Measuring Pulse Wave Research Articles

Can we boost screening for peripheral arterial disease?

Abstract Despite the high prevalence of peripheral artery disease (PAD), the diagnosis is often delayed. The delayed diagnosis is due in part to comorbidities which can mask PAD symptoms, and in large part to the low use of conventional diagnostic tools. For PAD diagnostics, the guidelines recommend Doppler-based ankle-brachial index (ABI). The method is time consuming and requires skills. The toe pressure measurement which helps to eliminate the falsely elevated ankle pressures due to mediasclerosis is an almost neglected method for screening. In recent years, automatic, oscillometric four-limb blood pressure monitors have become available that provide data within minutes. We aimed to compare an automatic four limb blood pressure monitor with devices regularly used in our department. Methods Blood pressure was measured in 92 individuals (mean age 65±14 years) using a Doppler device (Hadeco) and a conventional manual sphygmomanometer on all four limbs, as well as an automatic, four-limb pressure monitor (BOSO ABI system-100 PWV) which also measured pulse wave velocity (PWV). Toe pressure was measured with a laser Doppler fluxmeter (Periflux 5000) and a photophlethysmography based toe pressure monitor (Systoe). Patients without known PAD but with at least one abnormal test result underwent a vascular imaging including ultrasound, CT or digital subtraction angiography. Among the 92 individuals there were patients with confirmed PAD, persons at high or very high cardiovascular risk, patients with non-ischaemic cardial diseases and healthy volunteers. Results ABI values of the posterior tibial artery at the corresponding side measured by Doppler and BOSO showed a strong correlation with each other (Pearson's r: 0.8 and 0.7), while the Doppler ABI values of the dorsal pedal artery showed a moderate or weak correlation with BOSO ABI values (r: 0.63 and 0.27). The toe pressure measured by laser Doppler and Systoe did not differ significantly. The ROC curve analysis of the Periflux TBI values supported 0.6 as a cut-off level (91.6% sensitivity, 84% specificity). Of the 52 individuals with high or very high cardiovascular risk, 15 with Doppler, 12 with BOSO and 29 with Periflux could be considered as abnormal, the vascular imaging confirmed PAD in 12 of them. Doppler ABI was abnormal in 96%, BOSO ABI in 69%, BOSO ABI combined with PWV in 92%, Periflux and Systoe toe brachial index (TBI) in 100–100% in 72 limbs with confirmed PAD. In control subjects, ABI, TBI, and PWV were normal; in subjects with high or very high risk, PWV was 58% abnormal, in confirmed PAD, 85%. All patients with abnormal PWV showed atherosclerotic lesions by the vascular imaging. Summary For detection of PAD, the measurement of TBI had the highest sensitivity. PAD screening of a large population may be possible using automatic four limb blood pressure monitors. By combining with additional features (e.g. PWV) the detection ratio can be improved to the level of the Doppler ABI method. Funding Acknowledgement Type of funding sources: None.

Pen‐type pulse wave measurement system for detecting pathological changes in cardiac diseases

In this study, we have developed a new pen-type pulse wave measurement system to evaluate heart failure treatment based on cardiovascular information. In order to acquire minute pathological changes in diseases such as heart failure, the pen-type pulse wave measurement system is equipped with a high-resolution MEMS tactile sensor that achieves a displacement resolution of 0.4 μm and an input resolution of 50μN. This measurement system consists of a small sensor package, a pen-type measurement system, and a glass sensor package to enable physicians to measure the radial artery of men and women of all ages in a minimally invasive, rapid, and precise manner. Realizing this measurement system, simple and precise pulse wave measurement by direct measurement and measurement of pulse wave characteristics for individual differences has been possible.

