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BACKGROUND: Estimated continuous cardiac output (esCCO), a non-invasive technique for continuously measuring cardiac output (CO), is based on modified pulse wave transit time, which is determined by pulse oximetry and electrocardiography. OBJECTIVE: We examined the ability of esCCO to detect stroke volume index (SVI) and changes in SVI compared with currently available arterial waveform analysis methods. METHODS: We retrospectively reanalysed 15 of the cases from our previous study on esCCO measurement. SVI was calculated using an esCCO system, measured using the arterial pressure-based CO (APCO) method, and compared with a corresponding intermittent bolus thermodilution CO (ICO) method. Percentage error measurement and statistical methods, including concordance analysis and polar plot analysis, were performed. RESULTS: The difference in the SVI values between esCCO and ICO was -3.0 ± 8.8 ml (percentage error, 33.5%). The mean angular bias was 0.8 and the radial limits of agreement were ± 27.3. The difference in the SVI values between APCO and ICO was 0.9 ± 11.2 ml (percentage error, 42.6%). The mean angular bias was -6.8 and the radial limits of agreement were ± 44.1. CONCLUSION: This study demonstrated that the accuracy, precision, and dynamic trend of esCCO are better than those of APCO.

The review presents an analysis of the scientific literature on the assessment of the predictive value of hemodynamic parameters for predicting the immediate and long-term results of coronary artery bypass grafting (CABG). Modern options for hemodynamic and volumetric monitoring are considered, including transesophageal echocardiography, prepulmonary, transpulmonary thermodilution, as well as other methods based on estimation of pulse wave transit time. The information content of individual hemodynamic parameters is discussed to optimize the early diagnosis, prevention and intensive care of cardiovascular events associated with CABG. The scientific literature on stratification of the risks of postoperative complications and mortality based on the analysis of the predictive value of hemodynamic parameters is generalized. Variants of the integrated application of hemodynamic monitoring methods and artificial intelligence technologies for the development of automated systems for predicting the near and long-term results of CABG are analyzed.

The monitoring and optimization of cardiac output (CO) are central components of perioperative hemodynamic management in patients undergoing cardiothoracic surgery. Until recently, echocardiography and invasive indicator dilution methods have been the mainstays of CO monitoring in these patients. However, completely noninvasive methods to estimate CO have become available during recent years. In this review, the physical measurement principles, limitations, and measurement performance of the different techniques for continuous noninvasive CO estimation in the setting of cardiothoracic surgery are described. Methods to estimate CO in a completely noninvasive manner include noninvasive pulse wave analysis (using a finger cuff method or automated radial artery applanation tonometry), thoracic electrical bioimpedance and bioreactance, pulse wave transit time, and partial carbon dioxide rebreathing. All these technologies have been evaluated in cardiothoracic surgery patients, but the validation studies describing the measurement performance in comparison with invasive reference methods have shown inconsistent and, in part, contradictory results. In addition, all technologies have major limitations with regard to the applicability during routine clinical care in the operating room or the intensive care unit. Therefore, the methods for noninvasive CO estimation described in this review still require technological improvements with regard to measurement performance and clinical applicability before they can be recommended for routine perioperative hemodynamic management of cardiothoracic surgery patients outside of studies.

Hemodynamic monitoring is mandatory for perioperative management of cardiac surgery. Recently, the estimated continuous cardiac output (esCCO) system, which can monitor cardiac output (CO) non-invasively based on pulse wave transit time, has been developed. Patients who underwent cardiovascular surgeries with hemodynamics monitoring using arterial pressure-based CO (APCO) were eligible for this study. Hemodynamic monitoring using esCCO and APCO was initiated immediately after intensive care unit admission. CO values measured using esCCO and APCO were collected every 6 h, and stroke volume variation (SVV) data were obtained every hour while patients were mechanically ventilated. Correlation and Bland–Altman analyses were used to compare APCO and esCCO. Welch’s analysis of variance, and four-quadrant plot and polar plot analyses were performed to evaluate the effect of time course, and the trending ability. A p-value

Non-invasive and cuff-less real-time continuous blood pressure monitoring plays an important role in both intensive care unit (ICU) and the management of chronic diseases such as hypertension and cardiovascular disease. Although pulse wave transit time (PTT) and pulse waveform parameters (PWPs) can be extracted from photoplethysmography (PPG) and electrocardiographic (ECG) to estimate blood pressure, the value of blood pressure is also constrained by personal characteristics parameters (PCPs). For example, the blood pressure may vary with height, weight and age. In this paper, we present a cuff-less continuous blood pressure measurement method based on multiple types of information fusion. First, we recruited 186 volunteers and measured their personal data (PPG signal, ECG signal, height, age, weight, gender). Second, extract the PTT and PWPs from the PPG signal and ECG signal. Then, according to the extracted parameters, the blood pressure models of control group and experimental group were established respectively (the experimental group uses the multiple types of information fusion method to model, the control group only considers PTT and PWPs). Experiments show that, comparing with the control group, the experimental group systolic blood pressure (SBP) correlation was increased from 0.9355 to 0.9948, root mean square error (RMSE) was reduced from 5.2 mmHg to 1.5 mmHg, while the diastolic blood pressure (DBP) correlation was improved from 0.9331 to 0.9931, RMSE was reduced from 2.9 mmHg to 0.9 mmHg. Therefore, the modeling method proposed in this paper can get more accurate blood pressure values. Further promotion, to achieve the measurement with the "modeling" method, all "restriction" elements must be taken into account in order to obtain a more accurate and stable model.

