Electrocardiographic changes due to sauna bathing. Influence of acute reduction in circulating blood volume on body surface potentials with special reference to the Brody effect.

Sauna bathing causes profuse sweating, which could lead to an acute reduction in the circulating blood volume and the intraventricular blood volume. Sauna bathing thus provides a good clinical model with which to evaluate the inter-relation between the body surface potentials and the intraventricular blood mass. After bathing the internal dimension of the left ventricle in diastole was appreciably decreased, whereas the spatial QRS magnitude and the magnitudes of the R and Q waves in lead Z and of the S wave in lead X were significantly increased. These findings indicate that a decrease in the intraventricular volume was accompanied by an increase in the body surface potential and contradict the Brody effect.