Self-powered, high sensitivity printed e-tattoo sensor for unobtrusive arterial pulse wave monitoring

Self-powered, highly unobtrusive, low-cost and accurate arterial pulse wave monitoring devices need to be developed to enable cost-efficient monitoring of entire cardiovascular disease risk groups. We report the development of a scalable fabrication process for a highly unobtrusive piezoelectric ultra-thin (t ~ 4,2 µm) e-tattoo arterial pulse wave sensor which utilizes only transparent and biocompatible polymer-based materials. The ferroelectric performance of the ultra-thin P(VDF-TrFE) material layer is optimized through the use of crosslinked PEDOT:PSS electrodes; this results in ~70 % and ~34 % improvements in remanent polarization (Pr) and coercive field (Ec), respectively, when compared to the sensors with pristine PEDOT:PSS electrodes. The ultra-thin form factor enables access to the high bending mode sensitivity of the P(VDF-TrFE) material layer; the maximum sensitivity value achieved in uniaxial and multiaxial bending is ~1700 pC N-1, which is ~50 times higher than the measured normal mode sensitivity. The increased sensitivity is linked to a specific set of direct piezoelectric coefficients using combination of experimental results, statistical analysis and finite element modeling. Finally, the accuracy of the e-tattoo sensor is demonstrated in the non-invasive measurement of radial artery pulse wave by comparing the signal to that obtained with reference device from 7 study subjects.

Palpation localization of radial artery based on 3-dimensional convolutional neural networks

Palpation localization is essential for detecting physiological parameters of the radial artery for pulse diagnosis of Traditional Chinese Medicine (TCM). Detecting signal or applying pressure at the wrong location can seriously affect the measurement of pulse waves and result in misdiagnosis. In this paper, we propose an effective and high accuracy regression model using 3-dimensional convolution neural networks (CNN) processing near-infrared picture sequences to locate radial artery upon radius at the wrist. Comparing with early studies using 2-dimensional models, 3Dcnn introduces temporal features with the third dimension to leverage pulsation rhythms, and had achieved superior performance accuracy as 0.87 within 50 pixels at testing resolution of 1024 × 544. Model visualization shows that the additional dimension of the temporal convolution highlights dynamic changes within image sequences. This study presents the great potential of our constructed model to be applied in real wrist palpation location scenarios to bring the key convenience for pulse diagnosis.

Evaluation of Subclinical Vascular Disease in Diabetic Kidney Disease: A Tool for Personalization of Management of a High-Risk Population.

Background: Patients with diabetic kidney disease (DKD) are at increased risk for cardiovascular events but traditional risk factors do not fully explain this association. Evaluation of subclinical vascular disease might improve risk stratification and management of these patients. The aim of the study was to compare the prevalence of markers of arterial stiffness, carotid atherosclerosis and peripheral arterial disease between patients with DKD and patients with type 2 diabetes mellitus (T2DM) and preserved kidney function. Methods: We prospectively enrolled patients with DKD and age- and gender-matched patients with T2DM but without DKD (estimated glomerular filtration rate < and ≥60 mL/min/1.73 m2, respectively). The presence of arterial stiffness was evaluated by measuring pulse wave velocity (PWV), augmentation index (AIx), AIx adjusted to a heart rate of 75 beats/min (AIx@75) and central systolic, diastolic, pulse and mean blood pressure. The presence of carotid atherosclerosis was evaluated by measuring carotid stenosis, carotid intima-media thickness and maximal plaque thickness. The presence of PAD was evaluated with the measurement of ankle-brachial index (ABI). Results: Forty patients with T2DM were included in the study (mean age 71.6 ± 8.9 years). The prevalence of cardiovascular risk factors was similar in patients with and without DKD. PWV was higher in the former (9.8 ± 5.5 and 6.6 ± 4.4 m/s, respectively; p < 0.05) and carotid stenosis of the left carotid artery was also greater in patients with DKD (36.5 ± 12.6 and 22.1 ± 17.2%, respectively; p < 0.05). Other markers of arterial stiffness and carotid atherosclerosis and ABI did not differ between patients with DKD and those without DKD. Conclusions: Patients with DKD appear to have more pronounced arterial stiffness and carotid atherosclerosis than patients with T2DM and preserved kidney function despite the similar prevalence of traditional cardiovascular risk factors in the two groups. Therefore, evaluating the presence of subclinical vascular disease in these patients could be a useful tool for the personalization of their management.

