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End-tidal CO₂ pressure decreases during exercise in cardiac patients

Association with severity of heart failure and cardiac output reserve

^a Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
^* Internal Medicine, the Cardiovascular Institute, Tokyo, Japan

View larger version (15K): [in a new window]   Figure 1 End-tidal CO2 pressure (PETCO2) at rest and during exercise according to the NYHA functional class. There was a significant difference in the change of PETCO2 during exercise among the four groups at each time point (one way-ANOVA at each time point: rest p = 0.0016, 20 W p = 0.0001, 30 W p = 0.0001, AT p = 0.0001, RC p = 0.0001, Peak p = 0.0001). AT indicates anaerobic threshold; RC = respiratory compensation point; P = peak exercise. Values are mean ± SE. *p < 0.05 versus controls.

View larger version (26K): [in a new window]   Figure 2 End-tidal CO2 pressure (PETCO2) at rest and during exercise in relation to CO2 output (CO2), minute ventilation (E), tidal volume (VT), and respiratory rate (RR) at rest (R), during 20 W warming-up (WU), at anaerobic threshold (AT), at respiratory compensation point (RC), and at peak exercise (P) according to the NYHA functional class. Values are mean ± SE.

View larger version (15K): [in a new window]   Figure 3 End-tidal CO2 pressure (PETCO2) in relation to the cardiac index (CI) at rest, at 20 W, 40 W, and 60 W during exercise according to the NYHA functional class. Values are mean ± SE.

View larger version (29K): [in a new window]   Figure 4 Relationships of end-tidal CO2 pressure (PETCO2) at the respiratory compensation (RC) point with the cardiac index at peak exercise in 112 cardiac patients and 29 normal subjects. Dotted lines indicate mean–2SD values of PETCO2 at the respiratory compensation point and the cardiac index at peak exercise in the normal control subjects.

View larger version (24K): [in a new window]   Figure 5 Relationships of end-tidal CO2 pressure (PETCO2) at the respiratory compensation (RC) point with O2 uptake (O2) at peak exercise, or with the slope of minute ventilation-CO2 output (E-CO2 slope) in 112 cardiac patients and 29 normal subjects.

View larger version (12K): [in a new window]   Figure 6 End-tidal CO2 pressure (PETCO2) and arterial PCO2 (PaCO2) at rest and during exercise in 53 cardiac patients and 15 normal control subjects. There was a significant difference in the change between PaCO2 and PETCO2 variables and interaction with time in both the patients (variables p = 0.0001, interaction p = 0.0001, by ANOVA) and control subjects (variables p = 0.0001, interaction p = 0.0001, by ANOVA). Peak indicates peak exercise. Values are mean ± SE. *; p < 0.05 versus normal controls. ; p < 0.05 versus PaCO2.

View larger version (21K): [in a new window]   Figure 7 Relationships of end-tidal CO2 pressure (PETCO2) at the respiratory compensation point with the ratio of physiologic dead space to tidal volume (VD/VT) in 53 cardiac patients and 15 normal control subjects.