Abstract 11368: Heliox-Perfluorocarbon Aerosol Ventilation Rapidly Lowers Brain and Core Temperatures in Swine
Introduction: Time is of the essence for induction of therapeutic hypothermia (TH) following cardiac arrest. Mortality increases by an estimated 20% for every one-hour delay in reaching target temperature. Current TH methods are slow, cumbersome, unreliable or highly invasive. We propose a novel alternative method for rapid induction of TH using the lungs as a heat exchanger. Hypothesis: In swine, we tested the hypothesis that augmented heat extraction from the lungs through inhalation of cooled heliox and perfluorocarbon (PFC) aerosol rapidly lowers core body and brain temperatures.
Methods: In eight domestic cross-bred pigs (34-35 kg), brain temperatures were measured using a Camino® 4-Fr thermistor inserted through a right frontal burr hole. Core temperatures were recorded (~0.017 Hz or faster) from the pulmonary artery, lower esophagus, bladder, rectum, nasopharynx and tympanum. Following instrumentation, ventilation was switched from room air to cooled heliox (0±2°C, He 70%:O2 30%) and 0.14% (v/v) PFC mist. Heliox-PFC ventilation was continued for 90 minutes or until the target temperature of 32°C was reached.
Results: All core temperatures declined rapidly following initiation of heliox-PFC mist ventilation. Pulmonary artery temperature (mean ±SD) reached target in 56±6.8 minutes. Brain temperature declined to target in 68±5.5 minutes. Core temperatures cooled at the following relative rates: tympanum > esophagus > pulmonary artery > nasopharynx> brain > bladder > rectum (Figure).
Conclusion: The high thermal conductivity of helium and the vaporization of PFC produce rapid cooling of the alveolar gases. The thinness and the large surface area of the alveolar membrane facilitate rapid cooling of the pulmonary circulation. Depending on the blood flow, insulation and exposure to the external environment, organs cool at varying rates. In conclusion, transpulmonary cooling is a novel, minimally invasive and effective technique to induce TH.
- © 2012 by American Heart Association, Inc.