A Study on the Effect of Contact Pressure during Physical Activity on Photoplethysmographic Heart Rate Measurements.

Heart rate (HR) as an important physiological indicator could properly describe global subject's physical status. Photoplethysmographic (PPG) sensors are catching on in field of wearable sensors, combining the advantages in costs, weight and size. Nevertheless, accuracy in HR readings is unreliable specifically during physical activity. Among several identified sources that affect PPG recording, contact pressure (CP) between the PPG sensor and skin greatly influences the signals. METHODS: In this study, the accuracy of HR measurements of a PPG sensor at different CP was investigated when compared with a commercial ECG-based chest strap used as a test control, with the aim of determining the optimal CP to produce a reliable signal during physical activity. Seventeen subjects were enrolled for the study to perform a physical activity at three different rates repeated at three different contact pressures of the PPG-based wristband. RESULTS: The results show that the CP of 54 mmHg provides the most accurate outcome with a Pearson correlation coefficient ranging from 0.81 to 0.95 and a mean average percentage error ranging from 3.8% to 2.4%, based on the physical activity rate. CONCLUSION: Authors found that changes in the CP have greater effects on PPG-HR signal quality than those deriving from the intensity of the physical activity and specifically, the individual best CP for each subject provided reliable HR measurements even for a high intensity of physical exercise with a Bland-Altman plot within ±11 bpm. Although future studies on a larger cohort of subjects are still needed, this study could contribute a profitable indication to enhance accuracy of PPG-based wearable devices.

Computational modeling of bicuspid aortopathy: Towards personalized risk strategies.

This paper describes current advances on the application of in-silico for the understanding of bicuspid aortopathy and future perspectives of this technology on routine clinical care. This includes the impact that artificial intelligence can provide to develop computer-based clinical decision support system and that wearable sensors can offer to remotely monitor high-risk bicuspid aortic valve (BAV) patients. First, we discussed the benefit of computational modeling by providing tangible examples of in-silico software products based on computational fluid-dynamic (CFD) and finite-element method (FEM) that are currently transforming the way we diagnose and treat cardiovascular diseases. Then, we presented recent findings on computational hemodynamic and structural mechanics of BAV to highlight the potentiality of patient-specific metrics (not-based on aortic size) to support the clinical-decision making process of BAV-associated aneurysms. Examples of BAV-related personalized healthcare solutions are illustrated.

Cardiovascular and skeletal muscle health with lifelong exercise.

The purpose of this study was to examine the effects of aerobic lifelong exercise (LLE) on maximum oxygen consumption (V̇o2max) and skeletal muscle metabolic fitness in trained women ( n = 7, 72 ± 2 yr) and men ( n = 21, 74 ± 1 yr) and compare them to old, healthy nonexercisers (OH; women: n = 10, 75 ± 1 yr; men: n = 10, 75 ± 1 yr) and young exercisers (YE; women: n = 10, 25 ± 1 yr; men: n = 10, 25 ± 1 yr). LLE men were further subdivided based on intensity of lifelong exercise and competitive status into performance (LLE-P, n = 14) and fitness (LLE-F, n = 7). On average, LLE exercised 5 day/wk for 7 h/wk over the past 52 ± 1 yr. Each subject performed a maximal cycle test to assess V̇o2max and had a vastus lateralis muscle biopsy to examine capillarization and metabolic enzymes [citrate synthase, ß-hydroxyacyl-CoA dehydrogenase (ß-HAD), and glycogen phosphorylase]. V̇o2max had a hierarchical pattern (YE > LLE > OH, P < 0.05) for women (44 ± 2 > 26 ± 2 > 18 ± 1 ml·kg-1·min-1) and men (53 ± 3 > 34 ± 1 > 22 ± 1 ml·kg-1·min-1) and was greater ( P < 0.05) in LLE-P (38 ± 1 ml·kg-1·min-1) than LLE-F (27 ± 2 ml·kg-1·min-1). LLE men regardless of intensity and women had similar capillarization and aerobic enzyme activity (citrate synthase and ß-HAD) as YE, which were 20%-90% greater ( P < 0.05) than OH. In summary, these data show a substantial V̇o2max benefit with LLE that tracked similarly between the sexes, with further enhancement in performance-trained men. For skeletal muscle, 50+ years of aerobic exercise fully preserved capillarization and aerobic enzymes, regardless of intensity. These data suggest that skeletal muscle metabolic fitness may be easier to maintain with lifelong aerobic exercise than more central aspects of the cardiovascular system. NEW & NOTEWORTHY Lifelong exercise (LLE) is a relatively new and evolving area of study with information especially limited in women and individuals with varying exercise intensity habits. These data show a substantial maximal oxygen consumption benefit with LLE that tracked similarly between the sexes. Our findings contribute to the very limited skeletal muscle biopsy data from LLE women (>70 yr), and similar to men, revealed a preserved metabolic phenotype comparable to young exercisers.

