HUMAN CARDIODYNAMIC RESPONSES TO HEAT EXPOSURE: IMPEDANCE PLETHYSMOGRAPHIC MEASUREMENTS OF CARDIAC OUTPUT
Abstract
Cardiac outputs of seminude resting male subjects were estimated from measurements of transthoracic impedance pulses as recorded by the tetropolar impedance plethysmographic technic. Ambient temperature was increased from 28 to 43C and maintained at this level for 1.5-2.0 hours. Increases in cardiac output were small, variable (ranging from 0.3 to 1.8 liters/min.), and were caused by small increases both in heart rate and stroke volume. The greater cardiac output was temporally related more closely to the augmented stroke volume which was, in turn, closely related to cutaneous vadodilatation as demonstrated by the cutaneous opacity pulses, the implication being that the augmented stroke volume probably results from the greater cutaneous venous return. The ratio of increase in cardiac output to sweating was about the same as previously shown; changes in oral temperature were small in all subjects, averaging about 0.5F. Validation of the electrical impedance technic as a measure of right ventricular stroke output was accomplished in dogs through comparisons of pulmonary arterial blood flow (electromagnetic flowmeter) and dye dilution (cardiogreen) cardiac output with that obtained by the impedance method. The correlations between the three methods were 0.792 and 0.916, respectively.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1967
- Accession Number
- AD0665154
Entities
People
- Bernell Coleman
- Hubert F. Bonfili
- James W. Fletcher
Organizations
- Saint Louis University