Key result
Frequency analysis by a set of bandpass filters was more effective than a zero crossing counter or parallel phaselock loops for non-invasive continuous cardiac output measurement.
Observational
Bandpass filters are more effective than zero crossing counters or phaselock loops for non-invasive Doppler measurement of cardiac output.
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May improve non-invasive cardiac output signal processing; leaves open prospective clinical validation.
From the suprasternal notch blood flow velocity in the aorta can be measured non-invasively by a Doppler probe. Integration over systole after frequency analysis gives a measure of stroke volume if a separate diameter observation is incorporated. Frequency analysis by a zero crossing counter or by a set of parallel phaselock loops was less effective than a set of bandpass filters. Observations on dogs, baboons and humans before and after exercise or surgery suggest the indications to be useful. Application to judging heart failure by the effect of introducing a volume load is indicated. Changes in output also are measured in freely moving subjects.
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Mackay et al. (1975) reported an observational. Frequency analysis by a set of bandpass filters vs. Zero crossing counter or parallel phaselock loops was evaluated on Effectiveness of frequency analysis for measuring stroke volume. Frequency analysis by a set of bandpass filters was more effective than a zero crossing counter or parallel phaselock loops for non-invasive continuous cardiac output measurement.
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