Key result
Postural changes produced expected physiological changes, with ≤1% difference in left ventricular ejection time measured via carotid pulse versus thoracic impedance.
Observational
Non-invasive measurement of left ventricular ejection time using thoracic impedance correlates closely (within 1%) with external carotid pulse tracing.
Thoracic impedance closely matches carotid pulse for LVET; leaves open clinical adoption pending prospective validation.
Differences have been found, which are usually 1% or less, between the left ventricular ejection time measured from the external carotid pulse tracing, and from the rate of change of thoracic impedance (dZ/dt) waveform, using either the second heart sound or the X-point of the dZ/dt tracing as the end-point. The Heather Index obtained from the ECG and dZ/dt tracings has been correlated with other indices of cardiac performance. The changes observed in the physiological variables during head-up and head-down tilting were in the expected directions.
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Hill et al. (1976) reported an observational. Postural changes (head-up and head-down tilting) was evaluated on Left ventricular ejection time and Heather Index. Postural changes produced expected physiological changes, with ≤1% difference in left ventricular ejection time measured via carotid pulse versus thoracic impedance.
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