Age and Sex Differences in the Contribution of Mean Arterial Pressure to Pulse Pressure Before Middle Age.

INTRODUCTION: A lower ability to buffer pulse pressure (PP) in the face of increasing mean arterial pressure (MAP) may underlie the disproportionate increase in systolic blood pressure (SBP) in women from young adulthood through middle-aged relative to men. AIM: To evaluate the contribution of MAP to the change in PP and pressure wave contour in men and women from young adulthood to middle age. METHODS: Central pressure waveform was obtained from radial artery applanation tonometry in 312 hypertensive patients between 16 to 49 years (134 women, mean age 35 ± 9 years), 185 of whom were on antihypertensive treatment. RESULTS: Higher MAP levels (≥ 100 mmHg) were significantly associated with higher brachial and central SBP (P < 0.001), PP (P < 0.001), incident wave (P = 0.005), AP (P < 0.001), and PWV (P < 0.001) compared to lower MAP levels. The relationship between MAP and brachial PP (P < 0.001), central PP (P < 0.001), incident wave (P < 0.001), and AP (P < 0.01), but not PWV, strengthens with age. The age-related increase in the contribution of MAP to brachial PP (P < 0.001), central PP (P < 0.001), and incident wave (P < 0.001) was more prominent in women than in men beginning in the fourth decade. In multiple regression analyses, MAP remained a significantly stronger predictor of central PP and incident wave in women than in men, independent of age, heart rate, and antihypertensive treatment. In turn, age remained a significantly stronger predictor of central PP and incident wave in women than in men, independent of MAP, heart rate, and antihypertensive treatment. CONCLUSIONS: Women of reproductive age showed a steeper increase in PP with increasing MAP, despite comparable increases in arterial stiffness in both sexes. The difference was driven by a greater contribution of MAP to the forward component of the pressure wave in women.

An FBG-based optical pressure sensor for the measurement of radial artery pulse pressure.

One of the diagnostic tool for clinical evaluation and disease diagnosis is a pulse waveform analysis. High fidelity radial artery pulse waveforms have been investigated in clinical research to compute central aortic pressure, which has been demonstrated to be predictive of cardiovascular diseases. The radial artery must be inspected from several angles in order to obtain the best pulse waveform for estimate and diagnosis. In this study, we present the design and experimental testing of an optical sensor based on Fiber Bragg Gratings (FBG). A 3D printed device along with the FBG is used to measure the radial artery pulses. The proposed sensor is used for the purpose of quantifying the radial artery pulse waveform across major pulse position point. The suggested optical sensing system can measure the pulse signal with good accuracy. The main characteristic parameters of the pulse can then be retrieved from the processed signal for their use in clinical applications. By conducting experiments under the direction of medical experts, the pulse signals are measured. In order to experimentally validate the sensor, we used it to detect the pulse waveforms at Guan position of the wrist's radial artery in accordance with the diagnostic standards. The findings show that combining optical technologies for physiological monitoring and radial artery pulse waveform monitoring using FBG in clinical applications are highly feasible.

Assessing the Accuracy of Systolic Aortic Pressure Estimation From a Brachial Cuff Alone: A Comparison With Radial Tonometry.

BACKGROUND: A novel method for estimating central systolic aortic pressure (cSAP) has emerged, relying solely on the peripheral mean (MBP) and diastolic (DBP) blood pressures. We aimed to assess the accuracy of this Direct Central Blood Pressure estimation using cuff alone (DCBPcuff = MBP2/DBP) in comparison to the use of a generalized transfer function to derive cSAP from radial tonometry (cSAPtono). METHODS: This retrospective analysis involved the International Database of Central Arterial Properties for Risk Stratification (IDCARS) data (Aparicio et al., Am J Hypertens 2022). The dataset encompassed 10,930 subjects from 13 longitudinal cohort studies worldwide (54.8% women; median age 46.0 years; office hypertension: 40.1%; treated: 61.0%), documenting cSAPtono via SphygmoCor calibrated against brachial systolic BP (SBP) and DBP. Our analysis focused on aggregate group data from 12/13 studies (89% patients) where a full BP dataset was available. A 35% form factor was used to estimate MBP = (DBP + (0.35 × (SBP-DBP)), from which DCBPcuff was derived. The predefined acceptable error for cSAPtono estimation was set at ≤ 5 mm Hg. RESULTS: The cSAPtono values ranged from 103.8-127.0 mm Hg (n = 12). The error between DCBPcuff and cSAPtono was 0.2 ±â€…1.4 mm Hg, with no influence of the mean. Errors ranged from -1.8 to 2.9 mm Hg across studies. No significant difference in errors was observed between BP measurements obtained via oscillometry (n = 9) vs. auscultation (n = 3) (P = 0.50). CONCLUSIONS: Using published aggregate group data and a 35% form factor, DCBPcuff demonstrated remarkable accuracy in estimating cSAPtono, regardless of the BP measurement technique. However, given that individual BP values were unavailable, further documentation is required to establish DCBPcuff's precision.

