Determination of the V.E/V.CO2 slope from a constant work-rate exercise test in cardiac patients.
Incremental exercise testing to a symptom-limited maximum has been used to measure the ratio of the increase in ventilation (V.E) to the increase in CO(2) output (V.CO(2)) during exercise (V.E/V.CO(2) slope), a valuable index reflecting the severity of the ventilation-perfusion mismatch in heart failure. Here we studied whether this same value for the slope of V.E/V.CO(2) could be determined from a short constant work-rate exercise test of moderate intensity. Twenty-three patients with a previous myocardial infarction underwent moderate-intensity (69+/-15 W) constant work-rate exercise for 6 min and an incremental work-rate exercise test to the max. The V.E/V.CO(2) slope was calculated from the incremental exercise test from the start of increasing the work-rate to the ventilatory compensation point. The V.E/V.CO(2) slope was similarly calculated from the start of constant work-rate exercise until the 4th minute, when V.E and V.CO(2) changed minimally. The V.E/V.CO(2) slope determined from incremental exercise was 33.8+/-5.9, ranging from 20.9 to 42.8. The slope obtained from constant work-rate exercise was 32.9+/-5.7. The V.E/V.CO(2) slopes obtained from the two exercise tests did not differ significantly. The slope obtained from constant work-rate exercise was significantly positively correlated with the slope obtained from the incremental exercise (r=0.84, p<0.0001). The V.E/V.CO(2) slope can be determined from constant work-rate exercise at a moderate intensity. This indicates that the relationship between ventilation and CO(2) output is consistent and independent of the mode of exercise testing.
Hoshimoto-Iwamoto
Masayo
M
The Cardiovascular Institute, Minato-ku, Tokyo, Japan.
Koike
Akira
A
Nagayama
Osamu
O
Tajima
Akihiko
A
Uejima
Tokuhisa
T
Adachi
Hiromasa
H
Aizawa
Tadanori
T
Wasserman
Karlman
K
D000328:Adult; D002245:Carbon Dioxide / Q000378:metabolism*; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D009203:Myocardial Infarction / Q000378:metabolism / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D015203:Reproducibility of Results; D013997:Time Factors
D002245:Carbon Dioxide