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Background Central venous pressure (CVP) is measured to assess intravascular fluid status. Although the clinical gold standard for evaluating CVP is invasive measurement using catheterization, the use of catheterization is limited in a clinical setting because of its invasiveness. We developed novel non-invasive technique, enclosed-zone (ezCVPTM) measurement for estimating CVP. The purpose of this study was to assess the feasibility of ezCVP and the relationship between ezCVP and CVP measured by a catheter.Methods and Results:We conducted 291 measurements in 97 patients. Linear regression analysis revealed that ezCVP was significantly correlated with CVP (r=0.65, P 10 mmHg were 0.81 or 0.88, respectively. The sensitivity, specificity and positive likelihood ratio of ezCVP for the CVP ≥8.8 mmHg and CVP >10 mmHg were 0.59, 0.96 and 14.8 with a cut-off value of 11.9 and 0.79, 0.97 and 26.3 with a cut-off value of 12.7. Conclusions These findings suggest that ezCVP measurement is feasible and useful for assessing CVP.

Central venous pressure (CVP) is measured to assess intravascular fluid status. Although the clinical gold standard for evaluating CVP is invasive measurement using catheterization, the use of catheterization is limited in a clinical setting because of its invasiveness. We developed novel non-invasive technique, enclosed-zone (ezCVPThese findings suggest that ezCVP measurement is feasible and useful for assessing CVP.

This paper proposes a novel non-invasive method for assessing the vascular endothelial function of lower-limb arteries based on the dilation rate of air-cuff plethysmograms measured using the oscillometric approach. The principle of evaluating vascular endothelial function involves flow-mediated dilation. In the study conducted, blood flow in the dorsal pedis artery was first monitored while lower-limb cuff pressure was applied using the proposed system. The results showed blood flow was interrupted when the level of pressure was at least 50 mmHg higher than the subject’s lower-limb systolic arterial pressure and that blood flow velocity increased after cuff release. Next, values of the proposed index, %ezFMDL, for assessing the vascular endothelial function of lower-limb arteries were determined from 327 adult subjects: 87 healthy subjects, 150 subjects at high risk of arteriosclerosis and 90 patients with cardiovascular disease (CAD). The mean values and standard deviations calculated using %ezFMDL were 30.5 ± 12.0% for the healthy subjects, 23.6 ± 12.7% for subjects at high risk of arteriosclerosis and 14.5 ± 15.4% for patients with CAD. The %ezFMDL values for the subjects at high risk of arteriosclerosis and the patients with CAD were significantly lower than those for the healthy subjects (p, This work was supported by JSPS KAKENHI Grant Number 16K21076.

Background A new device for automatic measurement of flow‐mediated vasodilation ( FMD ) using an oscillometric method has been developed to solve technical problems of conventional FMD measurement. This device measures enclosed zone FMD (ez FMD ). The purpose of this study was to evaluate the prognostic value of endothelial function assessed by ez FMD for future cardiovascular events. Methods and Results We measured ez FMD in 272 participants who underwent health‐screening examinations. First, we investigated cross‐sectional associations between ez FMD and cardiovascular risk factors, and then we assessed the associations between ez FMD and first major cardiovascular events (death from cardiovascular causes, stroke, and coronary revascularization). Univariate regression analysis revealed that ez FMD was significantly correlated with age, triglycerides, glucose, smoking pack‐years, estimated glomerular filtration rate, high‐sensitivity C‐reactive protein, and Framingham risk score. During a median follow‐up period of 36.1 months (interquartile range 18.8–40.1 months), 12 participants died (6 from cardiovascular causes), 3 had stroke, 8 had coronary revascularization, and 10 were hospitalized for heart failure. There was no episode of acute coronary syndrome during the study period. Participants were divided into tertiles (low, intermediate, and high) based on ez FMD . Kaplan–Meier curves for first major cardiovascular events among the 3 groups were significantly different ( P =0.004). After adjustment for cardiovascular risk factors, the low group was significantly associated with an increased risk of first major cardiovascular events compared with the high group (hazard ratio 6.47; 95% CI 1.09–125.55; P =0.038). Conclusions These findings suggest that endothelial function assessed by ez FMD may be useful as a surrogate marker of future cardiovascular events. Clinical Trial Registration URL : https://upload.umin.ac.jp . Unique identifier: UMIN 000004902.

