Clinical measurement of arterial stiffness obtained from noninvasive pressure waveforms

Skin Adhesives with Controlled Adhesion by Polymer Chain Mobility

Wearable devices have attracted a lot of attention because of their importance in the biomedical and electronic fields. However, as one of the important fixing materials, skin adhesives with controlled adhesion are often ignored. Although remarkable progress has been achieved in revealing the natural adhesion mechanism and biomimetic materials to complex solid surfaces, it remains a great challenge to explore nonirritant, controlled skin adhesives without surface structure. Herein, we present skin-adhesive patches of polydimethylsiloxanes (SAPs) with controlled adhesion by simply modulating polymer chain mobility at the molecular level. The controlled adhesion of SAPs strongly depends on the proportion of polymer chains with different mobility exposed to the solid surface, including free chains, dangling chains, and cross-linking chains. As a proof of concept, we demonstrate that the SAP can act as a skin-friendly fix to monitor the human pulse by integrating with the poly(vinylidene fluoride-trifluorethylene)/reduced graphene oxide (P(VDF-TrFE)@rGO) nanofiber sensor. This study provides a clue to design durable and skin-friendly adhesives with controlled adhesion for wearable devices.

Molecule-Graphene Hybrid Materials with Tunable Mechanoresponse: Highly Sensitive Pressure Sensors for Health Monitoring

The development of pressure sensors is crucial for the implementation of electronic skins and for health monitoring integrated into novel wearable devices. Tremendous effort is devoted toward improving their sensitivity, e.g., by employing microstructured electrodes or active materials through cumbersome processes. Here, a radically new type of piezoresistive pressure sensor based on a millefeuille-like architecture of reduced graphene oxide (rGO) intercalated by covalently tethered molecular pillars holding on-demand mechanical properties are fabricated. By applying a tiny pressure to the multilayer structure, the electron tunnelling ruling the charge transport between successive rGO sheets yields a colossal decrease in the material's electrical resistance. Significantly, the intrinsic rigidity of the molecular pillars employed enables the fine-tuning of the sensor's sensitivity, reaching sensitivities as high as 0.82 kPa^-1 in the low pressure region (0-0.6 kPa), with short response times (≈24 ms) and detection limit (7 Pa). The pressure sensors enable efficient heartbeat monitoring and can be easily transformed into a matrix capable of providing a 3D map of the pressure exerted by different objects.

Central aortic pressure improves prediction of cardiovascular events compared to peripheral blood pressure in short-term follow-up of a hypertensive cohort

Objective: The aim of this study was to assess indices of a comprehensive panel of central aortic pressure and arterial stiffness for prediction of cardiovascular events in a hypertensive cohort.Methods: Noninvasive measurements of central aortic blood pressure, brachial pressure, wave reflection augmentation index, pressure amplification, pulse wave velocity (PWV) and carotid intima-media thickness (IMT) were obtained in 675 hypertensive patients (age 61 ± 9 years, 425 males) for a mean follow-up period 25 ± 4 months. The primary endpoints were defined as cardiovascular disease (CVD) events or death from CVD.Results: After adjusting for confounding factors, central systolic (cSBP) and pulse pressure (cPP) showed higher hazard ratios (HR/10 mmHg) for cardiovascular events (CV) compared to peripheral pressure indices (pSBP, pPP) at age >60 years (cSBP: HR = 1.18, pSBP: HR = 1.17, p = 0.034; cPP: HR = 1.28, pPP: HR = 1.2, p = 0.019). Each SD increase in IMT and in central augmented pressure (cAP) entailed a 1.4 times higher risk of increased total events in elderly patients (age >60 years). For males, each SD increase in cAP was associated with 1.36 times higher risk of increased total events. For females, each SD increase in cAIx and cAP was associated with 0.4 and 0.5 times lower risk of increased total and major CV, respectively. This sex difference is most likely due to lack of age-related increase of cAIx in females after age >60 years compared to males.Conclusions: Central pressure improved prediction of CVD compared to peripheral pressure during a relatively short-term follow up of approximately 2 years at age >60 years.

The Effect of Lower Body Positive Pressure on Left Ventricular Ejection Duration in Patients With Heart Failure

Lower body positive pressure (LBPP) treadmill activity might benefit patients with heart failure (HF). To determine the short-term effects of LBPP on left ventricular (LV) function in HF patients, LV ejection duration (ED), a measure of systolic function was prospectively assessed in 30 men with stable HF with LV ejection fraction ≤ 40% and 50 healthy men (N). Baseline measurements (100% body weight), including blood pressure (BP), heart rate (HR) and LVED, obtained via radial artery applanation tonometry, were recorded after 2 minutes of standing on weight support treadmill and after LBPP achieving reductions of 25%, 50%, and 75% of body weight in random sequence. Baseline, HR, and LVED (251 ± 5 vs 264 ± 4 ms; P = .035) were lower in the HF group. The LBPP lowered HR more (14% vs 6%, P = .009) and increased LVED more (15% ± 7% vs 10% ± 6%; P = .004) in N versus HF. Neither group had changes (Δ) in BP. On generalized linear regression, the 2 groups showed different responses (P < .001). Multivariate analysis showed %ΔHR (P < .001) and HF (P = .026) were predictive of ΔED (r² = 0.44; P < .001). In conclusion, progressive LBPP increases LVED in a step-wise manner in N and HF patients independent of HR lowering. The ΔLVED is less marked in patients with HF.

Transcatheter aortic valve replacement (TAVR) leads to an increase in the subendocardial viability ratio assessed by pulse wave analysis

Background

Pulse wave analysis (PWA) is a useful tool for non-invasive assessment of central cardiac measures as subendocardial perfusion (Subendocardial Viability Ratio, SEVR) or contractility (dP/dt_max). The immediate influence of transcatheter aortic valve replacement (TAVR) on these indices has not been investigated yet.

Methods

We prospectively enrolled 40 patients presenting with severe aortic stenosis receiving TAVR. Central pressure curves were derived from radial and carotid sites using PWA up to 2 days before and 7 days after TAVR. Parameters were compared between peripheral measurement sites. Changes in SEVR, dP/dt_max and in indices of vascular stiffness were assessed. Additionally, association of these variables with clinical outcome was evaluated during a 12-month follow-up.

Results

Central waveform parameters were comparable between measurement sites. SEVR, but not dP/dt_max, augmentation Index (AIx) or augmentation pressure height (AGPH) correlated significantly with disease severity reflected by peak transvalvular velocity and mean transvalvular pressure gradient over the aortic valve (V_max, ΔPm) [r = -0.372,p = 0.029 for V_max and r = -0.371,p = 0.021 for ΔPm]. V_max decreased from 4.5m/s (IQR:4.1–5.0) to 2.2m/s (IQR:1.9–2.7), (p<0.001). This resulted in a significant increase in SEVR [135.3%(IQR:115.5–150.8) vs. 140.3%(IQR:123.0–172.5),p = 0.039] and dP/dt_max [666mmHg(IQR:489–891) vs. 927mmHg(IQR:693–1092),p<0.001], and a reduction in AIx [154.8%(IQR:138.3–171.0) vs. 133.5%(IQR:128.3–151.8),p<0.001] and AGPH [34.1%(IQR:26.8–39.0) vs. 25.0%(IQR 21.8–33.7),p = 0.002], confirming the beneficial effects of replacing the stenotic valve. No association of these parameters could be revealed with outcome.

Conclusions

PWA is suitable for assessing coronary microcirculation and contractility mirrored by SEVR and _maxdP/dt in the setting of aortic stenosis. PWA parameters attributed to vascular properties should be interpreted with caution.

Maternal arterial stiffness and fetal cardiovascular physiology in diabetic pregnancy

OBJECTIVES

In mothers with pregestational or gestational diabetes, abnormal arterial stiffness (stiffer arteries) has been reported. The impact of abnormal maternal arterial stiffness on placental and fetal cardiovascular physiology is unknown. The purpose of this study was to determine the impact of maternal diabetes on maternal arterial stiffness and the association with fetal cardiovascular physiology as measured by fetal echocardiography.