Bioinspired engineering of gradient and hierarchical architecture into pressure sensors toward high sensitivity within ultra-broad working range

Introducing hierarchical microstructure on the soft material surface can effectively improve the sensitivity of the pressure sensor, however, the high sensitivity generates only at a low pressure range because of the limited compressibility of the microstructure and the incompressibility of the soft matrix. Herein, we first report a facile strategy of bioinspired engineering of hierarchical and gradient structures that can simultaneously improve the sensitivity and broaden the pressure working range. Such hierarchical and gradient structures feature hemispherical arrays and gradient pores that allow the structural deformation from tiny pressure to high pressure, significantly boosting the sensitivity over the full pressure range. By integrating these unique structures on one sensor, the sensor exhibits an ultrahigh sensitivity over a broad pressure regime (i.e., from 102.3 kPa−1 within 0–1.9 kPa to 0.34 kPa−1 within 169.6–400 kPa), a fast response time (35 ms), low limit detection (0.4 Pa) and excellent stability (>5000). The facile strategy and structure design achieve high sensitivity and broad pressure working range for an advanced pressure sensor, endowing it with wide applications, including pressure/weight monitoring, real-time human pulse wave measurements, joint motion detection and human-computer interaction.

Assessing Variability in Vascular Response to Cocoa With Personal Devices: A Series of Double-Blind Randomized Crossover n-of-1 Trials.

Controlled clinical intervention studies have demonstrated that cocoa flavanols (CF) can decrease blood pressure and arterial stiffness in healthy humans, although a large variability in the effect size across trials has been reported. In this study, we evaluated the intra- and inter-individual variability of responses to CF in everyday life using a series of n-of-1 trials in healthy free-living individuals with normal blood pressure carrying personal devices. In total, eleven healthy young humans participated in a repeated crossover randomized controlled double-blind n-of-1 trial. On 8 consecutive days, each volunteer consumed on alternating days 6 CF capsules (862 mg CF) on 4 days and 6 matched placebo capsules (P, 0 mg CF/day) on another 4 days in one of the two randomized sequences (CF-P-CF-P-CF-P-CF-P or P-CF-P-CF-P-CF-P-CF). On each day, the capsules were taken at the same time in the morning with breakfast after baseline measurements. Each subject was provided with an upper arm blood pressure monitor and a finger clip that measures pulse wave velocity (PWV). Measurements of blood pressure, heart rate, and PWV were taken at least hourly over 12 h during the day by the participants. On the first 2 days, measurements were performed under supervision to provide training. The overall mixed model analysis showed that CF significantly decreased 12-h systolic blood pressure and PWV by −1.4 ± 0.3 mmHg and −0.11 ± 0.03 m/s, respectively. Peak effects were observed within the first 3 h (1.5 h SBP: −4.9 ± 2.2 mmHg, PWV: −0.32 ± 0.17 m/s) and again after 8 h post-ingestion. Large inter-individual variation in responses was found [intra-cluster correlation coefficients (ICC): 0.41, 0.41]. When analyzing single individuals’ datasets, there was also considerable between-day variation in individual responses that varied greatly between subjects (ICC: 0–0.30, 0–0.22, 0–0.45). Effect sizes inversely correlated with baseline blood pressure values both between- and within-subjects. The data confirm that cocoa can decrease blood pressure and arterial stiffness in everyday life when elevated within the normal range. The large inter- and intra-individual variation in responses calls for more personalized nutritional intervention strategies.

DIFFERENCES IN METABOLOMICS IN CHILDREN WITH HIGH AND LOW ARTERIAL STIFFNESS. A CASE-CONTROL STUDY

Objective: Studies in children have shown a progressive increase in arterial stiffness by measuring pulse wave velocity (PWV) during childhood, indicating a structural alteration to the arterial wall starting already in early life. Metabolomic studies also show differences in molecules between different disease states in children. The aim of the current study was to identify molecular markers between age and gender-matched children with high and low PWV. Design and method: The study included the screening of 132 children that came for random visits to a tertiary pediatric clinic. 50 children (25 in the highest PWV tertile-Group 1, and 25 in the lowest PWV tertile-Group 2) were chosen for the metabolomic study. The groups were matched for age and gender and underwent an ABPM, and PWV, Aix measurements as well as measurements of central BP. We used t-test to explore differences between the two groups. We used mass spectrometry and constructed a heat map displaying the differences in each metabolite concentration between the two groups. Results: The mean age of the study population was 11.4 ± 2.7 years. Group 1 had significantly higher BMI percentiles than Group 2 (94.7 ± 8.7 and 74.3 ± 27.6, p &lt; 0.001), higher 24-hour SBP (117.3 ± 110.9 ± 9.0mmHg, p = 0.025) and higher 24-hour DBP (70.7 ± 7.3 vs 65.8 ± 5.8mmHg, p = 0.018), higher central SBP (95.1 ± 8.5 vs 89.3 ± 9.7mmHg, p = 0.028), and DBP 69.6 ± 8.6 vs 60.8 ± 11.0mmHg, p = 0.003). Similarly, significant differences occurred also between clinic SBP and DBP. Table 1. shows the metabolites that were significantly upregulated in Group 1. Conclusions: The current metabolomic study found differences in certain metabolites between children in the highest and lowest ends of arterial stiffness. These metabolites involve sphingolipids, sterol lipids, fatty acyls, carboxylic acids, glycerophospholipids as well as other compounds that are not yet fully identified on their properties.