BackgroundIt is clinically important to estimate the degree of endothelial dysfunction. Several methods have been used to assess endothelial function in humans. Recently, we developed a new noninvasive method for measurement of vascular response to reactive hyperemia in the brachial artery, named enclosed zone flow-mediated vasodilation (ezFMD). The purpose of this study was to determine the validity of ezFMD for assessment of endothelial function.Methods and resultsWe measured ezFMD by a new device using an oscillometric method and conventional FMD using ultrasonography in 306 subjects, including patients with hypertension, dyslipidemia, and diabetes mellitus (218 men and 88 women, 30 ± 16 yr). Univariate regression analysis revealed that ezFMD significantly correlated with age (r = −0.42, P

Measurement of flow-mediated dilatation (FMD) is the conventional non-invasive method for assessment of endothelial function; however, it requires an expensive ultrasound system and high levels of technical skill. Therefore, we developed a novel method for measurement of endothelial function, namely, measurement of ezFMD. ezFMD estimates the degree of vasodilatation from the oscillation signals transmitted to a sphygmomanometer cuff attached to the upper arm. The objective of this study was to validate the principle underlying the measurement of ezFMD, and to evaluate the repeatability of the ezFMD measurements. We observed the blood vessel behavior and oscillometric pattern in ten subjects. When the cuff was inflated to the level of the mean blood pressure, the oscillation amplitude increased with increasing degree of vasodilatation. In experiment to evaluate the repeatability of the ezFMD measurement, the average difference between the paired measurements was 3.7 %, the standard deviation was 11.5 %, and the average coefficient of variation value for the 11 paired measurements was 23.7 %. These results suggest the validity of the principle underlying the measurement of the ezFMD for the assessment of endothelial function. And, this study suggests that the repeatability of the ezFMD measurements is superior to that of the conventional measurement of FMD.

This paper proposes a novel technique to monitor peripheral vascular conditions by using biological signals, such as electrocardiogram, arterial pressure, and pulse oximetric plethysmogram. A second-order log-linearized model (called the log-linearized peripheral arterial viscoelastic model) is used to describe the nonlinear viscoelastic relationship between the blood pressure waveform and the transillumination plethysmographic waveform. The proposed index is able to estimate the changes of stiffness of peripheral arterial wall induced by sympathetic nervous activity, and the validity of the proposed method is then discussed by monitoring peripheral vascular conditions during arm position tests and during endoscopic thoracic sympathectomies (ETSs). As results of the arm position tests, the stiffness was arm position-independent (Up: 4.0 [%], Down: 5.5 [%]). Then, as results of the ETSs, the variation of the stiffness was significantly changed between before and during the ETS procedure (p < 0.01), and between during and after the ETS procedure (p < 0.01). The above experimental results clearly show that the proposed method can assess changes in the sympathetic nervous activity during ETSs.

This paper proposes a noninvasive method for estimating the viscoelastic characteristics of arterial walls using pulse waves measured in various parts of the body using a foil-type pressure sensor (FPS) and a photoplethysmogram. The FPS was employed to measure pulse waves based on the tonometry approach for its characteristics of high sensitivity and flexibility as well as its ability to continuously measure the alternating-current component of pulse waves. First, in order to accurately measure the amplitude variation of blood pressure waves, suitable mechanical forces externally applied to the FPS were examined, and it was found that values of 5 - 25 (N) yielded the best performance. Next, to verify the time characteristics of pulse waves, the brachial-ankle pulse wave velocity (baPWV) was measured. The results showed that baPWV determined using the FPS and that found with a noninvasive vascular screening device were almost the same. Estimation was then performed to establish arterial viscoelastic indices for the radial artery and the dorsal pedis artery during the application of mechanical pain stimuli. The results suggested that the estimated indices could be used to quantitatively assess vascular response caused by sympathicotonia. Thus, it was concluded that the proposed method enabled noninvasive measurement of pulse waves and estimation of viscoelastic indices.

This paper proposes a noninvasive method for estimating the dynamic characteristics of arterial walls using pulse waves measured in various parts of the body by a foil-type pressure sensor. The sensor not only has high sensitivity and flexibility but also features the ability to continuously measure the alternating-current component of pulse waves. These capabilities make it suitable for estimating the dynamic characteristics of arterial walls. In this paper, a foil-type pressure sensor was employed to measure pulse waves based on the tonometry approach, and a method of estimating changes in arterial viscoelastic indices was proposed based on the measured pulse waves and photoplethysmograms. In order to accurately measure blood pressure, first, we examined suitable mechanical forces to the sensor, and found that values of 5-25[N] yielded the best performance. We then estimated the arterial viscoelastic indices of a radial artery and a dorsal pedis artery when mechanical pain stimuli were applied to the subjects. The results suggested that the estimated indices can be used to quantitatively assess vascular response caused by sympathicotonia. We thus concluded that the proposed method enabled noninvasive measurement of pulse waves in the dorsal pedis artery and estimation of arterial viscoelastic indices.