METHODS

Between December 2013 and January 2017 a prospective study was conducted on diabetic (but otherwise healthy) and non-diabetic, healthy pregnant mothers aged 18-40 years at 20-28 weeks' gestation who had a normal fetal cardiac echocardiogram and obstetric ultrasound. Clinical data were collected by means of a patient questionnaire and measurement of blood pressure, height, weight, arterial augmentation index (AIx) and placental and fetal cardiovascular parameters were collected by fetal echocardiography. Descriptive statistics were calculated. Comparisons were made using parametric and non-parametric tests between controls and diabetic mothers.

RESULTS

Twenty-three healthy pregnant controls and 43 diabetic pregnant women (22 with pregestational and 21 with gestational diabetes) were included in the study. Maternal AIx was higher in those with diabetes than in healthy controls (12.4 ± 10.6% vs 4.6 ± 7.9%; P = 0.003). Fetal aortic valve (AoV) velocity time integral (VTI) was higher in fetuses whose mothers had diabetes than in those with non-diabetic mothers (7.7 ± 1.9 cm vs 6.3 ± 3.0 cm; P = 0.022). Left ventricular (LV) myocardial performance index (MPI) was lower in diabetic pregnancies than in controls (0.40 ± 0.09 vs 0.46 ± 0.11; P = 0.021). Umbilical artery (UA) resistance index (RI) was lower in diabetic pregnancies with glycated hemoglobin (HbA1c) levels ≥ 6.5% than in those with HbA1c levels < 6.5% (0.69 ± 0.06, n = 15 vs 0.76 ± 0.08, n = 21; P = 0.009) but not at higher HbA1C cut-offs. No correlation between AIx and AoV-VTI, LV-MPI or UA-RI was found.

CONCLUSIONS

Arterial stiffness is higher in pregnant women with diabetes than in controls. Fetuses of diabetic mothers show altered cardiovascular parameters, with higher AoV-VTI and lower LV-MPI, which are markers of myocardial function. Placental function assessed by UA-RI was normal despite differences between groups. Arterial stiffness did not correlate with placental or fetal cardiovascular variables. Instead, the findings are likely to represent a shared response to the environment of abnormal glucose metabolism. The clinical significance of these findings is yet to be determined. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

The First Harmonic of Radial Pulse as an Early Predictor of Silent Coronary Artery Disease and Adverse Cardiac Events in Type 2 Diabetic Patients

Background

It has been reported that harmonics of radial pulse is related to coronary artery disease (CAD) in patients with type 2 diabetes mellitus (T2DM). It is still unclear whether or not the first harmonics of the radial pulse spectrum is an early independent predictor of silent coronary artery disease (SCAD) and adverse cardiac events (ACE).

Objectives

To measure the risk of SCAD in patients with T2DM and also to survey whether or not an increment of the first harmonic (C1) of the radial pulse increases ACE.

Methods

1968 asymptomatic individuals with T2DM underwent radial pulse wave measurement. First harmonic of the radial pressure wave, C1, was calculated. Next, the new occurrence of ACE and the new symptoms and signs of coronary artery disease were recorded. The follow-up period lasted for 14.7 ± 3.5 months.

Results

Out of 1968 asymptomatic individuals with T2DM, ACE was detected in 239 (12%) of them during the follow-up period. The logrank test demonstrated that the cumulative incidence of ACE in patients with C1 above 0.96 was greater than that in those patients with C1 below 0.89 (P < 0.01). By comparing the data of patients with C1 smaller than the first quartile and the patients with C1 greater than the third quartile, the hazard ratios were listed as follows: ACE (hazard ratio, 2.29; 95% CI, 1.55–3.37), heart failure (hazard ratio, 2.22; 95% CI, 1.21–4.09), myocardial infarction (hazard ratio, 2.44; 95% CI, 1.51–3.93), left ventricular dysfunction (Hazard ratio, 2.01; 95% CI, 0.86–4.70), and new symptoms and signs for coronary artery disease (hazard ratio, 2.03; 95% CI, 1.45–2.84). As C1 increased, the risk for composite ACE (P < 0.001 for trend) and for coronary disease (P < 0.001 for trend) also increased. The hazard ratio and trend for cardiovascular-cause mortality were not significant.

Conclusions

This study showed that C1 of the radial pulse wave is correlated with cardiovascular events. Survival analysis showed that C1 value is an independent predictor of ACE and SCAD in asymptomatic patients with T2DM. Thus, screening for the first harmonic of the radial pulse may improve the risk stratification of cardiac events and SCAD in asymptomatic patients although they had no history of coronary artery disease or angina-related symptom.

Flexible and Highly Sensitive Resistive Pressure Sensor Based on Carbonized Crepe Paper with Corrugated Structure

Recently, cellulose paper based materials have emerged for applications in wearable "green" electronics due to their earth abundance, low cost, light weight, flexibility, and sustainability. Herein, for the first time, we develop an almost all cellulose paper based pressure sensor through a facile, cost-effective, scalable, and environment-friendly approach. The screen-printed interdigital electrodes on the flat printing paper and the carbonized crepe paper (CCP) with good conductivity are integrated into a flexible pressure sensor as substrates and active materials, respectively. The porous and corrugated structure of the CCP endows the pressure sensor with high sensitivity (2.56-5.67 kPa^-1 in the range of 0-2.53 kPa), wide workable pressure range (0-20 kPa), fast response time (<30 ms), low detection limit (∼0.9 Pa), and good durability (>3000 cycles). Additionally, we demonstrate the practical applications of the CCP pressure sensor in detection of finger touching, wrist pulse, respiration, phonation, acoustic vibration, etc., and real-time monitoring of spatial pressure distribution. The proposed CCP pressure sensor has great potentials in various applications as wearable electronics. Moreover, the subtle fabrication of the desired materials based on commercially available products provides new insights into the development of green electronics.

Nutrition Questionnaires plus (NQplus) study, a prospective study on dietary determinants and cardiometabolic health in Dutch adults

PURPOSE

During the past decades, the number of people with cardiometabolic conditions substantially increased. To identify dietary factors that may be responsible for this increase in cardiometabolic conditions, the Nutrition Questionnaires plus (NQplus) study was initiated. The aim of this article is to provide an overview of the study design and baseline characteristics of the NQplus population.

PARTICIPANTS

The NQplus study is a prospective cohort study among 2048 Dutch men (52%) and women (48%) aged 20-70 years.

FINDINGS TO DATE

At baseline, we assessed habitual dietary intake, conducted physical examinations (measuring, eg, anthropometrics, body composition, blood pressure, pulse wave velocity, advanced glycation end product accumulation, cognitive performance), collected blood and 24-hour urine and administered a variety of validated demographic, health and lifestyle questionnaires. Participants had a mean BMI of 26.0±4.2 kg/m², were mostly highly educated (63%), married or having a registered partnership (72%) and having a paid job (72%). Estimated daily energy and macronutrient intakes (mean±SD) were 8581±2531 kJ, 15±2energy (en%) of protein, 43±6 en% of carbohydrates, 36±5 en% of fat and 11±13 g of alcohol. Mean systolic blood pressure was 126±15 mm Hg, total cholesterol 5.3±1.1 mmol/L and haemoglobin A1c 36±5 mmol/mol. A total of 24% of the participants reported to be diagnosed with hypertension, 18% with hypercholesterolaemia and 4% with diabetes mellitus. All measurements were repeated after 1 and 2 years of follow-up.

FUTURE PLANS

We endeavour to continue measurements on the long-term. Moreover, dietary assessment methods used in the NQplus study will be extensively validated, that is, Food Frequency Questionnaires, 24-hour recalls and urinary and blood biomarkers of exposure. As such, the NQplus study will provide a unique opportunity to study many cross-sectional and longitudinal associations between diet and cardiometabolic health outcomes using the best dietary assessment methods available so far.

