Radial Artery Pressure Waveforms Research Articles

Reconstruction of central arterial pressure waveform based on CBi-SAN network from radial pressure waveform

The central arterial pressure (CAP) is an important physiological indicator of the human cardiovascular system which represents one of the greatest threats to human health. Accurate non-invasive detection and reconstruction of CAP waveforms are crucial for the reliable treatment of cardiovascular system diseases. However, the traditional methods are reconstructed with relatively low accuracy, and some deep learning neural network models also have difficulty in extracting features, as a result, these methods have potential for further advancement. In this study, we proposed a novel model (CBi-SAN) to implement an end-to-end relationship from radial artery pressure (RAP) waveform to CAP waveform, which consisted of the convolutional neural network (CNN), the bidirectional long-short-time memory network (BiLSTM), and the self-attention mechanism to improve the performance of CAP reconstruction. The data on invasive measurements of CAP and RAP waveform were used in 62 patients before and after medication to develop and validate the performance of CBi-SAN model for reconstructing CAP waveform. We compared it with traditional methods and deep learning models in mean absolute error (MAE), root mean square error (RMSE), and Spearman correlation coefficient (SCC). Study results indicated the CBi-SAN model performed great performance on CAP waveform reconstruction (MAE: 2.23 ± 0.11 mmHg, RMSE: 2.21 ± 0.07 mmHg), concurrently, the best reconstruction effect was obtained in the central artery systolic pressure (CASP) and the central artery diastolic pressure(CADP) (RMSECASP: 2.94 ± 0.48 mmHg, RMSECADP: 1.96 ± 0.06 mmHg). These results implied the performance of the CAP reconstruction based on CBi-SAN model was superior to the existing methods, hopped to be effectively applied to clinical practice in the future.

Study of the accuracy of a radial arterial pressure waveform cardiac output measurement device after cardiac surgery

BackgroundLess invasive monitoring, such as radial arterial pulse contour analysis (ProAQT® sensor), represents an alternative when hemodynamic monitoring is necessary to guide postoperative management and invasive monitoring is not technically feasible. The aim of the study is to evaluate the accuracy of the ProAQT® sensor cardiac output measurements in comparison with Pulmonary Artery Catheter (PAC) during the postoperative course of patients who underwent cardiac surgery with cardiopulmonary bypass.Case presentationProspective observational study in a Surgical Intensive Care Unit of a tertiary university hospital. Ten patients with a mean age of 73.5 years were included. The main comorbidities were hypertension, diabetes, dyslipidemia and the preoperative left ejection fraction was 43.8 ± 14.5%. Regarding the type of surgery, six patients underwent valve surgery, two underwent coronary artery bypass grafting and two underwent aortic surgery. The cardiac index measured simultaneously by the ProAQT® sensor was compared with the PAC. The parameters were evaluated at predefined time points during the early postoperative courses (6 h, 12 h, 24 h, 48 h and 72 h). The degree of agreement with the cardiac index between the PAC and the ProAQT® sensor along the time points was measured using the concordance correlation coefficient, Bland–Altman analysis, and four-quadrant plot. Sixty-three pairs of measurements were analyzed. We showed that measurements of cardiac index were slightly higher with PAC (β ̂ = − 0.146, p-value = 0.094). The concordance correlation coefficient for the additive model of cardiac index was 0.64 (95% Confidence Interval: 0.36, 0.82), indicating a high concordance between both sensors. Bland-Altmann analysis showed a mean bias of 0.45 L·min−1·m−2, limits of agreement from − 1.65 to 2.3 L·min−1·m−2, and percentage of error was 82.5%. Four-quadrant plot of changes in cardiac index showed a good concordance rate (75%), which increases after applying the exclusion zone (87%).ConclusionsIn patients undergoing cardiac surgery, the ProAQT® sensor may be useful to monitor cardiac index during the postoperative period, especially when more invasive monitoring is not possible.

MO728: Association of Interleukin-6 with Subendocardial Viability Ratio in Haemodialysis Patients