This paper proposes a method for qualitatively estimating the mechanical properties of arterial walls on a beat-to-beat basis through noninvasive measurement of continuous arterial pressure and arterial diameter using an ultrasonic device. First, in order to describe the nonlinear relationships linking arterial pressure waveforms and arterial diameter waveforms as well as the viscoelastic characteristics of arteries, we developed a second-order nonlinear model (called the log-linearized arterial viscoelastic model) to allow estimation of arterial wall viscoelasticity. Next, to verify the validity of the proposed method, the viscoelastic indices of the carotid artery were estimated. The results showed that the proposed model can be used to accurately approximate the mechanical properties of arterial walls. It was therefore deemed suitable for qualitative evaluation of arterial viscoelastic properties based on noninvasive measurement of arterial pressure and arterial diameter.

The paper discusses the arterial stiffness during the flow-mediated dilation (FMD) test The FMD test is a method of evaluating the vascular endothelial function and has been popular as it is non-invasive and readily performed by a skillful ultrasound technician. The FMD test, however, evaluates only the maximal increase in vascular diameter mediated by the increases in blood flow after the release of the occlusive cuff and does not evaluate the arterial viscoelastic properties. This paper thus estimates the log-linearlized stiffness, to evaluate the arterial stiffness properties using the arterial diameter and blood pressure measured in a beat-to-beat manner during the FMD test. To six healthy volunteers, we performed the FMD test to measure the arterial diameter and blood pressure with ultrasound diagnostic imaging equipment and non-invasive continuous arterial blood pressure monitor, respectively. As a result, the maximal vasodilatation ratio of FMD (FMD) was obtained after cuff occlusion. In comparison with the arterial stiffness before the FMD test, the stiffness of the arterial wall is temporarily decrease and increase. It was concluded the the arterial stiffness can be estimated on a beat-to-beat basis during the FMD test.

This paper proposes a novel technique to support the monitoring of peripheral vascular conditions using biological signals such as electrocardiograms, arterial pressure values and pulse oximetry plethysmographic waveforms. In this approach, a second-order log-linearized model (referred to here as a log-linearized peripheral arterial viscoelastic model) is used to describe the non-linear viscoelastic relationship between blood pressure waveforms and photo-plethysmographic waveforms. The proposed index enables estimation of peripheral arterial wall stiffness changes induced by sympathetic nerve activity. The validity of the method is discussed here based on the results of peripheral vascular condition monitoring conducted during endoscopic thoracic sympathectomy (ETS). The results of ETS monitoring showed significant changes in stiffness variations between the periods before and during the procedures observed (p

Errors in measurement by pulse oximeters were thought to be caused by electric warming blankets in patients with peripheral hypoperfusion. This hypothesis was tested experimentally on healthy volunteers. Large fluctuations (0-99%) of oxygen saturation (SpO2) were observed with peripheral hypoperfusion experimentally induced by compression of the upper arm. An oscilloscope displayed cyclic noises of 50Hz from light absorbance signals when the blanket was on. The mean noise voltage decreased by 99% when the blanket was shielded with a conductive cover, and decreased by 5-63% when the probe of the pulse oximeter was shielded.No fluctuations of SpO2 were recorded after changing the frequency of light absorbance measurements from intervals of 3.3msec to 4.4msec. These results demonstrated that pulse-oximetric errors induced by an electric blanket can be avoided by changing the frequency of light absorbance measurements.

A new technology called estimated continuous cardiac output (esCCO) uses pulse wave transit time (PWTT) obtained from an electrocardiogram and pulse oximeter to measure cardiac output (CO) non-invasively and continuously. This study was performed to evaluate the accuracy of esCCO during exercise testing. We compared esCCO with CO measured by the echo Doppler aortic velocity-time integral (VTIao_CO). The correlation coefficient between esCCO and VTIao_CO was r= 0.87 (n= 72). Bias and precision were 0.33 ± 0.95 L/min and percentage error was 31%. The esCCO could detect change in VTIao_CO larger than 1 L/min with a concordance rate of 88%. In polar plot, 83% of data are within 0.5 L/min, and 100% of data are within 1 L/min. Those results show the acceptable accuracy and trend ability of esCCO. Change in pre-ejection period (PEP) measured by using M-mode of Diagnostic Ultrasound System accounted for approximately half of change in PWTT. This indicates that PEP included in PWTT has an impact on the accuracy of esCCO measurement. In this study, the validity of esCCO during exercise testing was assessed and shown to be acceptable. The result of this study suggests that we can expand its application.

