Systolic blood pressure, arterial rigidity and risk of stroke: the Framingham Study. This is a preview of subscription content, access via your institution. ITAB 2007. The effects of heart rate are most apparent during exercise, when, with tachycardia, pulse pressure may be more than twice as great in the radial artery as in the ascending aorta, and when radial systolic pressure may be > 80 mmHg higher [42]. To scale the finger-cuffderived arterial blood pressure to brachial arterial blood pressure, different systems use different approaches. 2000;13:16571. These pressure wave changes account for the marked increase in peripheral pulse pressure and systolic pressure between infancy and late adolescence which is so apparent in population studies [36]. Passive leg raising: Five rules, not a drop of fluid! Circulation. Gunarathne A, Patel JV, Hughes EA, Lip GY. However, the clinically important difference in the incidence of postoperative complications was not statistically significant. This is progressive from the early twenties, with gradual increase in aortic pulse wave velocity and progressively early return of wave reflection, such that the secondary wave in diastole moves into systole with greater augmentation of pressure in late systole. Pulse volume recordings (PVRs) are another noninvasive test to assess local tissue perfusion, which use air plethysmography to provide waveform analysis of blood flow. We use the carotid pulse waveform to check against the radial when this appears unusual. 2001;19:103744. 1997;95(7):182736. The greatest problem in accurate noninvasive estimation of aortic pressure relates not to the tonometric pressure wave method or convolutional process but to calibration from the sphygmomanometer cuff. Usage of SwanGanz catheterization during the past 2 decades in United States. Our initial observation of relative maintenance of peripheral systolic pressure despite considerable fall in central aortic and LV systolic pressure after vasodilators such as nitroglycerin has been confirmed [64, 65], and indicates a more potent effect of such drugs on the heart than measured by conventional methods. the contents by NLM or the National Institutes of Health. Contemporary reports (Figure 1) provide information on variability of pulse pressure and diastolic pressure and recorded waveforms as a quality control measure. Value is enhanced through use of glyceryl trinitrate which, through reduction in wave reflection, decreases left ventricular load and increases cardiac output and left ventricular ejection duration; capacity to increase ejection duration is related to the severity of left ventricular dysfunction [60]. Cardiac output (CO)guided therapy is a promising approach to hemodynamic management in high-risk patients having major surgery1 and in critically ill patients with circulatory shock.2 Pulmonary artery thermodilution remains the clinical reference method for CO measurement,3 but the use of the pulmonary artery catheter decreased over the past two decades.4 Today, various CO monitoring methods with different degrees of invasiveness are available, including pulse wave analysis.5 Pulse wave analysis is the mathematical analysis of the arterial blood pressure waveform and enables CO to be estimated continuously and in real time.6 In this article, we review pulse wave analysis methods for CO estimation, including their underlying measurement principles and their clinical application in perioperative and intensive care medicine. This leads to alteration in contour of the arterial pressure wave, especially the summation of reflected waves with the incident wave generated by ventricular ejection. The importance of clinical validation of semi-automatic and automatic blood pressure monitors in adults according to national standards or guidelines. These systems only require an arterial catheter (most commonly inserted in the radial artery) and are therefore referred to as minimally invasive methods.5 Compared with externally calibrated pulse wave analysis systems, all internally calibrated systems may exhibit poorer measurement performance and may become unreliable in patients whose biometric (e.g., weight, height), demographic (e.g., age, sex), and hemodynamic data used for statistical calibration are not in the standard range of the underlying database or physiologic assumptions of the pulse wave analysis system.17 The latter may particularly occur during pathophysiologic conditions, e.g., in patients having liver failure, septic shock, or rapid changes in vasomotor tone caused by rapid fluid or vasopressor administration. Proena M, Sol J, Lemay M, Verjus C. Method, apparatus and computer program for determining a blood pressure value. J Cardiol. Atherosclerosis must stiffen the aorta, and must contribute to early wave reflection. Karamanoglu MMAR, ORourke MF, Avolio AP, Kelly RP. Vaitkevicius PV, Fleg JL, Engel JH, et al. The FloTrac system (Edwards Lifesciences) is a minimally invasive internally calibrated pulse wave analysis system based on the main assumption of a close relation between pulse pressure (the difference between systolic and diastolic arterial blood pressure) and CO. Such a change in Murrell's radial artery tracing after nitroglycerin [61] (Figure 5), explains the antianginal effect of this drug is due at least in part to decrease in left ventricular load [5, 6, 62, 63] (Figure 4). Assessment of relationships between blood pressure, pulse wave velocity and digital volume pulse. Borow KM, Newburger JW. Systolic hypertension may be a consequence of aortic degeneration. Ascending aortic waveforms are ensemble averaged into a single calibrated wave whose different features can be identified automatically with clinically important measures of pressure and time intervals measured and printed out in an interpretive report (Figure 1). Noninvasive methods analyze arterial blood pressure waveforms recorded continuously with noninvasive sensors and estimate cardiac output using internal calibration. Estimation of central aortic blood pressure: a systematic meta-analysis of available techniques. The impact of continuous non-invasive arterial blood pressure monitoring on blood pressure stability during general anaesthesia in orthopaedic patients: A randomised trial. Analysis of the radial pulse alone may be adequate for many, and certainly improves on sphygmomanometric measurement of brachial systolic and diastolic pressure alone. Mitchell GF. The demonstrated impairment of upper limb endothelial function with age in different diseases is not associated with definite alterations in pulse wave velocity or other indices of arterial stiffness in the upper limb [5, 21, 24]. CrossRef The system statistically analyzes pulse pressure characteristics and corrects them for waveform features resembling vascular tone. Influence of sex on arterial hemodynamics and blood pressure: role of body height. We have seen (as did Mahomed [7] and his contemporaries [10] innate cardiovascular events develop in persons with greater than expected augmentation for age (or heart rate, arterial pressure), and have noted that such persons often have adverse family histories. Am J Phys Heart Circ Phys. If one accepts the innate inaccuracy of the cuff and Korotkov method for determining intra-arterial pressure [30], then use of this technique is a step forward towards greater accuracy in determining central pressure from what currently exists. Federal government websites often end in .gov or .mil. 2014;32(9):172740. Use of sildenafil (Viagra) in patients with cardiovascular disease. The work of McDonald, Womersley, Taylor and others, originally from Harvey's own hospital (St Bartholomew's, London) has led on to the techniques described here for pulse wave analysis. How vascular hemodynamics affects blood pressure. In evaluating the system we have used, Cameron et al. These include patient-centered factors; the invasiveness, measurement performance, clinical applicability, and signal stability of the pulse wave analysis system; institutional factors such as the availability and the costs; and personal experience with monitoring systems of the caregiver.41 A profound understanding of pulse wave analysis measurement principles and strengths and limitations of pulse wave analysis systems is important for clinicians to choose the appropriate pulse wave analysis system for the individual patient. Pressure waves recorded in the ascending aorta (above), and brachial artery (below), of an adult man at cardiac catheterization under control conditions (left) and following 0.3 mg nitroglycerine sublingually. Late systolic pressure augmentation, caused by early wave reflection may easily account for a 4050 mmHg boost to systolic pressure in central arteries [5, 48]. Search for other works by this author on: From the Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center HamburgEppendorf, Hamburg, Germany (K.K., B.S. It results in progressive increase in pulse pressure and systolic pressure, which is described as isolated systolic hypertension. Change in radial pulse wave contour with glyceryl nitrate as a method to assess severity of left ventricular falure. Further, the methods can be classified based on their type of calibration into externally calibrated, internally calibrated, and uncalibrated methods. In patients with circulatory shock, absolute CO measurement by minimally invasive internally calibrated or uncalibrated pulse wave analysis systems may become unreliable because of marked alterations in vasomotor tone.17 Noninvasive pulse wave analysis systems are not recommended in critically ill patients with shock because these patients will be equipped with an arterial catheter anyway.9. At this point in time, it can only be said that the effects of ageing and of hypertension appear to dominate over the lesser effects on aortic stiffness and on pulse wave contour of diseases such as diabetes mellitus and atherosclerosis [52]. In infants, the arterial pulse has the same contour in central and peripheral arteries, and is remarkably similar to that seen in elderly subjects. Its amplitude is of course low, but it shows no obvious secondary wave in diastole, and the peak of the wave is seen in late rather than early systole [5, 6, 34, 35]. Marcus RH, Korcarz C, McCray G, et al. 1-3 Both the forward and reflected pressure waves . End systolic pressure (the beginning of diastole) is some 12 mm lower in the radial artery than in the aorta [27, 28]. 