CLINICAL STUDIES: HEART FAILURE
End-tidal CO2 pressure decreases during exercise in cardiac patients
Association with severity of heart failure and cardiac output reserve
Akihiro Matsumoto, MDa,
Haruki Itoh, MD, FACC*,
Yoko Eto, MDa,
Toshio Kobayashi, MD*,
Makoto Kato, MD*,
Masao Omata, MDa,
Hiroshi Watanabe, MD*,
Kazuzo Kato, MD, FACC* and
Shin-ichi Momomura, MDa
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
Manuscript received December 17, 1998;
revised manuscript received December 30, 1999,
accepted March 1, 2000.
Reprint requests and correspondence: Dr. Akihiro Matsumoto, The Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan, 113 amatsu-tky{at}umin.u-tokyo.ac.jp
OBJECTIVES
We measured end-tidal CO2 pressure (PETCO2) during exercise and investigated the relationship between PETCO2 and exercise capacity, ventilatory parameters and cardiac output to determine the mechanism(s) of changes in this parameter.
BACKGROUND
It is unclear whether PETCO2 is abnormal at rest and during exercise in cardiac patients.
METHODS
Cardiac patients (n = 112) and normal individuals (n = 29) performed exercise tests with breath-by-breath gas analysis, and measurement of cardiac output and arterial blood gases.
RESULTS
PETCO2 was lower in patients than in normal subjects at rest and decreased as the New York Heart Association class increased, whereas the partial pressure of arterial CO2 did not differ among groups. Although PETCO2 increased during exercise in patients, it remained lower than in normal subjects. PETCO2 in relation to cardiac output was similar in patients and normal subjects. PETCO2 at the respiratory compensation point was positively correlated with the O2 uptake (r = 0.583, p < 0.0001) and the cardiac index at peak exercise (r = 0.582, p < 0.0001), and was negatively correlated with the ratio of physiological dead space to the tidal volume. The sensitivity and specificity of PETCO2 to predict an inadequate cardiac output were 76.6% and 75%, respectively, when PETCO2 at respiratory compensation point and a cardiac index at peak exercise that were less than the respective control mean2 SD values were considered to be abnormal.
CONCLUSIONS
PETCO2 was below normal in cardiac patients at rest and during exercise. PETCO2 was correlated with exercise capacity and cardiac output during exercise, and the sensitivity and specificity of PETCO2 regarding decreased cardiac output were good. PETCO2 may be a new ventilatory abnormality marker that reflects impaired cardiac output response to exercise in cardiac patients diagnosed with heart failure.
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Abbreviations and Acronyms
| | PETCO2 | = end-tidal CO2 pressure | | PaCO2 | = partial pressure of arterial CO2 | | P[a-ET]CO2 | = arterialend-tidal CO2 difference | | NYHA | = New York Heart Association | O2 | = O2 uptake | | VD/VT | = the physiologic dead space to tidal volume ratio | | %FVC | = forced vital capacity expressed as percent of predicted | | %FEV1 | = forced expiratory volume in 1 s expressed as percent of predicted | | VA/Q | = ventilation/perfusion |
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