Particle image velocimetry study of the celiac trunk hemodynamic induced by continuous-flow left ventricular assist device.

Whereas left ventricular assist device (LVAD) is the gold-standard therapy for patients with heart failure, gastrointestinal bleeding is one of the most common complications. LVAD implantation may remarkably impact aortic hemodynamics so that experimental and computational flow analyses can be used to study the disease mechanisms. Here we present an experimentally-calibrated computational model of the celiac trunk hemodynamic of a LVAD-supported patient who experienced bleeding after device implantation. Specifically, both particle image velocimetry (PIV) and echocardiography were used to measure and compare flow distributions in each branch of a phantom model of the patient abdominal aorta. Then, the distribution of wall shear stress (WSS) was estimated by computational flow analysis. At a cardiac output of 5 L/min, the highest flow division was found in the mesenteric artery (13.6% for PIV and 14.6% for echocardiography), while the left renal artery exhibited the lowest amount in the celiac trunk model (2.6% for PIV and 2.4% for echocardiography). Bland-Altman analysis demonstrated a high agreement between echocardiographic and PIV-related flow measurements, while computational flow analysis revealed that WSS was high in the LVAD graft anastomosis site and just after the ostia of both the celiac trunk and mesenteric artery. This altered shear stress distribution in the celiac trunk may lead to a flow-mediated mechanism of adverse remodeling of the von Willebrand factor and ultimately to gastrointestinal bleeding as seen clinically in this patient.

Shear stress alterations in the celiac trunk of patients with a continuous-flow left ventricular assist device as shown by in-silico and in-vitro flow analyses.

BACKGROUND: The use of left ventricular assist devices (LVADs) to treat advanced cardiac heart failure is constantly increasing, although this device leads to high risk for gastrointestinal bleeding. METHODS: Using in-silico flow analysis, we quantified hemodynamic alterations due to continuous-flow LVAD (HeartWare, Inc., Framingham, MA) in the celiac trunk and major branches of the abdominal aorta, and then explored the relationship between wall shear stress (WSS) and celiac trunk orientation. To assess outflow from the aortic branch, a 3-dimensional-printed patient-specific model of the celiac trunk reconstructed from an LVAD-supported patient was used to estimate echocardiographic outflow velocities under continuous-flow conditions, and then to calibrate computational simulations. Moreover, flow pattern and resulting WSS values were computed for 5 patients with LVAD implantation. RESULTS: Peak WSS values were estimated on the 3 branches of the celiac trunk and the LVAD cannula. The mean WSSs demonstrated that the left gastric artery underwent the highest WSS of 9.08 ± 5.45 Pa, with an average flow velocity of 0.57 ± 0.25 m/s compared with that of other vessel districts. The common hepatic artery had a less critical WSS of 4.58 ± 1.77 Pa. A positive correlation was found between the celiac trunk angulation and the WSS stress just distal to the ostium of the celiac trunk (R = 0.9), which may increase vulnerability of this vessel to bleeding. CONCLUSIONS: Although further studies are needed to confirm these findings in a larger patient cohort, computational flow simulations may enhance the information of clinical image data and may have an application in clinical investigations of hemodynamic changes in LVAD-supported patients.

Wooden panel paintings investigation: an air-coupled ultrasonic imaging approach.

In this paper, a method for the study of wooden panel paintings using air-coupled acoustical imaging is presented. In order to evaluate the advantages of the technique, several samples were made to mimic panel paintings along with their typical defects. These specimens were tested by means of both single-sided and through-transmission techniques using planar transducers. Image data were processed by means of a two-dimensional (2-D)-fast Fourier transform-based algorithm to increase the S/N ratio and 2-D representations (C-scans) were generated. The simulated defects were imaged using both configurations. Investigations were undertaken on four antique paintings from a private collection. The results presented and discussed in this investigation confirm both the robustness and the effectiveness of the technique in detecting defects such as delaminations and cracks in wooden panel paintings.