[External respiration and gas metabolism in orthostatic syncopes]

Cardiorespiratory reactions to tilt tests were compared in 80 healthy male subjects with an adequate orthostatic tolerance and in 19 subjects who fainted during tilting. They showed significant differences in the gas exchange, hemodynamics, and external respiration. Variations in the heart rate, pulmonary ventilation and the alveolar CO2 tension were most demonstrative. The findings, particularly the lack of the expected decrease o= oxygen consumption in the presyncopal state contribute to the concepts of the pathogenesis of the orthostatic collapse.