Immune correlates of cardiovascular co-morbidity in HIV infected participants from South India

BackgroundUnderstanding the immune correlates of cardiovascular disease (CVD) risk in HIV infection is an important area of investigation in the current era of aging with HIV infection. Less is known about CVD risk and HIV infection in developing nations where additional risk factors may be playing a role in the CVD development. In this study, we assessed the effects of systemic inflammation, microbial translocation (MT), T cell immune activation (IA), and nadir CD4 counts on cardiac function and arterial stiffness as markers of subclinical atherosclerosis in HIV-infected individuals. MethodsPeople with HIV (PWH) who were ART naïve (n = 102) or virally suppressed on ART (n = 172) were stratified on nadir CD4 counts and compared to HIV-uninfected controls (n = 64). Determination was made of cardiac function via radial pulse wave and carotid intima thickness (C-IMT) measurements. Plasma biomarkers of inflammation and MT by ELISA or multiplex assays, and immune activation (IA) of T cells based HLA-DR and CD38 expression were investigated by flow cytometry. T-test, Mann–Whitney U test, and Spearman correlation were used to analyze study parameters.ResultsReduction in cardiac function with lower cardiac ejection time (p < 0.001), stroke volume (p < 0.001), cardiac output (p = 0.007), higher arterial stiffness (p < 0.05) were identified in ART-naïve participants, compared to PWH on ART (p < 0.05). No significant difference in C-IMT values were noted. Higher inflammatory and MT markers were found in the ART-naïve group compared to treated group who were comparable to uninfected participants, except for having higher TNF-α (p < 0.001) and sCD14 (p < 0.001). Immune activation of CD4 and CD8 T-cells was greater in ART-naïve participants compared to ART-treated and uninfected controls (p < 0.05). Lower nadir CD4 counts, higher inflammation, and higher MT predicted poor cardiac measures in the ART-naïve with nadir CD4 < 200cells/mm3 manifesting the highest arterial stiffness, and lowest cardiac function, whereas ART-treated, even with nadir < 200 cells/mm3 were similar to uninfected in these measures.ConclusionsIn HIV-infected individuals, initiation of ART even at nadir of < 200 cells/mm3 may prevent or reverse cardiovascular disease outcomes that are easily measurable in low income countries.

PPARγ Deacetylation: A Novel Therapeutic Strategy to Mitigate Arterial Stiffness in Obese Male Mice