Blood flow effects of percutaneous peripheral nerve stimulation. A blinded, randomized clinical trial.

BACKGROUND: The vasculature function is mainly regulated by the autonomic nervous system. Importantly, the sensory-motor nervous system also innervates peripheral vessels and has the capacity to modulate vascular tone. Here we investigated the effects of electrical stimulation of a mixed nerve trunk on blood flow in deep arteries and muscle perfusion. Our hypothesis is that stimulation of a mixed nerve can modify blood flow. METHODS: Twenty-nine healthy participants were included into a randomized-crossover and blinded clinical trial. Each subject received a placebo and two percutaneous peripheral nerve stimulation (pPNS) protocols on the median nerve: Pain Threshold continuous Low Frequency (PT-cLF) and Sensory Threshold burst High Frequency (ST-bHF). Blood flow was then assessed bilaterally using Power Doppler Ultrasonography at the main arteries of the arm, and blood perfusion at the forearm muscles. Afterwards, blood flow was quantified using a semi-automatized software, freely shared here. RESULTS: Placebo, consisting in needle insertion, produced an immediate and generalized reduction on peak systolic velocity in all arteries. Although nerve stimulation produced mainly no effects, some significant differences were found: both protocols increased the relative perfusion area of the forearm muscles, the ST-bHF protocol prevented the reduction in peak systolic velocity and TAMEAN of the radial artery produced by the control protocol and PT-cLF produced a TAMEAN reduction of the ulnar artery. CONCLUSIONS: Therefore, the arterial blood flow in the arm is mainly impervious to the electrical stimulation of the median nerve, composed by autonomic and sensory-motor axons, although it produces mild modifications in the forearm muscles perfusion.

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.

[Feasibility study of arterial pressure measurement by snuff pot artery puncture].

OBJECTIVE: To explore the feasibility of snuff pot arterial pressure measurement for patients undergoing routine elective surgery during anesthesia. METHODS: A prospective randomized controlled trial was conducted. Patients undergoing elective surgery admitted to the Handan Hospital of Traditional Chinese Medicine from June 1, 2020 to June 1, 2022 were enrolled. Patients who needed arterial pressure measurement for hemodynamic monitoring were randomly divided into routine radial artery puncture group and snuff pot artery puncture group with their informed consent. The patients in the routine radial artery puncture group were placed a catheter at the styloid process of the patient's radius to measure pressure. In the snuff pot artery puncture group, the snuff pot artery, that was, the radial fossa on the back of the hand (snuff box), was selected to conduct the snuff pot artery puncture and tube placement for pressure measurement. The indwelling time of arterial puncture catheter, arterial blood pressure, and complications of puncture catheterization of patients in the two groups were observed. Multivariate Logistic regression analysis was used to screen the relevant factors that affect the outcome of arterial catheterization. RESULTS: Finally, a total of 252 patients were enrolled, of which 130 patients received routine radial artery puncture and 122 patients received snuff pot artery puncture. There was no statistically significant difference in general information such as gender, age, body mass index (BMI), and surgical type of patients between the two groups. There was no significant difference in the indwelling time of artery puncture catheter between the routine radial artery puncture group and the snuff pot artery puncture group (minutes: 3.4±0.3 vs. 3.6±0.3, P > 0.05). The systolic blood pressure (SBP) and the diastolic blood pressure (DBP) measured in the snuff pot artery puncture group were significantly higher than those in the conventional radial artery puncture group [SBP (mmHg, 1 mmHg ≈ 0.133 kPa): 162.3±14.3 vs. 156.6±12.5, DBP (mmHg): 85.3±12.6 vs. 82.9±11.3, both P < 0.05]. There was no statistically significant difference in the incidence of complications such as arterial spasm, arterial occlusion, and pseudoaneurysm formation between the two groups. However, the incidence of hematoma formation in the snuff pot artery puncture group was significantly lower than that in the conventional radial artery puncture group (2.5% vs. 4.6%, P < 0.05). Based on the difficulty of arterial puncture, multivariate Logistic regression analysis showed that gender [odds ratio (OR) = 0.643, 95% confidence interval (95%CI) was 0.525-0.967], age (OR = 2.481, 95%CI was 1.442-4.268) and BMI (OR = 0.786, 95%CI was 0.570-0.825) were related factors that affect the outcome of arterial catheterization during anesthesia in patients undergoing elective surgery (all P < 0.05). CONCLUSIONS: Catheterization through the snuff pot artery can be a new and feasible alternative to conventional arterial pressure measurement.

