Murata M; Kobayashi Y; Adachi H

Circulation Journal. 86(1):79-86, 2021 12 24.

BACKGROUND: Minute ventilation/carbon dioxide production (VE/VCO2) 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 VE/VCO2(Min) and VE vs. VCO2slope (Slope) and the relationship
between Min and Slope.
Methods and Results: 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, VE and
VCO2Y-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.
CONCLUSIONS: Over 80% of the Min and Slope values were revealed with the
above-mentioned 4 variables collected non-invasively. The formula,
MinSlope+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.