Keywords: heart rate variability/exercise/diabetes/hypertension/deep breathing Tohoku

In this paper, the design, analysis and fabrication of a micromachined piezoelectric endoscopic tactile sensor to determine the properties of tissues in minimally invasive surgery is presented. The viscoelastic Kelvin model is employed for tissue characterization. A closed form expression is derived to express the relationship between the force ratio, compliance and the equivalent viscous damping of the tissue. The designed sensor uses a PVDF film as its sensing element. The sensor consists of rigid and compliant elements which are mounted on the tip of an endoscopic surgical grasper tool. The relative force between adjacent parts of the contact object is used to measure the viscoelastic properties experimentally.

BackgroundVarious cardiovascular disease (CVD) risk factors have been implicated to correlate with the severity of the disease. Present study was conducted to correlate one such risk factor i.e. fasting serum C-peptide with the presence or absence and the severity of CVD in Indian population.Methods68 patients with metabolic syndrome who underwent coronary angiogram for suspected CVD were included. Their fasting serum C-peptide levels were measured in addition to routine biochemical and cardiological tests. They were divided into 2 groups – those with a positive coronary angiography findings (Group 1) and those with normal coronary angiograms (Group 2). The former group was further divided into those with an Acute Coronary Syndrome (ACS) (Group 1a) and those with Chronic Stable Angina (CSA) (Group 1b). SYNTAX scoring was done to assess the severity of coronary artery disease in groups 1a and 1b. Levels of C-peptide were compared between the groups.ResultsThe mean C-peptide of all patients was 1.9 (±0.8) ng/mL. Among the group 2 patients, mean serum C-peptide value was 1.6 (±0.4) ng/mL. And it was 2.7 (±0.8) ng/mL and 1.7 (±0.9) ng/mL among the ACS and the CSA groups respectively. The ACS and CSA group had statistically significant higher values of C-peptide compared to patients with normal coronary angiograms. The two-way ANOVA done to find out the variability of C-peptide among the 3 groups revealed significant differences among the groups with a p-value of <0.001. When correlated with SYNTAX scores, this yielded significant results.ConclusionC-peptide levels appear to correlate with the severity of the CVD as measured by SYNTAX score.

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Analytical and finite element methods are employed to determine the contact pressure on the surface of a tissue being grasped by an endoscopic grasper, in Minimally Invasive Surgery (MIS). Normally, an endoscopic grasper is corrugated (teeth-like) in order to grasp slippery tissues. It is highly important to avoid damage to the tissues while grasping and manipulation during endoscopic surgery. Therefore, it is essential to determine the exact contact pressure on the surface of the tissue. To this end, initially a comprehensive closed form, finite element and experimental analysis of grasping contact pressure on viscoelastic materials which have similar properties as that of biological tissues is studied. The behavior of a grasper with wedge-like teeth, when pressed into a linear viscoelastic material is examined. Initially, a single wedge penetrating into a solid is studied and then is extended to the grasper. The elastic wedge indentation is the basis of the closed form analysis and the effects of time are included in the equations by considering the corresponding integral operator from viscoelastic stress-stain relations. In addition, a finite element analysis is carried out in Ansys-10 software. Finally, the experimental results are presented to validate both analytical and FEM results. The results of this study provide a closed form expression for grasping contact pressure force and contact area along with the variations of stress in tissue obtained through FEM analysis. The variation of contact pressure and the rate of growth of the contact area with time are presented.