Global InformationPhotoplethysmogram information
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| Photoplethysmography | |
|---|---|
 Representative PPG taken from an ear pulse oximeter. Variation in amplitude are from Respiratory Induced Variation. | |
| MeSH | D017156 |
A photoplethysmogram (PPG) is an optically obtained plethysmogram that can be used to detect blood volume changes in the microvascular bed of tissue.[1][2] A PPG is often obtained by using a pulse oximeter which illuminates the skin and measures changes in light absorption.[3] A conventional pulse oximeter monitors the perfusion of blood to the dermis and subcutaneous tissue of the skin.
With each cardiac cycle the heart pumps blood to the periphery. Even though this pressure pulse is somewhat damped by the time it reaches the skin, it is enough to distend the arteries and arterioles in the subcutaneous tissue. If the pulse oximeter is attached without compressing the skin, a pressure pulse can also be seen from the venous plexus, as a small secondary peak.
The change in volume caused by the pressure pulse is detected by illuminating the skin with the light from a light-emitting diode (LED) and then measuring the amount of light either transmitted or reflected to a photodiode.[4] Each cardiac cycle appears as a peak, as seen in the figure. Because blood flow to the skin can be modulated by multiple other physiological systems, the PPG can also be used to monitor breathing, hypovolemia, and other circulatory conditions.[5] Additionally, the shape of the PPG waveform differs from subject to subject, and varies with the location and manner in which the pulse oximeter is attached.
Although PPG sensors are in common use in a number of commercial and clinical applications, the exact mechanisms determining the shape of the PPG waveform are not yet fully understood.[6]
- ^ Allen J (March 2007). "Photoplethysmography and its application in clinical physiological measurement". Physiological Measurement. 28 (3): R1–39. doi:10.1088/0967-3334/28/3/R01. PMID 17322588. S2CID 11450080.
- ^ Kyriacou PA, Allen J, eds. (2021). Photoplethysmography: Technology, Signal Analysis and Applications. Elsevier.
- ^ Shelley K, Shelley S, Lake C (2001). "Pulse Oximeter Waveform: Photoelectric Plethysmography". In Lake C, Hines R, Blitt C (eds.). Clinical Monitoring. W.B. Saunders Company. pp. 420–428.
- ^ Pelaez EA, Villegas ER (2007). "LED power reduction trade-offs for ambulatory pulse oximetry". 2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol. 2007. pp. 2296–2299. doi:10.1109/IEMBS.2007.4352784. ISBN 978-1-4244-0787-3. PMID 18002450. S2CID 34626885.
- ^ Reisner A, Shaltis PA, McCombie D, Asada HH (May 2008). "Utility of the photoplethysmogram in circulatory monitoring". Anesthesiology. 108 (5): 950–958. doi:10.1097/ALN.0b013e31816c89e1. PMID 18431132.
- ^ Charlton PH, Kyriaco PA, Mant J, Marozas V, Chowienczyk P, Alastruey J (March 2022). "Wearable Photoplethysmography for Cardiovascular Monitoring". Proceedings of the IEEE. Institute of Electrical and Electronics Engineers. 110 (3): 355–381. doi:10.1109/JPROC.2022.3149785. PMC 7612541. PMID 35356509.