Abstract BACKGROUND AND AIMS Inflammation is an important process in the pathogenesis of atherosclerosis, and chronic kidney disease (CKD) is recognized as a proinflammatory state. Interleukin-6 (IL-6) is associated with cardiovascular events and also predicts mortality in individuals with CKD patients. The subendocardial viability ratio (SEVR) is one of the pulse wave analysis parameters and represents a non-invasive measure of coronary perfusion. In a non-dialysis CKD population, we previously reported about the prognostic value of SEVR for cardiovascular outcome in these patients. The aim of this study was to investigate the association between inflammatory markers IL-6, tumour necrosis factor-α (TNF-α), high-sensitive C-reactive protein (hsCRP) and SEVR in CKD patients undergoing maintenance hemodialysis (HD). METHOD In a cross-sectional study, we enrolled only HD patients. SEVR was assessed using a generalized transfer function applied to the radial artery pressure wave form (Sphygmocor, Atcor Medical, Sydney, Australia). Plasma IL-6, TNF-α and hsCRP were measured by an enzyme-linked immunosorbent assay. RESULTS A total of 40 HD patients (mean age 65.2 ± 11.8 years, 72.5% male) were included. Other descriptive parameters are presented in Table 1. A statistically significant correlation was found between SEVR and IL-6 (r = 0.379; P = 0.016), but not between SEVR and TNF-α (P = 0.195), nor between SEVR and hsCRP (P = 0.686). In a multivariate adjusted model with SEVR as dependent variable and IL-6, TNF-α and hsCRP as independent variables we found a statistically significant association only between SEVR and IL-6 (β = 0.393; P = 0.017). CONCLUSION This study suggests an association between IL-6 and SEVR in HD patients.

Sex differences in aortic hemodynamics and associations with white matter hyperintensities in middle‐aged and older adults

Elevated blood pressure (BP) in midlife increases the risk of developing white matter hyperintensities (WMH) in the brain. WMH are associated with increased risk of cognitive decline and dementia. Structural changes of the large central arteries occur prior to changes in brachial BP. We have previously reported positive associations between aortic hemodynamics and WMH in normotensive postmenopausal women. The purpose of this study was to evaluate sex differences in aortic hemodynamics and associations with WMH burden in middle‐aged and older adults. Ninety‐nine participants (age = 63 ± 4y), including n = 35 men and n = 64 postmenopausal women participated in this study. Aortic hemodynamics were derived from radial artery pressure waveforms measured using applanation tonometry. Aortic systolic blood pressure (aSBP), aortic diastolic blood pressure (aDBP), augmented pressure (AP), aortic augmentation index (AIx), and aortic transit time were calculated. WMH lesion volume and intracranial volume (ICV) were measured using a FLAIR and T1 scan on a 3T MRI scanner, respectively. WMH fraction was calculated as (WMH lesion volume/ICV)*100 and cubic root transformed to reduce skewness. Age‐adjusted multiple linear regressions were used to determine the influence of aortic hemodynamics on WMH fraction. There were no sex differences in aSBP or aDBP. AP was greater in women compared with men (16 ± 5 mmHg vs. 11 ± 5 mmHg; P < 0.001). AIx was also greater in women compared with men (28 ± 6 % vs. 18 ± 9 %; P < 0.001). Aortic transit time was lower in women compared with men (140 ± 11 ms vs. 151 ± 12 ms; P < 0.001). There were no sex differences in WMH fraction. There was a positive association between aSBP and WMH fraction in both men (r = 0.37, P = 0.015) and women (r = 0.36, P = 0.017). In addition, aDBP was positively associated with WMH fraction in men (r = 0.47, P = 0.003) and women (r = 0.36, P = 0.017). AP was positively associated with WMH fraction in men (r = 0.34, P = 0.027), but not women (r = 0.24, P = 0.296). AIx was positively associated with WMH fraction in men (r = 0.46, P = 0.004), but not women (r = 0.22, P = 0.570). There were no significant associations between aortic transit time and WMH fraction. In conclusion, AP and AIx were greater in women compared with men. The positive associations between AP and WMH fraction and AIx and WMH fraction were only apparent in men. These findings suggest a sex‐specific association between augmented pressure and augmentation index and WMH burden in middle‐aged and older adults.

Reconstruction of central arterial pressure waveform based on CNN-BILSTM

Central arterial pressure is an important physiological indicator of the human cardiovascular system. Its noninvasive, continuous and accurate reconstruction and monitoring are essential to the evaluation, prevention and treatment of cardiovascular system diseases. However, it is difficult to improve the accuracy of noninvasive central arterial pressure reconstruction by traditional methods, which limits its clinical application and promotion. In this study, a model for reconstructing central artery pressure from radial arterial pressure waveforms based on a convolutional neural network and bi-directional long short-term memory (CNN-BiLSTM) was proposed. Central aortic pressure waveforms and radial arterial pressure waveforms were measured invasively before and after medication in 62 patients to evaluate the CNN-BiLSTM model for reconstructing central artery pressure. The CNN-BiLSTM model was compared with two traditional methods (autoregressive exogenous (ARX) and N-point moving average method (NPMA)) and four deep learning models (LSTM, BiLSTM, LSTM-BiLSTM and CNN-LSTM) in the mean absolute error (MAE), root mean square error (RMSE) and Spearman correlation coefficient (SCC). Experimental results showed that the proposed model achieved the best results on waveform reconstruction (MAE: 2.18 ± 0.13 mmHg, RMSE: 2.95 ± 0.16 mmHg). At the same time, a good reconstruction effect was obtained in the central arterial systolic pressure (RMSE: 3.34 ± 0.91 mmHg) and diastolic blood pressure (RMSE: 2.41 ± 0.18 mmHg). Therefore, the reconstruction model based on CNN-BILSTM is a potential method for noninvasive continuous monitoring of central arterial pressure.