Wood Derived Composites for High Sensitivity and Wide Linear-Range Pressure Sensing

Natural wood possesses a unique 3D microstructure containing hierarchical interconnected channels along its growth direction. This study reports a facile processing strategy to utilize such structure to fabricate carbon/silicone composite based flexible pressure sensors. The unique contribution of the multichannel structure on the sensor performance is analyzed by comparing the pressure response of the vertically cut and horizontally cut composite structures. The results show that the horizontally cut composite based sensors exhibit much higher sensitivity (10.74 kPa-1 ) and wider linear region (100 kPa, R2 = 99%), due to their rough surface and largely deformable microstructure. Besides, the sensors also show little hysteresis and good cycle stability. The overall outstanding sensing properties of the sensors allow for accurate continuous measurement of human pulse and respiration, benefiting the real-time health signal monitoring and disease diagnoses.

Multiscale Hierarchical Design of a Flexible Piezoresistive Pressure Sensor with High Sensitivity and Wide Linearity Range

Flexible piezoresistive pressure sensors have been attracting wide attention for applications in health monitoring and human-machine interfaces because of their simple device structure and easy-readout signals. For practical applications, flexible pressure sensors with both high sensitivity and wide linearity range are highly desirable. Herein, a simple and low-cost method for the fabrication of a flexible piezoresistive pressure sensor with a hierarchical structure over large areas is presented. The piezoresistive pressure sensor consists of arrays of microscale papillae with nanoscale roughness produced by replicating the lotus leaf's surface and spray-coating of graphene ink. Finite element analysis (FEA) shows that the hierarchical structure governs the deformation behavior and pressure distribution at the contact interface, leading to a quick and steady increase in contact area with loads. As a result, the piezoresistive pressure sensor demonstrates a high sensitivity of 1.2 kPa^-1 and a wide linearity range from 0 to 25 kPa. The flexible pressure sensor is applied for sensitive monitoring of small vibrations, including wrist pulse and acoustic waves. Moreover, a piezoresistive pressure sensor array is fabricated for mapping the spatial distribution of pressure. These results highlight the potential applications of the flexible piezoresistive pressure sensor for health monitoring and electronic skin.

Laminated Object Manufacturing of 3D-Printed Laser-Induced Graphene Foams

Laser-induced graphene (LIG), a graphene structure synthesized by a one-step process through laser treatment of commercial polyimide (PI) film in an ambient atmosphere, has been shown to be a versatile material in applications ranging from energy storage to water treatment. However, the process as developed produces only a 2D product on the PI substrate. Here, a 3D LIG foam printing process is developed on the basis of laminated object manufacturing, a widely used additive-manufacturing technique. A subtractive laser-milling process to yield further refinements to the 3D structures is also developed and shown here. By combining both techniques, various 3D graphene objects are printed. The LIG foams show good electrical conductivity and mechanical strength, as well as viability in various energy storage and flexible electronic sensor applications.

Arterial Stiffness: A Prognostic Marker in Coronary Heart Disease. Available Methods and Clinical Application

Multiple biomarkers may predict short and long-term prognosis in patients with coronary heart disease, but their impact is limited when used in addition to established risk factors such blood pressure, cholesterol levels, diabetes mellitus, smoking as well as age and sex. Arteries are an integral part of the cardiovascular (CV) system. Arterial stiffness has been shown to be a predictor of cardiovascular events and mortality independent of traditional risk factors. It has also been shown that increased arterial stiffness may predict cardiovascular events in asymptomatic individuals without overt cardiovascular disease. Measuring arterial stiffness may, therefore, identify patients at risk at an early stage. Antihypertensive treatment has been shown to reduce arterial stiffness beyond its antihypertensive effect. Arterial stiffness could, therefore, be a surrogate marker of treatment that relates to prognosis. Arterial stiffness has mostly been used in research protocols, and its use as a prognostic indicator in clinical practice is still uncommon. Several methods exist that can determine parameters related to arterial stiffness, both local and in specific artery beds such as the aorta. In this brief review we present methods to evaluate arterial stiffness, their clinical utility, limitations and the advantages of a novel method, the Cardio-Ankle Vascular Index. Easier and more reproducible methods to evaluate arterial stiffness may increase the use of parameter as a risk factor for coronary heart disease in common clinical practice.

Highly sensitive strain sensors based on fragmentized carbon nanotube/polydimethylsiloxane composites

Wearable strain sensors based on nanomaterial/elastomer composites have potential applications in flexible electronic skin, human motion detection, human-machine interfaces, etc. In this research, a type of high performance strain sensors has been developed using fragmentized carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites. The CNT/PDMS composites were ground into fragments, and a liquid-induced densification method was used to fabricate the strain sensors. The strain sensors showed high sensitivity with gauge factors (GFs) larger than 200 and a broad strain detection range up to 80%, much higher than those strain sensors based on unfragmentized CNT/PDMS composites (GF < 1). The enhanced sensitivity of the strain sensors is ascribed to the sliding of individual fragmentized-CNT/PDMS-composite particles during mechanical deformation, which causes significant resistance change in the strain sensors. The strain sensors can differentiate mechanical stimuli and monitor various human body motions, such as bending of the fingers, human breathing, and blood pulsing.

Effects of exercise intensity and cardiorespiratory fitness on the acute response of arterial stiffness to exercise in older adults

PURPOSE

Increased arterial stiffness is observed with ageing and in individuals with low cardiorespiratory fitness ([Formula: see text]O_2peak), and associated with cardiovascular risk. Following an exercise bout, transient arterial stiffness reductions offer short-term benefit, but may depend on exercise intensity. This study assessed the effects of exercise intensity on post-exercise arterial stiffness in older adults with varying fitness levels.

METHODS

Fifty-one older adults (72 ± 5 years) were stratified into fitness tertiles ([Formula: see text]O_2peak: low-, 22.3 ± 3.1; mid-, 27.5 ± 2.4 and high-fit 36.3 ± 6.5 mL kg^-1 min^-1). In a randomised order, participants underwent control (no-exercise), moderate-intensity continuous exercise (40% of peak power output; PPO), and higher-intensity interval exercise (70% of PPO) protocols. Pulse wave velocity (PWV), augmentation index (AIx75) and reflection magnitude (RM) were assessed at rest and during 90 min of recovery following each protocol.

RESULTS

After control, delta PWV increased over time (P < 0.001) and delta RM was unchanged. After higher-intensity interval exercise, delta PWV (P < 0.001) and delta RM (P < 0.001) were lower to control in all fitness groups. After moderate-intensity continuous exercise, delta PWV was not different from control in low-fit adults (P = 0.057), but was lower in the mid- and higher-fit older adults. Post-exercise AIx75 was higher to control in all fitness groups (P = 0.001).

CONCLUSIONS

In older adults, PWV increases during seated rest and this response is attenuated after higher-intensity interval exercise, regardless of fitness level. This attenuation was also observed after moderate-intensity continuous exercise in adults with higher, but not lower fitness levels. Submaximal exercise reveals differences in the arterial stiffness responses between older adults with higher and lower cardiorespiratory fitness.

Association of Haemodynamic Indices of Central and Peripheral Pressure with Subclinical Target Organ Damage

Background

Central aortic pressure has often been shown to be more closely associated with markers of vascular function and incidence of cardiovascular events compared to peripheral pressure. However, the potential clinical use of central aortic or peripheral haemodynamic indices as markers of target organ damage (TOD) has not been fully established.

