Rapid whole-body hypothermia: Analysis and modeling

Julia Cathy Klock, University of Rhode Island

Abstract

For subjects stricken by sudden cardiac arrest outside a medical facility, the overall survival rate approaches 25% (best scenario case) with advanced life support and only 5% without. Often survivors face sequelaes such as brain damage. Prior studies have revealed that resuscitative mild hypothermia (core temperature ranging from 34°C to 32°C) can alleviate damage to vital organs, including the brain. Although, the delayed cooling (up to several hours with no blood flow) has proven to be effective, time is believed to be critical to achieve maximum efficiency. A new cooling device, the Thermosuit™ System (TSS) induces hypothermia rapidly with direct ice-water contact to skin. This cooling means matches high cooling rate, ease-of-use and potential portability. ^ Objectives. The study (1) compares the performance of the TSS with a commercial water filled blanket product: The Gaymar Medi-Therm-III cooling blanket system; (2) examines whether advanced life support procedures such as defibrillation could be administered safely and effectively in water; (3) analyzes and models the body response to the cooling. ^ Methods. Three protocols were followed: (1) a randomized, unblinded, 2-period, cross-over comparison of the TSS with another non-invasive cooling method on a large swine model. (2) Conventional AED defibrillation shocks applied to animals in induced ventricular fibrillation during a TSS cooling. (3) TSS-induced hypothermia in different configurations. In every protocol, the swine were instrumented with arterial pressure monitoring, ECG and temperature sensors. These values were recorded with PC based laboratory computer systems. ^ Conclusions. TSS cooling was similar to Gaymar Medi-Therm III, with the exception that the overall temperature drop was much quicker. The TSS achieves a 18.64°±13.66°C/h rate versus the Gaymar at 4.61±3.11°C/h. Safe and efficient heart defibrillation and pacing are possible while cooling under water with the TSS with no additional safety recommendation. The body response to TSS cooling can be modeled by a 8th order (RC) low-pass filter. Vasoconstriction is often the only metabolic response established during the TSS cooling process. Induced pre-vasodilation could help improve the cooling rate and the active cooling can be shortened in time if the continuous fall in temperature is accounted for. ^

Subject Area

Engineering, Biomedical|Engineering, Electronics and Electrical

Recommended Citation

Julia Cathy Klock, "Rapid whole-body hypothermia: Analysis and modeling" (2007). Dissertations and Master's Theses (Campus Access). Paper AAI3276989.
http://digitalcommons.uri.edu/dissertations/AAI3276989

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