Central Versus Peripheral Arterial Pressure Monitoring in Patients Undergoing Cardiac Surgery: A Prospective Observational Study.

OBJECTIVE: The aortic-to-radial arterial pressure gradient is described during and after cardiopulmonary bypass (CPB), and can lead to underestimating arterial blood pressure. The authors hypothesized that central arterial pressure monitoring would be associated with lower norepinephrine requirements than radial arterial pressure monitoring during cardiac surgery. DESIGN: An observational prospective cohort with propensity score analysis. SETTING: At a tertiary academic hospital's operating room and intensive care unit (ICU). PARTICIPANTS: A total of 286 consecutive adult patients undergoing cardiac surgery with CPB (central group: 109; radial group: 177) were enrolled and analyzed. INTERVENTIONS: To explore the hemodynamic effect of the measurement site, the authors divided the cohort into 2 groups according to a femoral/axillary (central group) or radial (radial group) site of arterial pressure monitoring. MEASUREMENT AND MAIN RESULTS: The primary outcome was the intraoperative amount of norepinephrine administered. Secondary outcomes included norepinephrine-free hours and ICU-free hours at postoperative day 2 (POD2). A logistic model with propensity score analysis was built to predict central arterial pressure monitoring use. The authors compared demographic, hemodynamic, and outcomes data before and after adjustment. Central group patients had a higher European System for Cardiac Operative Risk Evaluation. (EuroSCORE) compared to the radial group-7.9 ± 14.0 versus 3.8 ± 7.0, p < 0.001. After adjustment, both groups had similar patient EuroSCORE and arterial blood pressure levels. Intraoperative norepinephrine dose regimens were 0.10 ± 0.10 µg/kg/min in the central group and 0.11 ± 0.11 µg/kg/min in the radial group (p = 0.519). Norepinephrine-free hours at POD2 were 38 ± 17 hours versus 33 ± 19 hours in central and radial groups, respectively (p = 0.034). The ICU-free hours at POD2 were greater in the central group: 18 ± 13 hours versus 13 ± 13 hours, p = 0.008. Adverse events were less frequent in the central group than in the radial group-67% versus 50%, p = 0.007. CONCLUSIONS: No differences in the norepinephrine dose regimen were found according to the arterial measurement site during cardiac surgery. However, norepinephrine use and length of stay in the ICU were shorter, and adverse events were decreased when central arterial pressure monitoring was used.

Flexible Sensors Array Based on Frosted Microstructured Ecoflex Film and TPU Nanofibers for Epidermal Pulse Wave Monitoring.