Discrimination of the Cognitive Function of Community Subjects Using the Arterial Pulse Spectrum and Machine-Learning Analysis.

Early identification of cognitive impairment would allow affected patients to receive care at earlier stage. Changes in the arterial stiffness have been identified as a prominent pathological feature of dementia. This study aimed to verify if applying machine-learning analysis to spectral indices of the arterial pulse waveform can be used to discriminate different cognitive conditions of community subjects. 3-min Radial arterial blood pressure waveform (BPW) signals were measured noninvasively in 123 subjects. Eight machine-learning algorithms were used to evaluate the following 4 pulse indices for 10 harmonics (total 40 BPW spectral indices): amplitude proportion and its coefficient of variation; phase angle and its standard deviation. Significant differences were noted in the spectral pulse indices between Alzheimer’s-disease patients and control subjects. Using them as training data (AUC = 70.32% by threefold cross-validation), a significant correlation (R2 = 0.36) was found between the prediction probability of the test data (comprising community subjects at two sites) and the Mini-Mental-State-Examination score. This finding illustrates possible physiological connection between arterial pulse transmission and cognitive function. The present findings from pulse-wave and machine-learning analyses may be useful for discriminating cognitive condition, and hence in the development of a user-friendly, noninvasive, and rapid method for the early screening of dementia.

The influence of intermittent apnea on aortic hemodynamics in healthy young men

Background: Sleep apnea is known as a high-risk factor for cardiovascular disease (CVD); However, the influence of apnea on aortic blood pressure and augmentation index (AIx), which cardiac load and independent risks for a future CVD event, remains unclear. Therefore, this study aimed to examine the influence of intermittent normoxic apnea on aortic arterial hemodynamics in healthy men. Methods: Sixteen healthy young men (23 ± 1.6 years mean ± SD) underwent the repetitive 20-s apnea with a 40 s interval for 20 min. During the interval, each subject maintained a breath pace at 15 breaths/min. Central hemodynamics were evaluated every 5 min by pulse wave analysis from peripheral (radial) arterial pressure waveforms via general transfer function method and compared among three phases defined as “breath” (for 20 s before apnea), “apnea”, and “rebreathe” (for 20 s after apnea). The baseline values were calculated from the first breathing cycle and compared with each breathing phase every 5 min. Results: Aortic systolic blood pressure and AIx were significantly higher at rebreathe phase than the other phases. Likewise, heart rate and double product (aortic systolic blood pressure × heart rate) were significantly higher in rebreathe phase than the other phases. Conclusions: These results suggest that cardiac load is increased by intermittent normoxic apnea, especially during the rebreathing phase.

A Lumped Parameter Model for Cardiac Output Estimation Using Arterial Blood Pressure Waveform.

This paper investigates a subject-specific lumped parameter cardiovascular model for estimating Cardiac Output (CO) using the radial Arterial Blood Pressure (ABP) waveform. The model integrates a simplified model of the left ventricle along with a linear third order model of the arterial tree and generates reasonably accurate ABP waveforms along with the Dicrotic Notch (DN). Non-linear least square optimization technique is used to obtain uncalibrated estimates of cardiovascular parameters. Thermodilution CO measurements have been used to evaluate the CO estimation accuracy. The model achieves less than 15% normalized error across 10 subjects with different shapes of ABP waveform.

