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FIGURE 2
Correlation of AVA by repeated CO. A - AVA by repeated Assumed VO2 CO. B - AVA by repeated TD CO. C - AVA by repeated direct continuous VO2 CO.
reproducibility of CO and AVA. The Phillips (XIMS, Philips Xper Connect, Melbourne, Fla.) system is in use at our CCL.
STATISTICS
Correlation of direct continuous
VO2, assumed VO2, and TD based
CO measurements were assessed
by linear regression analysis and by variance component analysis. The Pearson correlation (r), derived from linear regression, assesses the rank ordering of variable values whereas the intra-class correlation (ICC), derived from variance component analysis, assesses the degree of agreement
between variable values. The ICC is
the appropriate statistic for assessing agreement between tests purporting to measure the same thing on the same
scale of measurement. The ICC ranges between 0, indicating no agreement, and 1, indicating perfect agreement. Scatter variables included the regression line
as well as a 45 degree line of equality along which the paired variables would
lie if there was perfect agreement between echo-cath measurements
(as would the regression line). Bland- Altman plots were also constructed as complementary assessments of different CO measurements. All CO values,
where applicable, were then used to calculate aortic valve areas (AVA) in cases where this was the clinical issue and comparisons were made to the different methods in the same statistical manner.
RESULTS
The baseline characteristics of the 30 patients included in the study patients are displayed in Table 1. Direct continuously
All patients except one had suitable VO2 tracings for these measurements. One patient had unreliable VO2 tracings due to Cheyne-Stokes respiration. The three values from each cardiac output method
were averaged, and those values were compared. Another separate set of direct continuous VO2, assumed VO2, and TD CO was then repeated, after steady-state VO2
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Del Med J | September 2016 | Vol. 88 | No. 9
