Search query: photoplethysmography

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abstract: Photoplethysmography (PPG) is a simple and low cost optical technique that can be used to detect blood volume changes in the microvascular bed of tissue. It is often used non invasively to make measurements at the skin surface. The PPG waveform comprises a pulsatile 'AC' physiological waveform attributed to cardiac synchronous changes in the blood volume with each heart beat, and is superimposed on a slowly varying 'DC' baseline with various lower frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. Although the origins of the components of the PPG signal are not fully understood, it is generally accepted that they can provide valuable information about the cardiovascular system. There has been a resurgence of interest in the technique in recent years, driven by the demand for low cost, simple and portable technology for the primary care and community based clinical settings, the wide availability of low cost and small semiconductor components, and the advancement of computer based pulse wave analysis techniques. The PPG technology has been used in a wide range of commercially available medical devices for measuring oxygen saturation, blood pressure and cardiac output, assessing autonomic function and also detecting peripheral vascular disease. The introductory sections of the topical review describe the basic principle of operation and interaction of light with tissue, early and recent history of PPG, instrumentation, measurement protocol, and pulse wave analysis. The review then focuses on the applications of PPG in clinical physiological measurements, including clinical physiological monitoring, vascular assessment and autonomic function.
author_names: John Allen
title: Photoplethysmography and its application in clinical physiological measurement.
venue: Physiological measurement
year: 2007

abstract: The photoplethysmograph has been used for over 50 years but there are still misconceptions in how and what is the information obtained. A photoplethysmograph signal from any site on the skin can be separated into an oscillating (a.c. and a steady state (d.c. component, their amplitudes dependent upon the structure and flow in the vascular bed. Many simple applications are available: pulse counters, using the a.c. component, skin colour and haemoglobin saturation meters, using the d.c. component. The d.c. component of the photoplethysmograph signal is a function of the blood flux beneath the device. A good emitter for use in a photoplethysmograph of skin blood flow is one in the frequency range 600 700 nm and the best signal for a.c. analysis is obtained from the finger pulp. The frequency range of the electronic circuitry should be from 0.01 to 15 Hz, then all the information in the signal can be extracted about the autonomic nervous system control of the cardiovascular system, particularly between 0.01 and 2 Hz. Comparative studies may be drawn between similar skin sites on a subject or between subjects if the afferent inputs to the brain stem are controlled or driven at a known frequency. These afferents, inputs, will modulate the efferents, outputs, which generate variations in the a.c. component of the detected photoplethysmograph signal.
author_names: Ahmad A Kamal

J B Harness

Glenn Irving

Alan J Mearns
title: Skin photoplethysmography a review.
venue: Computer methods and programs in biomedicine
year: 1989

abstract: Motion artifact reduction in photoplethysmography, and therefore by implication in pulse oximetry, is achieved with a novel nonlinear methodology. The physical origins of the photoplethysmographic signals are explored in relation to a nonlinear measure of the observed intensity fluctuations. It is demonstrated that the nonlinearity renormalizes the received pulsations with optical information in a manner that aids physical interpretation. A heuristic physical model for the motion artifact is introduced and experimentally justified, with an inversion for artifact reduction being simplified by the nonlinearity. A practical implementation technique is discussed with emphasis placed on the resultant rescaling of the static and the dynamic portions of the signals. It is noted that this implementation also has the desirable effect of reducing any residual ambient artifact. The scope and power of this methodology is investigated with the presentation of results from a practical electronic system.
author_names: Matthew James Hayes

P R Smith
title: Artifact reduction in photoplethysmography.
venue: Applied optics
year: 1998

abstract: This report evaluates the efficacy of reflected type green light photoplethysmography (green light PPG) Transmitted infrared light was used for PPG and the arterial pulse was monitored transcutaneously. The reflected PPG signal contains AC components based on the heartbeat related signal from the arterial blood flow and DC components, which include reflectance and scattering from tissue. Generally, changes in AC components are monitored, but the DC components play an important role during heat stress. In this study, we compared the signal of green light PPG to infrared PPG and ECG during heat stress. The wavelengths of the green and infrared light were 525 nm and 880 nm, respectively. Experiments were performed on young healthy subjects in cold (10degC) hot (45degC) and normal environments. The pulse rates were compared among three measurement devices and the AC and DC components of the PPG signal were evaluated during heat stress. The pulse rates obtained from green light PPG were strongly correlated with the R R interval of an electrocardiogram in all environments, but those obtained from infrared light PPG displayed a weaker correlation with cold exposure. The AC components were of similar signal output for both wavelengths during heat stress. Also, the DC components for green light PPG were similar during heat stress, but showed less signal output for infrared light PPG during hot exposure. The main reason for the reduced DC components was speculated to be the increased blood flow at the vascular bed. Therefore, reflected green light PPG can be useful for pulse rate monitoring because it is less influenced by the tissue and vein region.
author_names: Yuka Maeda