Influences of smoking on central blood pressure in hypertensive subjects

Abstract Background/Introduction Smoking is known to induce systemic vascular damage, leading to cardiovascular diseases. Recent studies demonstrated that central blood pressure has a greater impact on cardiovascular events than brachial blood pressure. Purpose We investigated influences of habitual smoking on central systolic blood pressure (CSBP) in hypertensive subjects. Methods A total of 5630 subjects (male = 2622, 51.7±12.0 year-old at baseline), who visited our hospital for a physical check-up at least twice during the last 10 years and underwent CSBP measurement at each visit, were enrolled, and they were divided into three groups; normotensive (n=4634), non-treated hypertensive (n=91) and treated hypertensive subjects (n=905). Then, the influences of smoking on the average and yearly changes of CSBP (median follow-up 5 years) were analyzed. Brachial blood pressure (oscillometer) and radial artery pressure waveforms (tonometer) were recorded using an automated device, and the pressure corresponding to the second systolic peak of radial pressure waveforms was taken as CSBP (HEM-9000AI, Omron Healthcare, Kyoto). Hypertension was defined as brachial BP ≥140/90mmHg or the use of antihypertensive medications. A yearly change in CSBP was calculated in each subject by linear regression analysis using longitudinal data. Results The average CSBP was higher in habitual smokers than in non-smokers when analyzed in normotensive (109.1±11.7 vs. 107.6±12.8 mmHg, p<0.001) and non-treated hypertensive subjects (150.7±14.8 vs. 142.8±16.7 mmHg, p<0.05), whereas in hypertensive subjects under medication the average CSBP was lower in smokers than in non-smokers (124.6±12.4 vs. 127.8±13.6 mmHg, p<0.01). Smoking status did not affect yearly changes of CSBP in normotensive (habitual smokers vs. non-smokers; 1.38±6.00 vs. 1.44±6.04 mmHg/year), treated hypertensive (−0.16±7.08 vs. −0.66±8.24 mmHg/year), and non-treated hypertensive subjects (4.09±15.1 vs. −0.53±10.3 mmHg/year). Conclusions Habitual smoking increases CSBP, however, antihypertensive medications counteract the unfavorable effects of smoking on CSBP. These results imply a new pathway underlying the development of cardiovascular diseases in smokers. Unfavorable changes in the cardiovascular system caused by smoking may quite slowly progress that short period of observation in the present study could not have detected enhanced yearly increases of CSBP by smoking. Funding Acknowledgement Type of funding sources: None.

Lower-body dynamic exercise reduces wave reflection in healthy young adults.

What is the central question of this study? There is a paradoxical reduction in augmentation index during lower-body dynamic (LBD) exercise in the face of an increase in central pressure. To determine causality, the amplitudes of forward and backward pressure waves were assessed separately using wave separation analysis. What is the main finding and its importance? Reflection magnitude decreased during LBD exercise in healthy young adults and was attributable to an increased forward pressure wave amplitude and decreased backward pressure wave amplitude. This vasoactive response might limit the adverse effects of wave reflection during LBD exercise, optimizing ventricular-arterial interactions. Acute lower-body dynamic (LBD) exercise decreases surrogate measures of wave reflection, such as the augmentation index. However, the augmentation index is influenced by the combined effects of wave reflection timing, magnitude and other confounding factors external to wave reflection, which make it difficult to discern the origin of changes in surrogate measures. The relative contributions of forward (Pf) and backward (Pb) pressure wave amplitudes to central pressure can be determined by wave separation analysis. Reflection magnitude (RM=Pb/Pf) and the timing of apparent wave reflection return can also be determined. We tested the hypothesis that acute LBD exercise decreases RM and reflected wave transit time (RWTT). Applanation tonometry was used to record radial artery pressure waveforms in 25 adults (24 ± 4 years of age) at baseline and during light-, moderate- and vigorous-intensity exercise. Wave separation analysis was conducted offline using a personalized physiological flow wave to determine Pf, Pb, RM and RWTT. The RM decreased during all intensities of exercise compared with baseline (all P<0.001; baseline, 43 ± 5%; light, 33 ± 6%; moderate, 23 ± 7%; vigorous, 17 ± 5%). The reduction in RM was attributable to the combined effect of increased Pf and decreased Pb during exercise. The RWTT decreased during all intensities of exercise compared with baseline (all P<0.04; baseline, 156 ± 17ms; light, 144 ± 15ms; moderate, 129 ± 16ms; vigorous, 121 ± 17ms). Lastly, in a stepwise multilinear regression, Pf, but not Pb and RWTT, contributed to increased central pulse pressure during LBD exercise. These data show that wave reflection decreased and that central pulse pressure is most influenced by Pf during LBD exercise.

Arterial stiffness is not acutely modified by consumption of a caffeinated soft drink sweetened with high fructose corn syrup in young healthy adults

