Synthetic photoplethysmography (PPG) of the radial artery through parallelized Monte Carlo and its correlation to body mass index (BMI)
Open accessPublished version of a preprint
Abstract
Cardiovascular disease is one of the leading causes of death in the United States and obesity significantly increases the risk of cardiovascular disease. The measurement of blood pressure (BP) is critical in monitoring and managing cardiovascular disease hence new wearable devices are being developed to make BP more accessible to physicians and patients. Several wearables utilize photoplethysmography from the wrist vasculature to derive BP assessment although many of these devices are still at the experimental stage. With the ultimate goal of supporting instrument development, we have developed a model of the photoplethysmographic waveform derived from the radial artery at the volar surface of the wrist. To do so we have utilized the relation between vessel biomechanics through Finite Element Method and Monte Carlo light transport model. The model shows similar features to that seen in PPG waveform captured using an off the shelf device. We observe the influence of body mass index on the PPG signal. A degradation the PPG signal of up to 40% in AC to DC signal ratio was thus observed.
AI snapshot
Written from the paper’s full text.
TL;DR
The paper combines finite element modeling of radial artery dilation with Monte Carlo light transport to synthesize photoplethysmography (PPG) waveforms at the wrist and study how body mass index (BMI)-related skin changes affect the signal. The model reproduces features of a commercial PPG waveform and predicts substantial AC/DC signal degradation with increasing BMI.
Key findings
- The synthetic PPG waveform showed features similar to those captured with an off-the-shelf Nellcor Covidien PPG device, and experimental waveforms from individuals could be overlaid with the simulated waveform.
- Isolated BMI-related physiological changes degraded the AC/DC signal ratio: trans-epidermal water loss caused a 14.0% total signal decline, dermal blood content 18.0%, dermal thickness 41.4%, and radial artery depth 32.1%.
- Combined obesity-level waveforms showed baseline signal changes ranging from 12.7% to 54.5%; the non-obese AC/DC ratio was 8.1% versus 4.66% at the maximum modeled obesity level, a total change of 43%.
- Increasing epidermal melanin concentration from 3% to 42% changed the AC/DC signal ratio by 17.1%.
Methods
- The model had two parts: finite element analysis of radial artery wall dilation under internal pressure, followed by Monte Carlo light transport using an adapted MCMatlab/mcxyz framework.
- The radial artery was modeled with 2.5 mm inner diameter, 0.2 mm wall thickness, 0.70 MPa Young’s modulus, and 130 mmHg internal pressure; the Monte Carlo geometry included epidermis, dermis, and subcutaneous tissue with the artery embedded at 2.5 mm depth.
- Simulations modeled a commercial Nellcor Covidien PPG sensor with 660 nm and 890 nm sources, source-detector separation of 0.97 cm, collector area 0.35 cm × 0.35 cm, numerical aperture 0.866, 89 pulse positions, and 100 million to 1 billion photons per waveform. Experimental PPG was collected from four healthy volunteers for about thirty seconds, with a representative pulse used in analysis.
Limitations
- The paper states the work is limited to detection of the radial artery and does not consider the pulsatile effect of superficial arterioles.
- The paper states the model geometry is limited to primary skin layers and an embedded dynamic blood vessel, excluding underlying structures around the radial artery such as muscle or the radial styloid process.
- Evident from the text: experimental validation is preliminary and small, with methods reporting four healthy volunteers while results show PPG from three individuals; the model also isolates individual BMI-related skin changes rather than simulating all physiological changes of obesity together.
Model-written summary. Check it against the paper before relying on it.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
0 of 43 cited sources checked · 0 supported · 0 flagged
- Findingown data
Applying 0.70 MPa stiffness to the finite element model, the vessel wall shows total dilation of 0.4 mm in diameter.
“Applying 0.70 MPa stiffness, vessel wall shows total dilation of 0.4 mm in diameter.”
Quote in the paperSubstantial claim - Findingown data
Increasing body mass index degrades the photoplethysmographic signal, with a reduction of up to 40% in the AC to DC signal ratio.
“We observe the influence of body mass index on the PPG signal. A degradation the PPG signal of up to 40% in AC to DC signal ratio was thus observed.”
- Also stated in: § Results · plain
“A comparison of the AC to DC signal ratio of each waveform shows the degradation of the signal with increasing BMI.”
Quote in the paperSubstantial claim - Also stated in: § Results · plain
- Findingown data
The model of the photoplethysmographic waveform derived from the radial artery at the volar surface of the wrist shows similar features to a PPG waveform captured using an off-the-shelf device.
“The model shows similar features to that seen in PPG waveform captured using an off the shelf device.”
- Also stated in: § Results · hedged
“Preliminary experimental data using the PPG sensor (Fig. 5) shows features similar to that seen in simulation curve.”
Quote in the paperSubstantial claim - Also stated in: § Results · hedged
- Findingown data
The presence of obesity degrades the quality of the signal even when the vessel mechanics remain unchanged.
“the presence of obesity degrades the quality of the signal even when the vessel mechanics remain unchanged.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingown data
At the non-obese BMI of 25 kg/m2, the AC/DC signal ratio is 8.1%.
“The non-obese BMI of 25 kg/m2, the AC/DC signal ratio is 8.1% and at the maximum level calculated the ratio is 4.66%.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingown data
The AC/DC ratio changes from 14 to 41% as BMI increases from 20 to 40 for isolated changes attributed with increasing level of obesity and BMI.
“The AC/DC ratio changes from 14 to 41% as BMI increases from 20 to 40 for isolated changes attributed with increasing level of obesity and BMI.”
Quote in the paperSubstantial claim- Rests on an assumption: The four physiological changes (trans-epidermal water loss, dermal blood content, dermal thickness, and radial artery depth) are the changes attributed to obesity that affect PPG.
- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingown data
Figure 6C shows total percentage change between smallest and largest dermal thickness is 41.4%.
“Figure 6C shows total percentage change between smallest and largest dermal thickness is 41.4%.”
Quote in the paperNot a substantial claim- Rests on an assumption: The four physiological changes (trans-epidermal water loss, dermal blood content, dermal thickness, and radial artery depth) are the changes attributed to obesity that affect PPG.
- Findingown data
Total AC to DC signal ratio change is seen at 17.1% between 3% epidermal melanin concentration and 42% epidermal melanin concentration.
“Total AC to DC signal ratio change is seen at 17.1% between 3% epidermal melanin concentration and 42% epidermal melanin concentration.”
Quote in the paperNot a substantial claim - Findingown data
Figure 6A shows a 14.0% total signal decline associated with changes to trans-epidermal water loss between normal to highest BMI level.
“Figure 6A shows a 14.0% total signal decline associated with changes to trans-epidermal water loss between normal to highest BMI level.”
Quote in the paperNot a substantial claim- Rests on an assumption: The four physiological changes (trans-epidermal water loss, dermal blood content, dermal thickness, and radial artery depth) are the changes attributed to obesity that affect PPG.
- Findingown data
In Fig. 6D, percentage change between shallowest and deepest arterial depth is 32.1%.
