RESUMO
The induction of mild hypothermia has been considered as an important means to provide protection against cerebral ischemia. Yet, to date, the relative clinical efficacies of different noninvasive methods for reducing core body temperature have not been thoroughly studied. The aim of the current investigation was to compare the relative effectiveness of several noninvasive cooling techniques for reducing core temperatures in healthy volunteers. Cooling methods included convective/conductive and evaporative/conductive combinations, as well as evaporative cooling alone. Additionally, focal facial warming was employed as a means to suppress involuntary motor activity and thus better enable noninvasive cooling. Core temperatures were measured so to monitor the relative efficiencies of these induced cooling methodologies. With each employed methodology, rectal temperature reductions were induced, with combined evaporative/conductive (n=4, 1.44°C±0.99°C) and convective/conductive (n=4, 1.51°C±0.89°C) approaches yielding the largest decreases: note, that evaporative cooling alone was not as efficient in lowering core body temperature (n=10, 0.56°C±0.20°C; n=16, 0.58°C±0.27°C). In this study on healthy volunteers, the evaporative/conductive and convective/conductive combination methods were more effective in reducing core temperatures as compared with an evaporative approach alone. These therapeutic approaches for the induction of mild hypothermia (including the use of facial warming) could be employed in warranted clinical cases, importantly without the need for administration of anesthetics or paralytics.
RESUMO
Noise-induced hearing loss includes both temporary (TTS) and permanent (PTS) threshold shifts. Although TTS and PTS have many similarities, their underlying mechanisms are different. Both TTS and PTS are seen in hearing-conservation programs, making it important to consider both when making physiological measurements of inner-ear damage in applied settings. There are many ways that physiological mechanisms could be useful in screening for NIHL. Can normal-hearing and NIHL ears be differentiated from one another? Can the physiological measure be used in place of behavioural hearing-threshold measures of TTS and PTS? Can it be used to indicate sub-clinical damage (i.e., noise-induced permanent alterations to the inner ear without a corresponding hearing decrement)? Can it be used to indicate pre-clinical hearing loss (i.e., the sub-clinical damage eventually turns into hearing loss)? Finally, can the physiological measure be used to predict susceptibility to NIHL? Evoked otoacoustic emissions (EOAEs) depend on normal outer hair cells for their generation. Because this is the site in the inner ear in humans that is most susceptible to noise, there has been considerable interest in the application of EOAEs to NIHL screening. In this review, the application of distortion-product EOAEs (DPOAEs) is considered for this purpose, emphasizing work from our laboratory, but including that of others as well. Wherever possible, we compare the performance of DPOAEs as a screening tool to transient-evoked otoacoustic emissions (TEOAEs). We emphasize the importance of how well DPOAEs perform in screening for NIHL in individuals rather than for groups of people; the importance of using large numbers of subjects; and the importance of longitudinal studies.
