Photoplethysmography and its application in clinical physiological measurement.
TL;DR: Photoplethysmography is a simple and low-cost optical technique that can be used to detect blood volume changes in the microvascular bed of tissue and is often used non-invasively to make measurements at the skin surface.
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.
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TL;DR: Plethysmographic signals were measured remotely (>1m) using ambient light and a simple consumer level digital camera in movie mode as discussed by the authors, which may be useful for medical purposes such as characterization of vascular skin lesions and remote sensing of vital signs (e.g., heart and respiration rates) for triage or sports purposes.
Abstract: Plethysmographic signals were measured remotely (>1m) using ambient light and a simple consumer level digital camera in movie mode. Heart and respiration rates could be quantified up to several harmonics. Although the green channel featuring the strongest plethysmographic signal, corresponding to an absorption peak by (oxy-) hemoglobin, the red and blue channels also contained plethysmographic information. The results show that ambient light photo-plethysmography may be useful for medical purposes such as characterization of vascular skin lesions (e.g., port wine stains) and remote sensing of vital signs (e.g., heart and respiration rates) for triage or sports purposes.
1,503 citations
TL;DR: This is the first demonstration of a low-cost accurate video-based method for contact-free heart rate measurements that is automated, motion-tolerant and capable of performing concomitant measurements on more than one person at a time.
Abstract: Remote measurements of the cardiac pulse can provide comfortable physiological assessment without electrodes. However, attempts so far are non-automated, susceptible to motion artifacts and typically expensive. In this paper, we introduce a new methodology that overcomes these problems. This novel approach can be applied to color video recordings of the human face and is based on automatic face tracking along with blind source separation of the color channels into independent components. Using Bland-Altman and correlation analysis, we compared the cardiac pulse rate extracted from videos recorded by a basic webcam to an FDA-approved finger blood volume pulse (BVP) sensor and achieved high accuracy and correlation even in the presence of movement artifacts. Furthermore, we applied this technique to perform heart rate measurements from three participants simultaneously. This is the first demonstration of a low-cost accurate video-based method for contact-free heart rate measurements that is automated, motion-tolerant and capable of performing concomitant measurements on more than one person at a time.
1,491 citations
TL;DR: A simple, low-cost method for measuring multiple physiological parameters using a basic webcam, by applying independent component analysis on the color channels in video recordings, which extracted the blood volume pulse from the facial regions.
Abstract: We present a simple, low-cost method for measuring multiple physiological parameters using a basic webcam. By applying independent component analysis on the color channels in video recordings, we extracted the blood volume pulse from the facial regions. Heart rate (HR), respiratory rate, and HR variability (HRV, an index for cardiac autonomic activity) were subsequently quantified and compared to corresponding measurements using Food and Drug Administration-approved sensors. High degrees of agreement were achieved between the measurements across all physiological parameters. This technology has significant potential for advancing personal health care and telemedicine.
1,269 citations
Cites background from "Photoplethysmography and its applic..."
...Regarding the choice of measurement epoch, a recording of 1–2 min is needed to assess the spectral components of HRV [5] and an averaging period of 60 beats improves the confidence in the single timing measurement from the BVP waveform [9]....
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...through variations in transmitted or reflected light [9]....
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TL;DR: A stretchable resistive pressure sensor is achieved by coating a compressible substrate with a highly stretchable electrode that contains an array of microscale pyramidal features and the electrode comprises a polymer composite.
Abstract: A stretchable resistive pressure sensor is achieved by coating a compressible substrate with a highly stretchable electrode. The substrate contains an array of microscale pyramidal features, and the electrode comprises a polymer composite. When the pressure-induced geometrical change experienced by the electrode is maximized at 40% elongation, a sensitivity of 10.3 kPa(-1) is achieved.
1,008 citations
TL;DR: Different types of artifact added to PPG signal, characteristic features of PPG waveform, and existing indexes to evaluate for diagnoses are discussed.
Abstract: Photoplethysmography (PPG) is used to estimate the skin blood flow using infrared light. Researchers from different domains of science have become increasingly interested in PPG because of its advantages as non-invasive, inexpensive, and convenient diagnostic tool. Traditionally, it measures the oxygen saturation, blood pressure, cardiac output, and for assessing autonomic functions. Moreover, PPG is a promising technique for early screening of various atherosclerotic pathologies and could be helpful for regular GP-assessment but a full understanding of the diagnostic value of the different features is still lacking. Recent studies emphasise the potential information embedded in the PPG waveform signal and it deserves further attention for its possible applications beyond pulse oximetry and heart-rate calculation. Therefore, this overview discusses different types of artifact added to PPG signal, characteristic features of PPG waveform, and existing indexes to evaluate for diagnoses.
