Normalization of Flow-mediated Dilation to Brachial Artery Material Property: A Feasibility Study. Annu Int Conf IEEE Eng Med Biol Soc 2023;2023:1-4. [PMID: 38083395 DOI: 10.1109/embc40787.2023.10341153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Endothelial reactivity (ER) is widely measured using flow-mediated dilation (FMD) of brachial artery. Conventional measurement of FMD is influenced by factors such as input shear stress, arterial transmural pressure, diameter and thereby arterial material properties (ε). Thus, for a reliable interpretation of FMD, it has to be normalized with respect to the above confounding factors. Normalization of FMD with shear stress at the time of measurement has been reported to reduce measurement variability. However, its widespread usage among the research community is limited. In this work, we examine the feasibility of normalizing the brachial FMD index (FMD%) to ε : extrema (εp), baseline (εb) and extrema change (∆ε) post-ischemia using its inter-day variability against FMD. In-vivo measurements were performed on 10 participants for 2 consecutive days and simultaneous pressure-diameter cycles were collected to estimate the material properties during reactive hyperemia (RH). The box-whisker plot reveals differences in the mean and deviation of FMD to FMD|εb. A significant value for repeatability (ICC ≥ 0.6) was obtained for normalized FMD (FMD|εb) for specific stiffness index (β), pressure-strain elastic modulus (Ep), and local pulse wave velocity (PWV) as compared to FMD. Hence, normalization of FMD% to arterial ε can potentially improve the measurement reliability of ER assessment.Clinical Relevance- This pilot study demonstrates the feasibility of brachial artery stiffness assessment during FMD and its potential use for normalizing the standard FMD measurement.

Assessment of Endothelial Reactivity by Measurement of Vascular Material Response to Shear Stress: A Feasibility Study

Flow-mediated dilation (FMD) evaluates the relative change in arterial diameter during hyperemia to assess the endothelial response due to a shear stimulus. However, conventional FMD measures diameter response alone and the alterations in the arterial wall's material properties during reactive hyperemia, which also influence dilation, go unaddressed. In this work, we examine the material response (MR) of the artery during reactive hyperemia using clinically relevant stiffness markers for the assessment of endothelial reactivity (ER). For this, we have developed an in-house brachial cuff control (BCC) system to continuously acquire brachial pressure which can be integrated with simultaneous measurement of brachial diameter and used to quantify the relative changes in wall property during hyperemia non-invasively. The assessment of endothelial reactivity using material response (ERAMR) was conducted on 20 healthy participants (12M/8F) and the results were compared with conventional FMD (FMD%). The mean pressure response gave an inverse trend to that of diameter response with varying magnitudes during reactive hyperemia (18.71% from baseline for diameter and 2.45% for pressure), there was a significant difference in the measurement of FMD and ERAMR (P < 0.05). The larger distribution of ERAMR compared to FMD% in box-plots further implies the inclusion of within-subject variations. Hence, ERAMR can be a potential estimate of ER, given the need for intensive validations in this line on larger cohorts.Clinical Relevance- This study demonstrates the independent role of arterial wall material properties to quantify endothelial reactivity in response to a shear stimulus.

Association of Local Arterial Stiffness and Windkessel Model Parameters with Ageing in Normotensives and Hypertensives

Computation of arterial stiffness is a well-established, widely accepted method for estimating vascular age. Although carotid-femoral pulse wave velocity is typically used for vascular age assessment, most recent studies have reported the need to consider a combination of local and regional stiffness indices possessing distinct association with the vascular structure and/or function for better prediction of early vascular ageing syndrome. In this work, we investigate the association of clinically validated local stiffness (obtained using biomechanical relations), global stiffness (obtained from 3-element Windkessel modelling), and pulse contour indices from the aorta with ageing and their distribution in normotensives and hypertensives. The analysis was performed on 420 (virtual) subjects (age: 65 ± 11 years) with an equal proportion of hypertensive (age: 65 ± 11 years) and normotensive (age: 65 ± 11 years) subjects. Multivariate linear regression analysis revealed an independent association of each of the indices with age (Adjusted r = 0.75 p < 0.01). Specific stiffness index (r = 0.67, p < 0.001), Augmentation index (r = 0.55, p< 0.001) and total arterial compliance (r = -0.50, p < 0.001) depicted highest correlation with age. There was a significant difference (> 16%, p < 0.001) in mean values of the measured indices between hypertensive and normotensive subjects. The study findings further emphasize the need to combine multiple non-invasive vascular markers to capture the unique aspects of age-induced arterial wall remodelling for reliable monitoring and management of the early vascular ageing syndrome. Clinical Relevance- This study demonstrates an independent and combined predictive role of local/global stiffness and pulse contour indices in ageing.

A Computational Method for the Estimation of the Geometrical and Thermophysical Properties of Tumor Using Contact Thermometry

Contact thermometry is the measurement of surface temperature using sensors in contact with the medium. These surface temperatures can be potential indicators of any abnormality possibly a tumor. This research work aims to present a computation method that makes use of contact thermometry to estimate the geometric center, size, and thermophysical properties of breast tumor. Wearable thermal sensors captured real-time surface temperature readings from discrete point locations. The continuous heat distribution over the domain was formulated using forward heat transfer analysis. The optimization method estimated tumor parameters of the breast, and a three-dimensional thermal model was developed from the estimated parameters. Laboratory experiments on breast phantoms were done to validate the estimation method. Furthermore, real-time temperature readings of human subjects were recorded, and the estimated location and size were then compared with the mammogram results. It was found that the estimated two-dimensional geometric center and the size in diameter of the tumor closely match with the mammogram results. Further, the thermophysical properties estimated using the proposed method had a higher order in subjects having a tumor making it a tool for breast cancer screening.