This paper presents an analysis of the common problems in identifying the key points of pulse wave. For the processing of synchronous recorded pulse wave and electrocardiogram signals a software module has been developed in MATLAB program. This module provides displaying of the signals, key points detection, pulse wave transit time calculation and evaluation of the variability of this parameter. For estimation of the characteristic form of the pulse wave an averaged model of several neighbor cardiac cycles depending on reference point is developed. The model allows visually evaluating the shape of the pulse wave and determining the average parameters values for the selected segment. To assess the variability of pulse wave shape overlapping could be implemented.

Background Non-invasive continuous blood pressure monitoring can provide an important reference and guidance for doctors wishing to analyze the physiological and pathological status of patients and to prevent and diagnose cardiovascular diseases in the clinical setting. Therefore, it is very important to explore a more accurate method of non-invasive continuous blood pressure measurement. Objective To address the shortcomings of existing blood pressure measurement models based on pulse wave transit time or pulse wave parameters, a new method of non-invasive continuous blood pressure measurement - the GA-MIV-BP neural network model - is presented. Method The mean impact value (MIV) method is used to select the factors that greatly influence blood pressure from the extracted pulse wave transit time and pulse wave parameters. These factors are used as inputs, and the actual blood pressure values as outputs, to train the BP neural network model. The individual parameters are then optimized using a genetic algorithm (GA) to establish the GA-MIV-BP neural network model. Results Bland-Altman consistency analysis indicated that the measured and predicted blood pressure values were consistent and interchangeable. Conclusions Therefore, this algorithm is of great significance to promote the clinical application of a non-invasive continuous blood pressure monitoring method.

Systolic blood pressure (SBP) is highly sensitive to various factors such as psychological stress, and hence its continuous monitoring is essential to evaluate different health conditions. However, conventional sphygmomanometers cannot continuously measure SBP given the time-consuming setup based on a pressure cuff. Moreover, continuous biological signal monitoring is more comfortable when no sensors are attached. A solution for continuous SBP estimation is based on pulse transit time (PTT), which determines the time difference between two pulse waves at different body parts. In previous studies, we successfully measured the PTT using a contactless setup composed by two digital color cameras recording the face and hand of subjects. Then, the acquired images were transformed into blood volume by combining multiple regression analysis and a Monte Carlo method. As a result, the delay among images allowed to determine the PPT from pulse waves. In this study, we simultaneously measured SBP and PTT by using a sphygmomanometer and the two cameras, respectively. We evaluated SBP increases (i.e., stressful situations) and the corresponding PPT by asking participants to either grasp a handgrip or momentarily interrupting breath. We also determined the SBP and PTT without asking for such exercises. Comparison results show that the mean PTT under stress was significantly lower than that without stress, which is consistent with an increased SBP. Finally, we related the SBP and PTT by a nonlinear formula with a coefficient of determination of 0.59, thus confirming the effectiveness of the proposed system.

Spahr et al. recently commented on our latest paper "Retinal pulse wave velocity measurement using spectral-domain optical coherence tomography" with a conclusion that the measured retinal pulse wave velocity (rPWV) in our paper was contradictory to theoretical predictions and previously published results. However, the theoretical predictions by Spahr et al. based on Moens-Korteweg equation are questionable, since the Moens-Korteweg equation should not be used for small arteries like retinal arteries. Previously, various measurements of rPWV using different technologies have been reported. The results on human and rats are not consistent. As the rPWV is an unknown value, we argue that the time delay derived between 2 arterial sites should be verified to see if the delay truly represents the pulse wave transit time. In the future, special emphasis should be placed on demonstration of the reproducibility of technologies and data analysis of large samples.

The widely used non-invasive blood pressure measurement methods occlude the brachial artery with a cuff. The occlusion modifies the blood flow and affects the systolic and diastolic blood pressure. The paper presents the results of measurements taken from patients with cardiovascular diseases and from healthy senior and young persons. Changes in pulse wave transit time (PWTT) were found to be applicable to characterize the effect of occlusion. PWTT was cut into two parts: PWTTHC from the heart to the cuff and PWTTCF from the cuff to the fingertip. The occlusion affected PWTTHC and PWTTCF differently: increased the former and decreased the latter. Increased PWTTHC reflects a less rigid arterial wall resulting in an underestimation of blood pressure using the cuff-based measurement method.

