Change in Cardiovascular Indices with Position and Isometric Exercise Throughout Pregnancy: Assessment by Impedance Cardiography and Oscillometric Sphygmomanometry

Abstract

Background The poor predictive values of the supine pressor and isometric handgrip exercise tests for pregnancy-induced hypertension may relate to interobserver errors asSociated with mercury column sphygmomanometry or to the timing of blood pressure measurements relative to position change or isometric exercise.

Objective: To evaluate the Bomed NCCOM-3, in combination with oscillometric measurement of mean arterial pressure (MAP), as a means of assessing beat-to-beat changes in hemodynamic indices at various stages of pregnancy.

Setting: The Prince of Wales Hospital, teaching hospital to the Chinese University of Hong Kong.

Methods: A longitudinal study of 20 normotensive Chinese women to assess the normal hernodynamic responses to changes in posture and isometric handgrip exercise; cardiac index (CI) obtained from a Bomed NCCOM-3 impedance cardiograph, and MAP from a Finapres digital blood pressure monitor.

Results: Position change did not significantly alter CI. Significant changes in MAP and, hence, total peripheral resistance index (TPRI) following position change were observed at all gestational ages and in the puerperium. Regression analysis shows that the major contributing factor to changes in TPRI was change in CI with a variable effect of change in MAP. Isometric handgrip exercise caused significant decreases in CI in the second and third trimesters and also in the puerperium, but not in early pregnancy. Increases in TPRI following isometric exercise were significant at all gestations tested and in the postnatal period. Regression analysis shows that the changes are equally effected by the increase in MAP and the decreases in CI.

Conclusions: The combination of impedance cardiography and oscillo-metric sphygmomanometry provides excellent recordings of beat-to-beat changes in hemodynamic indices during physiological testing. The changes observed throughout normal pregnancy were similar to those reported using Doppler ultrasound with echocardiography, remaining consistent after 20–24 weeks' gestation, with the exception of a significant rise in TPRI between the second and third trimesters.