Impact of lockdown due to COVID-19 pandemic on groundwater salinity in Punjab, India: some hydrogeoethics issues

In the present study, a total of 48 groundwater samples (13 from shallow aquifers depth < 50 m and 35 samples from deep aquifers in the depth range 50-200 m) were collected from three industrial dominant districts (Ludhiana, Jalandhar and Moga) of Punjab after the lockdown period and before the start of southwest monsoon in the month of June, 2020 (pre-monsoon). The values for total dissolved solids (TDS) observed in Monsoon season (August, 2020) and November-December, 2019 (post-monsoon) were compared with the values taken in June, 2020 (pre-monsoon) to see the impact of lockdown due to COVID-19 pandemic on groundwater salinity. ~ 60% of samples were found to have TDS values more than acceptable limit (500 mg/l) before lockdown (post-monsoon season of 2019) period and after or during lockdown period (June, 2020) number of samples more than the acceptable limit (500 mg/l) reduced to 45%. Average TDS values reduced by 25% in shallow aquifers after lockdown and area under TDS values in acceptable limit (500 mg/l) increased by 23% of samples as compared to the TDS values found in monsoon season of year 2019. In deeper aquifers, increase of only 3% area under TDS values in acceptable limit of 500 mg/l was found. Reductions in TDS values in shallow aquifers clearly show that there is an urgent need for proper management of salinity causing elements and regulating these to check groundwater contaminations using the holistic and hydro-geoethical approach.

Breast tumor parameter estimation and interactive 3D thermal tomography using discrete thermal sensor data

This work uses a simple low-cost wearable device embedded with discrete thermal sensors to map the breast skin surface temperature. A methodology has been developed to estimate diameter, blood perfusion, metabolic heat generation and location in X, Y, Z coordinate of tumor from this discrete set of data. An interactive 3D thermal tomography was developed which provides a detailed 3D thermal view of the breast anatomy. Using this system, the user can interactively rotate and slice the 3D thermal image of the breast for a detailed study of the tumor. Finite element method (FEM) and an evolution-based inverse method were used for the parameter estimation. The method was first validated using phantom experiments and the results obtained were within an error of 10% (0.005 W cm^-3) for heat generation and 15% (0.3 cm) for heater location. Further validation was carried out through clinical trials on 60 human subjects. Estimated blood perfusion rate and metabolic heat generation rate exhibit distinguishable difference between cancerous and non-cancerous breast. Estimated diameter and location of tumor in cancerous breast shows good agreement with the actual clinical reports. We have obtained a sensitivity of 82.78% and specificity of 87.09%. Proposed breast tumor parameter estimation methodology with interactive 3D thermal tomography is a good screening tool for breast cancer detection and also useful for clinicians to find out location including depth.

Assessing the influence of work-life balance dimensions among nurses in the healthcare sector

Purpose

The purpose of this paper is to investigate the influence of work-related factors, namely work overload and work support on work-life balance (WLB) dimensions and its significant impact on work satisfaction particularly among South Indian nurses in the healthcare sector.

Design/methodology/approach

The study was carried out in the healthcare sector comprising of 182 nurses employed in various hospitals located in southern parts of India through a structured questionnaire. The study adopted Barron and Kenny’s mediated regression analysis.

Findings

Work satisfaction showed a significant negative relationship with work overload and a positive relationship with work support. WLB dimensions, namely work to personal life strains, personal life to work strains, work to personal life gains (WPLG) and personal life to work gains mediated the relationships between work support and work satisfaction. However, WPLG mediated the relationships between work overload and work satisfaction.

Practical implications

The present investigation directed toward the importance of work-personal life balance experienced by the nurses in the healthcare sector imperatively influence both work and personal life domains and the study suggests that support from the organization, superiors and peers can go a long way in helping the incumbents to attain improved organizational outcomes.

Originality/value

This study focuses on investigating the mediating role of WLB dimensions in the relationship between organizational-related factors and work satisfaction among nurses in the healthcare sector in South India.

Riboswitches in eubacteria sense the second messenger cyclic di-GMP

Cyclic di-guanosine monophosphate (di-GMP) is a circular RNA dinucleotide that functions as a second messenger in diverse species of bacteria to trigger wide-ranging physiological changes, including cell differentiation, conversion between motile and biofilm lifestyles, and virulence gene expression. However, the mechanisms by which cyclic di-GMP regulates gene expression have remained a mystery. We found that cyclic di-GMP in many bacterial species is sensed by a riboswitch class in messenger RNA that controls the expression of genes involved in numerous fundamental cellular processes. A variety of cyclic di-GMP regulons are revealed, including some riboswitches associated with virulence gene expression, pilus formation, and flagellum biosynthesis. In addition, sequences matching the consensus for cyclic di-GMP riboswitches are present in the genome of a bacteriophage.

Immobilized RNA switches for the analysis of complex chemical and biological mixtures

A prototype biosensor array has been assembled from engineered RNA molecular switches that undergo ribozyme-mediated self-cleavage when triggered by specific effectors. Each type of switch is prepared with a 5'-thiotriphosphate moiety that permits immobilization on gold to form individually addressable pixels. The ribozymes comprising each pixel become active only when presented with their corresponding effector, such that each type of switch serves as a specific analyte sensor. An addressed array created with seven different RNA switches was used to report the status of targets in complex mixtures containing metal ion, enzyme cofactor, metabolite, and drug analytes. The RNA switch array also was used to determine the phenotypes of Escherichia coli strains for adenylate cyclase function by detecting naturally produced 3',5'- cyclic adenosine monophosphate (cAMP) in bacterial culture media.