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Editorial

Continuous Non-Invasive Cardiac Output: Myth or Reality

Cardiac output (CO) is an important cardiovascular system function parameter. Changes in cardiac function are commonly observed as a response to physical training and pharmacological interventions. Unfortunately, the methods for assessing CO are invasive, leading to well-known complications and considered inconvenient in daily practice. For this reason, the search for new noninvasive methods that can accurately detect CO at rest, at physical exertion or as a response to a clinical intervention has become desirable in academic and non-academic circles. The ideal method for measuring CO at rest and during exercise should be noninvasive, safe, reproducible and inexpensive.

The Cardiopulmonary Exercise Testing (CPT) is recommended in the evaluation of cardiorespiratory fitness and exercise tolerance in athletes, the general population and in patients. Briefly, CO and systolic volume can be estimated during CPT through measured VO₂. In 2001, Williams et al. were the first ones to integrate CPT with non-invasive measures of CO using rebreathing (RB) of carbon dioxide, but the technique was quickly abandoned due to its difficulty and inaccuracy. Another non-invasive method is thoracic electrical bioimpedance (TEB), first described in 1966 by Kubicek et al., which measures thoracic resistance as a result of changes in blood velocity during the cardiac cycle and uses an algorithm to calculate the CO.

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Artigo Original

Non-invasive estimate of cardiac output during exercise based on impedance cardiography and oxygen uptake in the elderly

Maurício Nunes Rodrigues et al. Jacques Henri-Paul Vanfraechem Paulo de Tarso Veras Farinatti

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.

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Continuous Non-Invasive Cardiac Output: Myth or Reality

Non-invasive estimate of cardiac output during exercise based on impedance cardiography and oxygen uptake in the elderly

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Electronic Document Format (Vancouver)

Electronic Document Format (ABNT)

Electronic Document Format (APA)

Electronic Document Format (ISO)