Endothelial dysfunction is considered as an early event in the development of atherosclerosis and vascular diseases. The conventional non-invasive method used to assess endothelial function, namely, measurement of flow-mediated dilatation (FMD), needs an ultrasound system, which is expensive, and high levels of technical skill. We developed the novel method, measurement of the ezFMD, for the assessment of endothelial function. ezFMD estimates the degree of vasodilatation from the cuff oscillation signal transmitted by the cuff attached to the upper arm. The objective of this study was to clarify the factors influencing the variability of ezFMD, improve the repeatability of ezFMD measurement, and determine the correlation between ezFMD and FMD. We assumed that the following two factors are variable factors, and investigated the following two factors to improve the measurement accuracy. (1) brachial artery occlusion by cuff pressure for oscillation measurement; (2) change of the arterial wall viscosity at dilatation. Repeatability was improved by using the mean pressure method. Also, the correlation was improved by calculating the oscillation amplitude from the pulse wave area. These results suggest that ezFMD has potential for clinical use

This paper proposes a noninvasive method for estimating the dynamic characteristics of arterial walls using pulse waves measured in various parts of the body by a foil-type pressure sensor (FPS) and a photoplethysmography. The FPS not only has high sensitivity and flexibility but also features the ability to continuously measure the alternating-current component of pulse waves, and was employed to measure pulse waves based on the tonometry approach. Then a method of estimating changes in arterial viscoelastic indices was proposed based on the measured pulse waves and photoplethysmograms. First, in order to measure amplitude variation of the blood pressure wave shape accurately, we examined suitable mechanical forces externally applied to the FPS, and found that values of 5 – 25 [N] yielded the best performance. Next, in order to verify the time characteristics of the pulse waves, the brachial-ankle Pulse Wave Velocity (baPWV) was measured and found that baPWVs measured by the FPS and the noninvasive vascular screening device are quite similar. We then estimated the arterial viscoelastic indices of a radial artery and a dorsal pedis artery when mechanical pain stimuli were applied to the subjects. The results suggested the estimated indices could be used to quantitatively assess vascular response caused by sympathicotonia. We thus concluded the proposed method enabled noninvasive measurement of pulse waves and estimation of viscoelastic indices.

This chapter proposes a new nonlinear model, called a log-linearized viscoelastic model, to estimate the dynamic characteristics of human arterial walls. The model employs mechanical impedance factors, including stiffness and viscosity, in beat-to-beat measured from biological signals such as arterial blood pressure and photoplethysmograms. The validity of the proposed method is determined by demonstrating how arterial wall impedance properties change during arm position testing in the vertical direction. The estimated stiffness indices are compared with those of the conventional linear model. Estimated impedance parameters with contribution ratios exceeding 0.97 were used for comparison. The results indicated that stiffness and viscosity decrease when the arm is raised and increase when it is lowered, in the same pattern as mean blood pressure. However, the changes seen in the proposed nonlinear viscoelastic parameter are smaller (P < 0.05) than those of the linear model. This result suggests that the proposed nonlinear arterial viscoelastic model is less affected by changes in mean intravascular pressure during arm position changes.

Monitoring cardiac output (CO) is important for the management of patient circulation in an operation room (OR) or intensive care unit (ICU). We assumed that the change in pulse wave transit time (PWTT) obtained from an electrocardiogram (ECG) and a pulse oximeter wave is correlated with the change in stroke volume (SV), from which CO is derived. The present study reports the verification of this hypothesis using a hemodynamic analysis theory and animal study. PWTT consists of a pre-ejection period (PEP), the pulse transit time through an elasticity artery (T 1 ), and the pulse transit time through peripheral resistance arteries (T 2 ). We assumed a consistent negative correlation between PWTT and SV under all conditions of varying circulatory dynamics. The equation for calculating SV from PWTT was derived based on the following procedures. 1. Approximating SV using a linear equation of PWTT. 2. The slope and y-intercept of the above equation were determined under consideration of vessel compliance (SV was divided by Pulse Pressure (PP)), animal type, and the inherent relationship between PP and PWTT. Animal study was performed to verify the above-mentioned assumption. The correlation coefficient of PWTT and SV became r = −0.710 (p < 0.001), and a good correlation was admitted. It has been confirmed that accurate continuous CO and SV measurement is only possible by monitoring regular clinical parameters (ECG, SpO2, and NIBP).