Purpose Excessive intake of fructose is associated with an increased risk of developing cardiovascular disease. A major source of dietary fructose is the ingestion of high fructose corn syrup (HFCS) in sugar sweetened beverages (e.g., soft drinks). High arterial stiffness is an independent risk factor for cardiovascular morbidity and mortality. Thus, it is possible that regular consumption of beverages containing HFCS acutely and/or chronically increase arterial stiffness. However, this has never been explored. This study tested the hypothesis that ingestion of a caffeinated soft drink containing HFCS acutely increases arterial stiffness. Methods Fourteen healthy adults (25 ± 3 y, 6 women) reported to the laboratory for two experimental visits and consumed either 500 mL of tap water (H2O) or 500 mL of Mountain Dew® (an HFCS containing caffeinated beverage, DEW) in their first visit and consumed the other beverage in their next experimental visit, employing a counterbalanced, crossover, randomized design. Data were collected pre-consumption, 30 min post-consumption and 120 min post-consumption. Arterial stiffness was measured as carotid-to-femoral pulse wave velocity (cfPWV) using applanation tonometry. Peripheral (brachial) blood pressure was measured via electrosphygmomanometry. Central (aortic) blood pressure was estimated from transfer function analysis of the radial artery pressure waveform. Indices of pulse wave reflection were calculated from the synthesized central pressure waveforms. Data are presented as mean ± SD. Results cfPWV did not differ pre-consumption (DEW: 5.5 ± 0.6 m/s, H2O: 5.3 ± 0.7 m/s, P=0.69). At 30 min post-consumption, cfPWV was higher in the DEW trial (5.7 ± 0.6 m/s) compared to the H2O trial (5.3 ± 0.6 m/s, P=0.01), but cfPWV was not different between DEW and H2O at 120 min post-consumption (DEW: 5.7 ± 0.6 m/s, H2O: 5.5 ±0.6 m/s, P=0.13). Notably however, changes in cfPWV from pre-consumption did not differ between DEW and H2O at 30 min post- (DEW: 0.2 ± 0.3 m/s, H2O 0.0 ± 0.3 m/s, P=0.34) or 120 min post-consumption (DEW: 0.3 ± 0.4 m/s, H2O: 0.2 ± 0.3 m/s, P=0.77). Peripheral and central systolic (P≥0.50) and diastolic (P≥0.25) pressures did not differ between the DEW and H2O trials at any time point. Thus, peripheral (at 120 min post-consumption – DEW: 94 ± 6 mmHg, H2O: 92 ± 6 mmHg, P=0.31) and central (at 120 min post-consumption – DEW: 89 ± 7 mmHg, H2O: 85 ± 7 mmHg, P=0.13) mean arterial pressure also did not differ between trials. Moreover, aortic augmentation pressure, augmentation index, augmentation index corrected to a heart rate of 75 bpm, and reflection magnitude did not differ between the DEW and H2O trials at pre- (P≥0.22), 30 min post- (P≥0.55) or 120 min post-consumption (P>0.18). Conclusion Compared to drinking an equivalent volume of water, consumption of 500 mL of a commercially available caffeinated soft drink containing HFCS has little acute effect on indices of arterial stiffness or central blood pressure. The effect of chronic consumption of soft drinks containing HFCS on arterial stiffness and blood pressure regulation remain largely unknown.

EFFECTS OF SMOKING ON CENTRAL BLOOD PRESSURE

Abstract Objective: Smoking is known to induce systemic vascular damage, leading to cardiovascular diseases. Recent studies demonstrated that central blood pressure has a greater impact on cardiovascular events than brachial blood pressure. We investigated effects of habitual smoking on central systolic blood pressure (CSBP) in the general population. Design and method: A total of 5630 subjects (male = 2622, 51.7 ± 12.0 year-old at baseline), who visited our hospital for a physical check-up at least twice during the last 10 years and underwent CSBP measurement at each visit, were enrolled, and effects of smoking on the average and yearly changes of CSBP (median follow-up 5 years) were analyzed. Brachial blood pressure (oscillometer) and radial artery pressure waveforms (tonometer) were recorded using an automated device, and the pressure corresponding to the second systolic peak of radial pressure waveforms was taken as CSBP (HEM-9000AI, Omron Healthcare, Kyoto). Hypertension was defined as brachial BP &gt; = 140/90mmHg or the use of antihypertensive medications. A yearly change in CSBP was calculated in each subject by linear regression analysis using longitudinal data. Results: The average CSBP during the follow-up was higher in habitual smokers than in non-smokers when analyzed in normotensive (n = 4634, 109.1 ± 11.7 vs. 107.6 ± 12.8 mmHg, p &lt; 0.001) and non-treated hypertensive subjects (n = 91, 150.7 ± 14.8 vs. 142.8 ± 16.7 mmHg, p &lt; 0.05), whereas in hypertensive subjects under medication the average CSBP was lower in smokers than in non-smokers (n = 905, 124.6 ± 12.4 vs. 127.8 ± 13.6 mmHg, p &lt; 0.01). Although smoking status did not affect yearly changes of CSBP in both normotensive (habitual smokers vs. non-smokers; 1.38 ± 6.00 vs. 1.44 ± 6.04 mmHg/year) and treated hypertensive subjects (-0.16 ± 7.08 vs. -0.66 ± 8.24 mmHg/year), the unfavorable effect of smoking on yearly increase of CSBP was found in non-treated hypertensive subjects (4.09 ± 15.1 vs. -0.53 ± 10.3 mmHg/year). Conclusions: Habitual smoking increases CSBP especially in subjects with hypertension, however, antihypertensive medications counteract the unfavorable effects of smoking on CSBP. These results imply a new pathway underlying the development of cardiovascular diseases in smokers. Unfavorable changes in the cardiovascular system caused by smoking may quite slowly progress that short period of observation in the present study could not have detected enhanced yearly increases of CSBP by smoking.

