Cerebral blood flow (CBF) and cerebral autoregulation (CA) are critically important to maintain proper brain perfusion and supply the brain with the necessary oxygen and energy substrates. Adequate brain perfusion is required to support normal brain function, to achieve successful aging, and to navigate acute and chronic medical conditions. We review the general principles of CBF measurements and the current techniques to measure CBF based on direct intravascular measurements, nuclear medicine, X-ray imaging, magnetic resonance imaging, ultrasound techniques, thermal diffusion, and optical methods. We also review techniques for arterial blood pressure measurements as well as theoretical and experimental methods for the assessment of CA, including recent approaches based on optical techniques. The assessment of cerebral perfusion in the clinical practice is also presented. The comprehensive description of principles, methods, and clinical requirements of CBF and CA measurements highlights the potentially important role that noninvasive optical methods can play in the assessment of neurovascular health. In fact, optical techniques have the ability to provide a noninvasive, quantitative, and continuous monitor of CBF and autoregulation.

https://www.spiedigitallibrary.org/journals/neurophotonics/volume-3/issue-3/031411/Cerebral-blood-flow-and-autoregulation--current-measurement-techniques-and/10.1117/1.NPh.3.3.031411.pdf

Cerebral blood flow and autoregulation: current measurement techniques and prospects for noninvasive optical methods.

There is an unmet clinical need for a low cost and easy to use wearable devices for continuous cardiovascular health monitoring. A flexible and wearable wristband, based on microelectromechanical sensor (MEMS) elements array was developed to support this need. The performance of the device in cardiovascular monitoring was investigated by (i) comparing the arterial pressure waveform recordings to the gold standard, invasive catheter recording (n = 18), (ii) analyzing the ability to detect irregularities of the rhythm (n = 7), and (iii) measuring the heartrate monitoring accuracy (n = 31). Arterial waveforms carry important physiological information and the comparison study revealed that the recordings made with the wearable device and with the gold standard device resulted in almost identical (r = 0.9–0.99) pulse waveforms. The device can measure the heart rhythm and possible irregularities in it. A clustering analysis demonstrates a perfect classification accuracy between atrial fibrillation (AF) and sinus rhythm. The heartrate monitoring study showed near perfect beat-to-beat accuracy (sensitivity = 99.1%, precision = 100%) on healthy subjects. In contrast, beat-to-beat detection from coronary artery disease patients was challenging, but the averaged heartrate was extracted successfully (95% CI: −1.2 to 1.1 bpm). In conclusion, the results indicate that the device could be useful in remote monitoring of cardiovascular diseases and personalized medicine.

/pdf/clinical-assessment-of-a-non-invasive-wearable-mems-pressure-3ojrs51dvi.pdf

Clinical assessment of a non-invasive wearable MEMS pressure sensor array for monitoring of arterial pulse waveform, heart rate and detection of atrial fibrillation.

Self-Shaping Soft Electronics Based on Patterned Hydrogel with Stencil-Printed Liquid Metal

Blood pressure (BP) monitoring has significant importance in the treatment of hypertension and different cardiovascular health diseases. As photoplethysmogram (PPG) signals can be recorded non-invasively, research has been highly conducted to measure BP using PPG recently. In this paper, we propose a U-net deep learning architecture that uses fingertip PPG signal as input to estimate arterial BP (ABP) waveform non-invasively. From this waveform, we have also measured systolic BP (SBP), diastolic BP (DBP), and mean arterial pressure (MAP). The proposed method was evaluated on a subset of 100 subjects from two publicly available databases: MIMIC and MIMIC-III. The predicted ABP waveforms correlated highly with the reference waveforms and we have obtained an average Pearson's correlation coefficient of 0.993. The mean absolute error is 3.68 ± 4.42 mmHg for SBP, 1.97 ± 2.92 mmHg for DBP, and 2.17 ± 3.06 mmHg for MAP which satisfy the requirements of the Association for the Advancement of Medical Instrumentation (AAMI) standard and obtain grade A according to the British Hypertension Society (BHS) standard. The results show that the proposed method is an efficient process to estimate ABP waveform directly using fingertip PPG.

https://www.mdpi.com/1424-8220/21/5/1867/pdf

An Estimation Method of Continuous Non-Invasive Arterial Blood Pressure Waveform Using Photoplethysmography: A U-Net Architecture-Based Approach

Cardiovascular diseases (CVD) are the leading cause of morbidity and mortality in the western world In the last three decades, fluid dynamics investigations have been an important component in the study of the cardiovascular system and CVD A large proportion of studies have been restricted to computational fluid dynamic (CFD) modeling of blood flow However, with the development of flow measurement techniques such as particle image velocimetry (PIV), and recent advances in additive manufacturing, experimental investigation of such flow systems has become of interest to validate CFD studies, testing vascular implants and using the data for therapeutic procedures This article reviews the technical aspects of in-vitro arterial flow measurement with the focus on PIV CAD modeling of geometries and rapid prototyping of molds has been reviewed Different processes of casting rigid and compliant models for experimental analysis have been reviewed and the accuracy of construction of each method has been compared A review of refractive index matching and blood mimicking flow circuits is also provided Methodologies and results of the most influential experimental studies are compared to elucidate the benefits, accuracy and limitations of each method

A Review of Arterial Phantom Fabrication Methods for Flow Measurement Using PIV Techniques

Extracted from text ... REGISTRAR PRIZE 
40 
Understanding arterial pressure waveforms 
their relation to the cardiac cycle 
the difference in waveforms recorded from different body 
sites 
The arterial pulse is the result of a wave of vascular distention, 
initiated by the impact of the stroke volume ejected into 
a closed system with every heartbeat. The forward-propagating 
pressure wave has both a fast-moving (10m/sec) and slower 
(0, 5m/sec) component.5 The wave is reflected back mostly by 
the arteriole, which provides the majority of peripheral vascular 
resistance.6 Peak aortic blood flow acceleration produces 
the initial rise of the pressure pulse, whereas the ejection ..

Understanding Arterial Pressure Waveforms

(2003). Physics of Invasive Blood Pressure Monitoring. Southern African Journal of Anaesthesia and Analgesia: Vol. 9, No. 1, pp. 33-38.

IM Moxham

Papers

Understanding Arterial Pressure Waveforms

Physics of Invasive Blood Pressure Monitoring