Reliability of hemodynamic parameters measured by bioimpedance cardiography at different intensities during incremental exercise testing

Raphael Schoch ¹ Jonathan Wagner ¹ Max Niemeyer ² Fabienne Bruggisser ¹ Denis Infanger ¹ Justin Carrard ¹ Benedikt Andreas Gasser ¹ Arno Schmidt-Trucksäss ^1,3* Raphael Knaier ¹

• ¹ Department of Sport, Exercise and Health, Division Sports and Exercise Medicine, University of Basel, Basel, Switzerland
• ² Department Medicine, Training and Health, Institute of Sport Science and Motology, Philipps-University Marburg, Marburg, Germany
• ³ Department of Clinical Research, University of Basel, Basel, Switzerland

Background Bioimpedance cardiography offers a noninvasive and time-efficient method to measure hemodynamic parameters. Previous studies only investigated its reliability under steady-state conditions and at maximum load but not at ventilatory thresholds (VT). This is the first study which assesses the reliability of measured hemodynamic parameters at different exercise stages during a cardiopulmonary exercise testing (CPET) using pre-specified strict criteria to assess reliability.Methods Data from 31 healthy, well-trained adults were analyzed. Each participant completed two CPETs, both following the same ramp protocol, with a seven-day interval between them.Hemodynamic parameters were measured with PhysioFlow ® (Manatec Biomedical, Poissy, France) at characteristic phases and thresholds (VT1, VT2, and V ̇O2peak). To ensure comparability, the wattage (power) corresponding to the thresholds in Test1 (PVT1, PVT2, PV̇O2peak) was used for Test2.Heart rate, stroke volume, and cardiac output demonstrated good reliability on a group level (mean intraclass correlation > 0.75) at both thresholds (0.91, 0.80, 0.77 at PVT1; 0.92, 0.80, 0.77 at PVT2) and at PV̇O2peak (0.93, 0.82, 0.80). For SV at PV̇O2peak, both, individual differences (-39.0 to 36.9 mL for females and -39.9 to 45.2 mL for males) as well as mean detectable change (17.5 mL) were larger than the a priori defined acceptable ranges of agreement (-3.6 to 3.8 mL for females and -4.5 to 3.3 mL for males).PhysioFlow ® reliably measures heart rate, stroke volume, and cardiac output during CPET on a group level. However, as shown by Bland-Altman plots, reliability is too low to be used for individual comparisons.