BACKGROUND: Orthotopic liver transplantation (OLT) is characterized by significant intraoperative hemodynamic variability. Accurate and real-time cardiac output (CO) monitoring aids clinical decision making during OLT. The purpose of this study is to compare accuracy, precision, and trending ability of CO estimation obtained noninvasively using pulse wave transit time (estimated continuous cardiac output [esCCO; Nihon Kohden, Tokyo, Japan]) or thoracic bioimpedance (ICON; Osypka Medical GmbH, Berlin, Germany) to thermodilution cardiac output (TDCO) measured with a pulmonary artery catheter. METHODS: Nineteen patients undergoing OLT were enrolled. CO measurements were collected with esCCO, ICON, and thermodilution at 5 time points: (T1) pulmonary artery catheter insertion; (T2) surgical incision; (T3) portal reperfusion; (T4) hepatic arterial reperfusion; and (T5) abdominal closure. The results were analyzed with Bland-Altman plot, percentage error (the percentage of the difference between the CO estimated with the noninvasive monitoring device and CO measured with the thermodilution technique), 4-quadrant plot with concordance rate (the percentage of the total number of points in the I and III quadrant of the 4-quadrant plot), and concordance correlation coefficient (a measure of how well the pairs of observations deviate from the 45-degree line of perfect agreement). RESULTS: Although TDCO increased at T3-T5, both esCCO and ICON failed to track the changes of CO with sufficient accuracy and precision. The mean bias of esCCO and ICON compared to TDCO were -2.0 L/min (SD, ±2.7 L/min) and -3.3 L/min (SD, ±2.8 L/min), respectively. The percentage error was 69% for esCCO and 77% for ICON. The concordance correlation coefficient was 0.653 (95% confidence interval [CI], 0.283-0.853) for esCCO and 0.310 (95% CI, -0.167 to 0.669) for ICON. Nonetheless, esCCO and ICON exhibited reasonable trending ability of TDCO (concordance rate: 95% [95% CI, 88-100] and 100% [95% CI, 93-100]), respectively. The mean bias was correlated with systemic vascular resistance (SVR) and arterial elastance (Ea) for esCCO (SVR, r = 0.610, 95% CI, 0.216-0.833, P

Objective To compare the noninvasive estimated continuous cardiac output (esCCO), device-derived cardiac output (CO) to simultaneous pulmonary artery catheter (PAC) thermodilution (TD) CO. Design A prospective study comparing pulse wave transit time (estimated continuous cardiac output, esCCO; Nihon Kohden, Tokyo, Japan) to intermittent TD CO. Setting One academic hospital. Participants Patients presenting for cardiac surgery. Interventions Intraoperative CO measurements at 4 distinct time points (after induction, after sternotomy, after cardiopulmonary bypass, and after chest closure). Measurements and Main Results The study population consisted of American Society of Anesthesiologists (ASA) IV subjects, 27 (77%) males and 8 (23%) females, with a mean age of 64.6±12.2 years. Data points from esCCO and TD were collected simultaneously and means per time point compared using Bland-Altman, Pearson R coefficient, and percent error. Mean TD CO for the study was 5.4 L/min. The Pearson R coefficient, percent error, and bias in L/min were: 0.57, 44%, 0.66 (after induction); 0.54, 51%, 0.88 (after sternotomy); 0.60, 60%, 0.95 (after cardiopulmonary bypass); and 0.57, 60%, 0.75 (after chest closure) respectively. Conclusions esCCO is easy to use and provides continuous CO measurements, but has wide limits of agreement and large percentage errors with a consistently positive bias in comparison to TD.

Estimated continuous cardiac output (esCCO) is a new and noninvasive cardiac output (CO) monitoring device using pulse wave transit time. The aim of this study was to assess rapid changes in CO using esCCO (ΔCOesCCO) without invasive calibration and to compare the results with those using transthoracic Doppler echocardiography (ΔCOTTE).Fifty-four consecutive patients were enrolled in this study following elective cardiac surgery. The COesCCO and COTTE were collected during four consecutive steps: 1) at baseline, 2) during passive leg raising (PLR), 3) at return to baseline, and 4) after a fluid challenge. The relationship between ΔCOesCCO and ΔCOTTE induced by PLR and a fluid challenge was assessed and a polar plot analysis was performed. Relationship, Bland-Altman analysis, and percentage error for absolute values of COesCCO and COTTE were also performed.Twenty-four patients were excluded from the analysis. No correlation was found between ΔCOesCCO and ΔCOTTE during PLR (r = 0.07; P = 0.732; n = 30) and after a fluid challenge (r = 0.24; P = 0.394; n = 14). The polar plot analysis showed that 21 data points (87%) of significant changes in CO were above the 30° radial sector lines and confirmed that esCCO was unable to track changes in CO. A weak positive relationship was found between absolute values of COesCCO and COTTE (r = 0.28; P = 0.004). Bias, precision, and limits of agreement were 0.25 L·min(-1), 2.4 L·min(-1), and -4.4 to 4.9 L·min(-1), respectively. The percentage error was 80%.Estimated continuous cardiac output without external calibration seems unable to assess rapid changes in CO following cardiac surgery and was not interchangeable with transthoracic Doppler echocardiography.

