Usefulness of thoracic electrical bioimpedance in detection of ejection fraction changes

The aim of this study was to evaluate a usefulness of thoracic electrical bioimpedance (TEB) in following adaptive haemodynamic adjustments to postural change and isometric exercise. Sixteen subjects with intact cardiovascular system took part in this study. Haemodynamic parameters were obtained in recumbency and after taking up erect posture. Besides, TEB was performed during handgrip test and the results were compared with baseline resting data. Each time the radionuclide ventriculography (RV) was performed concurrently with TEB to obtain an independent measurement of ejection fraction (EF). Active orthostasis was associated with a change in stroke volume, cardiac output and total vascular resistance by -29.7%, -3.4%, +3.9%, respectively. The handgrip produced a significant increase in cardiac output by 16.3%, however it was not associated with an enhancement of stroke volume. Although there was a moderate correlation between EF calculated by TEB and RV in supine position (r=0.66; p < 0.001), TEB failed to reflect changes of EF in orthostasis and isometric exercise. In conclusion, our results suggest that TEB offers in subjects with normal cardiovascular function a valuable alternative to cardiovascular monitoring of stroke volume and cardiac output, but calculation of EF is associated with a risk of serious error.