“In Fig. 6D, percentage change between shallowest and deepest arterial depth is 32.1%.”
Quote in the paperNot a substantial claim- Rests on an assumption: The four physiological changes (trans-epidermal water loss, dermal blood content, dermal thickness, and radial artery depth) are the changes attributed to obesity that affect PPG.
- Findingown data
Across each level of obesity, at both 100 million and one billion photon counts, there is a significant diminishing of the amplitude of the signal.
“Across each level of obesity, at both 100 million and one billion photon counts, there is a significant diminishing of the amplitude of the signal.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingnone given
Similar changes are seen in both the 100 million photons set as well as the one billion photons set as to be expected.
“Similar changes are seen in both the 100 million photons set as well as the one billion photons set as to be expected.”
Quote in the paperNot a substantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingown data
The baseline change ranges from 12.7 to 54.5%.
“The baseline change ranges from 12.7 to 54.5%.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingreasoning
This accumulates to the total percentage change of 43% between the Non-Obese waveform and Obese 3 waveform.
“This accumulates to the total percentage change of 43% between the Non-Obese waveform and Obese 3 waveform.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingown data
Modeled AC to DC PPG signal ratio suggests that physiological changes due to BMI lower the ratio up to 40%.
“Modeled AC to DC PPG signal ratio suggests that physiological changes due to BMI lower the ratio up to 40%”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingown data
Similar trends of signal degradation are seen across the four different changes which occur with obesity: trans-epidermal water loss, blood perfusion, dermal thickness, and radial artery depth.
“Similar trends of signal degradation are seen across the four different changes which occur with obesity: trans-epidermal water loss, blood perfusion, dermal thickness, and radial artery depth.”
Quote in the paperNot a substantial claim- Rests on an assumption: The four physiological changes (trans-epidermal water loss, dermal blood content, dermal thickness, and radial artery depth) are the changes attributed to obesity that affect PPG.
- Findingown data
Our simulations demonstrate that with no changes to the underlying vessel mechanical behavior, an increase in BMI significantly impacts the PPG waveform.
“Our simulations demonstrate that with no changes to the underlying vessel mechanical behavior, an increase in BMI significantly impacts the PPG waveform.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingown data
A loss in signal quality is shown to increase as BMI and obesity level increase with changes in dermal thickness and arterial depth.
“A loss in signal quality is shown to increase as BMI and obesity level increase with changes in dermal thickness and arterial depth.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Findingown data
Figure 6B shows an 18.0% change with dermal blood content.
“Figure 6B shows an 18.0% change with dermal blood content.”
Quote in the paperNot a substantial claim- Rests on an assumption: The four physiological changes (trans-epidermal water loss, dermal blood content, dermal thickness, and radial artery depth) are the changes attributed to obesity that affect PPG.
- Findingown data
At the maximum level calculated, the AC/DC signal ratio is 4.66%.
“The non-obese BMI of 25 kg/m2, the AC/DC signal ratio is 8.1% and at the maximum level calculated the ratio is 4.66%.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
- Premisecitation
Vessel walls experience 10-20% diametral strain.
“Vessel walls have been reported to experience 10–20% diametral strain52,53.”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [52] Taylor, C. A., Hughes, T. J. & Zarins, C. K. Finite element modeling of blood flow in arteries. Comput. Methods Appl. Mech. Eng. 158, 155–196 (1998). source
Not checked in the free run.
- cites [53] Choudhari, P. & Panse, M. Finite element modeling and simulation of arteries in the human arm to study the aortic pulse wave propagation. Procedia Comput. Sci. 93, 721–727 (2016). source
Not checked in the free run.
- Interpretationcitation
Physiological changes in individuals with obesity may increase measurement uncertainties for optical blood pressure monitoring.
“Physiological changes that occur in individuals with obesity may increase the measurement uncertainties, and optical means for monitoring blood pressure will have to account for obesity-related changes to the skin optical properties12 and increased subcutaneous tissue thickness.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [12] Yosipovitch, G., DeVore, A. & Dawn, A. Obesity and the skin: skin physiology and skin manifestations of obesity. J. Am. Acad. Dermatol. 56, 901–916 (2007). source
Not checked in the free run.
- Premisecitation
Blood pressure in the radial artery at the volar surface of the wrist is more representative of blood pressure in the main arterial network than pressure in superficial vasculature of the skin.
“The blood pressure in the radial artery at the volar surface of the wrist is more representative of blood pressure in the main arterial network as opposed to pressure in superficial vasculature of the skin28.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [28] 28Chaudhry, R. & Rehman, A. in StatPearls [Internet] (StatPearls Publishing, 2020).
Not checked in the free run.
- Premisecitation
Radial artery pressure is 5 to 15 mmHg higher than brachial artery pressure.
“Radial artery pressure has been shown to be 5 to 15 mmHg50 higher than the brachial artery, where blood pressure is often measured using the sphygmomanometer.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [50] Armstrong, M. K. et al. Brachial and radial systolic blood pressure are not the same: evidence to support the popeye phenomenon. Hypertension 73, 1036–1041 (2019). source
Not checked in the free run.
- Premisecitation
Arterial pulsatile flow can be modeled as pulsatile flow through elastic-walled tubing.
“The behavior of arterial pulsatile flow can be modeled as a pulsatile flow through an elastic walled tubing19.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [19] Zamir, M. & Budwig, R. Physics of pulsatile flow. Appl. Mech. Rev. 55, B35–B35 (2002). source
Not checked in the free run.
- Premisecitation
Smaller peripheral vessels, such as the radial artery, exhibit similar mechanical behaviors to larger vessels like the aorta, carotid artery, and large coronary arteries.
“The mechanics of large vessels such as the aorta, carotid artery, and large coronary arteries has been studied extensively39–44 but several authors have noted that smaller peripheral vessels, such as the one under study here, exhibit similar mechanical behaviors to larger ones45,46.”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [45] Monson, K. L., Goldsmith, W., Barbaro, N. M. & Manley, G. T. Significance of source and size in the mechanical response of human cerebral blood vessels. J. Biomech. 38, 737–744 (2005). source
Not checked in the free run.
- cites [46] Khamdaeng, T., Luo, J., Vappou, J., Terdtoon, P. & Konofagou, E. E. Arterial stiffness identification of the human carotid artery using the stress-strain relationship in vivo. Ultrasonics 52, 402–411. https://doi.org/10.1016/j.ultras.2011.09.006 (2012). source
Not checked in the free run.
- Premisecitation
The depth of the radial artery signal varies with obesity, from 2.5 mm for non-obese individuals at BMI of 25 to 3.5 mm for BMI of 45.
“The signal from the radial artery is discovered to vary in depth with different levels of obesity from 2.5 mm for non-obese individuals at BMI of 25 to 3.5 mm for BMI of 4547,48.”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [47] Kim, J. U., Lee, Y. J., Lee, J. & Kim, J. Y. Differences in the properties of the radial artery between Cun, Guan, Chi, and nearby segments using ultrasonographic imaging: a pilot study on arterial depth, diameter, and blood flow. Evidence Based Complement. Altern. Med. 2015 (2015). source
Not checked in the free run.
