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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.

Objective To establish the relationship between pulse wave transit time (PWTT) before anaesthesia induction and blood pressure variability (BPV) during anaesthesia induction. Methods This prospective observational cohort study enrolled consecutive patients that underwent elective surgery. Invasive arterial pressure, electrocardiography, pulse oximetry, heart rate and bispectral index were monitored. PWTT and BPV were measured with special software. Anaesthesia was induced with propofol, sufentanil and rocuronium. Results A total of 54 patients were included in this study. There was no correlation between BPV and the dose of propofol, sufentanil and rocuronium during anaesthesia induction. Bivariate linear regression analysis demonstrated that PWTT ( r = –0.54), age ( r = 0.34) and systolic blood pressure ( r = 0.31) significantly correlated with systolic blood pressure variability (SBPV). Only PWTT ( r = –0.38) was significantly correlated with diastolic blood pressure variability (DBPV). Patients were stratified into high PWTT and low PWTT groups according to the mean PWTT value (96.8 ± 17.2 ms). Compared with the high PWTT group, the SBPV of the low PWTT group increased significantly by 3.4%. The DBPV of the low PWTT group increased significantly by 2.1% compared with the high PWTT group. Conclusions PWTT, assessed before anaesthesia induction, may be an effective predictor of haemodynamic fluctuations during anaesthesia induction.

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.

Purpose. Estimation of cardiac output (CO) and evaluation of change in CO as a result of therapeutic interventions are essential in critical care medicine. Whether noninvasive tools estimating CO, such as continuous cardiac output (esCCOTM) methods, are sufficiently accurate and precise to guide therapy needs further evaluation. We compared esCCOTM with an established method, namely, transpulmonary thermodilution (TPTD). Patients and Methods. In a single center mixed ICU, esCCOTM was compared with the TPTD method in 38 patients. The primary endpoint was accuracy and precision. The cardiac output was assessed by two investigators at baseline and after eight hours. Results. In 38 critically ill patients, the two methods correlated significantly (r = 0.742). The Bland–Altman analysis showed a bias of 1.6 l/min with limits of agreement of −1.76 l/min and +4.98 l/min. The percentage error for COesCCO was 47%. The correlation of trends in cardiac output after eight hours was significant (r = 0.442), with a concordance of 74%. The performance of COesCCO could not be linked to the patient’s condition. Conclusion. The accuracy and precision of the esCCOTM method were not clinically acceptable for our critical patients. EsCCOTM also failed to reliably detect changes in cardiac output.

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

Goal of the study: to evaluate the accuracy of invasive measurement of cardiac output (CO) by pulse wave transit time (PWTT) (esCCO, Japan) compared to transpulmonary thermodilution (TPTD) (PiCCO2 , Germany) after aortocoronary bypass (ACB) without cardiopulmonary bypass (ACB without CPB). Methods. 21 patients with ACB without CPB were enrolled into the study. During early post-operative period CO was simultaneously registered at eight stages basing on PWTT (COPWTT) and TPTD (COTPTD). Statistic analysis included evaluation of congruence of CO absolute values and capability to follow-up changes in CO. Results. In accordance with Bland-Altman analysis the average difference between two methods made 0.3 l/min. with consistency limits of ± 2.1 l/min. and percent error of 40%. Polar chart analysis showed the angular difference of 2.6°, radial consistency limits ± 53.3° and polar concordance of 69%. Conclusion: Lower repeatability of CO measurement by PWTT and insufficient capability to follow the changes in CO after ACB without CPB don not allow recommending this method in its invasive variant for routine practice as an alternative to thermodilution methods.

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.

Background: Pulse wave transit time (PWTT) is widely used to characterize the dynamic properties of the arteries. PWTT is most often calculated as the time interval from the R peak in the electrocardiogram (start of the pulse wave) to the rise in the finger photoplethysmogram (arrival of the pulse wave). This is the PWTTHF. The aim of this study was to analyse the effect of cuff occlusion on PWTT, and using this information to improve the reliability of cuff-based indirect blood pressure (BP) measurement.Methods: PWTT was measured with a home health monitoring device that inflates and deflates the cuff slowly (6 mmHg/s). The change in the arterial wall rigidity caused by cuff occlusion is different in the parts of the arterial section proximal and distal to the cuff. Accordingly, PWTT was divided into two parts: PWTT from the heart to the cuff (PWTTHC) and PWTT from the cuff to the fingertip (PWTTCF). Seven patients with various cardiovascular diseases (55–66 years old), seven healthy senior subjects (55–65 years old) and seven healthy young subjects (22–26 years old) were included in the research.Results: Changes in PWTT characterise appropriately the effect of cuff occlusion on BP measurement. Cuff occlusion affected PWTTHC and PWTTCF differently; it increased the former and decreased the latter. Increased PWTTHC reflects a less rigid arterial wall, resulting in an underestimation of BP. The changes in PWTT values are person-specific and not group-specific (patient, healthy senior, and healthy youth).Conclusion: Occlusion with the cuff is an excitation to the cardiovascular system, causing a temporary change in the dynamic properties of the arteries from the heart to the cuff. The change influences the result of indirect BP measurement. Arterial rigidity in the part proximal to the cuff can be characterized by PWTTHC, which provides different information about the arteries than the widely used PWTTHF.

