Abstract

A study was made of the pulse rate, blood pressure, oxygen consumption, arterio-venous oxygen difference, and cardiac output changes which followed the oral administration of moderate doses of alcohol (in various forms), and caffeine (as caffeinecitrate), and the smoking of tobacco for varying lengths of times.

The administration of even small doses (10 cc.) of alcohol to non-drinkers resulted in a psychic response characterized by a transient rise in pulse rate, blood pressure, and cardiac output, with a drop in the arterio-venous oxygen difference. Where no psychic reaction was elicited (e.g., in moderate drinkers), such changes did not occur. In such cases amounts of alcohol (equivalent to 60 cc. of whiskey) showed no demonstrable changes in blood pressure, oxygen consumption, arterio-venous oxygen difference, or cardiac output, with a change of only a few beats per minute in the pulse rate during the first half-hour after its administration. Larger quantities of alcohol (35 cc. or more) caused slight changes in the pulse rate with appreciable increases in the blood pressure and cardiac output.

Small doses of caffeine were without effect on the cardio-vascular system. Larger doses (0.5 to 1.0 gram) caused, in most cases, a rise in the oxygen consumption (10 to 35 per cent), slight or no changes in the pulse rate, an increase in the arterio-venous oxygen difference, and a slight rise in the cardiac output. In some individuals (in whom there was a subjective nervous effect after caffeine), the rise in arterio-venous oxygen difference was less or absent and the increase in cardiac output, as well as in the blood pressure and pulse rate were quite pronounced.

Tobacco when indulged in its usual forms in moderate amounts by habitual smokers produced no demonstrable changes in blood pressure or cardiac output with only slight or no increase in the pulse rate. Excessive smoking or smoking of tobacco in unaccustomed forms (e.g., a strong cigar by an habitual cigarette smoker) resulted in very large rises in pulse rate (20 per minute), moderate rises in blood pressure, and moderate increases in cardiac output. When the blood pressure changes were slight (despite a great increase in pulse rate), the cardiac output changes were minimal or absent.

The value of cardiac output measurements in studying the pharmacological and therapeutic effects of substances on the cardio-vascular system of normal man was emphasized. The relation of the cardiac output to other cardio-vascular and metabolic functions was also discussed.