The maximal oxygen uptake in COPDpatients (mean+/-SE) was 1061.2+/-65.6ml/min which was significantly lower than 2137.6+/-1.4ml/min of normal subjects(p or =1.09) was accomplished in 7 of 36 COPDpatients(19.4%) and in 18 of 42 normal subjects(42.9%). The BRIAT of COPDpatients was higher(0.50+/-0.03) than that of control subject(0.28+/-0.02, p<0.01), reflecting early hyperventilation in COPDpatient during exercise. The correlation between BRIAT and BRI at maximal exercise in COPDpatients was good(r=0.9687, p<0.01).