Estimativa Não-Invasiva do Débito Cardíaco Durante o Exercício a Partir de Impedância Cardiográfica e Consumo de Oxigênio em Idosos

Abstract

Objective: This study assessed the agreement between cardiac output (Q) measurements generated by two indirect methods and their applicability in 54 men e 77 women (aged 60-90). Methods: The subjects performed a cardiopulmonary test with incremental to maximal exercise on a cycle-ergometer. "Q" was estimated based on oxygen uptake and on impedance cardiography at 50% and 100% of the maximal workload (Wmax) reached during the test. The limits of agreement and mean differences (biases) were estimated using the methodology proposed by Bland-Altman, whereas the relationship between the methods was analyzed by linear regression and intra-class correlation (ICC). Results: For the load equivalent do 50% of Wmax, the bias between the means of the two methods was -0.58 L·min-1 (6.3% smaller for the impedance measurement) and the limit of agreement was ± 2.54 L·min -1 (24.7%). At 100% of Wmax, the bias was 1.03 L·min-1 (8.5% greater for the impedance measurement) with a limit of agreement of ± 3.35 L·min-1 (27.6%). ICC values and the regression curves obtained between the methods were: Q imp=1.82+0.75QV̇O2 (r2=0.765, p<0.001; ICC=0.727, p<0.01) at 50% Wmax; and Qimp=0.93+1. 00QV̇O2 (r2=0.755, p<0.001; ICC=0.796, p<0.01) at 100% Wmax. Conclusion: These results suggest that there is a good agreement between the two methods for the measurement of Q during exercise in the elderly, which is compatible with the findings of similar studies with young subjects.