To evaluate the accuracy of estimated continuous cardiac output (esCCO) based on pulse wave transit time in comparison with cardiac output (CO) assessed by transpulmonary thermodilution (TPTD) in off-pump coronary artery bypass grafting (OPCAB). We calibrated the esCCO system with non-invasive (Part 1) and invasive (Part 2) blood pressure and compared with TPTD measurements. We performed parallel measurements of CO with both techniques and assessed the accuracy and precision of individual CO values and agreement of trends of changes perioperatively (Part 1) and postoperatively (Part 2). A Bland-Altman analysis revealed a bias between non-invasive esCCO and TPTD of 0.9 L/min and limits of agreement of ±2.8 L/min. Intraoperative bias was 1.2 L/min with limits of agreement of ±2.9 L/min and percentage error (PE) of 64 %. Postoperatively, bias was 0.4 L/min, limits of agreement of ±2.3 L/min and PE of 41 %. A Bland-Altman analysis of invasive esCCO and TPTD after OPCAB found bias of 0.3 L/min with limits of agreement of ±2.1 L/min and PE of 40 %. A 4-quadrant plot analysis of non-invasive esCCO versus TPTD revealed overall, intraoperative and postoperative concordance rate of 76, 65, and 89 %, respectively. The analysis of trending ability of invasive esCCO after OPCAB revealed concordance rate of 73 %. During OPCAB, esCCO demonstrated poor accuracy, precision and trending ability compared to TPTD. Postoperatively, non-invasive esCCO showed better agreement with TPTD. However, invasive calibration of esCCO did not improve the accuracy and precision and the trending ability of method.

Pulse wave transit time (PWTT) method has been widely used in continuous blood pressure estimation by simultaneously measuring electrocardiogram and pulse signals in most researches [1]. Comparing with the morphological characteristic of photoplethysmograph (PPG) [2], the alternative sphygmogram (SPG) signal is much sharper and promising to improve the accuracy of onset point detection in PWTT estimation. Consequently, a hardware and software close-loop control scheme for SPG sampling with less distortion is proposed, through which the signal amplitude and baseline self-adjustment is realized such that the resulted SPG signal is more properly suitable for onset point detection. Testing results show out its superior features for adapting PWTT in e-home healthcare.

Many technologies have been developed for minimally invasive monitoring of cardiac output. Estimated continuous cardiac output (esCCO) measurement using pulse wave transit time is one noninvasive method. Because it does not require any additional sensors other than those for conducting 3 basic forms of monitoring (electrocardiogram, pulse oximeter wave, and noninvasive (or invasive) arterial blood pressure measurement), esCCO measurement is potentially useful in routine clinical circulatory monitoring for any patient including low-risk patients. We evaluated the efficacy of noninvasive esCCO using pulse wave transit time in this multicenter study.We compared esCCO and intermittent bolus thermodilution cardiac output (TDCO) in 213 patients, 139 intensive care units (ICUs), and 74 operating rooms (ORs), at 7 participating institutions. We performed electrocardiogram, pulse oximetry, TDCO, and arterial blood pressure measurements in patients in ICUs and ORs; a single calibration was performed to measure esCCO continuously. TDCO measurement was performed once daily for ICU patients and every hour for OR patients, and just before the removal of the pulmonary arterial catheter from patients in both the ICU and OR. We evaluated esCCO against TDCO with correlation analysis and Bland and Altman analysis and also assessed the change of bias over time. Furthermore, we inspected the impact of change in systemic vascular resistance (SVR) on change in bias because abnormal SVR was assumed to be a factor contributing to the change of the bias.From among 588 esCCO and TDCO datasets (excluding calibration points), 587 datasets were analyzed for 213 patients. The analysis results show a correlation coefficient of 0.79 (P0.0001, 95% confidence limits of 0.756-0.819), a bias (mean difference between esCCO and TDCO) of 0.13 L/min (95% confidence interval of bias 0.04-0.22 L/min), and a precision (1 SD) of 1.15 L/min (95% prediction interval was -2.13 to 2.39 L/min). There were no significant differences among 3 defined time intervals over 48 hours after calibration (repeated-measures analysis of variance P = 0.781) in the ICU. The influence of SVR on esCCO analysis showed a correlation coefficient between SVR and an error of 0.37 (P0.0001, 95% confidence interval 0.298-0.438).The efficacy of noninvasive esCCO technology was compared with TDCO in 213 cases. Five hundred eighty-seven datasets comparing esCCO and TDCO showed close correlation and small bias and precision, which were comparable to current arterial waveform analysis technologies.