- cites [48] Lee, B. J., Jeon, Y. J. & Kim, J. Y. Association of obesity with anatomical and physical indices related to the radial artery in Korean adults. Eur. J. Integr. Med. 14, 22–27 (2017). source
Not checked in the free run.
- Premisecitation
Dermal thickness varies with BMI, ranging from 1.0 mm to over 2.5 mm.
“Dermal thickness variations with BMI is shown to range from 1.0 mm to over 2.5 mm thickness58.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [58] Derraik, J. G. et al. Effects of age, gender, BMI, and anatomical site on skin thickness in children and adults with diabetes. PLoS ONE 9, e86637 (2014). source
Not checked in the free run.
- Interpretationreasoning
Increased radial artery depth also increases the total travel distance for photons to reach the vessel wall as and return to detector.
“Increased radial artery depth also increases the total travel distance for photons to reach the vessel wall as and return to detector.”
Quote in the paperSubstantial claim - Interpretationown data
The degradation of the return signal gives an indication to the decrease in quality of the signal that will be received by the PPG device.
“The degradation of the return signal gives an indication to the decrease in quality of the signal that will be received by the PPG device.”
Quote in the paperSubstantial claim - Premisecitation
Obese individuals have lesser values for absorption and reduced scattering coefficients in adipose tissue.
“When studying the optical properties of adipose tissue, Lanka38 et al. results show that obese have lesser values for absorption and reduced scattering coefficients.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Lanka38
Not checked in the free run.
- Premisecitation
Vessel expansion and contraction, under pressure changes of the cardiac cycle, is directly associated with the pulsatility of the PPG waveform.
“Vessel expansion and contraction, under pressure changes of the cardiac cycle, is directly associated with the pulsatility of the PPG waveform67”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [67] Vlachopoulos, C., O’Rourke, M. & Nichols, W. W. McDonald’s Blood Flow in Arteries: Theoretical, Experimental and Clinical Principles (CRC Press, Boca Raton, 2011). source
Not checked in the free run.
- Study design and conductown data
Each scenario shows changes isolated to each feature of obesity.
“Each scenario shows changes isolated to each feature of obesity.”
Quote in the paperNot a substantial claim - Interpretationown data
This loss of signal amplitude could explain some of the errors observed by obese population.
“this loss of signal amplitude could explain some of the errors observed by obese population.”
Quote in the paperSubstantial claim - Interpretationown data
Increase to dermal thickness increases the total volume of absorbers and scatterers through which photons must traverse to reach the artery and return to the detector.
“Increase to dermal thickness increases the total volume of absorbers and scatterers through which photons must traverse to reach the artery and return to the detector.”
Quote in the paperSubstantial claim
- May combine two claims. 16
- Classified as probably not a substantial claim. 10
May combine two claims.
Findingown dataThe generated PPG waveform for the non-obese case comprises an AC signal representing vascular pulsatility and a DC baseline signal.
“Figure 4C shows an example of PPG waveform generated for the non-obese case. The returned signal is comprised of an AC and a DC baseline signal, where the AC signal represents the pulsatility of the vasculature.”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataThere is significant variation in PPG waveforms between individuals, but the shape features can be identified in all three experimentally captured cases.
“The PPG of three different individuals was captured experimentally (Fig. 5A). There is significant variation between individuals (Fig. 5A green, red, blue), however the features of the shape can be identified in all three cases.”
Quote in the paperNot a substantial claimProbably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
Findingnone givenThe advantage of using lower number of photons is the computational time for each simulation in exchange for a higher standard deviation at each point.
“The advantage of using lower number of photons is the computational time for each simulation in exchange for a higher standard deviation at each point.”
Quote in the paperNot a substantial claimMay combine two claims.
Findingown dataA comparison of the waveform shows the degradation of the baseline signal as well as changes to the wave shape itself.
“A comparison of the waveform shows the degradation of the baseline signal as well as changes to the wave shape itself.”
Quote in the paperSubstantial claim- Rests on an assumption: Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
Probably not a substantial claim: may not pass S3 (load-bearing).
PremisecitationThe epidermis consists of multiple sublayers with various components, including melanin and melanocytes.
“The epidermis consists of multiple sublayers with various components, including melanin and melanocytes54.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [54] Thody, A. J. et al. Pheomelanin as well as eumelanin is present in human epidermis. J. Investig. Dermatol. 97, 340–344 (1991). source
Not checked in the free run.
May combine two claims.
PremisecitationThe arterial wall is often treated as incompressible, so internal pressure changes translate to vessel wall dilation while total wall volume is conserved.
“The arterial wall is often treated as incompressible44,51, pressure changes applied internally translates to vessel wall dilation, but the total wall volume is conserved.”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [44] Peterson, L. H., Jensen, R. E. & Parnell, J. Mechanical properties of arteries in vivo. Circ. Res. 8, 622–639 (1960). source
Not checked in the free run.
- cites [51] Holzapfel, G. A. & Ogden, R. W. Constitutive modelling of arteries. Proc. R. Soc. A Math. Phys. Eng. Sci. 466, 1551–1597. https://doi.org/10.1098/rspa.2010.0058 (2010). source
Not checked in the free run.
May combine two claims.
PremisecitationPrior Monte Carlo light propagation studies have not attempted to capture the PPG waveform in its entirety and have focused on an idealized skin model.
“In order to derive a better understanding of devices based on PPG, several groups have conducted light propagation models using Monte Carlo (MC) simulations29–31. Yet to our knowledge, these studies have not attempted to capture the PPG waveform in its entirety and have focused on an idealized skin model.”
Quote in the paperSubstantial claim0 of 3 sources checked- cites [29] Marti, D., Aasbjerg, R. N., Andersen, P. E. & Hansen, A. K. MCmatlab: an open-source, user-friendly, MATLAB-integrated three-dimensional Monte Carlo light transport solver with heat diffusion and tissue damage. J. Biomed. Opt. 23, 121622 (2018). source
Not checked in the free run.
- cites [30] Jacques, S. & Li, T. Monte Carlo Simulations of Light Transport in 3D Heterogenous Tissues (mcxyz. c). See http://omlc.org/software/mc/mcxyz/index.html. Accessed 30.01. 2017 (2013).
Not checked in the free run.
- cites [31] Chatterjee, S. & Kyriacou, P. A. Monte Carlo analysis of optical interactions in reflectance and transmittance finger photoplethysmography. Sensors 19, 789 (2019). source
Not checked in the free run.
May combine two claims.
PremisecitationThe radial artery has an inner diameter of 2.5 mm and a wall thickness of 0.2 mm.
“The radial artery has been reported to have 2.5 mm inner diameter and 0.2 wall thickness46–48.”
Quote in the paperSubstantial claim0 of 3 sources checked- cites [46] Khamdaeng, T., Luo, J., Vappou, J., Terdtoon, P. & Konofagou, E. E. Arterial stiffness identification of the human carotid artery using the stress-strain relationship in vivo. Ultrasonics 52, 402–411. https://doi.org/10.1016/j.ultras.2011.09.006 (2012). source
Not checked in the free run.
