A new impedance cardiograph device for the non-invasive evaluation of cardiac output at rest and during exercise: comparison with the "direct" Fick method

Abstract

The objectives of this study were to evaluate the reliability and accuracy of a new impedance cardiograph device, the Physio Flow, at rest and during a steady-state dynamic leg exercise (work intensity ranging from 10 to 50 W) performed in the supine position. We compared cardiac output determined simultaneously by two methods, the Physio Flow (QcPF) and the direct Fick (QcFick) methods. Forty patients referred for right cardiac catheterisation, 14 with sleep apnoea syndrome and 26 with chronic obstructive pulmonary disease, took part in this study. The subjects' oxygen consumption values ranged from 0.14 to 1.19 l x min(-1). The mean difference between the two methods (QcFick - QcPF) was 0.04 l x min(-1) at rest and 0.29 l x min(-1) during exercise. The limits of agreement, defined as mean difference +/- 2SD, were -1.34, +1.41 l x min(-1)] at rest and -2.34, +2.92 l x min(-1) during exercise. The difference between the two methods exceeded 20% in only 2.5% of the cases at rest, and 9.3% of the cases during exercise. Thoracic hyperinflation did not alter QcPF. We conclude that the Physio Flow provides a clinically acceptable and non-invasive evaluation of cardiac output under these conditions. This new impedance cardiograph device deserves further study using other populations and situations.

Assessment of aortic stiffness by local and regional methods

“…20,21 For example, a very low electrical current at high frequency (3.8 mA, 75 kHz) was administered through the first pair of electrodes at the chest wall (electrodes 1 and 4), and the differential electrical potential was recorded by the second pair (electrodes 2 and 3) (see refs. [22][23][24][25]. The two pairs of electrodes were separated by a distance of 20 cm.…”

Stroke work progressively increased until maximal exercise in long distance runners, but plateaued at submaximal exercise in sprinters

“…During cardiopulmonary exercise testing, stroke volume and cardiac output were measured in all subjects by the impedance method, as previously described elsewhere in detail [25][26][27][28] . In brief, an impedance cardiography device (Physioflow type PF05L1, Manatec Biomedical, Paris, France) was used to determine HR, stroke volume, and cardiac output at rest and during exercise.…”

“…Furthermore, 15-day cessation of training in middle-distance runners can cause a decrease in V ・ O2 max and a similar percentage decrease in C(a-v)O2 at maximal exercise 9) , which is consistent with the findings in the present study. The cardiac output, determined by the impedance method of Physioflow, was validated against the direct Fick method during exercise in healthy subjects 36) and patients 25) . Charloux et al 25) showed that cardiac output measured by this impedance method was as accurate as that obtained with the Fick method during exercise in patients with sleep apnea syndrome and chronic obstructive pulmonary disease.…”

“…The cardiac output, determined by the impedance method of Physioflow, was validated against the direct Fick method during exercise in healthy subjects 36) and patients 25) . Charloux et al 25) showed that cardiac output measured by this impedance method was as accurate as that obtained with the Fick method during exercise in patients with sleep apnea syndrome and chronic obstructive pulmonary disease. Also, the stroke volume values obtained by the Physioflow were reproducible, and the coefficient of variation was 1.8% in our previous findings and 3.6% in other reports 37) .…”

“…Also, the stroke volume values obtained by the Physioflow were reproducible, and the coefficient of variation was 1.8% in our previous findings and 3.6% in other reports 37) . Furthermore, the superior aspect of the Physioflow is that it calculates stroke volume independently from baseline impedance values 25,37) , and that sweating and dehydration cannot affect stroke volume 37) . Therefore, the measurement of cardiac output and stroke volume by this impedance method is a useful noninvasive method to assess the hemodynamic profile of subjects during exercise, and there have been many studies which evaluated cardiac output and stroke volume during exercise using this method [24][25][26][36][37][38] .…”