In order to study the effects of the type of mental activity on the function of the cardiovascular system in humans, the following indices were used: the heart rate (HR), RR interval, variation magnitude (VM), systolic wave amplitude (SWA), and pulse wave transit time (PWTT). These indices were recorded when the subjects solved verbal-logical or spatial mental tasks. The HR was substantially increased during solving of the spatial tasks as compared to solving of the verbal-logical tasks, whereas the SWA showed the opposite changes. The latencies of the performance of the tasks of various types were similar in the subjects; therefore, the changes in the autonomic indices did not depend on the difficulties of the mental tasks. They rather depended on specific features of the mental processes involved in the performance of the tasks of different types. Thus, changes in the HR and the decreased SWA, which was related to elevated blood pressure, represent the effect of the sympathetic nervous system on the heart function during solving verbal-logical tasks. Our data demonstrate that the HR and blood pressure can be used as additional indices for the development of new techniques for assessment of different types of mental processes together with the indices of electrical brain activity.

Pulse waveform characteristics (Augmentation Index--AIx and pulse wave transit time) are measures of the timing and extent of arterial wave reflections. Although previous studies reported an independent association with cardiovascular morbidity, it remains to be established that waveform characteristics, derived from noninvasive pulse waveform analysis, predict cardiovascular outcomes independent of and additional to brachial blood pressure.We prospectively assessed AIx, heart-rate corrected AIx, and pulse wave transit time, using radial applanation tonometry and a validated transfer function to generate the aortic pressure curve, in 520 male patients undergoing coronary angiography. Primary endpoint was a composite of all-cause mortality, myocardial infarction, stroke, cardiac, cerebrovascular, and peripheral revascularization.During a follow-up of 49 months, 170 patients reached the primary endpoint. On the basis of Cox proportional hazards regression models, all pressure waveform characteristics predicted the primary endpoint. A 10% increase of AIx and heart-rate corrected AIx was associated with a 20.5% (95% confidence interval 6.5-36.4, P = 0.003) and 31.4% (95% confidence interval 13.2-52.6, P = 0.0004) increased risk of the primary endpoint, respectively. A 10-ms increase of pulse wave transit time was associated with a 20.8% (95% confidence interval 10.8-29.6, P = 0.0001) lower risk of the primary endpoint. In multiple adjusted models, AIx, heart-rate corrected AIx, and pulse wave transit time were independently associated with the combined endpoint even after adjustments for brachial blood pressure, age, extent of coronary artery disease, clinical characteristics, and medications.The study provides evidence that pulse waveform characteristics consistently and independently predict cardiovascular events in coronary patients.

Different components of the autonomic nervous system may be affected by different disorders to varying de- grees. The aim of this study is to report first experiences with a new device (FAN®, Schwarzer, Germany) which meas- ures heart rate variability (HRV), sympathetic skin responses (SSR) and the pulse wave transit time (PTT). We examined 190 healthy volunteers (102 men, 88 women) and in 89 subjects (46 men, 43 women) PTT during VM was investigated. In a subset of 24 subjects PTT was compared to conventional blood pressure recording. Thereafter, normal data were compared to patients with polyneuropathy (PNP) and Parkinson syndromes. All parameters of HRV decreased with age. 6 parameters for HRV at rest, during deep respiration and the valsalva ratio were reclassified into three age categories: un- der 40 (n=96), 40 - 60 (n=71) and 60 or older (n=23). Applying the lower limits of normal (5%-tile) subjects did not have more than 2 of these 6 parameters in the pathological range PTT reduction during phase IV of the valsalva manoeuvre was greater than 7.7 ms (5%-tile) but not age dependent. Patients with PNP had reduced HRV and SSR, Parkinson patients had more frequently impaired blood pressure regulation according to PTT assessment. Our investigation shows that the FAN® might be useful for clinicians to detect autonomic disorders.

In this study, we investigate the beat-to-beat respiratory fluctuations in pulse wave transit time (PTT) and its subcomponents, the cardiac pre-ejection period (PEP) and the vessel transit time (VTT) in ten healthy subjects. The three transit times were found to fluctuate in pace with respiration. When applying a simple breath detecting algorithm, 88% of the breaths seen in a respiration air-flow reference could be detected correctly in PTT. Corresponding numbers for PEP and VTT were 76 and 81%, respectively. The performance during hypo- and hypertension was investigated by invoking blood pressure changes. In these situations, the error rates in breath detection were significantly higher. PTT can be derived from signals already present in most standard monitoring set-ups. The transit time technology thus has prospects to become an interesting alternative for respiration rate monitoring.