- cites [47] Kim, J. U., Lee, Y. J., Lee, J. & Kim, J. Y. Differences in the properties of the radial artery between Cun, Guan, Chi, and nearby segments using ultrasonographic imaging: a pilot study on arterial depth, diameter, and blood flow. Evidence Based Complement. Altern. Med. 2015 (2015). source
Not checked in the free run.
- cites [48] Lee, B. J., Jeon, Y. J. & Kim, J. Y. Association of obesity with anatomical and physical indices related to the radial artery in Korean adults. Eur. J. Integr. Med. 14, 22–27 (2017). source
Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
PremisecitationThe dermis is comprised of connective tissue along with blood vessels (capillaries and arterioles) with blood volume ratios ranging from 0.2 to 7% and water volume concentration around 65%.
“The dermis is comprised of connective tissue along with blood vessels (capillaries and arterioles) with blood volume ratios ranging from 0.2 to 7% and water volume concentration around 65%55,56.”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [55] Jacques, S. L. Origins of tissue optical properties in the UVA, visible, and NIR regions. OSA TOPS Adv. Opt. Imaging Photon Migr. 2, 364–369 (1996). source
Not checked in the free run.
- cites [56] Otto, J. M. et al. Hemoglobin concentration, total hemoglobin mass and plasma volume in patients: implications for anemia. Haematologica 102, 1477–1485 (2017). source
Not checked in the free run.
May combine two claims.
PremisecitationObesity creates variations in skin physiology, including skin barrier function, epidermal changes, dermal changes, and changes to vascular and capillary recruitment function.
“Recent studies have shown that obesity creates variations in skin physiology5,35–38. These changes include but are not limited to skin barrier function, epidermal changes, dermal changes, and changes to the vascular and capillary recruitment function.”
Quote in the paperSubstantial claim0 of 5 sources checked- cites [5] Ndumele, C. E. et al. Obesity and subtypes of incident cardiovascular disease. J. Am. Heart Assoc. 5, e003921 (2016). source
Not checked in the free run.
- cites [35] Mori, S. et al. Characterization of skin function associated with obesity and specific correlation to local/systemic parameters in American women. Lipids Health Dis. 16, 214 (2017). source
Not checked in the free run.
- cites [36] Hirt, P. A., Castillo, D. E., Yosipovitch, G. & Keri, J. E. Skin changes in the obese patient. J. Am. Acad. Dermatol. 81, 1037–1057 (2019). source
Not checked in the free run.
- cites [37] Spinelli, L. et al. Bulk optical properties and tissue components in the female breast from multiwavelength time-resolved optical mammography. J. Biomed. Opt. 9, 1137–1143 (2004). source
Not checked in the free run.
- cites [38] Lanka, P. et al. Non-invasive investigation of adipose tissue by time domain diffuse optical spectroscopy. Biomed. Opt. Exp. 11, 2779–2793 (2020). source
Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
PremisecitationThe subcutis consists of subcutaneous adipose tissue and other connective tissue.
“The subcutis consists of subcutaneous adipose tissue and other connective tissue57.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [57] Anderson, R. R. & Parrish, J. A. The optics of human skin. J. Investig. Dermatol. 77, 13–19 (1981). source
Not checked in the free run.
May combine two claims.
PremisecitationLightly pigmented skin adults have a melanin volume fraction of 1.3-6.3%, moderately pigmented skin adults have 11-16%, and darkly pigmented skin adults have 18-43% melanin volume fraction in the epidermis.
“Lightly pigmented skin adults have a melanin volume fraction of 1.3–6.3%, moderately pigmented skin adults have a 11–16% melanin volume fraction, and darkly pigmented skin adults have an 18–43% melanin volume fraction in the epidermis55.”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [55] Jacques, S. L. Origins of tissue optical properties in the UVA, visible, and NIR regions. OSA TOPS Adv. Opt. Imaging Photon Migr. 2, 364–369 (1996). source
Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
PremisecitationTrans-epidermal water loss is disrupted in the obese, and as BMI increases, TEWL increases, contributing to dry skin and skin irritation.
“Trans-epidermal water loss (TEWL) the process where water evaporates through the epidermis from the dermis is disruption in the obese36. As BMI increases so does TWEL66, and this effect directly contributed to dry skin and skin irritation often seen in the obese population.”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [36] Hirt, P. A., Castillo, D. E., Yosipovitch, G. & Keri, J. E. Skin changes in the obese patient. J. Am. Acad. Dermatol. 81, 1037–1057 (2019). source
Not checked in the free run.
- cites [66] Löffler, H., Aramaki, J. & Effendy, I. The influence of body mass index on skin susceptibility to sodium lauryl sulphate. Skin Res. Technol. 8, 19–22 (2002). source
Not checked in the free run.
May combine two claims.
InterpretationcitationThis effect has been documented by other investigators68 and it may account for some of the errors experienced by dark skin individuals utilizing wearable based on PPG68-71.
“This effect has been documented by other investigators68 and it may account for some of the errors experienced by dark skin individuals utilizing wearable based on PPG68–71.”
Quote in the paperNot a substantial claim0 of 4 sources checked- cites [68] Fallow, B. A., Tarumi, T. & Tanaka, H. Influence of skin type and wavelength on light wave reflectance. J. Clin. Monit. Comput. 27, 313–317 (2013). source
Not checked in the free run.
- cites [69] Bent, B., Goldstein, B. A., Kibbe, W. A. & Dunn, J. P. Investigating sources of inaccuracy in wearable optical heart rate sensors. NPJ Digit. Med. 3, 1–9 (2020). source
Not checked in the free run.
- cites [70] Zonios, G., Bykowski, J. & Kollias, N. Skin melanin, hemoglobin, and light scattering properties can be quantitatively assessed in vivo using diffuse reflectance spectroscopy. J. Investig. Dermatol. 117, 1452–1457 (2001). source
Not checked in the free run.
- cites [71] Weiler, D. T., Villajuan, S. O., Edkins, L., Cleary, S. & Saleem, J. J. In Proceedings of the Human Factors and Ergonomics Society Annual Meeting. 1292–1296 (SAGE Publications Sage CA: Los Angeles, CA).
Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
PremisecitationThe thickness of human epidermis is approximately 0.10 mm.
“The thickness of human epidermis is approximately 0.10 mm58,59.”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [58] Derraik, J. G. et al. Effects of age, gender, BMI, and anatomical site on skin thickness in children and adults with diabetes. PLoS ONE 9, e86637 (2014). source
Not checked in the free run.
- cites [59] Oltulu, P., Ince, B., Kökbudak, N. & Kılıç, F. Measurement of epidermis, dermis, and total skin thicknesses from six different body regions with a new ethical histometric technique. Türk Plast. Rekonstrüktif Estetik Cerrahi Dergisi (Turk J Plast Surg) 26, 56–61 (2018).
Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
PremisecitationThere is a positive correlation between BMI and lipid and total hemoglobin, and a negative correlation between BMI and water content in breast tissue.
“Spilenlli37 et al. studies the optical properties of breast tissue and discovered a positive correlation between BMI and lipid and total hemoglobin, and a negative correlation between BMI and water content.”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites Spilenlli37
Not checked in the free run.