Recent advances in flexible pressure sensors have fueled increasing attention as promising technologies with which to realize human epidermal pulse wave monitoring for the early diagnosis and prevention of cardiovascular diseases. However, strict requirements of a single sensor on the arterial position make it difficult to meet the practical application scenarios. Herein, based on three single-electrode sensors with small area, a 3 × 1 flexible pressure sensor array was developed to enable measurement of epidermal pulse waves at different local positions of radial artery. The designed single sensor holds an area of 6 × 6 mm2, which mainly consists of frosted microstructured Ecoflex film and thermoplastic polyurethane (TPU) nanofibers. The Ecoflex film was formed by spinning Ecoflex solution onto a sandpaper surface. Micropatterned TPU nanofibers were prepared on a fluorinated ethylene propylene (FEP) film surface using the electrospinning method. The combination of frosted microstructure and nanofibers provides an increase in the contact separation of the tribopair, which is of great benefit for improving sensor performance. Due to this structure design, the single small-area sensor was characterized by pressure sensitivity of 0.14 V/kPa, a response time of 22 ms, a wide frequency band ranging from 1 to 23 Hz, and stability up to 7000 cycles. Given this output performance, the fabricated sensor can detect subtle physiological signals (e.g., respiration, ballistocardiogram, and heartbeat) and body movement. More importantly, the sensor can be utilized in capturing human epidermal pulse waves with rich details, and the consistency of each cycle in the same measurement is as high as 0.9987. The 3 × 1 flexible sensor array is employed to acquire pulse waves at different local positions of the radial artery. In addition, the time domain parameters including pulse wave transmission time (PTT) and pulse wave velocity (PWV) can be obtained successfully, which holds promising potential in pulse-based cardiovascular system status monitoring.

Central arterial pressure and patient-specific model parameter estimation based on radial pressure measurements.

One-dimensional arterial flow simulations are suitable to estimate the aortic pressure from peripheral measurements in a patient-specific arterial network. This study introduces a reduction of the system parameters, and a novel calculation method to estimate the patient-specific set and the aortic curve based on radial applanation tonometry. Peripheral and aortic pressure curves were measured in patients, optimization were carried out. The aortic pressure curves were reproduced well, with an overestimation of the measured Systolic and Mean Blood Pressures on average by 0.6 and 0.5 mmHg respectively, and the Root Mean Square Difference of the curves was 3 mmHg on average.

Feasibility study of arterial pressure measurement by snuff pot artery puncture / 中华危重病急救医学

OBJECTIVE@#To explore the feasibility of snuff pot arterial pressure measurement for patients undergoing routine elective surgery during anesthesia.@*METHODS@#A prospective randomized controlled trial was conducted. Patients undergoing elective surgery admitted to the Handan Hospital of Traditional Chinese Medicine from June 1, 2020 to June 1, 2022 were enrolled. Patients who needed arterial pressure measurement for hemodynamic monitoring were randomly divided into routine radial artery puncture group and snuff pot artery puncture group with their informed consent. The patients in the routine radial artery puncture group were placed a catheter at the styloid process of the patient's radius to measure pressure. In the snuff pot artery puncture group, the snuff pot artery, that was, the radial fossa on the back of the hand (snuff box), was selected to conduct the snuff pot artery puncture and tube placement for pressure measurement. The indwelling time of arterial puncture catheter, arterial blood pressure, and complications of puncture catheterization of patients in the two groups were observed. Multivariate Logistic regression analysis was used to screen the relevant factors that affect the outcome of arterial catheterization.@*RESULTS@#Finally, a total of 252 patients were enrolled, of which 130 patients received routine radial artery puncture and 122 patients received snuff pot artery puncture. There was no statistically significant difference in general information such as gender, age, body mass index (BMI), and surgical type of patients between the two groups. There was no significant difference in the indwelling time of artery puncture catheter between the routine radial artery puncture group and the snuff pot artery puncture group (minutes: 3.4±0.3 vs. 3.6±0.3, P > 0.05). The systolic blood pressure (SBP) and the diastolic blood pressure (DBP) measured in the snuff pot artery puncture group were significantly higher than those in the conventional radial artery puncture group [SBP (mmHg, 1 mmHg ≈ 0.133 kPa): 162.3±14.3 vs. 156.6±12.5, DBP (mmHg): 85.3±12.6 vs. 82.9±11.3, both P < 0.05]. There was no statistically significant difference in the incidence of complications such as arterial spasm, arterial occlusion, and pseudoaneurysm formation between the two groups. However, the incidence of hematoma formation in the snuff pot artery puncture group was significantly lower than that in the conventional radial artery puncture group (2.5% vs. 4.6%, P < 0.05). Based on the difficulty of arterial puncture, multivariate Logistic regression analysis showed that gender [odds ratio (OR) = 0.643, 95% confidence interval (95%CI) was 0.525-0.967], age (OR = 2.481, 95%CI was 1.442-4.268) and BMI (OR = 0.786, 95%CI was 0.570-0.825) were related factors that affect the outcome of arterial catheterization during anesthesia in patients undergoing elective surgery (all P < 0.05).@*CONCLUSIONS@#Catheterization through the snuff pot artery can be a new and feasible alternative to conventional arterial pressure measurement.