Estimation of cardiac output variations induced by hemodynamic interventions using multi-beat analysis of arterial waveform: a comparative off-line study with transesophageal Doppler method during non-cardiac surgery

Multi-beat analysis (MBA) of the radial arterial pressure (AP) waveform is a new method that may improve cardiac output (CO) estimation via modelling of the confounding arterial wave reflection. We evaluated the precision and accuracy using the trending ability of the MBA method to estimate absolute CO and variations (ΔCO) during hemodynamic challenges. We reviewed the hemodynamic challenges (fluid challenge or vasopressors) performed when intra-operative hypotension occurred during non-cardiac surgery. The CO was calculated offline using transesophageal Doppler (TED) waveform (COTED) or via application of the MBA algorithm onto the AP waveform (COMBA) before and after hemodynamic challenges. We evaluated the precision and the accuracy according to the Bland & Altman method. We also assessed the trending ability of the MBA by evaluating the percentage of concordance with 15% exclusion zone between ΔCOMBA and ΔCOTED. A non-inferiority margin was set at 87.5%. Among the 58 patients included, 23 (40%) received at least 1 fluid challenge, and 46 (81%) received at least 1 bolus of vasopressors. Before treatment, the COTED was 5.3 (IQR [4.1–8.1]) l min−1, and the COMBA was 4.1 (IQR [3–5.4]) l min−1. The agreement between COTED and COMBA was poor with a 70% percentage error. The bias and lower and upper limits of agreement between COTED and COMBA were 0.9 (CI95 = 0.82 to 1.07) l min−1, −2.8 (CI95 = −2.71 to−2.96) l min−1 and 4.7 (CI95 = 4.61 to 4.86) l min−1, respectively. After hemodynamic challenge, the percentage of concordance (PC) with 15% exclusion zone for ΔCO was 93 (CI97.5 = 90 to 97)%. In this retrospective offline analysis, the accuracy, limits of agreements and percentage error between TED and MBA for the absolute estimation of CO were poor, but the MBA could adequately track induced CO variations measured by TED. The MBA needs further evaluation in prospective studies to confirm those results in clinical practice conditions.

Fiber Bragg Grating-Based Pulse Monitoring Device for Real-Time Non-Invasive Blood Pressure Measurement—A Feasibility Study

The real-time, continuous, beat-to-beat blood pressure (BP) monitoring is vital in clinical scenarios such as operations theatres, ambulances etc. In the present study, a non-invasive BP monitoring methodology based on Fiber Bragg Grating sensors is reported. The design and development of Fiber Bragg Grating based Pulse Monitoring Device (FBGPM) is demonstrated which is capable of acquiring the radial arterial pulse pressure waveform effectively in real time. The Radial Arterial Pulse Pressure Waveform is acquired on beat to beat basis employing developed FBGPM in a clinical environment. Further, the recorded radial arterial pulse pressure waveform is processed to obtain systolic and diastolic BP by utilizing a standard non-invasive BP measurement device as a reference. The BP values obtained through FBGPM are then compared with the BP values obtained through an Intra-Arterial (IA) probe. The FBGPM is a chemically and electrically inert device which makes it an effective candidate for monitoring the real-time BP. The focus of the study is to demonstrate the feasibility of deploying developed FBGPM device in clinical environment to acquire beat-to-beat BP and subsequently compare the present device to the IA probe method of BP acquisition.

PULSE-WAVEFORM AND LASER-DOPPLER INDICES FOR IDENTIFYING COLORECTAL-CANCER PATIENTS

This study aimed to determine the effectiveness of using noninvasive arterial pulse-wave and laser-Doppler flowmetry (LDF) measurements to discriminate between colorectal-cancer (CC) patients and healthy control subjects. Radial-artery blood pressure waveform (BPW), finger photoplethysmography (PPG), and skin-surface LDF signals were measured noninvasively in 12 CC patients and 25 control subjects. Beat-to-beat, spectral, and variability analyses were applied to 20-minute-long recorded signals. Significant intergroup differences were found. In BPW, [Formula: see text]–[Formula: see text] amplitude indices were significantly larger while [Formula: see text]–[Formula: see text] phase-angle indices were significantly smaller in the CC patients than in the controls. The PPG and LDF variability indices were significantly larger and smaller, respectively, in CC patients. The relative energy contributions of the endothelial-, neural-, and myogenic-related frequency bands in LDF were significantly smaller in CC patients. The present findings indicate that pulse and LDF waveform analysis can be used to evaluate the arterial pulse-wave transmission condition, the responses of the blood-flow perfusion, and its regulatory activities in CC patients. There could be some similarities and differences in the present indices for different types of cancer. These findings could be utilized in the development of a rapid, noninvasive, and objective technique for evaluating the CC-induced blood-flow responses.