May combine two claims.
PremisecitationIncreasing obesity is associated with changes in dermal water content, dermal blood content, dermal thickness, and increased radial artery depth.
“The significant changes to the skin which we have highlighted include changes to dermal water content66 and blood content content66 as well as dermal thickness and increased radial artery depth all with increasing levels of obesity47,48,58.”
Quote in the paperSubstantial claim0 of 3 sources checked- cites [66] Löffler, H., Aramaki, J. & Effendy, I. The influence of body mass index on skin susceptibility to sodium lauryl sulphate. Skin Res. Technol. 8, 19–22 (2002). source
Not checked in the free run.
- cites [47] Kim, J. U., Lee, Y. J., Lee, J. & Kim, J. Y. Differences in the properties of the radial artery between Cun, Guan, Chi, and nearby segments using ultrasonographic imaging: a pilot study on arterial depth, diameter, and blood flow. Evidence Based Complement. Altern. Med. 2015 (2015). source
Not checked in the free run.
- cites [48] Lee, B. J., Jeon, Y. J. & Kim, J. Y. Association of obesity with anatomical and physical indices related to the radial artery in Korean adults. Eur. J. Integr. Med. 14, 22–27 (2017). source
Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Study design and conductnone givenThe model geometry is limited to the primary layers of the skin and an embedded dynamic blood vessel, however underlying structures around the radial artery such as the muscle or radial styloid process has not been included.
“The model geometry is limited to the primary layers of the skin and an embedded dynamic blood vessel, however underlying structures around the radial artery such as the muscle or radial styloid process has not been included.”
Quote in the paperNot a substantial claimProbably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
Study design and conductnone givenThis work is limited to the detection of the radial artery and does not consider the pulsatile effect of the superficial arterioles.
“This work is limited to the detection of the radial artery and does not consider the pulsatile effect of the superficial arterioles”
Quote in the paperNot a substantial claimProbably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
Study design and conductnone givenThe study protocol was approved by the Institutional Review Board of Florida International University and followed the tenets of the Declaration of Helsinki, with written informed consent obtained from subjects.
“The protocol for the study was approved by the Institutional Review Board of Florida International University and followed the tenets of the Declaration of Helsinki. Written informed consent was obtained from the subjects after explanation of the nature and possible consequences of the study.”
Quote in the paperNot a substantial claim
The authors state this as an assumption.
Blood flow in the radial artery can be approximated as a Newtonian fluid and modeled as a homogeneous fluid.
“In vessels of this size, the vessel diameter is large compared to cell size and fluid can be approximated as a Newtonian fluid25,26 and flow can be modeled as a homogenous fluid27 flow.”
The paper relies on this without support.
The four physiological changes (trans-epidermal water loss, dermal blood content, dermal thickness, and radial artery depth) are the changes attributed to obesity that affect PPG.
“Figure 6 shows changes AC/DC signal from four different changes attributed to obesity across different BMI levels.”
The paper relies on this without support.
Varying dermal thickness and arterial depth alone adequately represents the effect of increasing BMI/obesity on the PPG waveform.
“Waveforms for different levels of obesity are generated through varying the combined dermal thickness and arterial depth to indicate corresponding physiological changes.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
Pooled comparisons by BMI category did not reach significance; however, several device-level contrasts indicated small directional biases with higher adiposity.
“In contrast, pooled comparisons by BMI category did not reach significance; however, several device-level contrasts indicated small directional biases with higher adiposity (e.g., [12,13]).”
From PPG-Based Heart Rate Accuracy in Hispanic Adults with Fitzpatrick III–V Skin Tones: An Evaluation of Body Composition and Skin-Tone Effects (2026) · cites this paper as [13]
The Results (Figures 6 and 8–9; page not provided) show that simulated PPG signals decline as modeled obesity increases, supporting the direction of the reported effect. The paper does not report pooled statistical comparisons by BMI category or device-level contrasts, and its modeled signal changes are not described as small device biases. (LLM, conf=0.84)
Experimental — accuracy not yet measuredBoonya-Ananta et al. showed that with increasing melanin concentration, there was a consistent and measurable decline in PPG signal strength.
“Boonya-Ananta et al. [13] showed that with increasing melanin concentration, there was a consistent and measurable decline in PPG signal strength.”
From PPG-Based Heart Rate Accuracy in Hispanic Adults with Fitzpatrick III–V Skin Tones: An Evaluation of Body Composition and Skin-Tone Effects (2026) · cites this paper as [13]
Boonya-Ananta et al. showed a 43% decrease in signal amplitude as BMI increased from 25 to 45 kg/m2.
“Boonya-Ananta et al. [13] confirmed these findings using hybrid FEM and Monte Carlo models, showing a 43% decrease in signal amplitude as BMI increased from 25 to 45 kg/m2.”
From PPG-Based Heart Rate Accuracy in Hispanic Adults with Fitzpatrick III–V Skin Tones: An Evaluation of Body Composition and Skin-Tone Effects (2026) · cites this paper as [13]
Statistically reliable patterns tied to phenotype, particularly adiposity, and to a lesser extent skin pigmentation, were evident and align with optical and physiological mechanisms described in prior work.
“Nonetheless, statistically reliable patterns tied to phenotype, particularly adiposity, and, to a lesser extent, skin pigmentation, were evident and align with the optical and physiological mechanisms described in prior work [13,43].”
From PPG-Based Heart Rate Accuracy in Hispanic Adults with Fitzpatrick III–V Skin Tones: An Evaluation of Body Composition and Skin-Tone Effects (2026) · cites this paper as [13]
These often-overlooked disparities with diversity (e.g., skin tone and obesity) are now becoming more documented in the literature.
“These often-overlooked disparities with diversity (e.g., skin tone and obesity) are now becoming more documented in the literature [34,35,36].”
From Sources of inaccuracy in photoplethysmography for continuous cardiovascular monitoring (2021) · cites this paper as [36]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Maximum modeled artery depth is stated as both 3.5 and 4.5 mm
MajorThe Methods says artery depth reaches 3.5 mm at BMI 45, whereas the Results says the obesity waveforms use depths up to 4.5 mm. It is unclear which maximum depth underlies the reported waveforms.
“The signal from the radial artery is discovered to vary in depth with different levels of obesity from 2.5 mm for non-obese individuals at BMI of 25 to 3.5 mm for BMI of 4547,48.”
“Changes to BMI and obesity level is presented through the increase of dermal thickness from 1.0 to 2.5 mm and arterial depth from 2.5 to 4.5 mm.”
Table 3 gives radial-artery depth in centimeters rather than millimeters
MinorTable 3 labels the baseline radial-artery depth as 2.5 cm, but the model description places it at 2.5 mm. These are tenfold different depths.
“| Body mass index (kg/m2) | Trans-epidermal water loss (%) | Dermal blood content change (%) | Dermal thickness (cm) | Radial artery depth (cm) | | --- | --- | --- | --- | --- | | 25 | 0 | 0 | 1.0 | 2.5 |”
“Within this layer, the radial artery is modeled as a cylinder situated at 2.5 mm depth from the top surface47,48.”
