oa Cardiovascular Journal of Africa - Repeatability in measurement of cardiac output by thoracic electrical bio-impedance in normal pregnancy



Measurements of stroke volume and cardiac output (CO) are important parameters in the management of pregnant women who have or develop serious cardiorespiratory or renal complications, Measurement by thermodilution utilising a pulmonary artery flotation catheter has numerous limitations. This study evaluates the measurement of CO in normal pregnant women by non-invasive, thoracic electrical bio-impedance. The study design was cross-sectional, involving all trimesters of pregnancy and the postpartum period. One hundred and one normal pregnant women were studied. The procedure for measurement of CO entailed 15 minutes of rest followed by 3 measurements at 5-minute intervals. The results demonstrate a coefficient of repeatability of 22 % for CO measurement as defined by the protocol in this study. The cross-sectional CO data analysis was not able to detect the expected trend in CO changes during normal pregnancy. The limitations of CO measurement by thoracic electrical bio-impedance and thermodilution method are discussed, and refinements in methods are suggested to achieve acceptable repeatability of these measurements.


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