The arterial pulse-wave transit time can be measured between the ECG R-wave and the finger pulse ( rPTT), and has been shown previously to have a linear correlation with blood pressure (BP). We hypothesized that the relationship between rPTT, preejection period (PEP; the R-wave/mechanical cardiac delay), and BP would vary with different vasoactive drugs. Twelve healthy men (mean age 22 yr) were studied. Beat-to-beat measurements were made of rPTT (using ECG and photoplethysmograph finger probe), intra-arterial radial pressure, PEP (using cardiac bioimpedance), and transit time minus PEP ( pPTT). Four drugs (glyceryl trinitrate, angiotensin II, norepinephrine, salbutamol) were administered intravenously over 15 min, with stepped dosage increase every 5 min and a 25-min saline washout between agents. All subjects in all conditions had a negative linear correlation ( R2 = 0.39) between rPTT and systolic BP (SBP), generally constant between different drugs, apart from four subjects who had a positive rPTT/SBP correlation with salbutamol. The 95% limits of agreement between measured and rPTT-predicted SBP were ±17.0 mmHg. Beat-to-beat variability of rPTT showed better coherence with SBP variability than it did with heart rate variability ( P < 0.001). PEP accounted for a substantial and variable proportion of rPTT (12–35%). Diastolic (DBP) and mean arterial BP (MAP) correlated poorly with rPTT ( R2 = 0.02 and 0.08, respectively) but better with pPTT ( rPTT corrected for PEP, R2 = 0.41 and 0.45, respectively). The 95% limits of agreement between measured and pPTT-predicted DBP were ± 17.3 mmHg. In conclusion, the negative correlation between rPTT and SBP is generally constant, even with marked hemodynamic perturbations. However, the relationship is not reliable enough for rPTT to be used as a surrogate marker of SBP, although it may be useful in assessing BP variability. DBP and MAP cannot be predicted from rPTT without correction for PEP. The significant contribution of PEP to rPTT means that rPTT should not be used as a marker of purely vascular function.

Aims and Objectives: Cardiac output (CO) measurement is essential for many therapeutic decisions in anesthesia and critical care. Most available non-invasive CO measuring methods have an invasive component. We investigate "pulse wave transit time" (estimated continuous cardiac output [esCCO]) a method of CO measurement that has no invasive component to its use. Materials and Methods: After institutional ethical committee approval, 14 adult (21-85 years) patients undergoing surgery and requiring pulmonary artery catheter (PAC) for measuring CO, were included. Postoperatively CO readings were taken simultaneously with thermodilution (TD) via PAC and esCCO, whenever a change in CO was expected due to therapeutic interventions. Both monitoring methods were continued until patients′ discharge from the Intensive Care Unit and observer recording values using TD method was blinded to values measured by esCCO system. Results: Three hundred and one readings were obtained simultaneously from both methods. Correlation and concordance between the two methods was derived using Bland-Altman analysis. Measured values showed significant correlation between esCCO and TD ( r = 0.6, P < 0.001, 95% confidence limits of 0.51-0.68). Mean and (standard deviation) for bias and precision were 0.13 (2.27) L/min and 6.56 (2.19) L/min, respectively. The 95% confidence interval for bias was - 4.32 to 4.58 L/min and for precision 2.27 to10.85 L/min. Conclusions: Although, esCCO is the only true non-invasive continuous CO monitor available and even though its values change proportionately to TD method (gold standard) with the present degree of error its utility for clinical/therapeutic decision-making is questionable.

We present a case of severe tracheobronchial compression from a complex aorto-subclavian aneurysm in a patient with Turner's syndrome undergoing open surgical repair. Significant airway compression is a challenging situation and requires careful preoperative preparation, maintenance of spontaneous breathing when possible, and consideration of having an alternative source of oxygenation and circulation established prior to induction of general anesthesia. Cardiopulmonary monitoring is essential for safe general anesthesia and diagnosis of unexpected intraoperative events.

We developed and tested a health monitoring device capable of measuring a subject’s ECG, blood pressure, blood oxygenation, respiration, temperature and motion – almost equivalent to the feature set of a hospital bedside patient monitor. The main contribution of this paper include: the device has been a highly integrated design incorporating the radio and all associated circuitry on a single PCB; a new non-invasive and cuff-less measurement of blood pressure using pulse wave transit time has been designed and validated. The device stores data locally on microSD flash and /or transmits via Bluetooth and/or Zigbee. We have developed a bandage vest which embeds reusable electrodes for data acquisition as well as a desktop and mobile application for real-time data telemetry. We have evaluated the performance of the device in capturing and recording ambulatory data and found the device easy to use and with high precision.

Systolic blood pressure (SBP) is one of the important vital signs that need to be monitored for personal healthcare. Measuring SBP via pulse wave transit time (PWTT) requires monitoring ECG and pulse wave signals simultaneously, which has no portability. And before the measurement the parameters indicating the relationship between BP and PWTT must be calculated through training. This paper describes a portable method developed by the authors to measure SBP from PWTT using one Android smart phone. Volume pulse waves were acquired by a smart phone with its built-in camera, and then accelerated pulse waves were gotten through filtering, amplifying and processing the signals. The PWTT between the progressive and reflected waves of the accelerated pulse waves was calculated. The tester swayed his arm with hand holding the same phone to change the SBP for the training. The displacement of the hand was calculated through the accelerometer of the smart phone. Experimental results indicated that there is no obvious difference between SBP measured by the new system and by an electronic sphygmomanometer with error less than 10mmHg.

