Examination of the Relationship and Dissociation Between Minimum Minute Ventilation/Carbon Dioxide Production and Minute Ventilation vs. Carbon Dioxide Production Slope.

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Minute ventilation/carbon dioxide production (V̇E/V̇CO2) is a variable of cardiopulmonary exercise testing (CPET), which is evaluated by arterial CO2pressure and ventilation-perfusion mismatch via invasive methods. This study evaluated substitute non-invasively obtained variables for minimum V̇E/V̇CO2(Min) and V̇E vs. V̇CO2slope (Slope) and the relationship between Min and Slope. This study enrolled 1,052 patients with heart disease who underwent CPET and impedance cardiography simultaneously. At first, the correlations between the end-tidal CO2pressure (PETCO2), tidal volume/respiratory rate (TV/RR) ratio, V̇E and V̇CO2Y-intercept (Y-int), and cardiac index (CI) and the Min and Slope were investigated. Second, the correlation between Min and Slope was investigated. PETCO2showed the largest correlation value among the 4 variables. These 4 variables could reveal 84.2% and 81.9% of Min and Slope, respectively. Although Slope correlated with Min (R=0.868) and predicted 78.9% of Min, considering these 4 variables, Slope+Y-int was more strongly correlated with Min (R=0.940); the Slope+Y-int revealed 90.6% of the Min relationship in the multiple regression analysis. Over 80% of the Min and Slope values were revealed with the above-mentioned 4 variables collected non-invasively. The formula, Min∝Slope+Y-int, can reveal >90% of the Min/Slope relationships, and the Y-int may be a crucial factor to clarify the relationship between Min and Slope.