[Quantitative analysis of the effect of contact pressure on the reflection characteristics of radial pressure wave].

The radial artery pulse wave contains a wealth of physiological and pathological information about the human body, and non-invasive studies of the radial artery pulse wave can assess arterial vascular elasticity in different age groups.The piezoelectric pulse wave transducers were used to non-invasively acquire radial artery pulse waves at different contact pressures in young and middle-aged and elderly populations. The radial artery waveforms were decomposed using a triangular blood flow model fitting method to obtain forward and reflected waves and calculate reflection parameters. Finally a correlation analysis and regression analysis of the contact pressure Psensor with the reflection parameters was carried out. The results showed that the reflection parameters RM, RI and Rd had a strong negative correlation with Psensor in both types of subjects, and the correlation coefficients and slopes of the regression curves were significantly different between the two types of subjects (P<0.05). Based on the results of this study, excessive contact pressure on the transducer should be avoided when detecting radial artery reflection waves in clinical practice. The results also show that the magnitude of the slope of the regression curve between the reflection parameters and the transducer contact pressure may be a potentially useful indicator for quantifying the elastic properties of the vessel.

Machine-Learning Classification of Pulse Waveform Quality.

Pulse measurements made using wearable devices can aid the monitoring of human physiological condition. Accurate estimation of waveforms is often difficult for nonexperts; motion artifacts may occur during tonometry measurements when the skin-sensor contact pressure is insufficient. An alternative approach is to extract only high-quality pulses for use in index calculations. The present study aimed to determine the effectiveness of using machine-learning analysis in discriminating between high-quality and low-quality pulse waveforms induced by applying different contact pressures. Radial blood pressure waveform (BPW) signals were measured noninvasively in healthy young subjects using a strain-gauge transducer. One-minute-long trains of pulse data were measured when applying the appropriate contact pressure (67.80 ± 1.55 mmHg) and a higher contact pressure (151.80 ± 3.19 mmHg). Eight machine-learning algorithms were employed to evaluate the following 40 harmonic pulse indices: amplitude proportions and their coefficients of variation and phase angles and their standard deviations. Significant differences were noted in BPW indices between applying appropriate and higher skin-surface contact pressures. The present appropriate contact pressure could not only provide a suitable holding force for the wearable device but also helped to maintain the physiological stability of the underlying tissues. Machine-learning analysis provides an effective method for distinguishing between the high-quality and low-quality pulses with excellent discrimination performance (leave-one-subject-out test: random-forest AUC = 0.96). This approach will aid the development of an automatic screening method for waveform quality and thereby improve the noninvasive acquisition reliability. Other possible interfering factors in practical applications can also be systematically studied using a similar procedure.

Does Radial Artery Cannulation Affect the Perfusion of the Dominant Hand in Adult Patients with Normal Modified Allen's Test Undergoing Cardiac Surgeries? Data Derived from the Peripheral Perfusion Index.

