Correction of cardiac output obtained by Modelflow® from finger pulse pressure profiles with a respiratory method in humans

The beat-by-beat non-invasive assessment of cardiac output (Q, litre (.) min(-1)) based on the arterial pulse pressure analysis called Modelflow(R) can be a very useful tool for quantifying the cardiovascular adjustments occurring in exercising humans. 0 was measured in nine young subjects at rest and during steady-state cycling exercise performed at 50, 100, 150 and 200 W by using Modelflow(R) applied to the Portapres(R) non-invasive pulse wave (Q(Modeoflow)) and by means of the open-circuit acetylene uptake (QC(2)H(2)). Q values were correlated linearly (r = 0.784), but Bland-Altman analysis revealed that mean Q(Molodelflow) - QC(2)H(2) difference (bias) was equal to 1.83 litre (.) min(-1) with an S.D. (precision) of 4.11 litre (.) min(-1) and 95% limits of agreement were relatively large, i.e. from - 6.23 to + 9.89 litre (.) min(-1). Q(Modelflow) values were then multiplied by individual calibrating factors obtained by dividing QC(2)H(2) by Q(Modelflow) for each subject measured at 150 W to obtain corrected Q(Modelflow) (Q(corrected)) values. Q(corrected) values were compared with the corresponding QC(2)H(2) values, with values at 150 W ignored. Data were correlated linearly (r = 0.931) and were not significantly different. The bias and precision were found to be 0.24 litre (.) min(-1) and 3.48 litre (.) min(-1) respectively, and 95% limits of agreement ranged from -6.58 to + 7.05 litre (.) min(-1). In conclusion, after correction by an independent method, Modelflow(R) was found to be a reliable and accurate procedure for measuring Q in humans at rest and exercise, and it can be proposed for routine purposes.