Methods

We evaluated associations of TOD with central aortic and peripheral haemodynamic indices (central aortic [cPP] and peripheral pulse pressure [pPP], central aortic augmentation index, and central and peripheral waveform factor) in 770 hospital inpatients (age 60 ± 10 years, 473 males) with primary hypertension. TOD was quantified in terms of arterial stiffness as measured by carotid-femoral pulse wave velocity (cfPWV), carotid intima-media thickness (IMT), and urine albumin-to-creatinine ratio (ACR). Subclinical TOD was defined as carotid IMT >0.9 mm, urine ACR >3.5 mg/mmol in females and >2.5 mg/mmol in males and/or cfPWV >12 m/s.

Results

Both cPP and pPP showed significant correlation with cfPWV (r = 0.41 vs. 0.40; p < 0.01), ACR (r = 0.24 vs. 0.27; p < 0.01) and carotid IMT (r = 0.14 vs. 0.15; p < 0.01). Each SD increase in pPP and cPP was associated with increased risk of cfPWV >12 m/s (odds ratio [OR] = 2.7 and 2.9 for pPP and cPP, respectively), ACR >2.5 mg/mmol (OR = 1.2 and 1.4, respectively), and carotid IMT >0.9 mm (OR = 1.46 and 1.53, respectively). Compared to pPP, cPP had higher predictive power for TOD for age ≥60 years (OR = 3.07, p < 0.001).

Conclusions

Although both pPP and cPP show an association with TOD in a hypertensive population, cPP provides additional information beyond pPP associated with TOD in a hypertensive cohort. Central aortic haemodynamic indices as potential biomarkers of subclinical TOD need to be validated by further prospective studies.

Parameters of pulse wave velocity: determinants and reference values assessed in the population-based study LIFE-Adult

AIMS AND BACKGROUND

Parameters of arterial stiffness such as pulse wave velocity (PWV) were recently proposed as independent risk factors of cardiovascular events. We analyse three PWV parameters in the large population-based study LIFE-Adult to identify risk factors, normal and reference values.

METHODS AND RESULTS

Brachial-ankle (ba), brachial-femoral (bf) and carotid-femoral (cf) PWV assessment was performed using Vicorder device. 8509 participants aged 19-80 were analysed. PWV parameters were moderately correlated (r(ba/bf) = 0.6, r(ba/cf) = 0.46, r(bf/cf) = 0.59). Age and blood pressure are the dominant determinants of PWV parameters explaining > 18% of variability. Sex was only relevant for bfPWV and cfPWV. All further analysed cardiovascular and other risk factors are of minor importance. We provide age-dependent percentiles for the population (reference values) and for the subgroup of normotonic individuals. All percentiles show a strong increase with age. The difference between normotonic and all individuals is small for younger age groups but increases up to 1 m/s for elderly subjects.

CONCLUSION

Our study confirms and further underpins the strong impact of age and blood pressure on arterial stiffness and the relatively weak contribution of other factors, supporting an independent role of arterial stiffness in cardiovascular disease development. Age-dependent reference and normal values were provided on the basis of the so far largest study sample facilitating the implementation of PWV assessment in clinical practice. Due to better compliance, handling and stronger association with age and blood pressure, baPWV could serve as an alternative to cfPWV. Follow-up data are required to estimate the clinical significance of specified PWV cut-offs.

Left ventricular remodeling and arterial afterload in older women with uncontrolled and controlled hypertension

OBJECTIVE

The prevalence of hypertension increases with advancing age in women. Blood pressure control is more difficult to achieve in older women, and despite well-controlled blood pressure, the cardiovascular mortality remains high. However, the underlying mechanisms are not understood.

METHODS

Nineteen women with uncontrolled hypertension on drug treatment (70 ± 2 [SE] years, ambulatory awake blood pressure; 152 ± 2/84 ± 2 mm Hg), 19 with controlled hypertension (68 ± 1 years, 128 ± 2/71 ± 2 mm Hg), and 31 healthy normotensive women (68 ± 1 years, 127 ± 1/73 ± 1 mm Hg) were recruited. Participants were weaned from antihypertensive drugs and underwent 3 weeks of run-in before cardiac-vascular assessments. Left ventricular morphology was evaluated with cardiac magnetic resonance imaging. Arterial load and vascular stiffness were measured via ultrasound and applanation tonometry.

RESULTS

Left ventricular mass normalized by body surface area was not different between hypertension groups (uncontrolled vs controlled: 50.0 ± 1.7 vs 51.8 ± 2.3 g/m), but it was lower in the normotensive group (41.7 ± 0.9 g/m; one-way analysis of variance [ANOVA] P = 0.004). Likewise, central pulse wave velocity was not different between hypertension groups (11.5 ± 0.6 vs 11.1 ± 0.5 m/s) and lower in the normotensive group (9.1 ± 0.3 m/s; 1-way ANOVA P = 0.0001). Total peripheral resistance was greater in uncontrolled hypertension (HTN) compared with normotensive group (2051 ± 323 vs 1719 ± 380 dyns/cm), whereas controlled HTN group (1925 ± 527 dyns/cm) was not different to either groups.

CONCLUSION

Regardless of current blood pressure control, hypertensive older women exhibited increased cardiac mass and arterial stiffness compared with normotensives. Future large-scale longitudinal studies are warranted to directly investigate the mechanisms for the high cardiovascular mortality among older hypertensive women with well-controlled blood pressure.

Quantitative Vascular Evaluation: From Laboratory Experiments to Point-of-Care Patient (Experimental Approach)

This paper illustrates the evolution of our knowledge of arterial mechanics from our initial research works up to the present time. Several techniques focusing on this topic in terms of our experience are dis-cussed. An interdisciplinary team composed by different institutions from Argentina, Uruguay, France and Spain was created to conduct research, to train human resources and to fulfill the inevitable social role of gaining access to technological inno-vation to improve public health.

Flexible Ferroelectric Sensors with Ultrahigh Pressure Sensitivity and Linear Response over Exceptionally Broad Pressure Range

Flexible pressure sensors with a high sensitivity over a broad linear range can simplify wearable sensing systems without additional signal processing for the linear output, enabling device miniaturization and low power consumption. Here, we demonstrate a flexible ferroelectric sensor with ultrahigh pressure sensitivity and linear response over an exceptionally broad pressure range based on the material and structural design of ferroelectric composites with a multilayer interlocked microdome geometry. Due to the stress concentration between interlocked microdome arrays and increased contact area in the multilayer design, the flexible ferroelectric sensors could perceive static/dynamic pressure with high sensitivity (47.7 kPa^-1, 1.3 Pa minimum detection). In addition, efficient stress distribution between stacked multilayers enables linear sensing over exceptionally broad pressure range (0.0013-353 kPa) with fast response time (20 ms) and high reliability over 5000 repetitive cycles even at an extremely high pressure of 272 kPa. Our sensor can be used to monitor diverse stimuli from a low to a high pressure range including weak gas flow, acoustic sound, wrist pulse pressure, respiration, and foot pressure with a single device.

Serum calcification propensity is associated with renal tissue oxygenation and resistive index in patients with arterial hypertension or chronic kidney disease

BACKGROUND

Arterial calcifications increase arterial stiffness and are associated with a faster decline of kidney function in patients with arterial hypertension (AH) and/or chronic kidney disease (CKD). Yet the underlying mechanisms linking arterial calcifications, vascular stiffness and renal function decline are incompletely understood. A novel in-vitro blood test evaluates the propensity of patient's serum to prevent the formation of calcifications by measuring the maturation time of calciprotein particles (CPP) [transformation time of amorphous calcium phosphate-containing primary CPP to crystalline hydroxyapatite-containing secondary CPP (T50)]. We hypothesized that a high arterial stiffness and a high propensity to calcify may be associated with high renal vascular resistance and low renal tissue oxygenation.

METHODS

T50 was measured in patients with AH and a preserved renal function, in CKD patients and in healthy controls, a lower T50 indicating a higher risk of calcification. Pulse wave velocity (PWV) was assessed as a measure of arterial stiffness, and renal resistive index was measured by renal Doppler ultrasound. Renal tissue oxygenation was measured by blood oxygenation level-dependent MRI using the mean R2 values of the cortex, the medulla and layers of renal parenchyma. A high R2 value corresponds to a low tissue oxygenation.