OBJECTIVES: This study aimed to evaluate the effect of radial artery cannulation on hand perfusion in patients with normal modified Allen's test undergoing cardiac surgeries using cardiopulmonary bypass (CPB). DESIGN: Prospective follow-up study. SETTING: Single institution, Assiut University Cardiothoracic Hospital. PARTICIPANTS: Forty-nine patients who underwent cardiac surgeries using cardiopulmonary bypass were enrolled. INTERVENTIONS: Cannulation of radial artery in the dominant hand using a 20-gauge catheter. MEASUREMENTS AND MAIN RESULTS: The primary outcomes were the mean peripheral perfusion index (PPI) >60 seconds (mean PPI60) and the thumb temperature, which were measured at different times before and during the surgery. There was a statistically significant difference in the mean PPI60 between both hands (p = 0.033). Before skin incision, the mean PPI60 was significantly higher in the noncannulated hand (p < 0.001). Also, there was a statistically significant difference in the thumb temperature between both hands (p = 0.013). At low core body temperature, the thumb temperature was significantly lower in the noncannulated hand (p = 0.017). CONCLUSIONS: In adult patients undergoing cardiac surgeries using CPB, even with normal modified Allen's test, radial artery cannulation may affect the perfusion of the dominant hand, especially at low arterial blood pressure or low core body temperature. Since the PPI is one of the noninvasive methods used for intraoperative assessment of the peripheral perfusion, the authors recommend the use of the noncannulated hand for this purpose to not misguide this assessment.

Impact of acute dynamic exercise and arterial shear rate modification on radial artery low-flow mediated constriction in young men.

PURPOSE: Leg cycling exercise acutely augments radial artery low-flow mediated constriction (L-FMC). Herein, we sought to determine whether this is associated with exercise-induced changes in arterial shear rate (SR). METHODS: Ten healthy and recreationally active young men (23 ± 2 years) participated in 30 min of incremental leg cycling exercise (50, 100, 150 Watts). Trials were repeated with (Exercise + WC) and without (Exercise) the use of a wrist cuff (75 mmHg) placed distal to the radial artery to increase local retrograde SR while reducing mean and anterograde SR. Radial artery characteristics were measured throughout the trial, and L-FMC and flow mediated dilatation (FMD) were assessed before and acutely (~ 10 min) after leg cycling. RESULTS: Exercise increased radial artery mean and anterograde SR, along with radial artery diameter, velocity, blood flow and conductance (P < 0.05). Exercise + WC attenuated the exercise-induced increase in mean and anterograde SR (P > 0.05) but also increased retrograde SR (P < 0.05). In addition, increases in radial artery blood flow and diameter were reduced during Exercise + WC (Exercise + WC vs. Exercise, P < 0.05). After Exercise, L-FMC was augmented (- 4.4 ± 1.4 vs. - 13.1 ± 1.6%, P < 0.05), compared to no change in L-FMC after Exercise + WC (- 5.2 ± 2.0 vs. - 3.0 ± 1.6%, P > 0.05). In contrast, no change in FMD was observed in either Exercise or Exercise + WC trials (P > 0.05). CONCLUSIONS: These findings indicate that increases in L-FMC following exercise are abolished by the prevention of increases radial artery diameter, mean and anterograde SR, and by elevation of retrograde SR, during exercise in young men.

Noninvasive estimation of aortic pressure waveform based on simplified Kalman filter and dual peripheral artery pressure waveforms.

BACKGROUND AND OBJECTIVE: Aortic pressure (Pa) is important for the diagnosis of cardiovascular disease. However, its direct measurement is invasive, not risk-free, and relatively costly. In this paper, a new simplified Kalman filter (SKF) algorithm is employed for the reconstruction of the Pa waveform using dual peripheral artery pressure waveforms. METHODS: Pa waveforms obtained in a previous study were collected from 25 patients. Simultaneously, radial and femoral pressure waveforms were generated from two simulation experiments, using transfer functions. In the first, the transfer function is a known finite impulse response; and in the second, it is derived from a tube-load model. To analyze the performance of the proposed SKF algorithm, variable amounts of noise were added to the observed output signal, to give a range of signal-to-noise ratios (SNRs). Additionally, central aortic, brachial and femoral pressure waveforms were simultaneously collected from 2 Sprague-Dawley rats and the measured and reconstructed Pa waveforms were compared. RESULTS: The proposed SKF algorithm outperforms canonical correlation analysis (CCA), which is the current state-of-the-art blind system identification method for the non-invasive estimation of central aortic blood pressure. It is also shown that the proposed SKF algorithm is more noise-tolerant than the CCA algorithm over a wide range of SNRs. CONCLUSION: The simulations and animal experiments illustrate that the proposed SKF algorithm is accurate and stable in the face of low SNRs. Improved methods for estimating central blood pressure as a measure of cardiac load adds to their value as a prognostic and diagnostic tool.

