Abstract
Cardiac stroke volume (SV) is an essential hemodynamic indicator that can be used to assess whether the pump function of the heart is normal. Non-invasive SV measurement is currently performed using the impedance cardiography (ICG). In this technology, left ventricular ejection time (LVET) is an important parameter which can be determined from the ICG signals. However, the ICG signals are inherently susceptible to artificial noise interference, which leads to an inaccurate LVET measurement and then yields an error in the calculation of SV. Therefore, the goal of the study was to measure LVETs using both the transmission and reflection photoplethysmography (PPG), and to assess whether the measured LVET was more accurate by the PPG signal than the ICG signal. The LVET measured by the phonocardiography (PCG) was used as the standard for comparing with those by the ICG and PPG. The study recruited ten subjects whose LVETs were simultaneously measured by the ICG using four electrodes, the reflection PPG using neck sensors (PPGneck) and the transmission PPG using finger sensors (PPGfinger). In each subject, ten LVETs were obtained from ten heartbeats selected properly from one-minute recording. The differences of the measured LVETs between the PCG and one of the ICG, PPGneck and PPGfinger were −68.2 ± 148.6 ms, 4.8 ± 86.5 ms and −7.0 ± 107.5 ms, respectively. As compared with the PCG, both the ICG and PPGfinger underestimated but the PPGneck overestimated the LVETs. Furthermore, the measured LVET by the PPGneck was the closest to that by the PCG. Therefore, the PPGneck may be employed to improve the LVET measurement in applying the ICG for continuous monitoring of SV in clinical settings.
Highlights
Cardiogenic shock refers to a group of syndromes in which heart function is extremely decreased, resulting in a significant reduction in cardiac output and causing severe acute peripheral circulatory failure
Typical physiological signals measured from one subject in this study are shown in Figure 5, Typical physiological signals measured from(dotted one subject thisneck study aredash shown in Figure including the heart sound, impedance cardiography (ICG)
This paper proposes two concepts to improve the accuracy in calculating cardiac stroke volume (SV) with the ICG technique, in which PPG using neck sensors (PPGneck) signal is used to determine the left ventricular ejection time (LVET)
Summary
Cardiogenic shock refers to a group of syndromes in which heart function is extremely decreased, resulting in a significant reduction in cardiac output and causing severe acute peripheral circulatory failure. The thermal dilution ( called thermo dilution) is a method of cardiac output determination, in which a bolus of solution (usually saline) of known temperature and volume is injected into the right atrium, and the resultant change in blood temperature is sensed by a thermistor previously arranged in the pulmonary artery with a catheter. This method requires surgery to insert the catheter into the body, so its application may be strictly limited
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