RESULTS

Mean T50 was 246 ± 129 min in 58 CKD patients, 275 ± 111 min in 48 AH patients and 324 ± 96 min in 39 healthy controls (Panova = 0.008). In multivariable adjusted linear regression analysis, serum T50 correlated negatively with circulating calcium and phosphate levels, mean cortical and medullary R2, PWV, renal resistive index and being hypertensive. PWV was positively associated with R2 levels of outer and inner layers of renal parenchyma.

CONCLUSION

The current study shows that hypertensive patients with preserved renal function as well as CKD patients have a higher risk of calcification than controls. High arterial stiffness and calcification propensity are linked to low renal tissue oxygenation and perfusion in hypertensive and CKD patients. These results provide new insights on the relationships among arterial stiffness, renal tissue oxygenation and the risk of developing CKD.

A wearable pressure sensor based on ultra-violet/ozone microstructured carbon nanotube/polydimethylsiloxane arrays for electronic skins

Pressure sensors with high performance (e.g., a broad pressure sensing range, high sensitivities, rapid response/relaxation speeds, temperature-stable sensing), as well as a cost-effective and highly efficient fabrication method are highly desired for electronic skins. In this research, a high-performance pressure sensor based on microstructured carbon nanotube/polydimethylsiloxane arrays was fabricated using an ultra-violet/ozone (UV/O₃) microengineering technique. The UV/O₃ microengineering technique is controllable, cost-effective, and highly efficient since it is conducted at room temperature in an ambient environment. The pressure sensor offers a broad pressure sensing range (7 Pa-50 kPa), a sensitivity of ∼ -0.101 ± 0.005 kPa^-1 (<1 kPa), a fast response/relaxation speed of ∼10 ms, a small dependence on temperature variation, and a good cycling stability (>5000 cycles), which is attributed to the UV/O₃ engineered microstructures that amplify and transfer external applied forces and rapidly store/release the energy during the PDMS deformation. The sensors developed show the capability to detect external forces and monitor human health conditions, promising for the potential applications in electronic skin.

Fully Printed Wearable Vital Sensor for Human Pulse Rate Monitoring using Ferroelectric Polymer

The ability to monitor subtle changes in vital and arterial signals using flexible devices attached to the human skin can be valuable for the detection of various health conditions such as cardiovascular disease. Conventional Si device technologies are being utilised in traditional clinical systems; however, its fabrication is not easy owing to the difficulties in adapting to conventional processes. Here, we present the development of a fully printed, wearable, ferroelectric-polymer vital sensor for monitoring the human pulse wave/rate on the skin. This vital sensor is compact, thin, sufficiently flexible, and conforms to the skin while providing high pressure sensitivity, fast response time, superior operational stability, and excellent mechanical fatigue properties. Moreover, the vital sensor is connected to a communication amplifier circuit for monitoring the pulse waves with a wireless sensing system. This sensor system can realise the development of new healthcare devices for wearable sensor applications.

A Self-Powered Sensor Mimicking Slow- and Fast-Adapting Cutaneous Mechanoreceptors

Highly efficient human skin systems transmit fast adaptive (FA) and slow adaptive (SA) pulses selectively or consolidatively to the brain for a variety of external stimuli. The integrated analysis of these signals determines how humans perceive external physical stimuli. Here, a self-powered mechanoreceptor sensor based on an artificial ion-channel system combined with a piezoelectric film is presented, which can simultaneously implement FA and SA pulses like human skin. This device detects stimuli with high sensitivity and broad frequency band without external power. For the feasibility study, various stimuli are measured or detected. Vital signs such as the heart rate and ballistocardiogram can be measured simultaneously in real time. Also, a variety of stimuli such as the mechanical stress, surface roughness, and contact by a moving object can be distinguished and detected. This opens new scientific fields to realize the somatic cutaneous sensor of the real skin. Moreover, this new sensing scheme inspired by natural sensing structures is able to mimic the five senses of living creatures.

Blood flow characteristics of diabetic patients with complications detected by optical measurement

Background

Diabetes mellitus (DM) is one of the most common diseases worldwide. Uncontrolled and prolonged hyperglycemia can cause diabetic complications, which reduce the quality of life of patients. Diabetic complications are common in DM patients. Because it is impossible to completely recover from diabetic complications, it is important for early detection. In this study, we suggest a novel method of determining blood flow characteristics based on fluorescence image analysis with indocyanine green and report that diabetic complications have unique blood flow characteristics.

Methods

We analyzed time-series fluorescence images obtained from controls, DM patients, and DM patients with complications. The images were segmented into the digits and the dorsum of the feet and hands, and each part has been considered as arterial and capillary flow. We compared the blood flow parameters in each region among the three groups.

Results

The DM patients with complications showed similar blood flow parameters to the controls, except the area under the curve and the maximum intensity, which indicate the blood flow volume. These parameters were significantly decreased in DM patients with complications. Although some blood flow parameters in the feet of DM patients with complications were close to normal blood flow, the vascular response of the macrovessels and microvessels to stimulation of the hands was significantly reduced, which indicates less reactivity in DM patients with complications.

Conclusions

Our results suggest that DM patients, and DM patients with complications, have unique peripheral blood flow characteristics.

Comparison of laboratory and ambulatory measures of central blood pressure and pulse wave reflection: hitting the target or missing the mark?

Prior studies demonstrating clinical significance of noninvasive estimates of central blood pressure (BP) and pulse wave reflection have relied primarily on discrete resting measures. The aim of this study was to compare central BP and pulse wave reflection measures sampled during a single resting laboratory visit against those obtained under ambulatory conditions. The secondary aim was to investigate the reproducibility of ambulatory central BP and pulse wave reflection measurements. Forty healthy participants (21 males; 24 ± 3 years) completed three measurements of brachial artery pulse wave analysis (Oscar 2 with SphygmoCor Inside) in the laboratory followed by 24 hours of ambulatory monitoring. Seventeen participants repeated the 24-hour ambulatory monitoring visit after at least 1 week. Ambulatory measures were divided into daytime (9 AM-9 PM), nighttime (1 AM-6 AM), and 24-hour periods. Compared with laboratory measurements, central systolic BP, augmentation pressure, and augmentation index (with and without heart rate normalization) were higher (all P < .01) during daytime and 24-hour periods but lower during the nighttime period (all P < .001). The drop in nighttime brachial systolic BP was larger than central systolic pressure (Δ -20 ± 6 vs. -15 ± 6 mm Hg; P < .0001). Repeat ambulatory measurements of central BP and pulse wave reflection displayed good-to-excellent intraclass correlation coefficients (r = 0.58-0.86; all P < .01), although measures of pulse wave reflection had higher coefficients of variation (14%-41%). The results highlight absolute differences in central BP and pulse wave reflection between discrete laboratory and ambulatory conditions. The use of ambulatory measures of central BP and pulse wave reflection warrant further investigation for clinical prognostic value.

A data-driven approach for addressing the lack of flow waveform data in studies of cerebral arterial flow in older adults

OBJECTIVE

Blood flow waveforms-essential data for hemodynamic modeling-are often in practice unavailable to researchers. The objectives of this work were to assess the variability among the waveforms for a clinically relevant older population, and develop data-based methods for addressing the missing waveform data for hemodynamic studies.

APPROACH

We analyzed 272 flow waveforms from the internal carotid arteries of older patients (73  ±  13 yr) with moderate cardiovascular disease, and used these data to develop methods to guide new approaches for hemodynamic studies.

MAIN RESULTS

Profound variations in waveform parameters were found within the aged population that were not seen in published data for young subjects. Common features in the aged population relative to the young included a larger systole-to-diastole flow rate ratio, increased flow during late systole, and absence of a dicrotic notch. Eight waveforms were identified that collectively represent the range of waveforms in the older population. A relationship between waveform shape and flow rate was obtained that, in conjunction with equations relating flow rate to diameter, can be used to provide individualized waveforms for patient-specific geometries. The dependence of flow rate on diameter was statistically different between male and female patients.

