Reproducibility of cardiac output derived by impedance cardiography during postural changes and exercise

Abstract

Background: Evaluation of cardiac output (CO) and other haemodynamic parameters may aid in understanding factors involved in arterial blood pressure (BP) changes with exercise and postural stress. Impedance cardiography offers a rapid, non-invasive means to acquire this information, however there is limited data assessing the reproducibility of this technique during haemodynamic perturbation. This study aimed to assess reproducibility of CO and other haemodynamic parameters derived from impedance cardiography during exercise and in different postures. Methods: 51 participants (mean age 57 ± 9 years, 57% male) had CO and other haemodynamic variables (including end diastolic volume, left ventricular work, ejection fraction and systemic vascular resistance) measured via impedance cardiography (Physio Flow) at two visits separated by 12 ± 7 days. Measures were recorded at rest in three postures (supine, seated and standing), during upright cycle ergometry at a fixed workload (40 W), and also during steady state exercise at an intensity of 60% and 70% of age-predicted maximum heart rate (HRmax). Results: CO reproducibility was assessed over a wide range (5.27 ± 1.00–12.09 ± 2.02 l/min). There was good agreement between CO measured at each visit in all postures and exercise conditions (intra-class correlation coefficient [ICC] range 0.729–0.888, P < 0.05 for all) with a small difference between visits (mean difference 0.06 ± 1.10 l/min). All other haemodynamic variables showed good agreement between visits (ICC range 0.714–0.970, P < 0.05 for all). Conclusions: Non-invasive impedance cardiography provides an acceptably reproducible means to evaluate CO and other haemodynamic variables relevant to arterial BP regulation during different postures and light-to-moderate intensity exercise.

Keywords

• Haemodynamics
• Cardiac output
• Impedance cardiography
• Blood pressure
• Reproducibility