Effect of vaccination on clinical outcomes in COVID-19 positive chronic kidney disease patients on haemodialysis

Introduction: Coronavirus disease 2019 (COVID-19) resulted in high mortality worldwide, with significantly higher mortality among patients with comorbidities including chronic kidney disease (CKD). Vaccines were developed against COVID-19 and it was given emergency approval because of the associated high mortality. There are only few studies on the efficacy of vaccine in CKD patients on haemodialysis. Effect of vaccination on clinical outcomes in COVID-19 positive CKD patients on haemodialysis was studied. Materials and methods: In this retrospective study on CKD patients on haemodialysis with confirmed COVID-19 infection, comparison was done on the clinical outcomes between the vaccinated and unvaccinated population. Results: Of the 104 patients, 74 patients were vaccinated against COVID-19 and 30 were unvaccinated. The study population received either covishield (50) or covaxin (24) which were the approved vaccines in India at that time. Among the vaccinated group 15 (20%) needed invasive mechanical ventilation and 16 (53%) in the unvaccinated group (P value 0.001). There were 16 (22%) deaths in the vaccinated group and 15 (50%) in the unvaccinated group with a significantly higher mortality in the unvaccinated group (P value 0.005). 11 (21%) patients on covishiled and 4 (18%) on covaxin needed invasive mechanical ventilation and there were 12 (24%) deaths in the covishield group and 4 (18%) in covaxin group. Conclusion: Severity of disease and mortality is less in vaccinated CKD patients on haemodialysis compared to unvaccinated reiterating the importance of vaccination against COVID-19 in high risk patients

Investigation of Fluid Loading Effects on CMUT arrays for Cardiac Imaging

This thesis presents a method to minimize the resonant frequency drift of Capacitive Micromachined Ultrasonic Transducers (CMUTs) due to fluid loading. A unified mathematical model for the resonant frequency of a CMUT that includes the electrostatic spring softening effect and the fluid loading effect due to the coupled fluidic layer has been developed that provides the basis of the proposed approach. The minimization method involves dynamic adjustment of the DC bias voltage to modify the electrostatic spring softening parameter to offset the effects of fluid loading. Analytical and COMSOL based 3D Finite Element Analysis (FEA) results show that the drift in the resonant frequency of a 6 MHz CMUT operated in water can be compensated by adjusting the bias voltage by 2% from its 75% pull-in voltage value to render an improvement of 4% in lateral and axial resolutions in imaging applications. A bias voltage adjustment of 9% of the 75% pull-in voltage value is necessary to achieve an improvement of 20.74% in glycerol medium. A microelectronics-based compensation scheme has been developed for dynamic voltage adjustment to offset the frequency drift. The developed scheme has been validated through simulation in MATLAB/Simulink