Table 3 gives dermal thickness in centimeters rather than millimeters
MinorTable 3 labels its dermal-thickness values in centimeters, while the Results describes the same 1.0-to-2.5 range in millimeters. The table's units make these modeled thicknesses ten times larger.
“| Body mass index (kg/m2) | Trans-epidermal water loss (%) | Dermal blood content change (%) | Dermal thickness (cm) | Radial artery depth (cm) | | --- | --- | --- | --- | --- | | 25 | 0 | 0 | 1.0 | 2.5 |”
“Changes to BMI and obesity level is presented through the increase of dermal thickness from 1.0 to 2.5 mm and arterial depth from 2.5 to 4.5 mm.”
Discussion gives a different simulated BMI range
MinorThe Discussion describes the isolated-change results as spanning BMI 20 to 40, but the simulation-parameter table spans BMI 25 to 45.
“The AC/DC ratio changes from 14 to 41% as BMI increases from 20 to 40 for isolated changes attributed with increasing level of obesity and BMI.”
“| Body mass index (kg/m2) | Trans-epidermal water loss (%) | Dermal blood content change (%) | Dermal thickness (cm) | Radial artery depth (cm) | | --- | --- | --- | --- | --- | | 25 | 0 | 0 | 1.0 | 2.5 | | 30 | 30 | 10 | 1.325 | 2.75 | | 35 | 40 | 20 | 1.75 | 3.0 | | 40 | 50 | 30 | 2.125 | 3.25 | | 45 | 60 | 40 | 2.5 | 3.5 |”
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Sources of inaccuracy in photoplethysmography for continuous cardiovascular monitoring
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“Despite these advantages, the accuracy of PPG sensors is limited by their susceptibility to motion artefacts 126,127 , by variations in skin tone and thickness 128,129 and by environmental interference from ambient light 130 and temperature 131 .”
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Piezoelectric Metamaterial Blood Pressure Sensor
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“Another study [25] managed to model the PPG with modeling the finite element method and monte carlo.”
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Wearable Devices for Remote Monitoring of Chronic Diseases: Systematic Review
Tegegne, M. D., Kalhori, S. R. N., Haas, P., Sobotta, V. M. G., Warnecke, J. M., & Deserno, T. M. (2025) · JMIR mhealth and uhealth · doi:10.2196/74071 · Cited by 31 · see citing works
A review of wearable flexible sensors for sports: from materials to applications
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Fabric‐Based Ultrasonic Sensor with Integrated Piezoelectric Composite for Blood Pressure Monitoring
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“…decrease in PPG sensitivity like skin tone, tattoos in the PPG sensor area, hairi-ness 16 or the BMI (due to different optical properties of the skin in obese patients 17,18 ) did not lead to any possible explanation for the reduced percentage of correctly identified AF burden in these patients.”
Ultraflexible Ring‐Shaped Organic Photodetectors for Motion Artifact‐Less Photoplethysmography
Liu, L., Lu, Z., Yan, Z., Wang, H., Su, Z., Yokota, T., Someya, T., & Wang, B. (2024) · Advanced Optical Materials · doi:10.1002/adom.202400665 · Cited by 17 · see citing works
Monte Carlo based simulations of racial bias in pulse oximetry
Arefin, M. S., Dumont, A. P., & Patil, C. A. (2022) · doi:10.1117/12.2610483 · Cited by 16 · see citing works
Wu, M., Liu, I.-F., Tzeng, Y.-H., & Wang, L. (2022) · Physiological Measurement · doi:10.1088/1361-6579/ac7d91 · Cited by 16 · see citing works
Printed soft skin electrodes for seamless bio-impedance measurements
Levit, B., Krebsbach, P., Bar-Haim, C., Hernandez‐Sosa, G., & Hanein, Y. (2023) · Flexible and Printed Electronics · doi:10.1088/2058-8585/acc540 · Cited by 16 · see citing works
“Deep penetration allows higher accuracy in detection of the blood volume change, as well as providing detailed characteristics of the hemodynamic parameters [9, 10, 35].”
Photoplethysmography upon cold stress—impact of measurement site and acquisition mode
Fleischhauer, V., Bruhn, J., Rasche, S., & Zaunseder, S. (2023) · Frontiers in Physiology · doi:10.3389/fphys.2023.1127624 · Cited by 18 · see citing works
Wearable Blood Pressure Monitoring Devices: Understanding Heterogeneity in Design and Evaluation
Cheung, M. Y., Sabharwal, A., Coté, G. L., & Veeraraghavan, A. (2024) · IEEE Transactions on Biomedical Engineering · doi:10.1109/tbme.2024.3434344 · Cited by 16 · see citing works
“Higher body-mass indices may lead to lower SNR [27].”
A 3D-Printed Piezoelectric Microdevice for Human Energy Harvesting for Wearable Biosensors
Sobianin, I., Psoma, S. D., & Tourlidakis, A. (2024) · Micromachines · doi:10.3390/mi15010118 · Cited by 14 · see citing works
“…and this in turn causes the pressure to rise 𝐅 = −𝐧 ∙ (−∇𝑝 + ∇ ∙ (𝜇(∇𝐮 + (∇𝐮) ))) (7) The signal amplitude, which dictates how far the radial artery domain travels, was selected µ diameter change of up to 200 µ m [30]. where n is the normal vector to the piezoelectric disc. amount of voltage.”
Guo, C.-Y., Chang, H., Wang, K.-J., & Hsieh, T.-L. (2022) · Micromachines · doi:10.3390/mi13081327 · Cited by 14 · see citing works
“The main factor is the body mass index (BMI) [41].”
BackgroundInfluentialQuantification of the Phenomena Affecting Reflective Arterial Photoplethysmography
Rovas, G., Bikia, V., & Stergiopulos, N. (2023) · Bioengineering · doi:10.3390/bioengineering10040460 · Cited by 14 · see citing works
Bhusal, A., Farahmand, M., Hasan, M. S., Vasudevan, S., Vogt, W. C., Ibarra, B., Weininger, S., Scully, C. G., Zhang, X. H., Chen, Y., et al. (2025) · Journal of Biomedical Optics · doi:10.1117/1.jbo.29.s3.s33314 · Cited by 11 · see citing works
“13,14 It should also be noted that a recent clinical study demonstrated that the broad spectral bandwidth of pulse oximeter light sources can result in erroneously high SpO 2 measurements for patients with higher melanin concentration 15 whereas narrow band sources are not impacted.”
Hardon, H. J., Kerkhof, Y. N. V., Bartelds, B., Kammeraad, J. A. E., & van Deutekom, A. W. (2025) · JMIR Formative Research · doi:10.2196/70835 · Cited by 9 · see citing works
“First, a positive but non-significant effect of BMI on CardioWatch performance was observed, contrasting with previous studies where higher BMI negatively impacted PPG accuracy [34, 35].”