Establishment of a Modular Hemodynamic Simulator for Accurate In Vitro Simulation of Physiological and Pathological Pressure Waveforms in Native and Bioartificial Blood Vessels.

PURPOSE: In vitro stimulation of native and bioartificial vessels in perfusable systems simulating natural mechanical environments of the human vasculature represents an emerging approach in cardiovascular research. Promising results have been achieved for applications in both regenerative medicine and etiopathogenetic investigations. However, accurate and reliable simulation of the wide variety of physiological and pathological pressure environments observed in different vessels still remains an unmet challenge. METHODS: We established a modular hemodynamic simulator (MHS) with interchangeable and modifiable components suitable for the perfusion of native porcine-(i.e. the aorta, brachial and radial arteries and the inferior vena cava) and bioartificial fibrin-based vessels with anatomical site specific pressure curves. Additionally, different pathological pressure waveforms associated with cardiovascular diseases including hyper- and hypotension, tachy- and bradycardia, aortic valve stenosis and insufficiency, heart failure, obstructive cardiomyopathy and arterial stiffening were simulated. Pressure curves, cyclic distension and shear stress were measured for each vessel and compared to ideal clinical pressure waveforms. RESULTS: The pressure waveforms obtained in the MHS showed high similarity to the ideal anatomical site specific pressure curves of different vessel types. Moreover, the system facilitated accurate emulation of physiological and different pathological pressure conditions in small diameter fibrin-based vessels. CONCLUSION: The MHS serves as a variable in vitro platform for accurate emulation of physiological and pathological pressure environments in biological probes. Potential applications of the system include bioartificial vessel maturation in cardiovascular tissue engineering approaches as well as etiopathogenetic investigations of various cardiovascular pathologies.

A randomized controlled trial of the effect of postoperative hand exercise training on arteriovenous fistula maturation in patients with chronic kidney disease.

OBJECTIVE: Immature arteriovenous fistula (AVF) is a critical problem in patients with chronic kidney disease (CKD) after creation. Exercise with 30% maximum voluntary contraction (MVC) encourages vascular functions in other populations. It is unknown which exercise type is superior on maturation in the CKD population. We compare effects of isometric (ISM) and isotonic (IST) hand exercise training, both at 30% MVC, on AVF maturation and grip strength in patients with CKD. METHODS: Fifty patients with CKD were randomized into the ISM program or IST program (25 per group). Each group performed exercise program at intensity of 30% MVC every day for 10 weeks. Cephalic vein (CV) and brachial artery diameters, brachial blood flows, and grip strength were measured at weeks 0, 2, 6, and 10 of the program. The number of patients meeting clinical and ultrasound maturation were evaluated at weeks 2, 6, and 10. RESULTS: At weeks 6 and 10 of the programs, the ISM group had greater CV diameters (week 6, 7.1 ± 1.2 vs 6.2 ± 1.0 mm; week 10, 7.1 ± 1.0 vs 6.2 ± 1.1 mm) than the IST group. Compared with the IST group, the ISM group had a higher number of patients meeting ultrasound maturation at weeks 2 (IST/ISM, 8/2), 6 (IST/ISM, 16/8), and 10 (IST/ISM, 21/12), and clinical maturation at week 10 (IST/ISM, 25/18). No adverse events were observed throughout the study. CONCLUSIONS: At 30% MVC, ISM is more effective at promoting increases in CV diameter and maturation than IST. Both exercise types are feasible and safe for patients with CKD after AVF creation.

