It has been noted previously1-4 that a warm and humid environment increases the output of the heart. Cardiac output was measured by the direct Fick method in five volunteer subjects resting in bed in wards of the Charity Hospital during the New Orleans tropical weather of July and August, 1957.3 The cardiac output in all patients was found to be higher (mean about 50%) when they were in a warm and humid ward open to the outside weather than when in an air-conditioned and comfortable one. Because of the importance of these findings it was considered advisable to repeat these studies in five more volunteer patients during the New Orleans tropical weather of August, 1958. This report is concerned with the data obtained during the summers of 1957 and 1958.
Materials and Methods
Five additional adult Negro subjects (Subjects 6 through 10), four of whom had no