Determination of the VE/VCO2 Slope from a Constant Work-Rate Exercise Test in Cardiac Patients

• Published in: Journal of Physiological Sciences Vol. 58; no. 4; pp. 291 - 295
• Main Authors: Hoshimoto-Iwamoto, Masayo, Koike, Akira, Nagayama, Osamu, Tajima, Akihiko, Uejima, Tokuhisa, Adachi, Hiromasa, Aizawa, Tadanori, Wasserman, Karlman
• Format: Journal Article
• Language: English
• Published: Japan PHYSIOLOGICAL SOCIETY OF JAPAN 2008; The Physiological Society of Japan; BioMed Central
• Subjects: Adult; Carbon Dioxide - metabolism; Exercise Test; exercise testing; Exercise Tolerance; Female; Heart Failure - metabolism; Heart Failure - physiopathology; Humans; Male; Middle Aged; Models, Cardiovascular; myocardial infarction; Myocardial Infarction - metabolism; Myocardial Infarction - physiopathology; Pulmonary Gas Exchange; Pulmonary Ventilation; Reproducibility of Results; respiratory gas analysis; Time Factors
• ISSN: 1880-6546; 1880-6562
• DOI: 10.2170/physiolsci.RP006108

Incremental exercise testing to a symptom-limited maximum has been used to measure the ratio of the increase in ventilation (VE) to the increase in CO2 output (VCO2) during exercise (VE/VCO2 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 VE/VCO2 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 VE/VCO2 slope was calculated from the incremental exercise test from the start of increasing the work-rate to the ventilatory compensation point. The VE/VCO2 slope was similarly calculated from the start of constant work-rate exercise until the 4th minute, when VE and VCO2 changed minimally. The VE/VCO2 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 VE/VCO2 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 VE/VCO2 slope can be determined from constant work-rate exercise at a moderate intensity. This indicates that the relationship between ventilation and CO2 output is consistent and independent of the mode of exercise testing.