2002;88:4818. CrossRef Karamanoglu MMAR, Feneley MP. Elgendi M. On the analysis of fingertip photoplethysmogram signals. 2004;92(5):6517. Millasseau SC, Kelly RP, Ritter JM, Chowienczyk PJ. thermodilution) or technically demanding (e.g. echocardiography) than other methods. Shevchenko YL, Tsitlik JE. Persons interested in using these techniques are advised to undertake their own studies of reproducibility, repeatability and interobserver error, as well as comparing results from both radial arteries and from the carotids. These changes in cuff pressure are used to reconstruct the arterial blood pressure waveform, which is then further analyzed using pulse wave analysis. [37], with permission of the American Heart Association. 1993;23:20717. In systolic left ventricular dysfunction, ejection duration is decreased on account of early wave reflection having a greater effect on flow than on pressure [56, 57]. Received 2000 Nov 22; Accepted 2001 Mar 1. One has to doubt the way that data were selected when the most recent report (which is typical of blinded studies) gave a mean offset using the Korotkov method of 7 mmHg, with 95% confidence intervals of almost 50 mmHg [83]. We describe the physiology of the AP waveform, basic . The PiCCO system is another invasive externally calibrated pulse wave analysis system. Frederick Akbar Mohamed established the foundation of pulse wave analysis in a short medical lifetime from 1872 to 1884. Noninvasive pulse wave analysis methods analyze arterial blood pressure waveforms recorded continuously with noninvasive sensors and estimate CO using internal calibration.29,30 The use of noninvasive sensors to record the arterial blood pressure waveform makes cannulation of an artery or a central vein unnecessary. Increased stiffness is caused by stresses being transferred from elastin to less extensible collagen elements in the wall, and is associated with progressive aortic dilation. The ClearSight system compensates for hydrostatic arterial blood pressure differences between the finger artery and the phlebostatic axis using a heart reference system to estimate brachial arterial blood pressure.31,32 The underlying pulse wave analysis algorithm primarily analyzes the systolic part of the arterial blood pressure waveform and determines aortic impedance based on the assumption of a three-element Windkessel model.33 The CNAP system scales the finger-cuffderived arterial blood pressure waveform to brachial arterial blood pressure using intermittent upper-arm cuff oscillometry.34 The pulse wave analysis algorithm of the CNAP systemcalled continuous noninvasive CO algorithmestimates CO by analyzing the whole arterial blood pressure waveform and thereby accounting for preload, afterload, contractility, and vascular compliance.35 A nomogram-derived calibration factor based on biometric data is used to obtain absolute CO values. Therefore, the arteries . On standing, time domain analysis showed a decrease in total variability, as measured by standard deviation and variance. Accessibility Dr. Saugel has received honoraria for consulting, honoraria for giving lectures, and refunds of travel expenses from Edwards Lifesciences (Irvine, California); honoraria for consulting, institutional restricted research grants, honoraria for giving lectures, and refunds of travel expenses from Pulsion Medical Systems (Feldkirchen,Germany); institutional restricted research grants, honoraria for giving lectures, and refunds of travel expenses from CNSystems Medizintechnik (Graz, Austria); institutional restricted research grants from Retia Medical (Valhalla, New York); honoraria for giving lectures from Philips Medizin Systeme Bblingen (Bblingen, Germany); and honoraria for consulting, institutional restricted research grants, and refunds of travel expenses from Tensys Medical (San Diego, California). Pulse wave velocity analysis is a classic index of aortic stiffness and is a predictor of cardiovascular mortality in hypertensive cases. Eur Heart J. Systematic review of uncalibrated arterial pressure waveform analysis to determine cardiac output and stroke volume variation. 