill time, Microcirculation, Pressure, Sepsis, Septic shock
@article{Ma2024-lq,
title = {Pilot study on optimizing pressure for standardized capillary refill time measurement},
author = {Zi-Yu Ma and Shen Sun and Shui-Cai Wu and Lan Lin and Yi-Xiong Chen and Dong Zhao and Stephen P Morgan},
doi = {10.1016/j.heliyon.2024.e35716},
year = {2024},
date = {2024-08-01},
urldate = {2024-08-01},
journal = {Heliyon},
volume = {10},
number = {15},
pages = {e35716},
publisher = {Elsevier BV},
abstract = {Purpose: Capillary Refill Time (CRT) measurement has gained
increasing attention in the field of sepsis and septic shock.
Recognizing pressure as a fundamental determinant in CRT
measurement is crucial for establishing a standardized CRT
measurement procedure. In this preliminary study, we elucidated
the optimal pressing strength for CRT measurement by analyzing
the CRTs measured under varying pressures. Method: Seventeen
healthy individuals were enlisted to undergo CRT tests on their
fingertips at various pressure levels. The applied force was
initiated at 0.5N and incrementally increased by 0.5N until it
reached 10.5N. An integrated Photoplethysmography (PPG) device
was employed to capture fluctuations in light intensity. The CRT
was automatically derived from the PPG signals via a specialized
algorithm. The study included correlation assessment and
reliability evaluation. Box plot and Bland-Altman plot were used
to visualize the impact of pressure levels on CRTs. Results: A
dataset of 1414 CRTs across 21 pressures showed significant
differences (Kruskal-Wallis test, p \< 0.0001), highlighting the
impact of pressure on CRT. CRT values between 4.5N and 10.5N
pressures varied less, with an Intraclass Correlation
Coefficient (ICC) of 0.499 indicating moderate consistency.
Notably, CRTs at 10N and 10.5N pressures revealed a high ICC of
0.790, suggesting strong agreement. Conclusion: A pressure range
of 4.5N-10.5N is recommended for stable CRT measurements, with
10.0N-10.5N providing optimal consistency and reliability.},
keywords = {Capillary refill time, Microcirculation, Pressure, Sepsis, Septic shock},
pubstate = {published},
tppubtype = {article}
}
Purpose: Capillary Refill Time (CRT) measurement has gained
increasing attention in the field of sepsis and septic shock.
Recognizing pressure as a fundamental determinant in CRT
measurement is crucial for establishing a standardized CRT
measurement procedure. In this preliminary study, we elucidated
the optimal pressing strength for CRT measurement by analyzing
the CRTs measured under varying pressures. Method: Seventeen
healthy individuals were enlisted to undergo CRT tests on their
fingertips at various pressure levels. The applied force was
initiated at 0.5N and incrementally increased by 0.5N until it
reached 10.5N. An integrated Photoplethysmography (PPG) device
was employed to capture fluctuations in light intensity. The CRT
was automatically derived from the PPG signals via a specialized
algorithm. The study included correlation assessment and
reliability evaluation. Box plot and Bland-Altman plot were used
to visualize the impact of pressure levels on CRTs. Results: A
dataset of 1414 CRTs across 21 pressures showed significant
differences (Kruskal-Wallis test, p < 0.0001), highlighting the
impact of pressure on CRT. CRT values between 4.5N and 10.5N
pressures varied less, with an Intraclass Correlation
Coefficient (ICC) of 0.499 indicating moderate consistency.
Notably, CRTs at 10N and 10.5N pressures revealed a high ICC of
0.790, suggesting strong agreement. Conclusion: A pressure range
of 4.5N-10.5N is recommended for stable CRT measurements, with
10.0N-10.5N providing optimal consistency and reliability.
increasing attention in the field of sepsis and septic shock.
Recognizing pressure as a fundamental determinant in CRT
measurement is crucial for establishing a standardized CRT
measurement procedure. In this preliminary study, we elucidated
the optimal pressing strength for CRT measurement by analyzing
the CRTs measured under varying pressures. Method: Seventeen
healthy individuals were enlisted to undergo CRT tests on their
fingertips at various pressure levels. The applied force was
initiated at 0.5N and incrementally increased by 0.5N until it
reached 10.5N. An integrated Photoplethysmography (PPG) device
was employed to capture fluctuations in light intensity. The CRT
was automatically derived from the PPG signals via a specialized
algorithm. The study included correlation assessment and
reliability evaluation. Box plot and Bland-Altman plot were used
to visualize the impact of pressure levels on CRTs. Results: A
dataset of 1414 CRTs across 21 pressures showed significant
differences (Kruskal-Wallis test, p < 0.0001), highlighting the
impact of pressure on CRT. CRT values between 4.5N and 10.5N
pressures varied less, with an Intraclass Correlation
Coefficient (ICC) of 0.499 indicating moderate consistency.
Notably, CRTs at 10N and 10.5N pressures revealed a high ICC of
0.790, suggesting strong agreement. Conclusion: A pressure range
of 4.5N-10.5N is recommended for stable CRT measurements, with
10.0N-10.5N providing optimal consistency and reliability.
2021
2.