Feasibility of Estimation of Aortic Wave Intensity Using Non-invasive Pressure Recordings in the Absence of Flow Velocity in Man.

BackgroundWave intensity analysis provides valuable information on ventriculo-arterial function, hemodynamics, and energy transfer in the arterial circulation. Widespread use of wave intensity analysis is limited by the need for concurrent measurement of pressure and flow waveforms. We describe a method that can estimate wave intensity patterns using only non-invasive pressure waveforms (pWIA).MethodsRadial artery pressure and left ventricular outflow tract (LVOT) flow velocity waveforms were recorded in 12 participants in the Southall and Brent Revisited (SABRE) study. Pressure waveforms were analyzed using custom-written software to derive the excess pressure (Pxs) which was scaled to peak LVOT velocity and used to calculate wave intensity. These data were compared with wave intensity calculated using the measured LVOT flow velocity waveform. In a separate study, repeat measures of pWIA were performed on 34 individuals who attended two clinic visits at an interval of ≈1 month to assess reproducibility and reliability of the method.ResultsPxs waveforms were similar in shape to aortic flow velocity waveforms and the time of peak Pxs and peak aortic velocity agreed closely. Wave intensity estimated using pWIA showed acceptable agreement with estimates using LVOT velocity tracings and estimates of wave intensity were similar to values reported previously in the literature. The method showed fair to good reproducibility for most parameters.ConclusionThe Pxs is a surrogate of LVOT flow velocity which, when appropriately scaled, allows estimation of aortic wave intensity with acceptable reproducibility. This may enable wider application of wave intensity analysis to large studies.

The role of the maximal first derivative of the radial pulse wave (Rad dP/dtmax) in monitoring cardiac function.

BackgroundThis study aimed to assess the clinical significance of the maximal first derivative of the radial pulse wave (Rad dP/dtmax) in monitoring cardiac function with different perioperative patients by researching the relationship between Rad dP/dtmax and cardiac output (CO).MethodsPatients with non-pump coronary artery bypass grafting (CABG) and open liver tumor resection (OLTR) were enrolled in this study (n=10). CO was measured using the thermodilution Swan-Ganz catheter method and Rad dP/dtmax was acquired by the analysis of patients’ left radial artery pressure waveform through the PowerLab data acquisition device. CO, Rad dP/dtmax, heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure, central venous pressure, mean pulmonary arterial pressure, pulmonary artery wedge pressure (PAW), and body surface area was recorded. Data were analyzed using a mixed linear model of time-dependent covariates to duplicate the data.ResultsThe bivariate correlation coefficients of Rad dP/dtmax and CO were 0.526 and 0.413. The result of the multivariate mixed linear model analysis showed that compared with other indicators, Rad dP/dtmax had the greatest standardized coefficient with CO in CABG patients. While in OLTR patients, HR, SBP, PAW, and DBP had larger standardized coefficients.ConclusionsRad dP/dtmax could be a useful indicator to reflect and predict the acute changes in cardiac function in perioperative patients, especially for patients with cardiac dysfunction or contractility abnormality.

Comparing the Accuracy of Physiologic and Triangular Pseudoflow Waveforms for Estimating Wave Reflection Indices in Adults

Central aortic pressure waveforms contain valuable prognostic information in addition to central systolic pressure. Using wave separation analysis, aortic pressure‐flow relations can be used to decompose aortic pressure waveforms into forward (Pf) and backward‐travelling (Pb) components. Pf and Pb are used to calculate reflection magnitude (RM=Pb/Pf) which is predictive of heart failure and all‐cause mortality. Aortic blood flow can be measured non‐invasively via ultrasonography or estimated using a triangular pseudoflow waveform; however, the latter can underestimate true flow and thus overestimate Pb and RM. Recently, a physiologic pseudoflow waveform has been developed that improves on the assumptions of triangulation and so may provide a more accurate estimation of wave reflection.PURPOSEThe purpose of this study was to compare estimates of Pf, Pb, and RM derived from physiologic and triangular pseudoflow waveforms relative to measured flow. We hypothesized that the physiologic waveform would provide a more accurate estimate of wave reflection indices compared to the triangular waveform.METHODSIn 75 adults (age 18–75 yrs), radial artery pressure waveforms were acquired with applanation tonometry and a generalized transfer function was used to synthesize central pressure waveforms. Aortic blood flow velocities were measured via echocardiography and estimated using physiologic (in‐house software) and triangular (SphygmoCor CvMS) pseudoflow waveforms. Pressure‐flow relations were established offline and wave separation analysis was performed. Accuracy of the physiologic and triangular‐derived estimates of Pf, Pb, and RM were assessed using 95% equivalence testing, paired t‐tests comparing the mean absolute biases, and Bland‐Altman plots.RESULTSUsing a 10% equivalence zone as the maximum acceptable difference, the physiologic and triangular pseudoflow waveforms were both comparable to the measured flow waveform in deriving Pf. However, only the physiologic waveform yielded similar estimates of Pb and RM compared to the measured waveform. Further, the physiologic waveform yielded lower mean absolute biases compared to the triangular waveform for Pf (1.7 ± 2.1 vs. 2.8 ± 2.6 mmHg, p&lt;0.001), Pb (1.0 ± 1.1 vs. 3.3 ± 2.7 mmHg, p&lt;0.001), and RM (3 ± 3 vs. 14 ± 13%, p&lt;0.001). Lastly, Bland‐Altman biases were smaller, and 95% limits of agreement were narrower, for all wave reflection indices derived from the physiologic waveform than from the triangular waveform.CONCLUSIONThese data suggest that the physiologic pseudoflow waveform provides a more accurate estimate of wave reflection indices compared to the triangular waveform, and thus may offer a superior alternative when true flow cannot be measured.