Masaki Sekine

Toshiyo Tamura
title: The Advantages of Wearable Green Reflected Photoplethysmography
venue: Journal of Medical Systems
year: 2010

abstract: Removing the motion artifacts from measured photoplethysmography (PPG) signals is one of the important issues to be tackled for the accurate measurement of arterial oxygen saturation during movement. In this paper, the motion artifacts were reduced by exploiting the quasi periodicity of the PPG signal and the independence between the PPG and the motion artifact signals. The combination of independent component analysis and block interleaving with low pass filtering can reduce the motion artifacts under the condition of general dual wavelength measurement. Experiments with synthetic and real data were performed to demonstrate the efficacy of the proposed algorithm.
author_names: Byung S Kim

Sun Kook Yoo
title: Motion artifact reduction in photoplethysmography using independent component analysis
venue: IEEE Transactions on Biomedical Engineering
year: 2006

abstract: In this paper we assessed the possibility of using the pulse rate variability (PRV) extracted from the photoplethysmography signal as an alternative measurement of the HRV signal in non stationary conditions. The study is based on analysis of the changes observed during a tilt table test in the heart rate modulation of 17 young subjects. First, the classical indices of HRV analysis were compared to the indices from PRV in intervals where stationarity was assumed. Second, the time varying spectral properties of both signals were compared by time frequency (TF) and TF coherence analysis. Third, the effect of replacing PRV with HRV in the assessment of the changes of the autonomic modulation of the heart rate was considered. Time invariant HRV and PRV indices showed no statistically significant differences (p 0.05) and high correlation >0.97) Time frequency analysis revealed that the TF spectra of both signals were highly correlated (0.99 0.01) the difference between the instantaneous power, in the LF and HF bands, obtained from HRV and PRV was small <10( 3) s( 2) and their temporal patterns were highly correlated (0.98 0.04 and 0.95 0.06 in the LF and HF bands, respectively) and TF coherence in the LF and HF bands was high (0.97 0.04 and 0.89 0.08, respectively) Finally, the instantaneous power in the LF band was observed to significantly increase during head up tilt by both HRV and PRV analysis. These results suggest that although some differences in the time varying spectral indices extracted from HRV and PRV exist, mainly in the HF band associated with respiration, PRV could be used as a surrogate of HRV during non stationary conditions, at least during the tilt table test.
author_names: Eduardo Gil

Michele Orini

Raquel Bailon

Jose Maria Vergara

Luca T Mainardi

Pablo Laguna
title: Photoplethysmography pulse rate variability as a surrogate measurement of heart rate variability during non stationary conditions.
venue: Physiological measurement
year: 2010

abstract: Heart rate variability (HRV) is traditionally derived from RR interval time series of electrocardiography (ECG) Photoplethysmography (PPG) also reflects the cardiac rhythm since the mechanical activity of the heart is coupled to its electrical activity. Thus, theoretically, PPG can be used for determining the interval between successive heartbeats and heart rate variability. However, the PPG wave lags behind the ECG signal by the time required for transmission of pulse wave. In this study, finger tip PPG and standard lead II ECG were recorded for five minutes from 10 healthy subjects at rest. The results showed a high correlation (median 0.97) between the ECG derived RR intervals and PPG derived peak to peak (PP) intervals. PP variability was accurate (0.1 ms) as compared to RR variability. The time domain, frequency domain and Poincare plot HRV parameters computed using RR interval method and PP interval method showed no significant differences (p 0.05) The error analysis also showed insignificant differences between the HRV indices obtained by the two methods. Bland Altman analysis showed high degree of agreement between the two methods for all the parameters of HRV. Thus, HRV can also be reliably estimated from the PPG based PP interval method.
author_names: Nandakumar Selvaraj