Modeling light-tissue interactions in pulse oximetry: effect of device design and skin pigmentation
Moradi, M., Vasudevan, S., Bhusal, A., Weininger, S., Chen, Y., & Pfefer, J. (2024) · Design and Quality for Biomedical Technologies · doi:10.1117/12.3004189 · Cited by 8 · see citing works
“Boonya-ananta et al., [29] in 2021 employed a wearable reflectance geometry-pulse oximetry, presenting outcomes for four melanin levels.”
BackgroundWu, H.-L., Wu, Y.-M., Wang, C.-W., Su, Y., Cata, J. P., Chen, J., Cherng, Y., & Tai, Y. (2024) · Journal of Cardiothoracic and Vascular Anesthesia · doi:10.1053/j.jvca.2024.08.006 · Cited by 7 · see citing works
Ghosh, A., Sarkar, S., Liu, H., & Mandal, S. (2023) · Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) · doi:10.1109/embc40787.2023.10340405 · Cited by 7 · see citing works
Monte Carlo method for assessment of a multimodal insertable biosensor
Fine, J. N., McShane, M. J., & Coté, G. L. (2022) · Journal of Biomedical Optics · doi:10.1117/1.jbo.27.8.083017 · Cited by 7 · see citing works
“Additionally, features such as skin tone or body mass index can vary across populations, making optical signal transduction more difficult and highly variable.(17) However, tools such as Monte Carlo simulation can be used to predict autofluorescence, scattering, and absorptive events.”
BackgroundFine, J. N., McShane, M. J., Coté, G. L., & Scully, C. G. (2022) · Biosensors · doi:10.3390/bios12080598 · Cited by 7 · see citing works
“Boonya-ananta et al. focused on individuals with dark skin tone and obesity, using MC to generate a single PPG period and then quantified the impact those features have on PPG AC/DC ratio [22].”
MethodHu, H., Li, J., & Chen, X. (2022) · International Congress on Image and Signal Processing (CISP) · doi:10.1109/cisp-bmei56279.2022.9979897 · Cited by 6 · see citing works
“It has been found that many factors may affect the signal characteristics during the acquisition of reflectance PPG, including blood perfusion [3], skin darkness and thickness [4], contact pressure [5], motion artifacts [6], and other factors.”
BackgroundOn the Origin of the Photoplethysmography Signal: Modeling of Volumetric and Aggregation Effects
Lapitan, D. G., Tarasov, A. P., Shtyflyuk, M. E., & Рогаткин, Д. А. (2024) · Photonics · doi:10.3390/photonics11070637 · Cited by 5 · see citing works
Jia, H., Chen, B., & Li, D. (2021) · Applied Sciences · doi:10.3390/app11072998 · Cited by 5 · see citing works
“Multilayered PWS vessels, particularly cross-bridge vessels, considerably influence laser propagation due to shading effects [5,6] (Figure 1).”
BackgroundBadolato, E., Little, A., & Le, V. N. D. (2024) · Optics Express · doi:10.1364/oe.510977 · Cited by 5 · see citing works
Wu, M. M., Horstmeyer, R. W., & Carp, S. A. (2023) · Journal of Biomedical Optics · doi:10.1117/1.jbo.28.10.100501 · Cited by 5 · see citing works
Thomas, J., Doyle, P., & Doyle, J. A. (2022) · bioRxiv (Cold Spring Harbor Laboratory) · doi:10.1101/2022.09.29.510075 · Cited by 4 · see citing works
Jones, Z. D., Reitzle, D., & Kienle, A. (2025) · Biomedical Optics Express · doi:10.1364/boe.573069 · Cited by 3 · see citing works
Fibricheck detection capabilities for atrial fibrillation (FDA–AF): a multicenter validation study
Sollee, J., Cheema, B. S., Slotwiner, D. J., Volodarskiy, A., Desteghe, L., Buyck, C., Heidbüchel, H., Stavrakis, S., Pison, L., Nuyens, D., et al. (2025) · npj Digital Medicine · doi:10.1038/s41746-025-02059-2 · Cited by 3 · see citing works
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“Each layer has its unique optical properties, which are essentially absorption and scattering coefficients and the reflection index [9].”
BackgroundToledano, B. R. F., Garganera, K. B., Prado, J. P. A., & Sabas, M. L. (2024) · Catheterization and Cardiovascular Interventions · doi:10.1002/ccd.31005 · Cited by 3 · see citing works
Flynn, K. A., Ownby, N. B., Wang, P., & Calhoun, B. H. (2021) · IEEE Biomedical Circuits and Systems Conference (BioCAS) · doi:10.1109/biocas49922.2021.9644946 · Cited by 3 · see citing works
Kostrna, J., Oparina, E., Palacios, C., Rodriguez, A. J., Pei, J., Ajmal, A., & Ramella-Roman, J. C. (2026) · Sensors · doi:10.3390/s26102922 · Cited by 2 · see citing works
“Nonetheless, statistically reliable patterns tied to phenotype, particularly adiposity, and, to a lesser extent, skin pigmentation, were evident and align with the optical and physiological mechanisms described in prior work [13,43].”
InfluentialSelf-citationJones, Z. D., Foschum, F., & Kienle, A. (2026) · Sensors · doi:10.3390/s26072070 · Cited by 2 · see citing works
Modification of oximeter ratio to reduce pigmentation bias in pulse oximetry
Arefin, M. S., Shmuylovich, L., & Patil, C. A. (2024) · Design and Quality for Biomedical Technologies · doi:10.1117/12.3003274 · Cited by 1 · see citing works
“Similarly, in silico Monte Carlo (MC) simulations have indicated that the oximeter ratio, R, which is used to estimate blood oxygen saturation level (SpO2) carries a pigmentation dependence, which likely contributes to reports of racial bias [9].”
BackgroundDecoding menstrual health across the lifespan: a scoping review of digital health tools in research
Johnson, S. C., O’Day, J. J., Kraus, E., Delp, S. L., & Hicks, J. L. (2026) · npj Women s Health · doi:10.1038/s44294-026-00146-7 · Cited by 1 · see citing works
“There is some evidence that photoplethysmography-measured heart rate can be in fl uenced by BMI 124 and skin tone 125 , but the temporal location ofthepeaksusedtodetectheartrateremainedstable.”
InfluentialJiao, Y. (2026) · Sensor Review · doi:10.1108/sr-08-2025-0630 · Cited by 1 · see citing works
Lin, C.-N., Wang, C., Chao, P.-C., Lin, J., Chang, C., Lu, H., Lin, P.-W., & Ko, P.-Y. (2026) · Frontiers in Physiology · doi:10.3389/fphys.2026.1779262 · Cited by 1 · see citing works
Body fat, skin tone, and the accuracy of smartwatch caloric expenditure estimates
Kostrna, J. R., Oparina, E., Palacios, C. S., Rodriguez, A. J., Pei, J., Ajmal, A., & Ramella‐Roman, J. C. (2026) · PLoS ONE · doi:10.1371/journal.pone.0353261 · Cited by 1 · see citing works
“Likewise, individuals with higher body mass index (BMI) often exhibit thicker, less perfused skin, which diminishes the intensity of light returning to the sensor [4,8].”