Pulse waveform characteristics (pulse wave transit time and augmentation index) are measures of arterial stiffness. Previous studies have found an association between severity of acute inflammatory states and increased arterial stiffness but it is not known whether non-invasive pulse waveform analysis could predict development of multiple organ failure in septic patients. The purpose of this study was to evaluate the photoplethysmographic brachial artery pulse wave transit time and augmentation index and their changes in response to induced forearm ischemia in septic ICU patients and correlate these indices to the development of subsequent end organ damage.

Measures of psychophysiological recovery were used to evaluate two rest break schedules; 7.5 minutes of rest after every 50 minutes of work versus 15 minutes of rest after every 100 minutes of work. Eleven examiners using a prototype computer system in the European Patent Office worked under both work/rest schedules. Electrodermal activity, heart rate, respiratory frequency, pulse wave transit time, neck electromyogram, and gross body movements were continuously recorded. Measures of emotional well-being and body comfort were obtained eight times per work day. Heart rate variability was significantly higher under the short break schedule, indicating decreased mental strain. Break duration and time of measurement interacted significantly for electrodermal responses, indicating that emotional strain was reduced under the short break schedule until mid-day, and under the long break schedule in the afternoon. The results indicate that a switch to longer breaks in the afternoon may be favorable during highly demanding computer work. Furthermore, it could be demonstrated that psychophysiological measures are useful for the evaluation of work/rest schedules, even if performance data are not available.

We describe highly reliable measurement method of the pulse wave transit time (PWTT) to human limbs by using simultaneous recordings of imaging photoplethysmography and electrocardiography. High accuracy of measurements was achieved by access to a larger number of statistically independent data obtained simultaneously in different points. The method is characterized by higher diagnostic reliability because of automatic selection of the regions less affected by environmental noise. The technique was tested in the group of 12 young healthy subjects aged from 21 to 33 years. Even though PWTT in right and left hands was comparable after averaging over the whole group of subjects, significant difference in the time delay of pulse wave between the hands was found in several individuals. The technique can be used for early-stage diagnostics of various vascular diseases.

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.

A new non-invasive continuous cardiac output (esCCO) monitoring system solely utilizing a routine cardiovascular monitor was developed, even though a reference cardiac output (CO) is consistently required. Subsequently, a non-invasive patient information CO calibration together with a new automated exclusion algorithm was implemented in the esCCO system. We evaluated the accuracy and trending ability of the new esCCO system. Either operative or postoperative data of a multicenter study in Japan for evaluation of the accuracy of the original version of esCCO system were used to develop the new esCCO system. A total of 207 patients, mostly cardiac surgical patients, were enrolled in the study. Data were manually reviewed to formulate a new automated exclusion algorithm with enhanced accuracy. Then, a new esCCO system based on a patient information calibration together with the automated exclusion algorithm was developed. CO measured with a new esCCO system was compared with the corresponding intermittent bolus thermodilution CO (ICO) utilizing statistical methods including polar plots analysis. A total of 465 sets of CO data obtained using the new esCCO system were evaluated. The difference in the CO value between the new esCCO and ICO was 0.34 ± 1.50 (SD) L/min (95 % confidence limits of −2.60 to 3.28 L/min). The percentage error was 69.6 %. Polar plots analysis showed that the mean polar angle was −1.6° and radial limits of agreement were ±53.3°. This study demonstrates that the patient information calibration is clinically useful as ICO, but trending ability of the new esCCO system is not clinically acceptable as judged by percentage error and polar plots analysis, even though it’s trending ability is comparable with currently available arterial waveform analysis methods.

The study of stress and fatigue among First Responders is a major step in mitigating this public health problem. Blood pressure, heart rate variability and fatigue related arrhythmia are three of the main “windows” to study stress and fatigue. In this paper we present a wearable medical device, capable of acquiring an electrocardiogram and estimating blood pressure in real time, through a pulse wave transit time approach. The system is based on an existent certified wearable medical device called “Vital Jacket” and is aimed to become a tool to allow cardiologists in studying stress and fatigue among first response professionals.

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).

Blood pressure is one of important parameter in assessing patients' health status. The measurement of blood pressure using conventional method is less practical in monitoring continuous blood pressure. This paper proposed an automatic technique for monitoring blood pressure continuously using the relation of pulse wave transit time (PWTT) with systolic blood pressure (SBP). The measurement of PWTT involves the marking of electrocardiograph R (ECG-R) peak from electrocardiograph (ECG) signal and the peak of peripheral pulse wave from photoplethysmography (PPG) signal. Data collection involves three different sessions, which are resting period, exercise period and recovery period, thus establishing the relationship between SBP and PWTT. The results of monitoring blood pressure based on pulse wave transit time will facilitate personal healthcare monitoring blood pressure continuously.

Blood pressure is one of important parameter in assessing patients’ health status. The measurement of blood pressure using conventional method is less practical in monitoring continuous blood pressure. This paper proposed an automatic technique for monitoring blood pressure continuously using the relation of pulse wave transit time (PWTT) with systolic blood pressure (SBP). The measurement of PWTT involves the marking of electrocardiograph R (ECG-R) peak from electrocardiograph (ECG) signal and the peak of peripheral pulse wave from photoplethysmography (PPG) signal. Data collection involves three different sessions, which are resting period, exercise period and recovery period, thus establishing the relationship between SBP and PWTT. The results of monitoring blood pressure based on pulse wave transit time will facilitate personal healthcare monitoring blood pressure continuously.

