Estimating stroke volume from oxygen pulse during exercise

This investigation aimed at verifying whether it was possible to reliably assess stroke volume (SV) during exercise from oxygen pulse (OP) and from a model of arterio-venous oxygen difference (a-vO₂D) estimation. The model was tested in 15 amateur male cyclists performing an exercise test on a cycle-ergometer consisting of a linear increase of workload up to exhaustion. Starting from the analysis of previous published data, we constructed a model of a-vO₂D estimation (a-vO₂D_est) which predicted that the a-vO₂D at rest was 30% of the total arterial O₂ content (CaO₂) and that it increased linearly during exercise reaching a value of 80% of CaO₂ at the peak workload (W_max) of cycle exercise. Then, the SV was calculated by applying the following equation, SV = OP/a-vO₂D_est, where the OP was assessed as the oxygen uptake/heart rate. Data calculated by our model were compared with those obtained by impedance cardiography. The main result was that the limits of agreement between the SV assessed by impedance cardiography and the SV estimated were between 22.4 and −27.9 ml (+18.8 and −24% in terms of per cent difference between the two SV measures). It was concluded that our model for estimating SV during effort may be reasonably applicable, at least in a healthy population.