912 citations
References
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TL;DR: Endothelial dysfunction is present in children and adults with risk factors for atherosclerosis, such as smoking and hypercholesterolaemia, before anatomical evidence of plaque formation in the arteries studied, suggesting this may be an important early event in atherogenesis.
4,662 citations
"Photoplethysmography and its applic..." refers background in this paper
...Vasospastic conditions, e.g. Raynaud’s phenomenon. The vasospastic or cold sensitivity condition known as Raynaud’s phenomenon has been investigated using a variety of optical measurement techniques, including PPG. Cooke et al (1985) characterized the PPG pulse shape in healthy subjects and Raynaud’s patients and found that both the pulse amplitude and the slope of the rising edge were good markers for the condition....
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...The low frequency respiratoryinduced intensity variations (RIIV) in the PPG signal are well documented (includes key workers, Johansson et al (1999) and Nilsson et al (2000))....
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TL;DR: An integrated review of the transfer of optical radiation into human skin is presented, aimed at developing useful models for photomedicine.
2,499 citations
"Photoplethysmography and its applic..." refers background in this paper
...The interaction of light with biological tissue is complex and includes the optical processes of (multiple) scattering, absorption, reflection, transmission and fluorescence (Anderson and Parrish 1981)....
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Book•
23 Nov 1987
TL;DR: The design of experiments, analysis of the means of small samples using the t-c Distribution, and selection of the statistical method for clinical measurement and the structure of human populations are reviewed.
Abstract: Introduction The design of experiments Sampling and observational studies Summarizing data Presenting data Probability The Normal Distribution Estimation, standard error, and confidence intervals Significance tests Analysis of the means of small samples using the t-c Distribution Choosing the statistical method Clinical measurement Mortality statistics and the structure of human populations Solutions to exercises.
2,245 citations
Book•
01 Jan 1990
1,308 citations
"Photoplethysmography and its applic..." refers background in this paper
...Modern PPG sensors often utilize low cost semiconductor technology with LED and matched photodetector devices working at the red and/or near infrared wavelengths (CIE IR-A near infrared band 0.8 to 1 µm, Duck (1990))....
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TL;DR: The results indicate that aging and not concomitant atherosclerosis (known to be rare in Asian populations) is the dominant factor associated with reduced arterial compliance and increased left ventricular load in these subjects.
Abstract: Pulse wave velocity (PWV) was measured by means of transcutaneous Doppler techniques in the aorta, right arm, and right leg of 480 normal subjects of both sexes in urban Beijing, China (age range 3 to 89 years, mean age 41 +/- 20.8 SD); supine blood pressure was recorded in the brachial artery of each subject with standard sphygmomanometric procedures. Serum cholesterol was determined in a subgroup of 79 subjects (age 17 to 85 years, mean 47 +/- 26 SD). PWV (y in cm/sec) was found to vary with age (x, years) at each of the three locations according to the following regression equations: aorta, y = 9.2x + 615, r = .673 (p less than .001); right arm, y = 4.8x + 998, r = .453 (p less than .001); right leg, y = 5.6x + 791, r = .630 (p less than .001). Systolic, diastolic, mean, and pulse pressures were found to increase with age. PWV also increased with mean supine blood pressure but was not related to serum cholesterol (average 4.49 +/- 0.11 [SEM], mmol/l). Compared with that of Western populations, serum cholesterol tended to be lower at all age groups, systolic pressure higher at ages over 35 years, and PWV higher at all ages. Because change in PWV is directly related to change in arterial compliance, these results indicate that aging and not concomitant atherosclerosis (known to be rare in Asian populations) is the dominant factor associated with reduced arterial compliance and increased left ventricular load in these subjects.
1,002 citations
"Photoplethysmography and its applic..." refers background in this paper
...The process of hardening (“stiffening”) of the arteries has been shown to start from around the first or second decades of life in healthy subjects, and it can be accelerated by medical conditions including renal disease and diabetes mellitus (Avolio et al 1983)....
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