Self-citationReiser, M. F., Müller, T., Flock, K., Amft, O., & Breidenassel, A. (2023) · Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) · doi:10.1109/embc40787.2023.10340790 · Cited by 1 · see citing works
“Sensor geometry, including the distance between source and detector, has an important influence on the PPG signal’s DC level, i.e. the non-pulsating signal part, and depends on measurement location and anatomy [4], [5].”
BackgroundSoft electrodes for simultaneous bio-potential and bio-impedance study of the face
Levit, B., Funk, P. F., & Hanein, Y. (2024) · Biomedical Physics & Engineering Express · doi:10.1088/2057-1976/ad28cb · Cited by 1 · see citing works
In-vivo human study of skin optical properties in individuals with obesity
Rodriguez, A. J., Alzamora, M., Ajmal, A., Boonya-ananta, T., Le, V. N. D., Fredriksson, I., Tomas Strömberg, A., & Ramella‐Roman, J. C. (2022) · Optical Diagnostics and Sensing: Toward Point-of-Care Diagnostics · doi:10.1117/12.2610464 · Cited by 1 · see citing works
“We have previously modeled the effects of obesity on clinical PPG sensors as well as commercial wearable devices and noticed that obesity and obesity combined with darker skin tones leads to a reduction in AC/DC signal among these optical sensors (17, 18).”
BackgroundSelf-citationAslam, M., Ahmad, I., Mangi, S. A., Bashar, K. U., Khan, M. K., & Ali, D. (2023) · Pakistan Journal of Medical and Health Sciences · doi:10.53350/pjmhs2023173664 · Cited by 1 · see citing works
Harrison-Smith, B., Arefin, M. S., Dumont, A., & Patil, C. A. (2022) · doi:10.1117/12.2610519
Using Monte Carlo simulated PPGs signals to train a deep learning model to predict hemoglobin levels
Alvarez, M. A., Arzuaga, E., & Sierra, H. (2023) · Emerging Topics in Artificial Intelligence (ETAI) · doi:10.1117/12.2677499
“PPG signals are obtained non-invasively by measuring the response of skin layers to incoming light, which reflects relative changes in blood volume and blood pressure waves.(3)”
BackgroundMethodInfluentialMonte Carlo Simulated Photoplethysmography Signals for the Validation of an in Vitro Wrist Phantom
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Hardon, H. J., Kerkhof, Y. N. V., Bartelds, B., Kammeraad, J. A. E., & van Deutekom, A. W. (2025) · doi:10.2196/preprints.70835
Wearable Devices for Remote Monitoring of Chronic Diseases: A Systematic Review (Preprint)Preprint
Tegegne, M. D., Kalhori, S. R. N., Haas, P., Sobotta, V. M. G., Warnecke, J. M., & Deserno, T. M. (2025) · doi:10.2196/preprints.74071
End-to-End Wrist PPG Generation Using Radial Artery Hemodynamics and Light Transport Simulation
Kuruppu, S., Fernando, B., Tharindu, D., Bandara, D., & Pasqual, A. A. (2025) · IEEE International Conference on Bioinformatics and Bioengineering (BIBE) · doi:10.1109/bibe66822.2025.00024
“While MC simulations provide highly accurate representations of photon behavior, they require significant computational effort due to the need to simulate a large number of photons to achieve statistical accuracy [16].”
InfluentialContinuous Non-Invasive Blood Pressure Estimation Based on Impedance Plethysmography Measurements
Shokri, F., Ashoorirad, M., & Baghbani, R. (2025) · National and International Iranian Conference on Biomedical Engineering (ICBME) · doi:10.1109/icbme68496.2025.11392299
“The numerical values of all properties are given in Table 1,[24-29]. radial artery, a combination of Gaussian functions in the form of Equation 9 is used.”
Kazemi, M., Fatouraee, N., & Rassoli, A. (2025) · National and International Iranian Conference on Biomedical Engineering (ICBME) · doi:10.1109/icbme68496.2025.11392480
“The density of the coronary artery wall was set to ρ=1120 kg·m⁻³, and that of the graft wall to 1160 kg·m⁻³, to account for the gravitational effect of the vascular wall mass [21, 22].”
Li, J., Pang, C., Zhou, W., Luo, X., Zhang, X., Li, Y., & Liu, J. D. (2026) · Biomedical Signal Processing and Control · doi:10.1016/j.bspc.2026.109964
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Skin Microcirculation in Obesity Using Modern Non-Invasive Research Methods (review)
Trunov, I. V., Александрович, Ф. А., Korolev, A. I., Ososkov, V. S., & Drapkina, O. M. (2026) · Regional blood circulation and microcirculation · doi:10.24884/1682-6655-2026-25-1-22-29
Wang, L., Hsiao, M.-Y., Chen, Z.-J., Wu, R.-J., & Wu, M.-T. (2026) · BMC Cardiovascular Disorders · doi:10.1186/s12872-026-05914-6
Noninvasive Estimation of Glycated Hemoglobin: A Comprehensive Review of Emerging Technologies
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Joshi, D. D., Saraboji, K., Shaik, A. T., Sakalabaktula, K. S. K., Purohit, S., Godugu, S., Nirmal, J., Kayarkar, R., Correa, B. H. M., Gangidi, N., et al. (2026) · Life · doi:10.3390/life16091530
“…open datasets also incorporate controlled variables such as contact pressure, temperature, posture, ambient light, and motion, enabling reproducible and direct comparisons of model performance while facilitating accurate performance evaluation and the identification of remaining challenges [44,86].”
- Authors
- Boonya-ananta, T., Rodriguez, A. J., Ajmal, A., Du Le, V. N., Hansen, A. K., Hutcheson, J. D., & Ramella-Roman, J. C.
- Affiliations
- Florida International University (US)
- Technical University of Denmark (DK)
- Venue
- Scientific Reports
- Published
- 2021-01-28
- Volume
- 11
- Issue
- 1
- Pages
- 2570-2570
- ISSN
- 2045-2322 (ISSN-L)
- PMC
- PMC7843978
- OpenAlex
- W3124155372
- Semantic Scholar
- 1fd540da48d0580669b8de63359d9300592af5f6
- Cited by
- 70
- References
- 64
- Citations by year
- 2026: 12 · 2025: 13 · 2024: 12 · 2023: 15 · 2022: 13 · 2021: 5
- FWCI
- 3.41
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Locations
- Scientific Reports (publishedVersion, cc-by)
- bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion, cc-by-nc-nd)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- Florida International University Digital Commons (Florida International University) (submittedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Technical University of Denmark, DTU Orbit (Technical University of Denmark, DTU) (submittedVersion, other-oa)
- Funders
- PATHS-UP, National Science Foundation, United States of America (EEC 1648451)
- Topics
- Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
- Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Cardiovascular Health and Disease Prevention
- Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Heart Rate Variability and Autonomic Control
- Keywords
- photoplethysmography, radial artery, Monte Carlo light transport, body mass index, obesity, wearable blood pressure monitoring, cardiovascular disease
- MeSH terms
- Animals, Biomechanical Phenomena, Blood Pressure, Humans, Monte Carlo Method, Body Mass Index, Photoplethysmography, Radial Artery, Finite Element Analysis
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