Cardiac output measurement during exercise in COPD: A comparison of dye dilution and impedance cardiography

Zafeiris Louvaris, Stavroula Spetsioti, Vasileios Andrianopoulos, Nikolaos Chynkiamis, Helmut Habazettl, Harrieth Wagner, Spyros Zakynthinos, Peter D. Wagner, Ioannis Vogiatzis

Research output: Contribution to journalArticlepeer-review

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Abstract

Introduction: Impedance cardiography (IC) derived from morphological analysis of the thoracic impedance signal is now commonly used for noninvasive assessment of cardiac output (CO) at rest and during exercise. However, in Chronic Obstructive Pulmonary Disease (COPD), conflicting findings put its accuracy into question. Objectives: We therefore compared concurrent CO measurements captured by IC (PhysioFlow: CO IC ) and by the indocyanine green dye dilution method (CO DD ) in patients with COPD. Methods: Fifty paired CO measurements were concurrently obtained using the two methods from 10 patients (FEV 1 : 50.5 ± 17.5% predicted) at rest and during cycling at 25%, 50%, 75% and 100% peak work rate. Results: From rest to peak exercise CO IC and CO DD were strongly correlated (r = 0.986, P < 0.001). The mean absolute and percentage differences between CO IC and CO DD were 1.08 L/min (limits of agreement (LoA): 0.05-2.11 L/min) and 18 ± 2%, respectively, with IC yielding systematically higher values. Bland-Altman analysis indicated that during exercise only 7 of the 50 paired measurements differed by more than 20%. When data were expressed as changes from rest, correlations and agreement between the two methods remained strong over the entire exercise range (r = 0.974, P < 0.001, with no significant difference: 0.19 L/min; LoA: −0.76 to 1.15 L/min). Oxygen uptake (VO 2 ) and CO DD were linearly related: r = 0.893 (P < 0.001), CO DD = 5.94 × VO 2 + 2.27 L/min. Similar results were obtained for VO 2 and CO IC (r = 0.885, P < 0.001, CO IC = 6.00 × VO 2 + 3.30 L/min). Conclusions: These findings suggest that IC provides an acceptable CO measurement from rest to peak cycling exercise in patients with COPD.

Original languageEnglish
Pages (from-to)222-231
Number of pages10
JournalClinical Respiratory Journal
Volume13
Issue number4
Early online date28 Feb 2019
DOIs
Publication statusPublished - 1 Apr 2019

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