China 
Africa 
Explore chapters and articles related to this topic
Contour of Pressure and Flow Waves in Arteries
Published in Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos, McDonald's Blood Flow in Arteries, 2022
Photoplethysmography is widely used for recording the arterial pulse by anesthetists and intensivists. It is not a recording of pressure but a recording of volume change between sensors that are usually applied to the finger. Japanese investigators have studied the contour of the finger plethysmograph extensively (Chapter 27). Takazawa (1987) has shown that the finger photoplethysmograph shows systolic augmentation very similar to that which is recorded in the carotid artery and so is presumably similarly related to aortic augmentation and to vascular and ventricular hyper-trophy. This subject is certainly worth pursuing, since finger plethysmography is far easier to apply, less uncomfortable and less hazardous than carotid tonometry.
Signs of Pressure Sores
Published in J G Webster, Prevention of Pressure Sores, 2019
The basic principle of photoplethysmography is the modulation of reflection, transmission, and absorption properties of light as a result of volume changes. A light source and a photosensitive detector are arranged so that the detector can measure the intensity of light reflected from or transmitted through a capillary bed (figure 3.11). Blood has a light absorption coefficient that is higher than that of surrounding tissue, thus an increase in the amount of blood causes a corresponding decrease in the intensity of light detected. Photoplethysmography does not provide accurate volume measurements because the signal detected is very small. Furthermore, it is very sensitive to motion.
Non-invasive physiological monitoring
Published in John Edward Boland, David W. M. Muller, Interventional Cardiology and Cardiac Catheterisation, 2019
Mark Butlin, Isabella Tan, Edward Barin, Alberto P. Avolio
Regardless of the probe configuration, a photoplethysmography device can measure the short-term time-varying changes in the absorption of light, which is associated with blood volume in the tissue, and changes in the wavelength of light absorbed, which is associated with the oxygen saturation of haemoglobin. By shining light of two wavelengths (red light at approximately 660 nm and near-infrared at approximately 940 nm) into the tissue, the arterial oxygen saturation (SpO2) can be estimated, as light intensity in these two wavelength ranges differ between oxyhaemoglobin (HbO2) and haemoglobin (Hb). While this is a well-validated technique and in common usage in clinical monitoring, the use of the photoplethysmogram (the short-term time-varying signal associated with blood volume changes at the frequency of the cardiac cycle) has no standard for clinical measurement. However, it is commonly used for measurement of heart rate, as it is observed to be reliably in phase with a simultaneously-recorded electrocardiogram. The photoplethysmogram has been used experimentally for derivation of cardiac output, respiration, arterial compliance, endothelial function, Raynaud’s disease, and autonomic function assessment.9 However, these have not yet had an uptake in common clinical usage.
The use of digital health in heart rhythm care
Published in Expert Review of Cardiovascular Therapy, 2023
Donald P. Tchapmi, Chris Agyingi, Antoine Egbe, Gregory M. Marcus, Jean Jacques Noubiap
This technique uses light to detect blood volume variation in tissues. A photoplethysmography (PPG) device contains a light source – infrared or green light emitting diode – and a photoreceptor that catches light transmitted through or reflected from the tissue. The device algorithm generates a waveform corresponding to blood volume variation in tissues due to cardiac activity [29]. Photoplethysmography is incorporated into most smartphones and smartwatches, making them easily accessible to the general population. Smartphone apps using PPG can accurately differentiate between normal sinus rhythm and AF with sensitivity, specificity, and accuracy of > 95% [29,30]. The first study to demonstrate that a smartwatch could detect AF utilized PPG to infer the arrhythmia from the irregularity of the pulse [31], an approach subsequently incorporated broadly into Apple Watches [32] and Fitbits [13].
EEG and ANS markers of attention response in vegetative state: Different responses to own vs. other names
Published in Neuropsychological Rehabilitation, 2020
Davide Crivelli, Irene Venturella, Marina Fossati, Francesca Fiorillo, Michela Balconi
Autonomic measures were collected via a wireless Biofeedback2000xpert system (Schuhfried GmbH, Mödling, Austria) by using a multipurpose integrated sensor placed on the distal phalanx of the second finger of participants’ non-dominant hand. The sensor monitored electrodermal (skin conductance level – SCL – and skin conductance response – SCR) and cardiovascular (heart rate – HR) activity. Heart rate was computed non-invasively from the modulation of peripheral blood perfusion, which was quantified via photoplethysmography. The SCR signal was computed in real time by the recording software by applying a 0.05 Hz high-pass filter to SCL data. Data were sampled at 40 Hz and inspected offline for the presence of artifacts. During recording, an online notch filter (50 Hz) was used to minimize potential biases due to external electrical noise. After artifact rejection, modulations of autonomic activity recorded at rest and during the task were segmented and averaged to compute condition-specific SCL, SCR and HR measures. The computation of such indices was automatized via an ad hoc VBA script designed to search for specific event-markers and then calculate condition-specific metrics.
The potential for photoplethysmographic (PPG)-based smart devices in atrial fibrillation detection
Published in Expert Review of Medical Devices, 2020
Stephanie L. Harrison, Deirdre A. Lane, Yutao Guo, Gregory Y. H. Lip
Photoplethysmography (PPG) involves optically measuring changes in tissue blood volume through the skin. PPG-based technologies detect the typical AF rhythm by monitoring heart rhythm intervals. This is different to ECG which measures electrophysiological events during cardiovascular contractions. Usually, to detect AF with ECG, significant clinical time and expertise is required to interpret and analyze the results. Initial screening with PPG-based smart devices linked with automated complex algorithms, which detect suspected AF have the potential to reduce clinical input and time. However, it is still unclear which features of the signal produced using PPG-based technologies should be utilized to develop algorithms for detection of AF. A recent study developed an algorithm for detection of AF with up to 97.2% sensitivity and 99.6% specificity but noted increased demands for signal quality were required to achieve this [5].