Did Jesus Repent?

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A comparison of the disposable versus the reusable laryngeal mask airway in paralyzed adult patients

A disposable (polyvinyl chloride) laryngeal mask airway (LMA) with dimensions identical to, but physical properties different from (stiffer tube/thicker cuff), the reusable (silicone) LMA has recently become available. We performed a randomized, cross-over study of 60 paralyzed, anesthetized patients to test the hypothesis that the use of these devices was different in terms of ease of insertion, airway sealing pressure, fiberoptic position, and changes in intracuff pressure during NO anesthesia. We also tested the hypothesis that the airway sealing pressure of the LMA is suboptimal if the cuff is inflated to a high intracuff pressure. Both the devices were inserted into each patient in random order, and their performance was assessed at two intracuff pressures (60 and 180 cm HO) by a blind observer. Subsequently, intracuff pressures were measured during NO anesthesia for the second device. Ease of insertion was similar: there was no difference in first attempt success rates (97% vs 98%) and insertion times (15 vs 13 s) for the disposable and reusable LMA, respectively. There were no differences in airway sealing pressure or fiberoptic position. Airway sealing pressure was significantly higher at 60 cm HO intracuff pressure compared with the airway sealing pressure at 180 cm HO for both devices (P < 0.02). During NO anesthesia, the intracuff pressure remained stable for the disposable LMA but increased significantly for the reusable LMA We conclude that the disposable and reusable LMAs perform similarly in paralyZed adult patients, but that the disposable LMA has more stable intracuff pressures during NO anesthesia. Inflation of the LMA to high intracuff pressures produces a suboptimal seal. Implications: This randomized, single-blind, within-patient study of 60 adult patients shows that the disposable (polyvinyl chloride) and reusable (silicone) laryngeal mask airways perform similarly, but that the disposable laryngeal mask airway has more stable intracuff pressures during NO anesthesia. Inflation of either device to high intracuff pressures produces a suboptimal seal

Performance analysis and validation of an explicit local time-stepping algorithm for complex hypersonic flows

A local time-stepping (LTS) algorithm has been implemented and tested into the open source computational fluid dynamics code (CFD), Eilmer. The goal of this work is to investigate the performance of LTS for simulating complex hypersonic flows, in particular, flows that include strong inviscid/viscous interactions. Results from a range of laminar and turbulent test cases spanning a hypersonic flow range of Mach 4.5 to Mach 14.1 are presented. The relative efficiency of the LTS implementation, as compared to a global time-stepping (GTS) implementation, is reported. The LTS implementation is validated against experimental data for each test case to assess the accuracy and applicability of LTS for hypersonic flows. The results presented in this work show that LTS can accelerate the steady-state solution of complex hypersonic flows, in particular, speedup factors ranging from 17.5 to 174 are reported for the test cases presented. The accuracy of the solutions obtained using LTS match favourably to those obtained using GTS, in addition to comparing well to experimental data. Performance is further validated against complex scramjet cavity combustor flow fields with shear layer, shock interactions and recirculation regions. Overall, the results presented in this paper demonstrate that LTS is an easy to implement technique that can provide fast and accurate results for a gamut of high-speed flow problems