Critically ill patients require close hemodynamic monitoring to titrate treatment on a regular basis. It allows administering fluid with parsimony and adjusting inotropes and vasoactive drugs when necessary. Although invasive monitoring is considered as the reference method, non-invasive monitoring presents the obvious advantage of being associated with fewer complications, at the expanse of accuracy, precision, and step-response change. A great many methods and devices are now used over the world, and this article focuses on several of them, providing with a brief review of related underlying physical principles and validation articles analysis. Reviewed methods include electrical bioimpedance and bioreactance, respiratory-derived cardiac output (CO) monitoring technique, pulse wave transit time, ultrasound CO monitoring, multimodal algorithmic estimation, and inductance thoracocardiography. Quality criteria with which devices were reviewed included: accuracy (closeness of agreement between a measurement value and a true value of the measured), precision (closeness of agreement between replicate measurements on the same or similar objects under specified conditions), and step response change (delay between physiological change and its indication). Our conclusion is that the offer of non-invasive monitoring has improved in the past few years, even though further developments are needed to provide clinicians with sufficiently accurate devices for routine use, as alternative to invasive monitoring devices.

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.

The inaccuracy of arterial waveform analysis for measuring continuos cardiac output (CCO) associated with changes in systemic vascular resistance (SVR) has been well documented. A new non-invasive continuous cardiac output monitoring system (esCCO) mainly utilizing pulse wave transit time (PWTT) in place of arterial waveform analysis has been developed. However, the trending ability of esCCO to measure cardiac output during changes in SVR remains unclear. After a previous multicenter study on esCCO measurement, we retrospectively identified two cases in which apparent changes in SVR developed in a short period during data collection. In each case, the trending ability of esCCO to measure cardiac output and time component of PWTT were analyzed. Recorded data suggest that the time component of PWTT may have a significant impact on the accuracy of estimating stroke volume during changes in SVR. However, further prospective clinical studies are required to test this hypothesis.

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.

A common research question in perioperative haemodynamics research concerns the assessment of whether a new measurement device can replace an existing device (often referred to as method comparison studies). Typically, a new measurement method is being compared with an established reference method (unfortunately often referred to as the ‘gold standard’). In a recent issue of the journal, Biais and colleagues reported the comparison of two cardiac output measurement devices, one based on pulse wave transit time (i.e. the new devices) and the other one based on transthoracic echocardiography (i.e. the reference method ‘gold standard’). The study concluded that devices were not interchangeable and that the new device cannot guide haemodynamic interventions in critically ill patients. Their conclusion was based on observing percentage errors exceeding the limits of 30%, suggested by Critchley and Critchley.

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.

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.

International audience; BACKGROUND:The finger-toe pathway could be a good alternative for assessing arterial stiffness conveniently.AIM:To evaluate the accuracy of the pOpmètre®--a new device that measures finger-toe pulse wave velocity (ft-PWV).METHODS:The pOpmètre has two photodiode sensors, positioned on the finger and the toe. Pulse waves are recorded continuously for 20 seconds, and the difference in pulse wave transit time between toe and finger (ft-TT) is calculated. The travelled distance is estimated using subject height. Study 1 compared ft-PWV with carotid-femoral PWV (cf-PWV) obtained by the reference method (SphygmoCor®) in 86 subjects (mean age 53±20 years), including 69 patients with various pathologies and 17 healthy normotensives. Study 2 compared changes in ft-PWV and cf-PWV during a cold pressor test in 10 healthy subjects. Study 3 assessed repeatability in 45 patients.RESULTS:ft-PWV correlated significantly with cf-PWV (R2=0.43; P

Pôle EAMERSCT3Hors Enjeu; Background We determined reliability of cardiac output (CO) measured by pulse wave transit time cardiac output system (esCCO system; COesCCO) vs transthoracic echocardiography (COTTE) in mechanically ventilated patients in the early phase of septic shock. A secondary objective was to assess ability of esCCO to detect change in CO after fluid infusion. Methods Mechanically ventilated patients admitted to the ICU, aged > 18 years, in sinus rhythm, in the early phase of septic shock were prospectively included. We performed fluid infusion of 500ml of crystalloid solution over 20 minutes and recorded CO by EsCCO and TTE immediately before (T0) and 5 minutes after (T1) fluid administration. Patients were divided into 2 groups (responders and non-responders) according to a threshold of 15% increase in COTTE in response to volume expansion. Results In total, 25 patients were included, average 64 +/- 15 years, 15 (60%) were men. Average SAPSII and SOFA scores were 55 +/- 21.3 and 13 +/- 2, respectively. ICU mortality was 36%. Mean cardiac output at T0 was 5.8 +/- 1.35 L/min by esCCO and 5.27 +/- 1.17 L/min by COTTE. At T1, respective values were 6.63 +/- 1.57 L/min for esCCO and 6.10 +/- 1.29 L/min for COTTE. Overall, 12 patients were classified as responders, 13 as non-responders by the reference method. A threshold of 11% increase in COesCCO was found to discriminate responders from non-responders with a sensitivity of 83% (95% CI, 0.52-0.98) and a specificity of 77% (95% CI, 0.46-0.95). Conclusion We show strong correlation esCCO and echocardiography for measuring CO, and change in CO after fluid infusion in ICU patients.

