Engineering aspects of controlled hypothermia

The investigation presented concerned applications of experimental and clinical hypothermia. The techniques and apparatus commonly utilized for its production have been reviewed and are described, both as regards to surface and extra-corporeal cooling. The heat transfer phenomenon has been examined both from the physiological and engineering standpoint. To enable the transient state of heat transfer to be studied and to provide another means of predicting the after-fall invitable with surface cooling, the concept of an isothermic body, having little or no temperature gradient, is considered. A study has been made on a large number of dogs in collaboration with the Department of Anaesthetics, Royal Infirmary, Glasgow, to investigate the effects of hypothermia on the circulatory system. Thirty-one cases are reported here for the purposes of hypothermic cabinet calibration; for pre-determination of the total heat extraction of the animal and for the study of temperature gradients across the muscles of the hind legs during the cooling process. In the experiments the Forrester-Brown (1961) technique of air cooling was employed, the cooling cabinet being part of the operating table for the animals. In all cases the desired temperature level of the oesophagus was 3