A thermal entrainment device for cardiovascular investigation.

Information on the temperature control mechanism of the body can be obtained from several body parameters such as the irregularities of the heart beat. Entrainment of the temperature control mechanism occurs when air is alternately heated and cooled as it passes over a subject's limb. The fluid flow, timing circuits and measuring devices for this experiment are described in detail. Experiments were carried out on normal healthy adults resting and during recovery from heavy exercise. Electrocardiogram and optical plethysmography of the little finger were analysed by Fast Fourier Transform. Entrainment occurs with period times between 8s and 80s with the best entrainment occurring at a period time of 30s. The value of the work and the areas presently under investigation are outlined.