BackgroundObesity has become a worldwide epidemic and is a major risk factor for the development of cardiovascular disease (CVD). Stiffening in the large arteries, such as the aorta, is a prevalent complication in obesity and frequently precedes hypertension. The mechanism by which obesity contributes to arterial stiffness remains unclear. Peroxisome proliferator‐activated receptor gamma (PPARγ) is a known vasculo‐protective factor. Post‐translational modifications of PPARγ by acetylation can regulate its function. Recently, our group identified that deacetylation of PPARγ enhances vascular endothelial function. We hypothesize that deacetylation of PPARγ protects against obesity‐related arterial stiffness.MethodsA mice model of Western diet (WD) induced obesity and our model of deacetylated PPARγ mimetic knock‐in mice with a double lysine to arginine mutation (Lys268Arg, Lys293Arg, termed 2KR mice) were utilized. Adult male C57BL/6 and 2KR mice were randomized into two dietary protocols. Control groups of C57BL/6 (n=8) and 2KR mice (n=5) received a regular chow diet (5% fat, 48.7% carbohydrates [3.2% sucrose], and 24.1% protein) for 24 weeks. WD groupsof C5 7BL/6 (n=10) and 2KR mice (n= 5) received a WD (40% fat, 43% carbohydrates [34% sucrose], and 17% protein) for 24 weeks. Metabolic profiles were assessed by using single‐mouse‐sized metabolic cages. Aortic stiffness was assessed by measuring pulse wave velocity (PWV) with high‐resolution ultrasound, the gold standard for arterial stiffness. Systolic blood pressure was measured using tail cuff plethysmography.ResultsWD‐induced obesity was confirmed by increased body weight in both WD C57BL/6 mice (36.5g vs. 28.6g controls, p&lt;0.001) and WD 2KR mice groups (44.7g vs. 29.86g controls, p&lt;0.0001). Results obtained from metabolic cages revealed reduction in food, energy and water intake, and urine and fecal output in the WD C57BL/6 and WD 2KR groups as compared to their respective controls. These results indicate that weight gain in WD‐fed mice is not explained by increased energy intake, but rather a reduced metabolic rate. As expected, the WD C57BL/6 group exhibited increased aortic stiffness (5.4 m/s vs. 4.1 m/s controls, p&lt;0.05), which was accompanied by elevated systolic blood pressure (143.8 ± 1.66 vs. 123.5 ± 4.76 mmHg controls, p&lt;0.05). Strikingly, while WD 2KR mice developed obesity, these mice did not exhibit increased aortic stiffness (4.3 m/s vs. 4/4 m/s controls, p=0.89) nor elevated systolic blood pressures (122.4 ± 3.93 mmHg vs. x 115.2 ± 4.15 mmHg controls, p=0.26), indicating that deacetylation of PPARγ protects against aortic stiffness and increases in arterial blood pressure in obesity.ConclusionsOur findings demonstrate that while deacetylation of PPARγ does not prevent the development of WD‐induced obesity, it does protect against arterial stiffness in obesity. These results indicate that PPARγ deacetylation is a potential therapeutic strategy in the prevention of obesity‐related arterial stiffness.

Ablation of Endothelial mTOR is Benign in Young Mice and Reverses Age‐Related Arterial and Metabolic Impairments in Old Mice

Systemic inhibition of mammalian target of rapamycin (mTOR) improves age‐related arterial and metabolic dysfunction. Although the mechanisms and tissues involved remain unknown, endothelial cells (ECs), key regulators of arterial and metabolic function, may be responsible for these effects. In this study, we tested the hypothesis that EC mTOR will mimic systemic mTOR inhibition. To examine this, we studied young (4‐6 mo) and old (22‐24 mo) wildtype (WT) and EC specific tamoxifen inducible mTOR knockout (KO) mice. Arterial function was determined by assessing aortic stiffness by measuring pulse wave velocity (PWV) using Doppler ultrasound in vivo as well as endothelium dependent dilation (EDD) and nitric oxide (NO) bioavailability in isolated arteries using pressure myography. Carotid artery superoxide production was measured using electric paramagnetic resonance. Two weeks after tamoxifen administration (4mg/day, 4 days, oral), we found a 60‐70% reduction in EC mTOR protein (p=0.04). EC mTOR deletion did not alter PWV and EDD in young mice (Fig 1A, 1C), suggesting that EC mTOR is not critical to arterial function in young mice. We next sought to examine whether EC mTOR deletion reverses age‐related arterial dysfunction. Aging resulted in an elevated aortic PWV, indicating higher stiffness, in WT mice and deletion of EC mTOR attenuated aortic stiffening in old mice (p˂0.001, Fig 1A, 1B). Likewise, EDD to acetylcholine (ACh) was lower in mesenteric arteries in old WT mice compared to young mice (p˂0.01, Fig 1C, 1D). However, deletion of EC mTOR markedly improved EDD in old mice (Fig 1D) resulting from an increase in NO bioavailability (31.6 ± 8.6 vs 8.4 ± 2.3; p=0.012). The superoxide scavenger, TEMPOL, increased EDD in old WT and KO mice (Fig 1E), eliminating differences between groups. Furthermore, superoxide production was lower in carotid arteries of KO compared to WT mice (Fig 1F). Collectively, these results suggest that oxidative stress promotes arterial stiffness and impairs EDD with advanced age and ablation of EC selective mTOR reverses this effect. We next examined if this improvement in vascular function resulted in an improvement in metabolic function in the aged mice. To do so, we assessed glucose (2g/kg, ip), insulin (1U/kg, ip), pyruvate (2g/kg, ip) and lipid (3mL/kg, oral) tolerance. Aged KO mice demonstrated greater glucose and lipid tolerance compared to WT littermates (Fig 2A, 2D). Insulin tolerance and glucose‐stimulated insulin secretion did not differ between groups (Fig 2B, 2C), indicating that the improvement in glucose tolerance was independent of peripheral insulin sensitivity and pancreatic beta cell function. EC mTOR deletion improved pyruvate tolerance and reduced hepatic expression of gluconeogenic genes (Fig 2E, 2F), suggesting that attenuated hepatic gluconeogenesis may underlie the enhanced glucose tolerance in the KO mice. Taken together, our findings demonstrate that although without effect on vascular function in young mice, EC specific deletion of mTOR provides beneficial effects on arterial function via reductions in oxidative stress and ameliorates metabolic dysfunction in old mice.

