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: Qimp=1.82+0.75Q VO2 (r²=0.765, p<0.001; ICC=0.727, p<0.01) at 50% Wmax; and Qimp=0.93+1.00Q VO2 (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.
Exercise; exercise test; impedance; cardiography; aging