8600 Rockville Pike Boca Raton, FL: CRC; 2011. Pulse wave analysis using a single pulse wave measurement in the radial artery is a convenient alternative. Wilkinson IB, MacCallum H, Flint L, Cockcroft JR, Newby DE, Webb DJ. The influence of heart rate on augmentation index and central arterial pressure in humans. Mastery of applanation tonometry is not difficult, but it does entail training, knowledge of theoretic principles, knowledge of normal waveforms and relatively frequent use. CAS [53] as modified by Federmann & Hess [54]. While widespread improvement of endothelial function may explain decreased augmentation in physically fit individuals, there is no known relationship between endothelial dysfunction and pulse wave contour. Google Scholar. Dr. de Backer has received honoraria for consulting from Edwards Lifesciences and honoraria for giving lectures from Fresenius Kabi (Bad Homburg, Germany). Estimates from this knowledge transfer exercise should help inform students and . 2002;20(12):234143. During running, vertical bodily movement generates additional pressure waves that become apparent in the arterial pulse [43, 44]. Diabetes Metab J. Noninvasive method for determination of arterial compliance using doppler echocardiography and subclavian pulse tracings; validation and clinical application of a physiological model of the circulation. Can a clinically useful aortic pressure wave be derived from a radial pressure wave? We have found it helpful to compare indices from ascending aortic pressure waves derived from the carotid waveform to compare against that derived from the radial waveform when the latter is unusual or suspect. O'Rourke MF, Gallagher DE. Prediction of fluid responsiveness by a continuous non-invasive assessment of arterial pressure in critically ill patients: Comparison with four other dynamic indices. The primary endpoint of the study is the incidence of postoperative infection within 30 days of randomization. In: Sol, J., Delgado-Gonzalo, R. (eds) The Handbook of Cuffless Blood Pressure Monitoring. Avolio AP, Deng F-Q, Li WQ, et al. EMBS06. During heart relaxation, the arteries contract to release the elastic energy accumulated during distension. 2002;20(12):241522. Estimation of central systolic blood pressure using an oscillometric blood pressure monitor. Cardiac output estimation by multi-beat analysis of the radial arterial blood pressure waveform. Unusually high or low systolic and pulse pressures may be recorded in the carotid artery when the transducer's internal calibration is used. The frequency spectrum exhibits a peak at 0.195 Hz and represents the . Wearable sensors: fundamentals, implementation and applications. c) Relationship between estimated aortic systolic pressure (ordinate) and simultaneously measured aortic systolic pressure (abscissa) for data shown in centre panel. Pressure Waveform Analysis. The Framingham Group reported association of pulse wave contour with stroke in 1981 [74], but with dubious technology; review with new technology is presently being undertaken at Framingham. Pulse wave analysis and pulse wave velocity. 1. Mukkamala R, Hahn JO. Methods: From a dataset of 140 subjects, cfPWV was measured and the radial pulse waveform was recorded . Giannattasio C, Mangoni AA, Failla M, et al. 2008;21(8):86672. Cheng HM, Chuang SY, Wang JJ, et al. Central blood pressure: current evidence and clinical importance. Takada H, Washino K, Harrell JS, Iwata H. Acceleration plethysmography to evaluate aging effect in cardiovascular system. Sol J, Proena M, Schoettker P, et al. Such correspondence may be attributed to the fact that upper arm length is not very different between different adults, that upper limb pulse wave velocity changes little with age [5, 20] or with elevation of arterial pressure [5, 21] or with the types of vasoactive therapy used in clinical practice [5, 17]. Calibrated ascending aortic pressure waves can be derived from the radial pulse using a generalised transfer function. 2015;62(8):1879901. The site is secure. Curr Cardiol Rev. Special emphasis is being given to this at present by our group so that others will know what degree of confidence is warranted. Independent determinants of second derivative of the finger photoplethysmogram among various cardiovascular risk factors in middle-aged men. PubMed O'Rourke MF, Lei J. Doppler flow pulses are recorded from the carotid and peripheral arteries to give variable information, unavailable with tonometry, on arterial narrowing [5]. 3.5 mmHg. Noninvasive continuous beat-to-beat radial artery pressure via TL-200 applanation tonometry. 2004;22(12):228593. We have not been able to show any definite difference in aortic pulse wave velocity in patients with generalized atherosclerosis, and can not propose this as a screening test for atherosclerosis. Further, differences in upper limb properties appear to have a greater effect on the frequency of maximal amplification, where components of the pressure wave are relatively small, with far less effect at the lower frequencies whose harmonic components are greatest. In treatment itself we can gauge peripheral vasodilation from fall in mean pressure, wave reflection from fall in augmented pressure (in patients without heart failure), and beneficial effect of a -adrenoceptor blocking drug from increase in diastolic period as well as decrease in heart rate (Figure 6). A randomized trial of continuous noninvasive blood pressure monitoring during noncardiac surgery. 