Extraction and Evaluation of Discriminative Indexes of the Wearing Condition for High-Precision Blood Pressure Pulse Wave Measurement.

In this paper, we report a new discriminant index for evaluating the wearing condition of a blood pressure pulse wave measurement device with small variability. The prototype device consists of MEMS 3-axis force sensors, a 3-axis push-in adjustment mechanism, a fixed jig, and a signal processing board. The arterial tonometry method is used by this device to measure blood pressure pulse waves. However, to accurately measure the blood pressure pulse wave, the device must be appropriately worn. The evaluation of the wearing condition using the amplitude of the blood pressure pulse wave was complicated by the wearing process due to the large variability. Therefore, we propose the ratio of the blood pressure pulse wave component to the noise component as an index that can evaluate the wear condition of the device. The correlation coefficient between the discriminant index and the amplitude of the blood pressure pulse wave had a correlation coefficient of 0.879. Furthermore, the discriminant index reduced the coefficient of variation by 12.8%. Therefore, it was suggested that the discriminant index is an index that can evaluate the pressing amount, one of the wearing conditions of the blood pressure pulse wave measurement device with a small influence of variation.

Frequency Characteristics of Pulse Wave Sensor Using MEMS Piezoresistive Cantilever Element.

Wearable sensor devices with minimal discomfort to the wearer have been widely developed to realize continuous measurements of vital signs (body temperature, blood pressure, respiration rate, and pulse wave) in many applications across various fields, such as healthcare and sports. Among them, microelectromechanical systems (MEMS)-based differential pressure sensors have garnered attention as a tool for measuring pulse waves with weak skin tightening. Using a MEMS-based piezoresistive cantilever with an air chamber as the pressure change sensor enables highly sensitive pulse-wave measurements to be achieved. Furthermore, the initial static pressure when attaching the sensor to the skin is physically excluded because of air leakage around the cantilever, which serves as a high-pass filter. However, if the frequency characteristics of this mechanical high-pass filter are not appropriately designed, then the essential information of the pulse-wave measurement may not be reflected. In this study, the frequency characteristics of a sensor structure is derived theoretically based on the air leakage rate and chamber size. Subsequently, a pulse wave sensor with a MEMS piezoresistive cantilever element, two air chambers, and a skin-contacted membrane is designed and fabricated. The developed sensor is 30 mm in diameter and 8 mm in thickness and realizes high-pass filter characteristics of 0.7 Hz. Finally, pulse wave measurement at the neck of a participant is demonstrated using the developed sensor. It is confirmed that the measured pulse wave contains signals in the designed frequency band.

IDF21-0021 Risk evaluation of retinopathy in patients with type 2 diabetes using harmonic features of the radial pulse wave

