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Remote Photoplethysmography for Evaluation of Cutaneous Sensory Nerve Fiber Function.

ABSTRACT: About 2% of the world's population suffers from small nerve fiber dysfunction, neuropathy, which can result in severe pain. This condition is caused by damage to the small nerve fibers and its assessment is challenging, due to the lack of simple and objective diagnostic techniques. The present study aimed to develop a contactless photoplethysmography system using simple instrumentation, for objective and non-invasive assessment of small cutaneous sensory nerve fiber function. The approach is based on the use of contactless photoplethysmography for the characterization of skin flowmotions and topical heating evoked vasomotor responses. The feasibility of the technique was evaluated on volunteers (n = 14) using skin topical anesthesia, which is able to produce temporary alterations of cutaneous nerve fibers function. In the treated skin region in comparison to intact skin: neurogenic and endothelial component of flowmotions decreased by ~61% and 41%, the local heating evoked flare area decreased by ~44%, vasomotor response trend peak and nadir were substantially reduced. The results indicate for the potential of the remote photoplethysmography in the assessment of the cutaneous nerve fiber function. It is believed that in the future this technique could be used in the clinics as an affordable alternative to laser Doppler imaging technique.

SUBMITTER: Marcinkevics Z

PROVIDER: S-EPMC7916836 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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Remote Photoplethysmography for Evaluation of Cutaneous Sensory Nerve Fiber Function.

Marcinkevics Zbignevs Z Aglinska Alise A Rubins Uldis U Grabovskis Andris A

Sensors (Basel, Switzerland) 20210211 4

About 2% of the world's population suffers from small nerve fiber dysfunction, neuropathy, which can result in severe pain. This condition is caused by damage to the small nerve fibers and its assessment is challenging, due to the lack of simple and objective diagnostic techniques. The present study aimed to develop a contactless photoplethysmography system using simple instrumentation, for objective and non-invasive assessment of small cutaneous sensory nerve fiber function. The approach is bas ...[more]

PMID: 33670087

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Project description:This work investigates the estimation biases of remote photoplethysmography (rPPG) methods for pulse rate measurement across diverse demographics. Advances in photoplethysmography (PPG) and rPPG methods have enabled the development of contact and noncontact approaches for continuous monitoring and collection of patient health data. The contagious nature of viruses such as COVID-19 warrants noncontact methods for physiological signal estimation. However, these approaches are subject to estimation biases due to variations in environmental conditions and subject demographics. The performance of contact-based wearable sensors has been evaluated, using off-the-shelf devices across demographics. However, the measurement uncertainty of rPPG methods that estimate pulse rate has not been sufficiently tested across diverse demographic populations or environments. Quantifying the efficacy of rPPG methods in real-world conditions is critical in determining their potential viability as health monitoring solutions. Currently, publicly available face datasets accompanied by physiological measurements are typically captured in controlled laboratory settings, lacking diversity in subject skin tones, age, and cultural artifacts (e.g, bindi worn by Indian women). In this study, we collect pulse rate and facial video data from human subjects in India and Sierra Leone, in order to quantify the uncertainty in noncontact pulse rate estimation methods. The video data are used to estimate pulse rate using state-of-the-art rPPG camera-based methods, and compared against ground truth measurements captured using an FDA-approved contact-based pulse rate measurement device. Our study reveals that rPPG methods exhibit similar biases when compared with a contact-based device across demographic groups and environmental conditions. The mean difference between pulse rates measured by rPPG methods and the ground truth is found to be ~2% (1 beats per minute (b.p.m.)), signifying agreement of rPPG methods with the ground truth. We also find that rPPG methods show pulse rate variability of ~15% (11 b.p.m.), as compared to the ground truth. We investigate factors impacting rPPG methods and discuss solutions aimed at mitigating variance.

