Using heat to kill SARS-CoV-2.

The current coronavirus pandemic has reached global proportions and requires unparalleled collective and individual efforts to slow its spread. One critically important issue is the proper sterilization of physical objects that have been contaminated by the virus. Here, we review the currently existing literature on thermal inactivation of coronavirus (SARS-CoV-2) and present preliminary guideless on temperatures and exposure durations required to sterilize. We also compare these temperatures/exposure durations with potential household appliances that may be thought capable of performing sterilization.

Transcutaneous Recharge: A Comparison of Numerical Simulation to In Vivo Experiments.

OBJECTIVE: Numerical simulation and animal experiments quantified tissue temperatures during the transcutaneous recharge of neuromodulation implants. The temperature results were used to determine the likelihood of tissue injury in humans. MATERIALS AND METHODS: Experiments were completed using sheep with implants at different depths ranging from 0.7 to 2.15 cm. The calculations were replicates of the experiments. Additional calculations were completed for laterally offset implants (up to 2 cm). Benchtop tests were performed to determine the power dissipation in the components. These power dissipation rates were inputs to the simulation. The now-verified model was next applied to a human situation with a core temperature of 37°C. RESULTS: There was excellent agreement between the simulations and the animal-model for all depths; the experimental and simulated temperatures near the implant were almost identical. The results were negligibly affected by a misalignment of the implant. The maximum experimental temperatures in the sheep were 41.8, 43.2, and 41.8°C while the calculated maxima were 41.9, 43.3, and 41.2°C for the shallow, medium, and deep cases, respectively. The experimental values are 3.1, 4.5, and 3.1°C above the body core temperature. The simulation results are 3.2, 4.6, and 2.5°C above the core temperature. The model was then applied to a human situation with a body core temperature of 37°C. The maximum values of the simulated temperatures are 39.9, 41.2, and 39.1°C. The cumulative equivalent exposure at 43°C (CEM43) for these three implant depths are 0.30, 0.88, and 0.12 min. These thermal exposures are below those known to cause thermal injury in human skin tissue. CONCLUSIONS: The numerical simulation predicts tissue temperatures during transcutaneous recharge of implants. Results show that the implant depth does not have a large impact on the tissue temperatures and thermal exposures are sufficiently low so that they are unlikely to have any physiologic consequence.

Alterations of Blood Flow Through Arteries Following Atherectomy and the Impact on Pressure Variation and Velocity.

Simulations were made of the pressure and velocity fields throughout an artery before and after removal of plaque using orbital atherectomy plus adjunctive balloon angioplasty or stenting. The calculations were carried out with an unsteady computational fluid dynamic solver that allows the fluid to naturally transition to turbulence. The results of the atherectomy procedure leads to an increased flow through the stenotic zone with a coincident decrease in pressure drop across the stenosis. The measured effect of atherectomy and adjunctive treatment showed decrease the systolic pressure drop by a factor of 2.3. Waveforms obtained from a measurements were input into a numerical simulation of blood flow through geometry obtained from medical imaging. From the numerical simulations, a detailed investigation of the sources of pressure loss was obtained. It is found that the major sources of pressure drop are related to the acceleration of blood through heavily occluded cross sections and the imperfect flow recovery downstream. This finding suggests that targeting only the most occluded parts of a stenosis would benefit the hemodynamics. The calculated change in systolic pressure drop through the lesion was a factor of 2.4, in excellent agreement with the measured improvement. The systolic and cardiac-cycle-average pressure results were compared with measurements made in a multi-patient study treated with orbital atherectomy and adjunctive treatment. The agreements between the measured and calculated systolic pressure drop before and after the treatment were within 3%. This excellent agreement adds further confidence to the results. This research demonstrates the use of orbital atherectomy to facilitate balloon expansion to restore blood flow and how pressure measurements can be utilized to optimize revascularization of occluded peripheral vessels.

Validation of Numerically Simulated Tissue Temperatures During Transcutaneous Recharge of Neurostimulation Systems.

OBJECTIVE: A research study combining numerical simulation and animal-model experiments has been performed to assess the ability of simulation to accurately calculate temperatures within living tissue during the recharge of a neuromodulation system (Restore Ultra device, Medtronic Neuromodulation, Minneapolis, MN, USA). MATERIALS AND METHODS: The experiments were carried out on a sheep with the neuromodulation implant set to depths of 0.6 cm and 2.1 cm. Temperatures were recorded on the surfaces of the implant and on the sheep skin. Finite element simulations were carried out to determine the degree to which the simulations and experiments match. Additional calculations were performed for an intermediate implant depth. RESULTS: It was found that there was excellent agreement between the simulations and the animal model for both depths. CONCLUSION: It is shown that numerical simulation using the Pennes bioheat equation is capable of predicting temperature increases within living tissues when implanted heat-generating devices are in use. The device used in the present study does not give rise to temperatures which cause concern of thermal injury or safety. The study was performed for aligned antenna and implant.

Estimating the time and temperature relationship for causation of deep-partial thickness skin burns.

The objective of this study is to develop and present a simple procedure for evaluating the temperature and exposure-time conditions that lead to causation of a deep-partial thickness burn and the effect that the immediate post-burn thermal environment can have on the process. A computational model has been designed and applied to predict the time required for skin burns to reach a deep-partial thickness level of injury. The model includes multiple tissue layers including the epidermis, dermis, hypodermis, and subcutaneous tissue. Simulated exposure temperatures ranged from 62.8 to 87.8°C (145-190°F). Two scenarios were investigated. The first and worst case scenario was a direct exposure to water (characterized by a large convection coefficient) with the clothing left on the skin following the exposure. A second case consisted of a scald insult followed immediately by the skin being washed with cool water (20°C). For both cases, an Arrhenius injury model was applied whereby the extent and depth of injury were calculated and compared for the different post-burn treatments. In addition, injury values were compared with experiment data from the literature to assess verification of the numerical methodology. It was found that the clinical observations of injury extent agreed with the calculated values. Furthermore, inundation with cool water decreased skin temperatures more quickly than the clothing insulating case and led to a modest decrease in the burn extent.