Background: In developing and developed countries, diabetic retinopathy is one of the leading causes of blindness in the 20-70 age group, and a high percentage of diabetic patients will eventually have retinopathy. Past research results indicate that microalbuminuria and renal function loss can be used as predictors of retinopathy in patients with type 2 diabetes, but the conclusions are still inconsistent. Harmonic analysis of the radial pulse wave can be used as an evaluation method for large and small vascular diseases, and may be used in the prediction of diabetic retinopathy. Aim: The purposes of this study was to examine if characteristics of the radial pulse spectrum could be an evaluation method of retinopathy in patients with type 2 diabetes. Method: The study consists of 915 asymptomatic patients with type 2 diabetes who had no history of retinopathy through the Division of Endocrinology and Metabolism of Zhongxiao Branch of Taipei City Hospital (IRB: ISRCTN14306167). We conducted the pulse wave measurement at baseline and divided the enrolled patients into quartile groups based on the first harmonic amplitude of the radial pulse (C1) value (>0.981, 0.981 to 0.908, 0.908 to 0.847, and < 0.847). Participating patients received over 3 years of follow-up. The outcome was the retinopathy which was diagnosed by an ophthalmologist. Cox proportional hazards model were used. Results: Kaplan-Meier curves of primary composite endpoints showed that the decreasing quartile level of C1 resulted in the increasing incidence of diabetic retinopathy. The incidence of diabetic retinopathy in the C1<0.847 group was 3-4 times lower than that in the other groups. Clinical events were analyzed using Cox proportional hazards model to compare hazard ratios of clinical events among quartile groups. The Cox regression model also demonstrated that after adjusting for age, gender, smoking, C1 was still an independent predictor of diabetic retinopathy (HR, 0.058; 95% CI 0.005-0.682, P=0.024). Discussion: This report suggested that C1 provides independent predictive value for risk assessment of diabetic retinopathy in asymptomatic patients with type 2 diabetes.

Wearable Pressure Sensors for Pulse Wave Monitoring.

Cardiovascular diseases remain the leading cause of death worldwide. The rapid development of flexible sensing technologies and wearable pressure sensors have attracted keen research interest and have been widely used for long-term and real-time cardiovascular status monitoring. Owing to compelling characteristics, including light weight, wearing comfort, and high sensitivity to pulse pressures, physiological pulse waveforms can be precisely and continuously monitored by flexible pressure sensors for wearable health monitoring. Herein, an overview of wearable pressure sensors for human pulse wave monitoring is presented, with a focus on the transduction mechanism, microengineering structures, and related applications in pulse wave monitoring and cardiovascular condition assessment. The conceptualizations and methods for the acquisition of physiological and pathological information related to the cardiovascular system are outlined. The biomechanics of arterial pulse waves and the working mechanism of various wearable pressure sensors, including triboelectric, piezoelectric, magnetoelastic, piezoresistive, capacitive, and optical sensors, are also subject to systematic debate. Exemple applications of pulse wave measurement based on microengineering structured devices are then summarized. Finally, a discussion of the opportunities and challenges that wearable pressure sensors face, as well as their potential as a wearable intelligent system for personalized healthcare is given in conclusion.

Estimation of central pulse wave velocity from radial pulse wave analysis

Background and Objective: Arterial stiffness, commonly assessed by carotid-femoral pulse wave velocity (cfPWV), is an independent biomarker for cardiovascular disease. The measurement of cfPWV, however, has been considered impractical for routine clinical application. Pulse wave analysis using a single pulse wave measurement in the radial artery is a convenient alternative. This study aims to identify pulse wave features for a more accurate estimation of cfPWV from a single radial pulse wave measurement.Methods: From a dataset of 140 subjects, cfPWV was measured and the radial pulse waveform was recorded for 30 s twice in succession. Features were extracted from the waveforms in the time and frequency domains, as well as by wave separation analysis. All-possible regressions with bootstrapping, McHenry's select algorithm, and support vector regression were applied to compute models for cfPWV estimation. Results: The correlation coefficients between the measured and estimated cfPWV were r = 0.81, r = 0.81, and r = 0.8 for all-possible regressions, McHenry's select algorithm, and support vector regression, respectively. The features selected by all-possible regressions are physiologically interpretable. In particular, the amplitude ratio of the diastolic peak to the notch of the radial pulse waveform (Rn,dr,P) is shown to be correlated with cfPWV. This correlation was further evaluated and found to be independent of wave reflections using a dataset (n = 3,325) of simulated pulse waves.Conclusions: The proposed method may serve as a convenient surrogate for the measurement of cfPWV. Rn,dr,P is associated with aortic pulse wave velocity and this association may not be dependent on wave reflection.

