Abstract
The purpose of this study was to determine the relationship between excessive ventilation during exercise and decreased respiratory function such as decreased respiratory muscle strength and decreased vital capacity, central chemosensitivity after coronary artery bypass graft surgery (CABG). Eighteen patients following CABG via median sternotomy performed cardiopulmonary exercise test, pulmonary function test, respiratory muscle strength test, and central chemosensitivity test. Pulmonary function such as vital capacity, forced expired volume in one second and respiratory muscle strength, central chemosensitivity, anaerobic threshold and the slope of minute ventilation (VE) and carbon dioxide output (VCO2) (VE/VCO2 slope) showed significant improvement after 2-week aerobic exercise training. However, no relationships were found between the improvement of VE/VCO2 slope and the improvement of respiratory function. Central chemosensitivity was moderately correlated with VE/VCO2 slope, and end-tidal CO2 pressure (PETCO2) at the respiratory compensation point significantly and strongly correlated with VE/VCO2 slope. In conclusion, improvement of pulmonary function did not affect excessive exercise ventilation after CABG. Improvement of excessive exercise ventilation after CABG may result from improvement of cardiac output since PETCO2 at the respiratory compensation point represents cardiac output during exercise.
