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. 2007 Jun;13(5):389-94.
doi: 10.1016/j.cardfail.2007.02.002.

The relationship between resting lung-to-lung circulation time and peak exercise capacity in chronic heart failure patients

Norman R Morris  1 , Eric M Snyder, Kenneth C Beck, Luke J Haseler, Lyle J Olson, Bruce D Johnson
Affiliations

The relationship between resting lung-to-lung circulation time and peak exercise capacity in chronic heart failure patients

Norman R Morris et al. J Card Fail. 2007 Jun.

Abstract

Background: Peak exercise capacity (VO2peak) is a measure of the severity of chronic heart failure (CHF); however, few indices of resting cardiopulmonary function have been shown to predict VO2peak. A prolonged circulation time has been suggested as an index of increased severity of CHF. The aim of this study was to investigate the relationship between resting lung-to-lung circulation time (LLCT) and VO2peak in CHF.

Methods and results: Thirty CHF patients (59 +/- 13 years, New York Heart Association: 1.9 +/- 1.0) undertook the study. Each subject completed resting pulmonary and echocardiography measures and an incremental exercise test. LLCT was measured using the reappearance of end-tidal acetylene (P(ET),C2H2) after a single inhalation. Univariate and multivariate stepwise linear regression was used to determine the predictors of VO2peak. Univariate correlates of VO2peak (group mean 1.53 +/- 0.44 L/min(-1)) included LLCT (r = -0.75), inspiratory capacity (r = 0.41), ejection fraction (r = 0.33), peak early flow velocity (r = -0.39), and the ratio of early to late flow velocity (r = -0.31). LLCT was the only independent predictor where VO(2peak) = 3.923-0.045 (LLCT); r2 = 54%.

Conclusions: These results suggest that resting LLCT determined using the soluble inert gas technique represents a simple, noninvasive method that provides additional information regarding exercise capacity in CHF.

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Figures

Figure 1
Figure 1
Graphical representative of the change in breath-by-breath end tidal C2H2/He following a single inhalation of 0.9% C2H2, 9% He for a single subject. Following inhalation C2H2/He falls as C2H2 is distributed in the pulmonary blood volume. At the point when a significant volume of C2H2 is returned to the right side of the heart and re-enters the pulmonary circulation, C2H2/He will start to rise. The time taken from inhalation (time 0) until where C2H2/He shows a significant rise and consistent rise was calculated as being the circulation time.
Figure 2
Figure 2
Panel A: Change in CO and lung-to-lung circulation time during exercise at 25%, 50%, 75% and 100% VO2peak in 8 healthy subjects; Panel B: Correlation of the relative change in CO with the relative change in lung-to-lung circulation time; Change in CO was positively correlated with the change in lung-to-lung circulation time (r=0.79, P<0.05). CO: Cardiac output; LLCT: Lung to lung circulation time.
Figure 3
Figure 3
Relationship between circulation time and peak exercise capacity in 30 patients with chronic hear failure. Circulation time was inversely related to peak exercise capacity, (r=−0.75, P<0.001)
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