Physiological Variations in the Cardiac Output of Man Vi. the Value of the Cardiac Output of the Normal Individual in the Basal, Resting Condition

Despite the obvious physiological and clinical importance of knowing the value of the cardiac output of the normal human individual, the difficulties and errors involved in the methods used for determining the cardiac output have heretofore precluded the possibility of obtaining this value. The present paper reports the results of a series of determinations of the cardiac output, pulse, oxygen consumption and, in certain cases, of the blood pressure of fifty-one individuals selected at random from a group of young, normal individuals. This series comprises the greatest number of cases heretofore reported and is sufficiently large and of a degree of accuracy to permit the evaluation of the normal cardiac output of man. The data also are evidence for the constancy of the cardiac output of man and the possibility of predicting a value for the normal individual. This ability to predict the cardiac output is particularly important for the clinical applications of determinations of the cardiac output, for it permits one to compare a given determination with the average normal value and thus conclude as to the degree of its abnormality. METHODS. For the determination of the cardiac outputs, acetylene was used as described in previous publications (Grollman, 1929a,b,c,d). The most likely cause of error in the use of this method is a failure on the part of the subject to mix properly in the rebreathing procedure. The criteria for complete mixing have been described in a previous paper (Grollman and Marshall, 1928) and the ease with which failure to attain complete mixture may lead to errors has been demonstrated (Grollman, 1928). However, to a certain group of individuals, acetylene has a very unpleasant taste despite the description of a %ot unpleasant, ethereal odor " which chemical treatises (Meyer and Jacobson, 1907) attribute to the purified gas. Such subjects may fail to breathe deeply and thus render even more difficult the attainment of correct results. It is, therefore, essential to insure that the breathing has not been influenced by the subject's reactions and that complete mixture has been attained. It is quite prob