Comparison of central SBP in children estimated from a brachial cuff alone, brachial cuff-calibrated applanation radial tonometry and brachial cuff-calibrated carotid wall-tracking.

We compared the agreement between different techniques to estimate central SBP (cSBP) in children and the relative impact of different methods of measuring peripheral blood pressure (BP). A total of 135 children, aged 12.9 ± 3.0 years including 67 boys, 85 with chronic kidney disease were studied. We measured cSBP using radiofrequency ultrasound carotid wall-tracking (Esaote ART.LAB system, a previously validated reference method), transformation of the radial artery pressure waveform obtained by tonometry (SphygmoCor) and a cuff-based system (cBP301; Centron Diagnostics) during a single visit. Carotid and radial tonometric-derived values were calibrated from mean and diastolic values of brachial BP obtained by aneroid sphygmomanometer. Brachial cuff only values were calibrated from the same aneroid sphygmomanometer values and from oscillometric values obtained from the brachial cuff. cSBP values estimated from radial tonometry were closely correlated with those obtained from the carotid (r = 0.959, mean difference -0.61 ± 3.5 mmHg). cSBP values estimated by the brachial cuff only method agreed reasonably well with those obtained from the carotid (r = 0.847, mean difference 5 ± 7.4 mmHg) when calibrated by the same method but when calibrated by oscillometric values from the brachial cuff, agreement was less good (r = 0.659, mean difference 8.7 ± 11.4 mmHg). Radial tonometry with a radial-to-central transfer function can be used to estimate cSBP in children with acceptable accuracy when compared with the invasively validated carotid reference method. All methods are subject to errors introduced by calibration from peripheral BP.

Cardiac output estimation by multi-beat analysis of the radial arterial blood pressure waveform versus intermittent pulmonary artery thermodilution: a method comparison study in patients treated in the intensive care unit after off-pump coronary artery bypass surgery

Cardiac output (CO) is a key hemodynamic variable that can be minimally invasively estimated by pulse wave analysis. Multi-beat analysis is a novel pulse wave analysis method. In this prospective observational clinical method comparison study, we compared CO estimations by multi-beat analysis with CO measured by intermittent pulmonary artery thermodilution (PATD) in adult patients treated in the intensive care unit (ICU) after off-pump coronary artery bypass surgery (OPCAB). We included patients after planned admission to the ICU after elective OPCAB who were monitored with a radial arterial catheter and a pulmonary artery catheter. At seven time points, we determined CO using intermittent PATD (PATD-CO; reference method) and simultaneously recorded the radial arterial blood pressure waveform that we later used to estimate CO using multi-beat analysis (MBA-CO; test method) with the Argos monitor (Retia Medical; Valhalla, NY, USA). Blood pressure waveforms impaired by inappropriate damping properties or artifacts were excluded. We compared PATD-CO and MBA-CO using Bland–Altman analysis accounting for repeated measurements, the percentage error, and the concordance rate derived from four-quadrant plot analysis (15% exclusion zone). We analyzed 167 CO values of 31 patients. Mean PATD-CO was 5.30 ± 1.22 L/min and mean MBA-CO was 5.55 ± 1.82 L/min. The mean of the differences between PATD-CO and MBA-CO was 0.08 ± 1.10 L/min (95% limits of agreement: − 2.13 L/min to + 2.29 L/min). The percentage error was 40.7%. The four-quadrant plot-derived concordance rate was 88%. CO estimation by multi-beat analysis of the radial arterial blood pressure waveform (Argos monitor) shows reasonable agreement compared with CO measured by intermittent PATD in adult patients treated in the ICU after OPCAB.