Measurement of systolic time intervals by electrical plethysmography: validation with invasive and noninvasive methods.

An experiment was conducted to validate the use of electrical impedance plethysmography for measuring systolic time intervals. This method is of interest in aerospace medicine since it is a noninvasive technique and very easy to use without causing discomfort to the subject. The equipment, with electrodes placed in front of the heart, gave both the first derivative of the electrical impedance variation and the E.C.G. The tracings were compared to simultaneous recordings of either the carotid pulse or blood pressures obtained by right and left catheterization. The results did not permit us to determine the right side systolic times. However, demarcated points of the plethysmogram permitted us to determine accurately the beginning of left mechanical systole and aortic opening and closure. Consequently, this method can determine the left ejection time (LPEP), the left isovolumetric contraction time (LIVCT), and the ventricular ejection time (LVET) with good accuracy.