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Objective To deduce analytic solution of the displacement and stress distributions for the coronary stent based on reasonable assumptions, and to investigate the influence from the wave number of support bars on stress distributions by combining the results of finite element analysis. Methods A local cylindrical coordinate system was established to deduce analytical solution of the displacement and stress components of the periodic support bar of the rectangular-wave type vascular stent under vascular systolic pressure. The support bar model was established by using ANSYS, to calculate the numerical results of stress analysis. By analyzing the consistency of stress curves obtained from the two methods, the accuracy and applicability of analytical solutions were verified. The influence from the number of wave crests for support bars on the stress under systolic pressure was investigated by analytic solution. Results The analytical stress curves were basically in conformity with those from the ANSYS results. When the number of wave crests was 6, there were both tensile and compressive stresses in circumferential direction of the cross bar. Conclusions When the number of wave crests was 6, such stents could effectively prevent restenosis in blood vessels during working. The derived analytical solution could be used to analyze mechanical properties of one-cycle support bars of rectangular-wave type stent, and the research findings provided a new idea to further recognize and study the stress distributions on coronary stent to reduce the restenosis rate of interventional therapy.
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Objective To explore the influence of different pressures and diameters in vitro on complete ligation degree of esophageal varices based on the principle of LDRf typing.Methods According to the different preset venous pressure,the experimental porcine veins were used to establish vascular pressure models and divided into three groups (group A 25-30 cmH2O,group B 35-40 cmH2O,group C 45-50 cmH2 O).The porcine esophagus was selected to establish models of esophageal varices,and divided into three groups according to the diameter of esophageal varices (group D1 0.4-1.0 cm,group D2 1.0-1.5 cm,group D3 1.6-2.0 cm).Influence of pressure and diameter on complete ligation degrees was evaluated by univariate and multivariate analysis.Results Group A completed 18 ligations (56.25％,18/32),group B 12 ligations (37.50％,12/32),and group C 11 ligations (33.33％,11/33),which were not significantly different by pressure (x2 =3.6126,P =0.0573).Group D1 completed 35 ligations (94.59％,35/37),group D2 6 ligations(16.67％,6/36),and D3 completed no ligation (0％,0/24),which were significantly different by diameter (x2 =38.0014,P =0.0000),indicating that the diameter of the varices exerted greater influence on the ligation degree.The logistic regression analysis showed that variceal pressure and diameter were the independent factors for complete ligation degree (P =0.000).Conclusion Complete ligation is effective and safe when the variceal diameter is 0.4-1.0 cm,or variceal pressure is 25-30 cm H2O.Endoscopic treatment for varices with the guide of LDRf typing is scientific and feasible.
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BACKGROUND: Autonomic reflex dysfunction in patients with diabetes is associated with unstable cardiovascular response in perioperative period. In this study we wanted to investigate the extent to which the intraoperative cardiovascular responses depend on the degree of autonomic dysfunction. METHODS: The influence of diabetic autonomic neuropathy upon the behavior of the circulatory system was investigated in 35 patients who had undergone ophthalmological surgery. A standardized test combination was used to study the patient's cardiovascular refractory reactions. The patients were then divided into a control group, non-diabetics without autonomic neuropathy (n = 18), and an experimental group, diabetics with autonomic neuropathy (n = 17). The anesthetic and surgical procedures (vitrectomy) were standardized and always identical. RESULTS: During the induction of anesthesia, patients in the experimental group didn't experience changes in mean arterial blood pressure and heart rate as compared to patients in control group. During the maintenance of anesthesia, there were significant decreases in mean arterial blood pressure and heart rate in the experimental group, but in the state of emergence of anesthesia, there were no significant differences in either group. CONCLUSION: Autonomic neuropathy represents a perioperative risk factor, especially during induction and maintenance of anesthesia. I therefore recommend an autonomic nervous function test for evaluation of diabetic autonomic neuropathy in preoperative anesthesiological examination.