STUDIES OF CARDIAC OUTPUT IN NORMAL MEN

Abstract

Experiments on the fundamental assumptions of the improved ethyl iodide method for the determination of cardiac output were repeated and yielded results which increased the authors'' confidence in the method. This method yielded duplicate determinations whose average difference was 6.4% of their mean. The results demonstrate that the cardiac output of resting normal adult <[male][male] is essentially constant. The average level in 10 normal young adult [male][male] in the post absorptive condition, after a prolonged rest period in the horizontal position, was 3.97 liters per min. or 2.08 liters per sq. meter of body surface. These results are quite similar to those of Grollman. The experiments indicated that food and excitement increase cardiac output. Cold caused changes in both directions; becoming warm after having been chilled was always accompanied by a decrease of cardiac output. The change from the lying to the standing position caused no significant alteration in 4 subjects; in 1 subject the cardiac output standing was constantly lower than that lying. These results are in satisfactory agreement with those of many other methods. A subject having a highly reactive type of circulation with inconstant blood pressure showed no difference in general level of cardiac output, nor in response to food, cold, position, and excitement from the other more stable subjects.