A K Jaryal

J Santhosh

Kishore Kumar Deepak

Sneh Anand
title: Assessment of heart rate variability derived from finger tip photoplethysmography as compared to electrocardiography
venue: Journal of medical engineering technology
year: 2008

abstract: Heart rate variability (HRV) extracted from an electrocardiogram, is known to be a noninvasive indicator reflecting the dynamic interplay between perturbations to cardiovascular function and the dynamic response of the cardiovascular regulatory system. Photoplethysmography (PPG) is a noninvasive method to monitor arterial oxygen saturation on a continuous basis. Given the rich cardiovascular information in the PPG signal, and the ubiquity and simplicity of pulse oximetry, we are investigating the feasibility of acquiring dynamics pertaining to the autonomic nervous system from PPG waveforms. To do this, we are quantifying PPG variability (PPGV) Detailed algorithmic approaches for extracting accurate PPGV signals are presented. We compare PPGV to HRV by computing time and frequency domain parameters often associated with HRV measurements, as well as approximate entropy calculations. Our results demonstrate that the parameters of PPGV are highly correlated with the parameters of HRV. Thus, our results indicate that PPGV could be used as an alternative measurement of HRV.
author_names: Sheng Lu

He Zhao

Kihwan Ju

Kun-Su Shin

Myoungho Lee

Kirk H Shelley

Ki H Chon
title: Can Photoplethysmography Variability Serve as an Alternative Approach to Obtain Heart Rate Variability Information?
venue: Journal of Clinical Monitoring and Computing
year: 2007

abstract: An apparatus for simultaneously monitoring heart and respiratory rates was developed using photoplethysmography (PPG) and digital filters, and compared with conventional methods. The PPG signal, which includes both heart and respiratory components, was measured at the earlobe with an original transmission mode photoplethysmographic device. A digital filtering technique was used to distinguish heart and respiratory signals from the PPG signal. The cut off frequency of the respiratory signal filter was selected automatically depending on the heart rate. Using digital filtering techniques, heart and respiratory signals were separated at rest and during exercise. The digital signal processor was employed to realize an adaptive and real time filtering. The heart rate was calculated by the zero crossing method and the respiratory rate from the peak interval of the filtered signal. To evaluate the newly developed monitor, an ECG for heart rate and a transthoracic impedance plethysmogram for respiratory rate were monitored simultaneously. To obtain higher heart and respiratory rates, exercise was performed on an electrical bicycle ergometer. Heart and respiratory rates calculated by the new method compare to those obtained from ECG and the transthoracic impedance plethysmogram. The maximum error of heart and respiratory rates was 10 beats/min and 7 breaths/min, respectively.
author_names: Kazuki Nakajima

Toshiyo Tamura

Hidetoshi Miike
title: Monitoring of heart and respiratory rates by photoplethysmography using a digital filtering technique.
venue: Medical engineering physics
year: 1996

abstract: This paper addresses the design considerations and critical evaluation of a novel embodiment for wearable photoplethysmography (PPG) comprising a magnetic earring sensor and wireless earpiece. The miniaturized sensor can be worn comfortably on the earlobe and contains an embedded accelerometer to provide motion reference for adaptive noise cancellation. The compact wireless earpiece provides analog signal conditioning and acts as a data forwarding device via a radio frequency transceiver. Using Bland Altman and correlation analysis, we evaluated the performance of the proposed system against an FDA approved ECG measurement device during daily activities. The mean standard deviation (SD) of the differences between heart rate measurements from the proposed device and ECG (expressed as percentage of the average between the two techniques) along with the 95% limits of agreement (LOA 1.96 SD) was 0.62% 4.51% (LOA 8.23% and 9.46% 0.49% 8.65% 17.39% and 16.42% and 0.32% 10.63% 21.15% and 20.52% during standing, walking, and running, respectively. Linear regression indicated a high correlation between the two measurements across the three evaluated conditions (r 0.97, 0.82, and 0.76, respectively with p 0.001) The new earring PPG system provides a platform for comfortable, robust, unobtrusive, and discreet monitoring of cardiovascular function.
author_names: Ming-Zher Poh

Nicholas C Swenson

Rosalind W Picard
title: Motion tolerant magnetic earring sensor and wireless earpiece for wearable photoplethysmography
venue: IEEE Transactions on Information Technology in Biomedicine
year: 2010