BACKGROUND New 2007 European Society of Hypertension guidelines recommend measuring arterial stiffness in patients with arterial hypertension, suggesting a carotid-femoral pulse wave velocity over 12 m/s as an estimate of subclinical organ damage. Considering this cutoff point, it is worth exploring whether or not there are significant differences in results obtained using various techniques for measuring aortic pulse wave velocity. The aim of the study was to compare aortic pulse wave velocity measurements using Complior, SphygmoCor, and Arteriograph devices, and to assess the effect of pulse wave transit time and traveled distance on pulse wave velocity values. METHODS Aortic pulse wave velocity was measured on a single visit, using these devices, in randomized order, in a group of 64 patients with grade 1 or 2 arterial hypertension. RESULTS Aortic pulse wave velocity measured using Complior (10.1 +/- 1.7 m/s) was significantly higher than that obtained using SphygmoCor (8.1 +/- 1.1 m/s) or Arteriograph (8.6 +/- 1.3 m/s). No differences were noted between pulse wave velocity measurements using SphygmoCor and Arteriograph. Between-method comparison revealed that differences in traveled distance were significant: Complior versus Arteriograph [0.09 m, Confidence interval (CI): 0.08-0.12 m, P < 0.05], Complior versus SphygmoCor (0.15 m, CI: 0.13-0.16 m, P < 0.05), Arteriograph versus SphygmoCor (0.05 m, CI: 0.03-0.07 m, P < 0.05). No between-method differences were found for transit times. CONCLUSION Differences in pulse wave velocity obtained by compared devices resulted primarily from using various methods for measuring traveled distance. It appears reasonable to establish uniform principles for the measurement of traveled distance. Because a large number of prognosis/survival studies used direct distance between carotid and femoral sites of pulse wave recording, this distance should be mostly recommended.

Blood pressure is often measured using a device called a sphygmomanometer, a stethoscope, and a blood pressure cuff. All the existing manual or automatic measuring techniques of blood pressure are based on this principle, which is not convenient for continuous monitoring of blood pressure. In this paper, we proposed the regression model which could estimate unspecified people’s systolic blood pressure (SBP) conveniently and continuously and checked its accuracy with blood pressure cuff. The method for estimating each individual SBP by using only pulse wave transit time (PWTT) has been studied, but it is difficult to estimate unspecified people’s SBP with the method using only PWTT. This study examines the relationships between arterial blood pressure and certain features of the photoplethysmographic (PPG) signals from 10 healthy subjects. The experiment involved three sessions, which is the resting period, exercise period and recovery period.

Wearable health monitoring sensors may support early detection of abnormal conditions and prevention of their consequences. Recent designs of three wireless photoplethysmography monitoring devices embedded in hat, glove and sock, and connected to PC or mobile phone by means of the Bluetooth technology, are described. First results of distant monitoring of heart rate and pulse wave transit time using the newly developed devices are presented.

The arterial blood pressure has long been known as one of the most important medical factors reflecting the state of the cardiovascular system. A useful and convenient parameter for continuous monitoring of blood pressure is pulse wave velocity or pulse wave transit time (PWTT) between different regions of human body. It is suggested that, although it may be difficult to estimate systolic blood pressure from PWTT with acceptable accuracy, possibilities still remain to use changes of pulse arrival time as an indicator of changes in systolic blood pressure. During the exercise, arterial blood pressure increases, which is mainly achieved by increasing the contractility of the heart and vasculature resistance. Both of these values result in the increase of pressure wave speed in the vascular system, which means that the time delay between the start of electromechanical contraction and PWTT to any particular point in the body decreases. In our previous studies, we have shown that it is possible to calculate the mean arterial pressure from pulse wave transit time. Keywords: pulse wave velocity; arterial blood pressure; pulse wave transit time; Doppler methods; self-mixing

In order to know the effect of the change in the pre-ejection period (PEP) included in the pulse wave transit time (PWTT), PWTT of the toe, finger and nose was measured in a clinical situation and the difference between each site's PWTT was calculated in order to eliminate the PEP. The slope of PWTT against systolic blood pressure (SBP) after administration of ephedrine and phenylephrine was calculated. The result suggested that because change in PEP caused inconsistency of the relationship between PWTT and blood pressure (BP), PEP had less effect on the toe PWTT than on the PWTT of other sites.

Eustachian valve (EV), a remnant of the right valve of sinus venosus in the right atrium can be puzzling. Often it is confused with Chiari network or atrial adhesions and is reported with unusual complications. We report a case of large EV impeding cannulation of inferior vena cava (IVC) during aortic valve replacement. Transesophageal echocardiography diagnosed the presence of large EV and warned of the difficulty with IVC cannulation and helped preparedness for an alternative plan during surgery.