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Aim: The study was designed to evaluate the accuracy of cardiac output (CO) measurements based on pulse wave transit time (PWTT) as compared to transpulmonary thermodilution (TPTD) in perioperative off-pump coronary artery bypass grafting (OPCABG).Methods: 20 patients scheduled for elective OPCABG were enrolled for a prospective study. Parallel measurements of CO by using PWTT (COPWTT) and TPTD (COTPTD) were carried out at five stages intraoperatively and at three stages postoperatively. Also analyzed was the agreement between CO absolute values and its ability to monitor cardiac output dynamics. Results: All in all, 153 pairs of CO data were obtained. According to Bland–Altman analysis, the mean intraoperative difference between the methods was 1.2 L/min, with boundaries of agreement reaching ± 2.9 L/min and a percentage error amounting to 64%. The intraoperative analysis of a polar plot revealed an increased angular difference of 6.9º and radial boundaries of agreement of ± 70.4º, and a decreased polar concordance rate (55%). The postoperative analysis of the data showed better agreement between the methods: mean difference was 0.4 L/min with boundaries of agreement of ± 2.3 L/min and percentage error of 41%. The postoperative trending ability was also more accurate (angular difference of 3.2º, angular boundaries of agreement ± 39º, polar concordance rate 81%).Conclusion: Poor accuracy and reproducibility of non-invasive COPWTT and its insufficient trending ability to monitor cardiac output during off-pump coronary artery bypass grafting makes it impossible to recommend this technology to be used intraoperatively as an alternative to transpulmonary thermodilution technique. The calibration and trending ability of COPWTT improved after OPCAB.

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.

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.

Multi-site photoplethysmograph (PPG) recording enables researchers to study the vascular and hemodynamic properties of human subjects. Currently, there is no commercial system available in the market to perform either one channel or multi-channel PPG recording. PPG is an optoelectronic technique that measures changes in blood volume associated with cardiac contraction. The measurements can be obtained from fingertips, ear lobes and toes due to their low absorption and high degree of vasculature. The main objective of this project is to develop a two-channel simultaneous PPG recording system to acquire PPG signals from two different physiological sites using a Nellcor equivalent PPG probe. MATLAB software was used during the development phase to ensure rapid prototyping. The experiment results show that there was no inter -channel delay in the developed two-channel PPG system. Our preliminary results show that the delays between the left and the right arm were from 4 to 12 ms in three healthy random subjects. The system is portable, powered by universal serial bus (USB) and allows the user to do the PPG data acquisition in a clinical setting.

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.

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.

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.

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.

The purpose of the study is to compare the accuracy of point-to-point measurement method of pulse wave propagation time from the multi-point. Electroimpedance method recorded pulse waves in the knees and ankles. Both the ECG signal and the digitized 16-bit analog-digital converter with a frequency of 1 kHz per channel. The study was conducted with 18 healthy volunteers, 20-22 years in the supine position for 3-4 minutes. With the help of LabVIEW tools created by the nine algorithms each subject were analyzed 250-300 pulse waves, highlighting the figure of the coefficient of variation. Their comparison showed that the analysis of pulse waves using different algorithms give different results. The most stable were made when times were measured between the highest peaks of the first derivatives of the forward pulse wave fronts. Similar results were found cross-correlation and cross-spectral analysis of second derivatives of the forward pulse wave fronts. It can be argued that the results of these algorithms allow the parameters obtained by averaging closer to the true results., Тyrimo tikslas - palyginti tiesioginių (point-to-point) PTT matavimo metodų tikslumą su daugiataškiais (multipoint) matavimo metodais. Elektropletizmografiniu būdu registravome pulsines bangas kelio ir čiurnos srityse. Abu signalai ir EKG kiekvienam kanalui buvo diskretizuojami per 16 bitų analoginį skaitmeninį keitiklį 1kHz dažniu. Tyrimas buvo atliktas su 18 sveikų asmenų (20-22 metų) jiems gulint 3-4 minutes. Naudojantis LabVIEW priemonėmis sukurtais devyniais algoritmais buvo analizuojamos jų kiekvieno 250–300 pulsinės bangos, išryškinant rodiklių variacijos koeficientą. Lyginamoji analizė parodė, kad pulsinės bangos analizei panaudojus įvairius algoritmus buvo gauti skirtingi rezultatai. Stabiliausi rezultatai pasiekti, kai laiko rodikliai buvo matuojami tarp priekinio bangų fronto pirmos eilių išvestinių maksimalių viršūnių. Panašūs rezultatai gauti atliekant priekinio bangų fronto antros eilės išvestinių kroskoreliacinę ir krosspektrinę analizę. Galima teigti, kad naudojant šiuos algoritmus gautų rezultatų suvidurkinimas leidžia priartėti prie tikrosios vertės.

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.