Project description:Study objectivesTo quantitatively evaluate the functional integrity of sensory nerve fibers of the palate in patients with obstructive sleep apnea (OSA) using the Neurometer system.MethodsA total of 32 patients with OSA and 18 healthy control patients were included in the study. All participants were selected based on medical history, physical examination, and nocturnal polysomnography (PSG) and divided into two groups. The palatal sensory status of participants was examined with a Neurometer current perception threshold (CPT) system. The system was used to deliver an electrical stimulus at three different frequencies (2,000 Hz, 250 Hz, and 5 Hz) by an investigator blinded to the PSG results.ResultsThere were no significant differences in the CPT values of the hard palate between the patients with OSA and control patients at any of the three stimulation frequencies. The differences in the CPT values of the soft palate between these groups failed to show any statistical significance at 250 Hz and 5 Hz. However, the patients with OSA showed significantly higher CPT values of the soft palate at 2,000 Hz than the age-matched healthy control patients (256.56 ± 129.34 versus 372.13 ± 152.06; P = .009).ConclusionsOur study revealed an impairment of 2,000 Hz-related sensory nerve function of the soft palate among patients with OSA. The CPT test could be a useful tool for the quantitative and selective assessment of the sensory nerve function in patients with OSA. Additional research is required to evaluate the different types of sensory nerve dysfunctions among such patients.Clinical trial registrationRegistry: ClinicalTrials.gov; Title: The Effects of Nasal Airflow on Upper Airway Dilator Muscles During Sleep; Identifier: NCT03506178; URL: https://clinicaltrials.gov/ct2/show/NCT03506178.CitationAn Y, Li Y, Chang W, Gao F, Ding X, Xu W, Han D. Quantitative evaluation of the function of the sensory nerve fibers of the palate in patients with obstructive sleep apnea. J Clin Sleep Med. 2019;15(9):1347-1353.

Project description:BackgroundRemote photoplethysmography (rPPG) can record vital signs (VSs) by detecting subtle changes in the light reflected from the skin. Lifelight (Xim Ltd) is a novel software being developed as a medical device for the contactless measurement of VSs using rPPG via integral cameras on smart devices. Research to date has focused on extracting the pulsatile VS from the raw signal, which can be influenced by factors such as ambient light, skin thickness, facial movements, and skin tone.ObjectiveThis preliminary proof-of-concept study outlines a dynamic approach to rPPG signal processing wherein green channel signals from the most relevant areas of the face (the midface, comprising the cheeks, nose, and top of the lip) are optimized for each subject using tiling and aggregation (T&A) algorithms.MethodsHigh-resolution 60-second videos were recorded during the VISION-MD study. The midface was divided into 62 tiles of 20×20 pixels, and the signals from multiple tiles were evaluated using bespoke algorithms through weighting according to signal-to-noise ratio in the frequency domain (SNR-F) score or segmentation. Midface signals before and after T&A were categorized by a trained observer blinded to the data processing as 0 (high quality, suitable for algorithm training), 1 (suitable for algorithm testing), or 2 (inadequate quality). On secondary analysis, observer categories were compared for signals predicted to improve categories following T&A based on the SNR-F score. Observer ratings and SNR-F scores were also compared before and after T&A for Fitzpatrick skin tones 5 and 6, wherein rPPG is hampered by light absorption by melanin.ResultsThe analysis used 4310 videos recorded from 1315 participants. Category 2 and 1 signals had lower mean SNR-F scores than category 0 signals. T&A improved the mean SNR-F score using all algorithms. Depending on the algorithm, 18% (763/4212) to 31% (1306/4212) of signals improved by at least one category, with up to 10% (438/4212) improving into category 0, and 67% (2834/4212) to 79% (3337/4212) remaining in the same category. Importantly, 9% (396/4212) to 21% (875/4212) improved from category 2 (not usable) into category 1. All algorithms showed improvements. No more than 3% (137/4212) of signals were assigned to a lower-quality category following T&A. On secondary analysis, 62% of signals (32/52) were recategorized, as predicted from the SNR-F score. T&A improved SNR-F scores in darker skin tones; 41% of signals (151/369) improved from category 2 to 1 and 12% (44/369) from category 1 to 0.ConclusionsThe T&A approach to dynamic region of interest selection improved signal quality, including in dark skin tones. The method was verified by comparison with a trained observer's rating. T&A could overcome factors that compromise whole-face rPPG. This method's performance in estimating VS is currently being assessed.Trial registrationClinicalTrials.gov NCT04763746; https://clinicaltrials.gov/ct2/show/NCT04763746.

Dataset Information

Remote Photoplethysmography for Evaluation of Cutaneous Sensory Nerve Fiber Function.

Publications

Remote Photoplethysmography for Evaluation of Cutaneous Sensory Nerve Fiber Function.

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