SIGNIFICANCE

It was shown that a single archetypal waveform cannot well-represent the diverse waveforms found within an aged population, although this approach is frequently used in studies of flow in the cerebral vasculature. Motivated by these results, we provided a set of eight waveforms that can be used to assess the hemodynamic uncertainty associated with the lack of patient-specific waveform data. We also provided a methodology for generating individualized waveforms when patient gender, age, and cardiovascular disease state are known. These data-driven approaches can be used to devise more relevant in vitro or in silico intra-cranial hemodynamic studies for older patients.

Development of pharmacological screening method for evaluation of effect of drug on elevated pulse pressure and arterial stiffness

INTRODUCTION

Elevated pulse pressure (PP) and amplification of arterial stiffness (AS) are responsible for various cardiovascular disease and deaths. Numerous investigations have identified that different antihypertensive agents influence PP and AS differently. None of the previous studies described any reliable animal model particularly to screen drugs having effects on PP and AS. In present study, we developed an animal model to screen such drugs particularly affecting PP and AS.

METHODS

Elevation of PP and amplification of AS were induced in rats by uninephrectomy along with high salt intake (NaCl 4% w/v) for a period of six weeks, and weekly changes in body weight, PP, systolic, diastolic, mean pressure and pulse wave velocity (PWV) were estimated. After six weeks, collagen elastin ratio of aortic segment was estimated. Histomorphometry of abdominal aortic section of rats was done using trinocular microscope.

RESULTS

After six weeks, uninephrectomized rats that were kept on high salt drinking water shown significant increase (P < 0.001) in MAP, PP and PWV indicates that hypertension along with elevated PP developed in rats, and increase in collagen/elastin ratio (P < 0.001) as well as PWV as compared to normal rats indicates the increase in AS.

CONCLUSION

The development of condition of hypertension in conjunction with increase in PP and AS in rats can be used as in-vivo screening model to determine the potency of drugs for the treatment of hypertension or other cardiovascular diseases associated with high PP and AS.

Noncontact Heartbeat and Respiration Monitoring Based on a Hollow Microstructured Self-Powered Pressure Sensor

Advances in mobile networks and low-power electronics have driven smart mobile medical devices at a tremendous pace, evoking increased interest in household healthcare, especially for those with cardiovascular or respiratory disease. Thus, flexible battery-free pressure sensors, with great potential for monitoring respiration and heartbeat in a smart way, are urgently demanded. However, traditional flexible battery-free pressure sensors for subtle physiological signal detecting are mostly tightly adhered onto the skin instead of working under the pressure of body weight in a noncontact mode, as the low sensitivity in the high-pressure region can hardly meet the demands. Moreover, a hollow microstructure (HM) with higher deformation than solid microstructures and great potential for improving the pressure sensitivity of self-powered sensors has never been investigated. Here, for the first time, we demonstrated a noncontact heartbeat and respiration monitoring system based on a flexible HM-enhanced self-powered pressure sensor, which possesses the advantages of low cost, a high dynamic-pressure sensitivity of 18.98 V·kPa^-1, and a wide working range of 40 kPa simultaneously. Specific superiority of physiological detection under a high pressure is also observed. Continuous reliable heartbeat and respiration information is successfully detected in a noncontact mode and transmitted to a mobile phone.

Highly Sensitive and Ultrastable Skin Sensors for Biopressure and Bioforce Measurements Based on Hierarchical Microstructures

Piezoresistive microsensors are considered to be essential components of the future wearable electronic devices. However, the expensive cost, complex fabrication technology, poor stability, and low yield have limited their developments for practical applications. Here, we present a cost-effective, relatively simple, and high-yield fabrication approach to construct highly sensitive and ultrastable piezoresistive sensors using a bioinspired hierarchically structured graphite/polydimethylsiloxane composite as the active layer. In this fabrication, a commercially available sandpaper is employed as the mold to develop the hierarchical structure. Our devices exhibit fascinating performance including an ultrahigh sensitivity (64.3 kPa^-1), fast response time (<8 ms), low limit of detection of 0.9 Pa, long-term durability (>100 000 cycles), and high ambient stability (>1 year). The applications of these devices in sensing radial artery pulses, acoustic vibrations, and human body motion are demonstrated, exhibiting their enormous potential use in real-time healthcare monitoring and robotic tactile sensing.

Chemically Designed Metallic/Insulating Hybrid Nanostructures with Silver Nanocrystals for Highly Sensitive Wearable Pressure Sensors

With the increase in interest in wearable tactile pressure sensors for e-skin, researches to make nanostructures to achieve high sensitivity have been actively conducted. However, limitations such as complex fabrication processes using expensive equipment still exist. Herein, simple lithography-free techniques to develop pyramid-like metal/insulator hybrid nanostructures utilizing nanocrystals (NCs) are demonstrated. Ligand-exchanged and unexchanged silver NC thin films are used as metallic and insulating components, respectively. The interfaces of each NC layer are chemically engineered to create discontinuous insulating layers, i.e., spacers for improved sensitivity, and eventually to realize fully solution-processed pressure sensors. Device performance analysis with structural, chemical, and electronic characterization and conductive atomic force microscopy study reveals that hybrid nanostructure based pressure sensor shows an enhanced sensitivity of higher than 500 kPa^-1, reliability, and low power consumption with a wide range of pressure sensing. Nano-/micro-hierarchical structures are also designed by combining hybrid nanostructures with conventional microstructures, exhibiting further enhanced sensing range and achieving a record sensitivity of 2.72 × 10⁴ kPa^-1. Finally, all-solution-processed pressure sensor arrays with high pixel density, capable of detecting delicate signals with high spatial selectivity much better than the human tactile threshold, are introduced.

Ultrasensitive and Highly Stable Resistive Pressure Sensors with Biomaterial-Incorporated Interfacial Layers for Wearable Health-Monitoring and Human-Machine Interfaces

Flexible piezoresistive sensors have huge potential for health monitoring, human-machine interfaces, prosthetic limbs, and intelligent robotics. A variety of nanomaterials and structural schemes have been proposed for realizing ultrasensitive flexible piezoresistive sensors. However, despite the success of recent efforts, high sensitivity within narrower pressure ranges and/or the challenging adhesion and stability issues still potentially limit their broad applications. Herein, we introduce a biomaterial-based scheme for the development of flexible pressure sensors that are ultrasensitive (resistance change by 5 orders) over a broad pressure range of 0.1-100 kPa, promptly responsive (20 ms), and yet highly stable. We show that employing biomaterial-incorporated conductive networks of single-walled carbon nanotubes as interfacial layers of contact-based resistive pressure sensors significantly enhances piezoresistive response via effective modulation of the interlayer resistance and provides stable interfaces for the pressure sensors. The developed flexible sensor is capable of real-time monitoring of wrist pulse waves under external medium pressure levels and providing pressure profiles applied by a thumb and a forefinger during object manipulation at a low voltage (1 V) and power consumption (<12 μW). This work provides a new insight into the material candidates and approaches for the development of wearable health-monitoring and human-machine interfaces.

Bio-inspired highly flexible dual-mode electronic cilia

Inspired by biological cilia, a highly flexible dual-mode electronic cilia (EC) sensor is fabricated from graphene-coated magnetic cilia arrays, which possesses excellent pressure and magnetic field sensing capabilities.

