Oxygen Consumption in Relation to Thermal Sensation on Cold Exposure

Experiments were made to study the regulatory mechanism of body temperature during cold exposure and the main emphasis was laid on the relation of reactions against cold, particularly of an increase in heat production, to thermal sensations.1) When a lepromatous patient with a wide-spread dermal lesion where thermal sensations were extensively affected was exposed to cold, the patient complained little, unlike a healthy control, of the cold for the first several minutes. The body temperature of the patient was steadily falling and after about 15 minutes when the fall of the temperature exceeded 1°C., the patient began to suffer a chill and oxygen consumption showed a marked increase.2) When the rectal temperature of a healthy man was lowered with a cold water bath the threshold of warmth on the flexor surface of the forearm suffered no change as long as the skin temperature was maintained at the same level, while the threshold of hot pain became higher distinctly and the threshold of cold pain became lower.3) Reactions in each stage of cold exposure leading to death was observed in an unanesthetized rabbit.A) EEG's of the cortex (the postcentral area), subcortex and thalamus showed very similar pattern though taken from different levels of the brain. The electrical activity of the brain was discussed in relation to EMG and heat production, and an introduction of some momentous change was highly conceivable at the rectal temperature level of 28-26°C.B) Sensory EEG arousal response revealed that the ascending reticular system was hyperresponsive in a rectal temperature zone of 34-30°C. and below it the system reacted less by degrees.C) The frequency of EEG from the sympathetic zone began to increase below the rectal temperature level of 37 or 36°C. A peak which was reached at 33-30°C. was followed by a progressive decrease. As to the parasympathetic pattern the frequency did not show an increasing tendency till the rectal temperature fell down below 33-31°C. A peak of increased frequency at 28-27°C. was followed by a gradual decrease. A transient rise was observed on both EEG's in the excitation stage before death.Based on these experimental findings some interrelationship on introduction of reactions to cold was discussed among the somatosensory cortex, ascending reticular system and autonomic nervous center.