1989;1:2417. This protocol study evaluates the relationships between the parameters of both PWA and PIA to . Correspondence to Effect of non-invasive calibration of radial waveforms on error in transfer-function-derived central aortic waveform characteristics. Ingestion of food - even just a glucose drink, can reduce wave reflection from the splanchnic bed, and so alter the contour of the arterial pressure wave, particularly the degree of late systolic augmentation [5, 17]; this may be due to insulin release [40]. It appears that in trained athletes during long distance running, a type of counter pulsation may be achieved, with heart rate and stride rate entrained, and with vertical bodily movement causing the greatest boost during diastole. PulseCO algorithm, waveform independent pulse power analysis: Yesexternal cardiac output (CO) input: Keycard b: . We have used this phenomenon to separate systolic and diastolic dysfunction, and to gauge the severity of systolic dysfunction [5, 60] as well as to separate systolic from diastolic left ventricular dysfunction as the predominant cause of cardiac failure. Decrease in amplitude of the secondary systolic wave in the radial artery, even with maintenance of the initial peak indicates decrease in ascending aortic and left ventricular systolic pressure (Figure 4). In patients having surgery, invasive externally calibrated methods are reserved for special indications (e.g., liver transplant surgery or esophagectomy). Hashimoto J, Chonan K, Aoki Y, et al. Otsuka T, Kawada T, Katsumata M, et al. Analysis of pressure wave propagation in the human upper limb: Physical determinants and clinical applications. Combined effects of hypertension and hypercholesterolemia on radial artery function. From Kelly et al. The potential value of this technique is apparent from previous argument. Karim Kouz, Thomas W. L. Scheeren, Daniel de Backer, Bernd Saugel; Pulse Wave Analysis to Estimate Cardiac Output. ); and the Outcomes Research Consortium, Cleveland, Ohio (B.S.). sharp upstroke, straight rise to the first systolic peak, a definite sharp incisura, and near-exponential pressure decay in late diastole (Figure 1). Murgo JP, Alter BR, Dorethy JF, et al. At bottom right are the systolic portions of the aortic pressure waves taken from these data and drawn on an expanded scale for phase 1 (normal:N), phase 2 (diastolic failure:D), and phase 3 (with onset of systolic failure:S). Yaginuma T, Noda T, Tsuchiya M, et al. Takazawa K, Kobayashi H, Shindo N, et al. Hypertension. Estimation of central aortic pressure waveform by mathematical transformation of radial tonometry pressure: validation of generalized transfer function. 6th International Special Topic Conference on IEEE; 2007. p. 7072. Effects of nitroglycerin on contour of the ascending aortic and brachial pressure waveforms. Mahomed FA. He also described the effects of arterial degeneration with ageing on the arterial pulse [7]. Continuous noninvasive pulse wave analysis using finger cuff technologies for arterial blood pressure and cardiac output monitoring in perioperative and intensive care medicine: A systematic review and meta-analysis. The finger volume pulse and assessment of arterial properties. Significance: For morphological PPG pulse wave analysis recording acceptability was indicated if <50% of beats have artifact and preferably that a minimum of 50 non-distorted PPG pulses are present (with at least 11-20 sequential) to be of diagnostic quality. From the thermodilution curve that represents the changes in blood temperature over time, CO can be calculated using a modified StewartHamilton formula.9,10 Transpulmonary thermodilution is considered a clinical reference method for CO measurement and has been validated against pulmonary artery thermodilution.10,12 Common sources of measurement error include indicator loss, regurgitation, or recirculation that can affect the thermodilution curve and alter CO measurements.10 Thus, regurgitation caused by valvulopathies and intracardiac shunts represents an important limitation.10,13. PubMed J Hypertens. We can confirm the diagnosis of hypertension by noting the presence of substantial late systolic augmentation in the aortic pressure wave, and question the diagnosis when brachial systolic pressure is high, but this feature is not present [1, 5, 7]. Recherches sur le pouls au moyen d'un nouvel appareil enregisteur: le sphygmographe. 