A Triple-Mode Flexible E-Skin Sensor Interface for Multi-Purpose Wearable Applications

This study presents a flexible wireless electronic skin (e-skin) sensor system that includes a multi-functional sensor device, a triple-mode reconfigurable readout integrated circuit (ROIC), and a mobile monitoring interface. The e-skin device's multi-functionality is achieved by an interlocked micro-dome array structure that uses a polyvinylidene fluoride and reduced graphene oxide (PVDF/RGO) composite material that is inspired by the structure and functions of the human fingertip. For multi-functional implementation, the proposed triple-mode ROIC is reconfigured to support piezoelectric, piezoresistance, and pyroelectric interfaces through single-type e-skin sensor devices. A flexible system prototype was developed and experimentally verified to provide various wireless wearable sensing functions-including pulse wave, voice, chewing/swallowing, breathing, knee movements, and temperature-while their real-time sensed data are displayed on a smartphone.

Resistance training-induced decrease in central arterial compliance is associated with decreased subendocardial viability ratio in healthy young men

High-intensity resistance training decreases central arterial compliance (CAC). Subendocardial viability ratio (SEVR) is a useful tool that reflects the balance between coronary perfusion and left ventricular afterload. Animal studies have demonstrated that decreased CAC is associated with SEVR deterioration. Therefore, resistance training-induced decrease in CAC may be associated with changes in SEVR. The objective of the present study was to investigate the association between SEVR and CAC using both cross-sectional and longitudinal (i.e., resistance training) study designs. To achieve this, we first conducted a cross-sectional study to investigate the association between SEVR and CAC in 89 young men. Thereafter, a longitudinal study was performed to examine the effects of resistance training on SEVR and CAC in young men. A total of 28 young men were divided into 2 groups: control (n = 13) and training (n = 15). In the training group, subjects underwent supervised resistance training for 4 weeks (5 sets of 10 repetitions at 75% of 1-repetition maximum, 3 times/week). CAC and SEVR were then measured in all subjects. In the cross-sectional study, SEVR was significantly positively correlated with CAC, whereas resistance training significantly decreased both SEVR and CAC. Moreover, training-induced changes in CAC were significantly correlated with changes in SEVR. Thus, these results suggest that resistance training-induced decrease in CAC is associated with decreased SEVR in young men.

Highly Sensitive Flexible Pressure Sensors Based on Printed Organic Transistors with Centro-Apically Self-Organized Organic Semiconductor Microstructures

A highly sensitive pressure sensor based on printed organic transistors with three-dimensionally self-organized organic semiconductor microstructures (3D OSCs) was demonstrated. A unique organic transistor with semiconductor channels positioned at the highest summit of printed cylindrical microstructures was achieved simply by printing an organic semiconductor and polymer blend on the plastic substrate without the use of additional etching or replication processes. A combination of the printed organic semiconductor microstructure and an elastomeric top-gate dielectric resulted in a highly sensitive organic field-effect transistor (FET) pressure sensor with a high pressure sensitivity of 1.07 kPa^-1 and a rapid response time of <20 ms with a high reliability over 1000 cycles. The flexibility and high performance of the 3D OSC FET pressure sensor were exploited in the successful application of our sensors to real-time monitoring of the radial artery pulse, which is useful for healthcare monitoring, and to touch sensing in the e-skin of a realistic prosthetic hand.

A Stretchable and Transparent Nanocomposite Nanogenerator for Self-Powered Physiological Monitoring

Smart sensing electronic devices with good transparency, high stretchability, and self-powered sensing characteristics are essential in wearable health monitoring systems. This paper innovatively proposes a stretchable nanocomposite nanogenerator with good transparency that can be conformally attached to the human body to harvest biomechanical energy and monitor physiological signals. The work reports an innovative device that uses sprayed silver nanowires as transparent electrodes and sandwiches a nanocomposite of piezoelectric BaTiO₃ and polydimethylsiloxane as the sensing layer, which exhibits good transparency and mechanical transformability with stretchable, foldable, and twistable properties. The highly flexible nanogenerator affords a good input-output linearity under the vertical force and the sensing ability to detect lateral stretching deformation up to 60% strain under piezoelectric mechanisms. Furthermore, the proposed device can effectively harvest touch energies from the human body as a single-electrode triboelectric nanogenerator. Under periodic contact and separation, a maximum output voltage of 105 V, a current density of 6.5 μA/cm², and a power density of 102 μW/cm² can be achieved, exhibiting a good power generation performance. Owing to the high conformability and excellent sensitivity of the nanogenerator, it can also act as a self-powered wearable sensor attached to different parts of the human body for real-time monitoring of the human physiological signals such as eye blinking, pronunciation, arm movement, and radial artery pulse. The designed nanocomposite nanogenerator shows great potential for use in self-powered e-skins and healthcare monitoring systems.

Arterial stiffness in fertile women with metabolic syndrome

INTRODUCTION

Although metabolic syndrome (MetS) is evidently associated with the risk of cardiovascular disease (CVD), recently its use has been questioned. We studied the utility of MetS diagnosis when estimating individual CVD risk.

METHODS

We compared 27 fertile women with MetS and 27 counterparts without the syndrome, matched pairwise according to well-known risk factors of CVD. Pulse wave velocity (PWV) and central blood pressure (cBP) were determined noninvasively via a SphygmoCor device. Arterial compliance was measured noninvasively with an HDI/PulseWave^TMCR-2000 arterial tonometer.

RESULTS

PWV (7.1 ± 2.5 versus 6.5 ± 1.1 m/s, p = .037), and both systolic (120.9 ± 12.2 versus 111.5 ± 16.0 mmHg, p = .031) and diastolic cBP (81.3 ± 8.5 versus 74.1 ± 11.2 mmHg, p = .035) were higher in the MetS group. Systemic arterial compliance values were lower in both large (15.1 ± 8.0 versus 16.1 ± 4.4 mL/mmHg × 10, p = .034) and small arteries (7.1 ± 2.5 versus 9.3 ± 3.2 mL/mmHg ×100, p = .010) in women with MetS.

CONCLUSIONS

Fertile women with MetS had increased arterial stiffness, as measured by three different methods. Our results highlight the utility of MetS when revealing increased individual CVD risks in fertile-aged women. Key messages Women with MetS have increased arterial stiffness when measured by different methods. MetS is a useful clinical tool to assess increased cardiovascular risk, particularly among fertile-aged women.

Designing Metallic and Insulating Nanocrystal Heterostructures to Fabricate Highly Sensitive and Solution Processed Strain Gauges for Wearable Sensors

All-solution processed, high-performance wearable strain sensors are demonstrated using heterostructure nanocrystal (NC) solids. By incorporating insulating artificial atoms of CdSe quantum dot NCs into metallic artificial atoms of Au NC thin film matrix, metal-insulator heterostructures are designed. This hybrid structure results in a shift close to the percolation threshold, modifying the charge transport mechanism and enhancing sensitivity in accordance with the site percolation theory. The number of electrical pathways is also manipulated by creating nanocracks to further increase its sensitivity, inspired from the bond percolation theory. The combination of the two strategies achieves gauge factor up to 5045, the highest sensitivity recorded among NC-based strain gauges. These strain sensors show high reliability, durability, frequency stability, and negligible hysteresis. The fundamental charge transport behavior of these NC solids is investigated and the combined site and bond percolation theory is developed to illuminate the origin of their enhanced sensitivity. Finally, all NC-based and solution-processed strain gauge sensor arrays are fabricated, which effectively measure the motion of each finger joint, the pulse of heart rate, and the movement of vocal cords of human. This work provides a pathway for designing low-cost and high-performance electronic skin or wearable devices.

Difference between ejection times measured at two different peripheral locations as a novel marker of vascular stiffness

Pulse wave velocity (PWV) has been recommended as an arterial damage assessment tool and a surrogate of arterial stiffness. However, the current technology does not allow to measure PWV both continuously and in real-time. We reported previously that peripherally measured ejection time (ET) overestimates ET measured centrally. This difference in ET is associated with the inherent vascular properties of the vessel. In the current study we examined ETs derived from plethysmography simultaneously at different peripheral locations and examined the influence of the underlying arterial properties on ET prolongation by changing the subject’s position. We calculated the ET difference between two peripheral locations (ΔET) and its corresponding PWV for the same heartbeat. The ΔET increased with a corresponding decrease in PWV. The difference between ΔET in the supine and standing (which we call ET index) was higher in young subjects with low mean arterial pressure and low PWV. These results suggest that the difference in ET between two peripheral locations in the supine vs standing positions represents the underlying vascular properties. We propose ΔET in the supine position as a potential novel real-time continuous and non-invasive parameter of vascular properties, and the ET index as a potential non-invasive parameter of vascular reactivity.