2Pb2-1 Local measurement of ultrasonic pulse wave by SPR type sensors

2Pb2-1 Local measurement of ultrasonic pulse wave by SPR type sensors

Central Noninvasive Hemodynamics in Combined Spinal Epidural Anesthesia with Expansion of the Epidural Space in Obese Patients

The objective: to substantiate the safety of using combined spinal epidural anesthesia with expansion of the epidural space in hernioplasty in obese patients.Subjects and Methods. Hemodynamic parameters were studied in 100 obese patients who underwent elective hernioplasty of the anterior abdominal wall using the neuroaxial block of two types ‒ combined spinal epidural anesthesia with epidural volume extension (CSEA with EVE) and spinal anesthesia (SA). The patients were randomly divided into two groups: Group 1 (n = 60) ‒ patients operated under combined spinal epidural anesthesia with the epidural volume extension, Group 2 (n = 40) ‒ patients operated under spinal anesthesia. The assessment of changes in main parameters of central hemodynamics, stroke volume (SV), cardiac output (CO), and cardiac index (CI) was performed using the Estimated Continuous Cardiac Output technology based on the measurement of pulse wave transit time.Results. It was revealed that in Group 1 patients, the listed parameters fluctuated slightly during the entire follow-up period. The average values were: SV 76.4 ± 0.37 ml, CO 5.8 ± 0.04 l/min, CI 3.56 ± 0.03 l/min/m2. In patients of Group 2, there was an increase in SV by 35.5%, CO by 24.2%, and CI by 23.6% at minutes 2-4 of the regional blockade.Conclusions. The most obvious fluctuations in hemodynamic parameters are observed in the group of patients who underwent spinal anesthesia using relatively high doses of local anesthetic. When using CSEA with EVE with low doses of bupivacaine, stable hemodynamic parameters are noted with a constant level of the neuroaxial block.

Discrimination of vascular aging using the arterial pulse spectrum and machine-learning analysis.

Aging contributes to the progression of vascular dysfunction and is a major nonreversible risk factor for cardiovascular disease. The aim of this study was to determine the effectiveness of using arterial pulse-wave measurements, frequency-domain pulse analysis, and machine-learning analysis in distinguishing vascular aging. Radial pulse signals were measured noninvasively for 3 min in 280 subjects aged 40-80 years. The cardio-ankle vascular index (CAVI) was used to evaluate the arterial stiffness of the subjects. Forty frequency-domain pulse indices were used as features, comprising amplitude proportion (Cn), coefficient of variation of Cn, phase angle (Pn), and standard deviation of Pn (n = 1-10). Multilayer perceptron and random forest with supervised learning were used to classify the data. The detected differences were more prominent in the subjects aged 40-50 years. Several indices differed significantly between the non-vascular-aging group (aged 40-50 years; CAVI <9) and the vascular-aging group (aged 70-80 years). Fivefold cross-validation revealed an excellent ability to discriminate the two groups (the accuracy was >80%, and the AUC was >0.8). For subjects aged 50-60 and 60-70 years, the detection accuracies of the two trained algorithms were around 80%, with AUCs of >0.73 for both, which indicated acceptable discrimination. The present method of frequency-domain analysis may improve the index reliability for further machine-learning analyses of the pulse waveform. The present noninvasive and objective methodology may be meaningful for developing a wearable-device system to reduce the threat of vascular dysfunction induced by vascular aging.

Electrical Impedance Plethysmography Versus Tonometry To Measure the Pulse Wave Velocity in Peripheral Arteries in Young Healthy Volunteers: a Pilot Study.

The leading cause of health loss and deaths worldwide are cardiovascular diseases. A predictor of cardiovascular diseases and events is the arterial stiffness. The pulse wave velocity (PWV) can be used to estimate arterial stiffness non-invasively. The tonometer is considered as the gold standard for measuring PWV. This approach requires manual probe fixation above the artery and depends on the skills of the operator. Electrical impedance plethysmography (IPG) is an interesting alternative using skin surface sensing electrodes, that is miniaturizable, cost-effective and allows measurement of deeper arteries. The aim of this pilot study was to explore if IPG can be a suitable technique to measure pulse wave velocity in legs as an alternative for the tonometer technique. The PWV was estimated by differences in the ECG-gated pulse arrival times (PAT) at the a. femoralis, a. popliteal, a. tibialis dorsalis and a. dorsalis pedis in nine healthy young adults using IPG and the SphygmoCor tonometer as a reference. The estimated PWV results from bioimpedance and the tonometer were fairly in agreement, and the beat-to-beat variability in PAT was similar. This pilot study indicates that the use of IPG may be a good alternative for estimating PWV in the legs.