2012;8(2):8090. Cardiac output estimation by pulse wave analysis using the pressure recording analytical method and intermittent pulmonary artery thermodilution: A method comparison study in patients after off-pump coronary artery bypass surgery. In patients with cardiac failure, diabetes mellitus, nephropathy, in the grey area of systolic 130140 mmHg, a decision of when and how aggressively to treat, is aided by interpretation of the arterial pulse. In: Computers in cardiology, 2006. This requires pressure from the operator with the vessel supported behind by the radius bone at the wrist or vertebral column and ligaments in the neck [14, 15, 16]. Early return of reflection is caused by arterial (and particularly aortic) stiffening, which increases pulse wave velocity [5]. This effect could well explain provocation of angina and of myocardial ischaemia with short-acting dihydropyridines. Physiol Meas. Our technique, which incorporates pulse waveform, results in very close approximation of estimated to measured aortic systolic pressure, and with small scatter (Figure 7). CAS The app lets you change waveform parameters and see how different parameter values affect the appearance and properties of the waveform. Digital pulse wave analysis is a technique that intends to assess arterial stiffness using the peripheral arterial pulse waveform. Underestimation of vasodilator effects of nitroglycerin by upper limb blood pressure. Separation of systolic from diastolic dysfunction as a cause of cardiac failure by analysis of the arterial pulse wave. Michael O'Rourke is a director of PWV Medical, a company developing products for pulse wave analysis. The value of arterial pressure waveform cardiac output measurements in the radial and femoral artery in major cardiac surgery patients. Features of the waves (foot, shoulder, peak, incisura) are identified automatically using differentials, and flagged. Epub 2013 Apr 2. Cheitlin MD, Hutter AM, Brindis RG, et al. Noninvasive continuous cardiac output monitoring in perioperative and intensive care medicine. An Updated Report by the American Society of Anesthesiologists Task Force on Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration, A Tool to Screen Patients for Obstructive Sleep Apnea, ACE (Anesthesiology Continuing Education), Pulse Wave Analysis Methods and Underlying Measurement Principles, Clinical Application of Pulse Wave Analysis, https://doi.org/10.1097/ALN.0000000000003553, 2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway, Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures, 2023 American Society of Anesthesiologists Practice Guidelines for Monitoring and Antagonism of Neuromuscular Blockade: A Report by the American Society of Anesthesiologists Task Force on Neuromuscular Blockade, Mechanical Ventilation Guided by Uncalibrated Esophageal Pressure May Be Potentially Harmful. Peripheral pulse contour analysis in determining stroke volume. Pulse wave analysis is particularly useful in studying beneficial effects of nitroglycerin, since this drug in conventional doses has no detectible effects on arterioles, or on peripheral resistance. As with atherosclerosis, diabetes mellitus has been described as increasing arterial stiffness. The study of the pulse: arterial, venous and hepatic, and of the movements of the heart. Reisner A, Shaltis PA, McCombie D, Asada HH. 6 Aortic PWV is determined noninvasively by measuring the pulse transit time (PTT) over a known distance of the aortic trunk. Consensus on circulatory shock and hemodynamic monitoring. Radial artery cannulation: a review article. This study aimed to comprehensively investigate the changes of waveform . and transmitted securely. Such was their explanation for the appearance of a bisferiens pulse with aortic regurgitation. Differences in body height largely explain differences in augmentation between males and females [47]. Br J Anaesth. Effect of a perioperative, cardiac output-guided hemodynamic therapy algorithm on outcomes following major gastrointestinal surgery: A randomized clinical trial and systematic review. In life insurance examinations sphygmocardiography was widely used for detecting persons with arterial senility and increased risk of premature death [10]. Interaction of left ventricular contraction and aortic input impedance in experimental and clinical studies. The DMP-Life system (Daeyomedi Co., South Korea) uses an array of sensors to estimate CO using an algorithm that analyzes the systolic part of the arterial blood pressure waveform and considers biometric and demographic data.37,38 The T-Line system (Shanshi Medical, China; formerly, Tensys Medical, USA) uses a single sensor that is integrated in a bracelet and electromechanically adjusted to identify the optimal applanation pressure.36 The system estimates CO using a complex mathematical model that incorporates arterial blood pressure waveform characteristics, biometric, and demographic data.39.
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