Development of a Human Surrogate Measurement Device for Testing Infants Undergoing Therapeutic Hypothermia

SUMMARYIn medical device development, bench models are preferred for testing as they minimize variables, are cheaper, and faster than in-vivo studies. Developers of patient temperature management systems that incorporate warming and cooling garments did not previously have a bench model that could simulate in-vivo studies due to the complex nature of human thermal physiology. To address this need, an adaptive thermal manikin system was developed to simulate infants undergoing therapeutic hypothermia. An adaptive manikin system, i.e., a thermal manikin that is controlled by a human thermal model, is a test device that can simulate thermoregulation to accurately predict core temperature and produce spatially varying skin temperatures and sweat rates consistent with that of the human body. An existing customizable human thermal modeling framework was used to create a 14 segment infant human thermal model and was combined with a commercially available sweating thermal manikin designed to represent the body build of a 9 month old infant. The infant model was tested by reproducing experiments described in the literature. This served to validate the model’s ability to predict transient core temperature and mean skin temperature in a step change in ambient conditions, as well as local skin temperatures and evaporation rates a various ambient conditions in relative steady-state. The adaptive manikin system was tested by simulating an infant undergoing therapeutic hypothermia. Consistent with past studies concerned with the cooling of neonate patients, the therapeutic device was able to reduce the predicted core temperature in the adaptive manikin system to 33.5°C within 94 minutes. In order to quantify the full range of core temperature reduction that could be achieved in patients with varying levels of impeded thermoregulatory function due to anesthesia, results are presented from testing with and without vasoconstriction and shivering.