Elsevier

Journal of Cardiology

Volume 70, Issue 6, December 2017, Pages 598-606
Journal of Cardiology

Original article
Clinical significance of the overshoot phenomena of respiratory gas indices during recovery from maximal exercise testing

https://doi.org/10.1016/j.jjcc.2017.03.012Get rights and content
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Abstract

Background

Overshoot phenomena of the gas exchange ratio (R:VCO2/VO2), ventilatory equivalent for O2 (VE/VO2), and end-tidal O2 pressure (PETO2) are commonly observed during recovery from maximal cardiopulmonary exercise testing (CPX). We investigated the clinical significance of the overshoots of these indices by comparing their magnitudes between healthy subjects and cardiac patients with left ventricular dysfunction.

Methods

In total, 121 subjects (73 healthy subjects and 48 cardiac patients with left ventricular ejection fraction < 40%) who underwent CPX and achieved peak R  1.10 were enrolled. We evaluated and calculated the presence and magnitude of the overshoot phenomena of R, VE/VO2, and PETO2.

Results

The overshoot phenomena of R, VE/VO2, and PETO2 were observed in all the subjects. The magnitudes of the R (21.4 ± 12.4% vs. 29.3 ± 10.0%, p < 0.001), VE/VO2 (45.5 ± 23.5% vs. 77.5 ± 28.5%, p < 0.001), and PETO2 (5.3 ± 3.4% vs. 10.1 ± 4.2%, p < 0.001) overshoots were significantly lower in cardiac patients than in healthy subjects. In cardiac patients, the magnitude of the PETO2 overshoot showed significant positive correlations with the peak O2 uptake (VO2) (r = 0.52, p < 0.001), anaerobic threshold (r = 0.43, p = 0.003), and ratio of the increase in VO2 to the increase in the work rate (r = 0.41, p = 0.005), and a negative correlation with the slope of the increase in ventilation versus the increase in CO2 output (r = −0.50, p < 0.001). The magnitudes of the R and VE/VO2 overshoots showed the same patterns of significant correlation with the CPX indices.

Conclusions

We concluded that the overshoots of R, VE/VO2, and PETO2 during recovery from maximal exercise reflect the natural cardiopulmonary adaptation after exercise and are more prominent in subjects with better cardiopulmonary function.

Keywords

Exercise recovery
Exercise testing
Cardiopulmonary function

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