High-performance wearable strain sensors based on fragmented carbonized melamine sponges for human motion detection

Strain sensors with a large strain sensing range and high sensitivity are in high demand due to their various potential applications ranging from human motion detection to soft robotics. In this study, high-performance strain sensors are developed by fragmenting carbonized melamine sponges that are commercially available. The strain sensors, based on fragmented carbonized melamine sponges (FCMS), demonstrate high sensitivity with a gauge factor (GF) of 18.7 at an FCMS density of 1.07 mg cm^-2 and a large strain sensing range of up to 80%. As a comparison, the strain sensor based on unfragmented carbonized melamine sponges has only a GF of ∼8.0 and limited stretchability (<7%). In situ tension tests indicate that the strain-response mechanism of the sensor is mainly ascribed to the reorientation of individual FCMS at low strains (<40%), while crack propagation dominates the strain-response behavior of the sensor at strains larger than 40%. The high sensitivity and large strain sensing range of the sensor, as well as the low-cost and scalable fabrication method, enable diverse applications. It can not only detect large-strain human arthrosis movements, but it also exhibits the capability to monitor subtle human physiological activity.

Acupuncture therapy improves vascular hemodynamics and stiffness in middle-age hypertensive individuals

Acupuncture (ACU) is becoming a more common practice among hypertensive individuals. However, the reported therapeutic effects of ACU in lowering brachial blood pressure (BP) are ambiguous. Therefore, evaluating more sensitive markers of arterial functioning might unveil the protective effects of ACU on hypertension. We examined the effects of an 8-week ACU therapy intervention on vascular hemodynamics and stiffness in middle-age hypertensive individuals. Participants were randomly assigned to either ACU (n = 23) or a control group (n = 22). Brachial and aortic BP, wave reflection (AIx) and arterial stiffness (SI) were measured before and after 8 weeks. There was a significant group x time interaction (P < 0.05) for brachial and aortic BP, AIx and SI which significantly decreased (P < 0.05) following ACU but not after control. ACU led to reductions in brachial and aortic BP, wave reflection and arterial stiffness in middle-age hypertensive individuals. ACU might be effective in the prevention and treatment of hypertension.

Paper/Carbon Nanotube-Based Wearable Pressure Sensor for Physiological Signal Acquisition and Soft Robotic Skin

A wearable and flexible pressure sensor is essential to the realization of personalized medicine through continuously monitoring an individual's state of health and also the development of a highly intelligent robot. A flexible, wearable pressure sensor is fabricated based on novel single-wall carbon nanotube /tissue paper through a low-cost and scalable approach. The flexible, wearable sensor showed superior performance with concurrence of several merits, including high sensitivity for a broad pressure range and an ultralow energy consumption level of 10^-6 W. Benefited from the excellent performance and the ultraconformal contact of the sensor with an uneven surface, vital human physiological signals (such as radial arterial pulse and muscle activity at various positions) can be monitored in real time and in situ. In addition, the pressure sensors could also be integrated onto robots as the artificial skin that could sense the force/pressure and also the distribution of force/pressure on the artificial skin.

Suitability of the forearm for non-invasive blood pressure measurement in children

BACKGROUND

Measurement of forearm blood pressure (BP) in pediatric patients during general anesthesia is periodically employed despite a lack of evidence for this practice. Upper arm BP measurement may be impossible to perform for either patient or surgical reasons, and the forearm has theoretical benefits over the lower leg when an alternate site is required. We hypothesize that forearm BP measurement provides an accurate and reliable alternative to the upper arm. Published adult data do not support this hypothesis, and the little pediatric data published contain methodological shortcomings.

METHODS

A dedicated, externally calibrated noninvasive oscillometer was used to compare BP measurements in the upper arm and ipsilateral forearm of pediatric patients undergoing general anesthesia prior to application of a surgical stimulus. Both upper arm BP and ipsilateral forearm BP were sequentially measured 20 seconds apart on 3 separate occasions with an appropriately sized cuff. The systolic, diastolic, and mean blood pressures were recorded under steady-state conditions.

RESULTS

Thirty-five elective surgical patients aged 1 to 10 years were studied. The bias (±limits of agreement) for forearm minus upper arm blood pressures were as follows: mean BP -1.3 mm Hg (±7.2), diastolic BP -3.3 (±5.3), and systolic BP +3.2 mm Hg (±8.3). Differences greater than ±5 mm Hg occurred in 59% (systolic BP), 42% (diastolic BP), and 46% (mean BP) of all observations and greater than ±10 mm Hg in 17% (systolic BP), 8.6% (diastolic BP), and 15% (mean BP).

CONCLUSION

The differences within mean ±1.96 standard deviations reside considerably outside the clinically accepted tolerance of ±5 mm Hg. Thus, the forearm may not be used interchangeably with upper limb BP readings in anesthetized healthy children. Future use of the forearm for BP measurement requires a validated anthropomorphically appropriate forearm cuff.

Heart failure: a story of damage, fatigue and injury?

Heart failure has been recognised for years but the complete picture has been difficult to clearly understand. This article aims to try and put forward a proposed mechanistic explanation to encompass all that we see within the clinical heart failure syndrome using supporting published evidence. The aim of the article is to link, using published evidence, all the known varieties of heart failure into a spectrum that is explained by simple interlinked processes. In addition, the concept of routinely looking for reversibility of left ventricular dysfunction is introduced.

Facile Fabrication of a Flexible LiNbO3 Piezoelectric Sensor through Hot Pressing for Biomechanical Monitoring

Wearable pressure sensors have attracted increasing attention for biomechanical monitoring due to their portability and flexibility. Although great advances have been made, there are no facile methods to produce sensors with good performance. Here, we present a simple method for manufacturing flexible and self-powered piezoelectric sensors based on LiNbO₃ (LN) particles. The LN particles are dispersed in polypropylene (PP) doped with multiwalled carbon nanotubes (MWCNTs) by hot pressing (200 °C) to form a flexible LN/MWCNT/PP piezoelectric composite film (PCF) sensor. This cost-effective sensor has high sensitivity (8 Pa), fast response time (ca. 40 ms), and long-term stability (>3000 cycles). Measurements of pressure changes from peripheral arteries demonstrate the applicability of the LN/MWCNT/PP PCF sensor to biomechanical monitoring as well as its potential for biomechanics-related clinical diagnosis and forecasting.

Self-Powered Real-Time Arterial Pulse Monitoring Using Ultrathin Epidermal Piezoelectric Sensors

Continuous monitoring of an arterial pulse using a pressure sensor attached on the epidermis is an important technology for detecting the early onset of cardiovascular disease and assessing personal health status. Conventional pulse sensors have the capability of detecting human biosignals, but have significant drawbacks of power consumption issues that limit sustainable operation of wearable medical devices. Here, a self-powered piezoelectric pulse sensor is demonstrated to enable in vivo measurement of radial/carotid pulse signals in near-surface arteries. The inorganic piezoelectric sensor on an ultrathin plastic achieves conformal contact with the complex texture of the rugged skin, which allows to respond to the tiny pulse changes arising on the surface of epidermis. Experimental studies provide characteristics of the sensor with a sensitivity (≈0.018 kPa^-1 ), response time (≈60 ms), and good mechanical stability. Wireless transmission of detected arterial pressure signals to a smart phone demonstrates the possibility of self-powered and real-time pulse monitoring system.