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.

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.

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.

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.

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.

The aim was to evaluate the performance of arterial pressure-based cardiac output (APCO) [1] and pulse wave transit time- based cardiac output (esCCO) [2] monitors in Thai patients undergoing coronary artery bypass graft surgery (CABG) with cardiopulmonary bypass.

The aim of this work is to evaluate perioperative hemodynamic monitoring for major abdominal surgery using the estimated continuous cardiac output (esCCO) technique available with the NIHON KOHDEN Vismo monitor as compared with the LiDCOrapid hemodynamic monitoring system.

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.

Background: Blood pressure is clinically used for monitoring shock patients and as a therapeutic indicator for them. Non-invasive blood pressure measurement has weak points such as the use of a cuff and it is a discontinuous measurement. A method of measuring the blood pressure by using the PWTT (pulse wave transit time) has been studied to make up for those weak points. If blood pressure monitoring can be done by using the difference of the PWTT between different points in the body, then this method wil l be a quite useful to monitor the BP of seriously ill patients. This study aimed to verify whether or not the PWTT has a significant correlation with the blood pressure of shock patients who received vasopressor infusion and whether this method is clinically applicable. Methods: The study subjects were 20 shock patients who were hospitalized in intensive care units and they had received vasopressor, and we measured the PWTT and we analyzed its correlation with the SBP (systolic blood pressure) and DBP (diastolic blood pressure), as measured by non-invasive monitoring. We then determined the effects of the PWTT on the SBP and DBP. Results: From the results of correlation analysis between the PWTT and the SBP and DBP, the SBP displayed a statistically significant negative correlation with the PWTT of 18 patients, while no significant correlation between the PWTT and DBP was observed. At the same time, from the results of the regression analysis of the blood pressures and the PWTT of each patient, it was found that the PWTT had a negative effect on the SBP of all the patients, except two. Conclusions: The PWTT has a negative correlation with the SBP of the patien ts who received vasopressor infusion.

Summary A prospective study has been undertaken on 24 patients to establish the relationship between the degree of internal carotid artery stenosis, as estimated by arteriography, and the pulse wave transit time in the carotid artery. The technique involves the simultaneous use of two continuous wave Doppler velocimeters, one on the carotid and one on the supraorbital artery, to measure the flow waves and hence deduce the pulse wave transit times. The measured transit times varied from 17 to 124 ms with a beat-to-beat variation of 11 per cent. The absolute transit time in any segment correlated moderately well with the estimated degree of stenosis (r = 0.68, P < 0.001). However, normalization of the transit times, to correct for the effects of blood pressure and age, produced an improved correlation between the variables (r = 0.8, P < 0.001). Normalization was achieved by dividing the common carotid to supraorbital transit time by the shortest transit time found between the common carotid and either the superficial temporal or brachial arteries. Significant differences in the normalized transit times were found between arteries that were diametrically stenosed by more than 50 per cent, by between 21 and 50 per cent and by 20 per cent or below. It is concluded that pulse wave transit time measurement can provide a simple and reproducible non-invasive technique for the diagnosis of varying degrees of carotid artery stenosis.

The common femoral to popliteal segments of 123 patients with radiologically confirmed arterial disease have been compared with those of 43 volunteers apparently free from disease. The comparisons have been based upon parameters derived from Doppler-shifted, continuous wave ultrasound. Simultaneous recordings of the Doppler signal were made from over the common femoral artery and the popliteal artery; these were analyzed subsequently to reveal variations of maximum frequency with time. Fifteen parameters were obtained from each segment. Of these the Pulsatility Index (P.I.) the Damping Factor(Δ), the pulse wave transit time(TT) the rise time ratio(RTR) from each segment were examined in detail. The Doppler results from the patient groups were compared also with the findings from arteriography. On the basis of these comparisons it was found that the RTR was simpler to measure than other more commonly used parameters such as Pulsatility Index and at least as sensitive for the differentiation between severe arterial disease and the mildly affected or normal state. However, none of these parameters was sufficiently sensitive to distinguish between mild to moderate disease and normal.

Sixteen subjects took part in a two-stage cardiovascular biofeedback experiment. For five sessions all subjects attempted to control their pulse wave transit time (TT), using TT feedback. The eight subjects who achieved control were given a further five sessions, during which they attempted to control their transit time without altering their interbeat interval (IBI) when provided with TT and IBI feedback. No evidence was found for complete dissociation of TT and IBI. When the single TT contingency was in operation, all subjects who had significant control of TT also showed significant changes in IBI in the same direction. When the dual contingency was introduced, subjects either controlled TT but failed to keep IBI stable or kept IBI stable but failed to control TT.