Ballaji, Hattan K; Correia, Ricardo; Liu, Chong; Korposh, Serhiy; Hayes-Gill, Barrie R; Musgrove, Alison; Morgan, Stephen P
Optical fibre sensor for capillary refill time and contact pressure measurements under the foot Journal Article
In: Sensors (Basel), vol. 21, no. 18, pp. 6072, 2021.
Abstract | Tags: blood volume changes, Capillary refill time, contact pressure, fibre Bragg grating (FBG), optical fibre, peripheral arterial disease, photoplethysmography (PPG), plastic optical fibre
@article{Ballaji2021-ti,
title = {Optical fibre sensor for capillary refill time and contact
pressure measurements under the foot},
author = {Hattan K Ballaji and Ricardo Correia and Chong Liu and Serhiy Korposh and Barrie R Hayes-Gill and Alison Musgrove and Stephen P Morgan},
year = {2021},
date = {2021-09-01},
journal = {Sensors (Basel)},
volume = {21},
number = {18},
pages = {6072},
publisher = {MDPI AG},
abstract = {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.},
keywords = {blood volume changes, Capillary refill time, contact pressure, fibre Bragg grating (FBG), optical fibre, peripheral arterial disease, photoplethysmography (PPG), plastic optical fibre},
pubstate = {published},
tppubtype = {article}
}
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.
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.
2020
1.
Liu, Chong; Correia, Ricardo; Ballaji, Hattan; Korposh, Serhiy; Hayes-Gill, Barrie; Morgan, Stephen
Optical fibre sensor for simultaneous measurement of capillary refill time and contact pressure Journal Article
In: Sensors (Basel), vol. 20, no. 5, pp. 1388, 2020.
Abstract | Tags: Capillary refill time, contact pressure, fibre bragg grating, photoplethysmography, plastic optical fibre
@article{Liu2020-xk,
title = {Optical fibre sensor for simultaneous measurement of capillary
refill time and contact pressure},
author = {Chong Liu and Ricardo Correia and Hattan Ballaji and Serhiy Korposh and Barrie Hayes-Gill and Stephen Morgan},
year = {2020},
date = {2020-03-01},
journal = {Sensors (Basel)},
volume = {20},
number = {5},
pages = {1388},
publisher = {MDPI AG},
abstract = {The widely applied capillary refill time (CRT) measurement is
currently performed by manually applying pressure and using a
stopwatch to record the time taken for the skin to recover its
normal colour after a blanching pressure is applied. This method
is highly subjective and observer-dependent. This paper presents
a new, integrated optical sensor probe, combining monitoring of
the capillary refilling process with the blanching pressure
applied. The sensor consists of an optical fibre-based
reflectance photoplethysmography (PPG) sensor to measure the
reflected light signal, as well as a fibre Bragg grating (FBG)
to measure the applied blanching pressure and to indicate the
time when pressure is released. This sensor was applied to
calculate the CRT (1.38 $±$ 0.66 s) of 10 healthy adult
volunteers with (55.2 $±$ 21.8 kPa) blanching pressures. The
form of the capillary refilling data was investigated by fitting
using an exponential regression model (R2 \> 0.96). The
integrated probe has the potential to improve the reliability of
CRT measurements by standardising the optimum duration and
magnitude of the pressure.},
keywords = {Capillary refill time, contact pressure, fibre bragg grating, photoplethysmography, plastic optical fibre},
pubstate = {published},
tppubtype = {article}
}
The widely applied capillary refill time (CRT) measurement is
currently performed by manually applying pressure and using a
stopwatch to record the time taken for the skin to recover its
normal colour after a blanching pressure is applied. This method
is highly subjective and observer-dependent. This paper presents
a new, integrated optical sensor probe, combining monitoring of
the capillary refilling process with the blanching pressure
applied. The sensor consists of an optical fibre-based
reflectance photoplethysmography (PPG) sensor to measure the
reflected light signal, as well as a fibre Bragg grating (FBG)
to measure the applied blanching pressure and to indicate the
time when pressure is released. This sensor was applied to
calculate the CRT (1.38 $±$ 0.66 s) of 10 healthy adult
volunteers with (55.2 $±$ 21.8 kPa) blanching pressures. The
form of the capillary refilling data was investigated by fitting
using an exponential regression model (R2 > 0.96). The
integrated probe has the potential to improve the reliability of
CRT measurements by standardising the optimum duration and
magnitude of the pressure.
currently performed by manually applying pressure and using a
stopwatch to record the time taken for the skin to recover its
normal colour after a blanching pressure is applied. This method
is highly subjective and observer-dependent. This paper presents
a new, integrated optical sensor probe, combining monitoring of
the capillary refilling process with the blanching pressure
applied. The sensor consists of an optical fibre-based
reflectance photoplethysmography (PPG) sensor to measure the
reflected light signal, as well as a fibre Bragg grating (FBG)
to measure the applied blanching pressure and to indicate the
time when pressure is released. This sensor was applied to
calculate the CRT (1.38 $±$ 0.66 s) of 10 healthy adult
volunteers with (55.2 $±$ 21.8 kPa) blanching pressures. The
form of the capillary refilling data was investigated by fitting
using an exponential regression model (R2 > 0.96). The
integrated probe has the potential to improve the reliability of
CRT measurements by standardising the optimum duration and
magnitude of the pressure.
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