Investigation of Pulse Transit Times utilizing multisite reflectance photoplethysmography under conditions of artificially induced peripheral vasoconstriction

Budidha, Karthik; Kyriacou, Panayiotis A.

doi:10.1109/embc.2014.6943998

Cited by 15 publications

(18 citation statements)

References 8 publications

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“…The monitoring was continued until the volunteer's hand rewarmed to a minimum temperature above 24°C. The minimum and maximum time it took the volunteers to rewarm their hand to 24°C was 7 min 9 s and 12 min 30 s. More information regarding the protocol is presented in Budidha and Kyriacou (2014a,b).…”

Section: Methodsmentioning

confidence: 99%

Photoplethysmography for Quantitative Assessment of Sympathetic Nerve Activity (SNA) During Cold Stress

Budidha

Kyriacou

2019

Front. Physiol.

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The differences in the degree of sympathetic nerve activity (SNA) over cutaneous blood vessels, although known to be more prominent in the periphery than the core vasculature, has not been thoroughly investigated quantitatively. Hence, two studies were carried out to investigate the differences in SNA between the periphery and the core during the cold pressor test (CPT) (right-hand immersion in ice water) and cold exposure (whole body exposed to cold air) using photoplethysmography (PPG). Two methods utilizing PPG, namely differential multi-site PTT measurements and low-frequency spectral analysis were explored for quantitative determination of SNA. Each study involved 12 healthy volunteers, and PPG signals were acquired from the right index finger (RIF), left index finger (LIF) (periphery) and the ear canal (core). During CPT, Pulse Transit Time (PTT) was measured to the respective locations and the mean percentage change in PTT during ice immersion at each location was used as an indicator for the extent of SNA. During cold exposure, the low-frequency spectral analysis was performed on the acquired raw PPGs to extract the power of the sympathetic [low-frequency (LF): 0.04–0.15 Hz] and parasympathetic components [high-frequency (HF): 0.15–0.4 Hz]. The ratio of LF/HF components was then used to quantify the differences in the influence of SNA on the peripheral and core circulation. PTT measured from the EC, and the LIF has dropped by 5 and 7%, respectively during ice immersion. The RIF PTT, on the other hand, has dropped significantly (P < 0.05) by 12%. During the cold exposure, the LF/HF power ratio at the finger has increased to 86.4 during the cold exposure from 19.2 at the baseline (statistically significant P = 0.002). While the ear canal LF/HF ratio has decreased to 1.38 during the cold exposure from 1.62 at baseline (P = 0.781). From these observations, it is evident that differential PTT measurements or low-frequency analysis can be used to quantify SNA. The results also demonstrate the effectiveness of the central auto-regulation during both short and long-term stress stimulus as compared to the periphery.

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Section: Methodsmentioning

confidence: 99%

Photoplethysmography for Quantitative Assessment of Sympathetic Nerve Activity (SNA) During Cold Stress

Budidha

Kyriacou

2019

Front. Physiol.

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“…5 PPG has found its utility in a vast number of applications, such as neonatal care, hemorheology assessment, pulse transit time investigation, and measurements from body cavities and organs. [6][7][8][9][10][11][12] Near-infrared spectroscopy (NIRS) is another noninvasive optical technique, which measures variations in local blood perfusion by estimating changes in oxy-hemoglobin, deoxyhemoglobin, and total hemoglobin. 13 These physiological variables are determined using the Beer-Lambert law, correlating the attenuation of light A, through a medium with the concentration C of the absorber (chromophore) present in the solution.…”

Section: Introductionmentioning

confidence: 99%

Investigating optical path and differential pathlength factor in reflectance photoplethysmography for the assessment of perfusion

