Application of bioreactance for cardiac output assessment during exercise in healthy individuals
Elliott A., Hull JH., Nunan D., Jakovljevic DG., Brodie D., Ansley L.
In patients with cardiac failure, bioreactance-based cardiac output (CO) monitoring provides a valid non-invasive method for assessing cardiac performance during exercise. The purpose of this study was to evaluate the efficacy of this technique during strenuous exercise in healthy, trained individuals. Fourteen recreational cyclists, mean (SD) age of 34 (8) years and relative peak oxygen uptake of (VO 2 ) 56 (6) ml kg -1 min -1 , underwent incremental maximal exercise testing, whilst CO was recorded continuously using a novel bioreactance-based device (CO bio ). The CO bio was evaluated against relationship with VO 2 , theoretical calculation of arterial-venous oxygen difference (C(a - v) O 2 ) and level of agreement with an inert gas rebreathing method (CO rb ) using a Bland-Altman plot. Bioreactance-based CO measurement was practical and straightforward in application, although there was intermittent loss of electrocardiograph signal at high-intensity exercise. At rest and during exercise, CO bio was strongly correlated with VO 2 (r = 0.84; P < 0.001), however, there was evidence of systematic bias with CO bio providing lower values than CO rb ; mean bias (limits of agreement) -19% (14.6 to -53%). Likewise, calculated (C(a - v) O 2 ) was greater when determined using CO bio than CO rb (P < 0.001), although both devices provided values in excess of those reported in invasive studies. Bioreactance-based determination of CO provides a pragmatic approach to the continuous assessment of cardiac performance during strenuous exercise in trained individuals. Our findings, however, suggest that further work is needed to refine the key measurement determinants of CO using this device to improve measurement accuracy in this setting. © Springer-Verlag 2010.