Quantitative analysis of the effect of contact pressure on the reflection characteristics of radial pressure wave / 生物医学工程学杂志

The radial artery pulse wave contains a wealth of physiological and pathological information about the human body, and non-invasive studies of the radial artery pulse wave can assess arterial vascular elasticity in different age groups.The piezoelectric pulse wave transducers were used to non-invasively acquire radial artery pulse waves at different contact pressures in young and middle-aged and elderly populations. The radial artery waveforms were decomposed using a triangular blood flow model fitting method to obtain forward and reflected waves and calculate reflection parameters. Finally a correlation analysis and regression analysis of the contact pressure Psensor with the reflection parameters was carried out. The results showed that the reflection parameters RM, RI and Rd had a strong negative correlation with Psensor in both types of subjects, and the correlation coefficients and slopes of the regression curves were significantly different between the two types of subjects (P<0.05). Based on the results of this study, excessive contact pressure on the transducer should be avoided when detecting radial artery reflection waves in clinical practice. The results also show that the magnitude of the slope of the regression curve between the reflection parameters and the transducer contact pressure may be a potentially useful indicator for quantifying the elastic properties of the vessel.

Evaluation of radial and ulnar artery blood flow after radial artery decannulation using colour Doppler ultrasound.

BACKGROUND: There is a lack of reports in the literature regarding changes in radial artery blood flow after decannulation. The objective of this study was to investigate changes in radial and ulnar artery blood flow after radial artery decannulation using Doppler ultrasound and to explore the factors that influence radial artery blood flow recovery. METHODS: In current observational study, we used colour Doppler ultrasound to measure the cross-sectional area of the radial (SR) and ulnar artery (SU) and peak systolic velocity of the radial (PSVR) and ulnar artery (PSVU) for both hands at four time points in patients with radial artery cannulation: pre-cannulation (T0), 30 min after decannulation (T1), 24 h after decannulation (T2), and 7 days after decannulation (T3). Repeated measures analysis of variance and logistic regression analysis were performed to analyse the data. RESULTS: Overall, 120 patients were included in the present study. We obtained the following results on the side ipsilateral to the cannulation: compared with T0, the ratio of PSVU/PSVR increased significantly at T1 and T2 (p < 0.01); compared with T1, the ratio of PSVU/PSVR decreased significantly at T2 and T3 (p < 0.01); compared with T2, the ratio of PSVU/PSVR decreased significantly at T3 (p < 0.01). Female sex (OR, 2.76; 95% CI, 1.01-7.57; p = 0.048) and local hematoma (OR 3.04 [1.12-8.25]; p = 0.029) were factors that were significantly associated with the recovery of radial artery blood flow 7 days after decannulation. CONCLUSIONS: There was a compensatory increase in blood flow in the ulnar artery after ipsilateral radial artery decannulation. Female sex and local hematoma formation are factors that may affect the recovery of radial artery blood flow 7 days after catheter removal.

Non-Invasive radial pressure wave analysis may digitally predict women's risks of type 2 diabetes (T2DM): A case and control group study.

BACKGROUND: Women not only have worse diabetes complications, but also have menstrual cycle, pregnancy, and menopause which can make managing diabetes more difficult. The aim of this study was to investigate if radial pressure wave analysis may non-invasively screen for women's risk of type 2 diabetes. METHODS: Spectrum analysis of the radial pressure wave was performed to evaluate the first five harmonic components, C1 to C5. The study consisted of a total of 808 non-pregnant female subjects aged 20-95 over the period of 4 years, and 404 of them were diagnosed with Type 2 diabetes as the case group. RESULT: The first five harmonic components are significantly different in a comparison of the case group and the control group. In the logistic regression analysis, T2DM was found to be associated with C1 (OR = 1.055, CI = 1.037-1.074, p < 0.001), C2 (OR = 1.051, CI = 1.019-1.085, p = 0.002), and C3 (OR = 0.972, CI = 0.950-0.994, p = 0.013). In the Receiver Operating Characteristic curve analysis, the Area Under Curve of using C3 only (70%, p <0.05), weighted C1, C2 and C3, (75%, p < 0.05), and weighted C1, C2 and C3 and Body mass Index (84%, p <0.05) were tested for the accuracy on how well these tests separate the women into the groups with and without the T2DM. CONCLUSION: We thus concluded that pulse spectrum was a non-invasive predictor for women's risk of T2DM.