et al. 2018

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Photoplethysmography (PPG) is an optical noninvasive technique with the potential for assessing tissue perfusion. The relative time-change in the concentration of oxyhemoglobin and deoxyhemoglobin in the blood can be derived from DC part of the PPG signal. However, the absolute concentration cannot be determined due to the inadequate data on PPG optical paths. The optical path and differential pathlength factor (DPF) for PPG at red (660 nm) and infrared (880 nm) wavelengths were investigated using a heterogeneous Monte Carlo model of the human forearm. Using the simulated DPFs, the absolute time-change in concentrations were determined from PPG signals recorded from the same tissue site. Results were compared with three conditions of approximated DPFs. Results showed the variation of the optical-path and DPF with different wavelengths and source-detector separations. Approximations resulted in significant errors, for example, using NIRS DPF in PPG led to "cross talk" of -0.4297 and 0.060 and an error of 15.16% to 25.18%. Results confirmed the feasibility of using the PPG (DC) for the assessment of tissue perfusion. The study also identified the inappropriateness of the assumption that DPF is independent of wavelength or source-detector separations and set the platform for further studies on investigating optical pathlengths and DPF in PPG.

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“…12 shows the calculated R-values from both the ZenPPG channels against the simulated SpO 2 values. A second-degree polynomial was used to derive the following calibration functions from the R-values: Using these calibration curves, the functionality and accuracy of both the ZenPPG channels as pulse oximeters was tested on eight healthy volunteers (aged [21][22][23][24][25][26][27][28][29][30][31][32]. In this brief study, PPG signals were recorded from index and the middle fingers (right hand) of the volunteers using two Masimo reusable sensors (Masimo Inc., California, USA) connected to the ZenPPG system for 2 min.…”

Section: B Preliminary Evaluationmentioning

confidence: 99%

“…Another example of the system's flexibility is the newly developed fiber optic TIA module that connects with traditional PPG sensors and/or fiber optic sensors [29]. These features have allowed the system to be adopted in a wide range of physiological studies investigating hemodynamic changes during mild hypothermia, occlusion, different hand elevations, and head down tilts [30]- [33].…”

Section: B Preliminary Evaluationmentioning

confidence: 99%

“…The accuracy of the system can be improved by deriving a calibration function through human hypoxic studies. The system has already been used to estimate various other parameter such as PTT [30], oxy and deoxyhemoglobin concentrations [31], HR variability [33], and other PPG morphological parameters [32]. The successive development of the system will be focused on two main aspects.…”

Section: B Preliminary Evaluationmentioning

confidence: 99%

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Design and Development of a Modular, Multichannel Photoplethysmography System

Budidha

Rybynok

Kyriacou

2018

IEEE Trans. Instrum. Meas.

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In this paper, we present the design, development, and validation of a 'modular photoplethysmography (PPG) system called ZenPPG. This portable, dual-channel system has the capability to produce "raw" PPG signals at two different wavelengths using commercial and/or custom-made PPG sensors. The system consists of five modules, each consisting of circuitry required to perform specific tasks, and are all interconnected by a system bus. The ZenPPG system also facilitates the acquisition of other physiological signals on-demand including electrocardiogram (ECG), respiration, and temperature signals. This report describes the technical details and the evaluation of the ZenPPG along with results from a pilot in vivo study on healthy volunteers. The results from the technical evaluations demonstrate the superiority and flexibility of the system. Also, the systems' compatibility with commercial pulse oximetry sensors such as the Masimo reusable sensors was demonstrated, where good quality raw PPG signals were recorded with the signal-to-noise ratio (SNR) of 50.65 dB. The estimated arterial oxygen saturation (SpO 2) values from the system were also in close agreement with commercial pulse oximeters, although the accuracy of the reported SpO 2 value is dependent on the calibration function used. Future work is targeted toward the development of variations of each module, including the laser driver and fiber optic module, onboard data acquisition and signal processing modules. The availability of this system will help researchers from a wide range of disciplines to customize and integrate the ZenPPG system to their research needs and will most definitely enhance research in related fields.

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Investigation of Pulse Transit Times utilizing multisite reflectance photoplethysmography under conditions of artificially induced peripheral vasoconstriction

Cited by 15 publications

References 8 publications

Photoplethysmography for Quantitative Assessment of Sympathetic Nerve Activity (SNA) During Cold Stress

Photoplethysmography for Quantitative Assessment of Sympathetic Nerve Activity (SNA) During Cold Stress

Investigating optical path and differential pathlength factor in reflectance photoplethysmography for the assessment of perfusion

Design and Development of a Modular, Multichannel Photoplethysmography System

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