The (V) over dotE/(V) over dotCO2 Slope During Maximal Treadmill Cardiopulmonary Exercise Testing REFERENCE STANDARDS FROM FRIEND (FITNESS REGISTRY AND THE IMPORTANCE OF EXERCISE: A NATIONAL DATABASE)

Purpose: Cardiopulmonary exercise testing (CPX) is the gold standard approach for the assessment of cardiorespiratory fitness (CRF). The primary aim of the current study was to determine reference standards for the minute ventilation/carbon dioxide production ((V) over dot(E)/(V) over dot(CO2)) slope in a cohort from the Fitness Registry and the Importance of Exercise: A National Database (FRIEND) Registry. Methods: The current analysis included 2512 tests from 10 CPX laboratories in the United States. Inclusion criteria included CPX data on apparently healthy men and women: (1) age >= 20 yr; and (2) with a symptom-limited exercise test performed on a treadmill. Ventilation and (V) over dot(CO2) data, from the initiation of exercise to peak, were used to calculate the (V) over dot(E)/(V) over dot(CO2) slope via least-squares linear regression. Reference values were determined for men and women by decade of life. Results: On average, (V) over dot(E)/(V) over dot(CO2) slope values were lower in men and increased with age independent of sex. Fiftieth percentile values increased from 27.1 in the second decade to 33.9 in the eighth decade in men and from 28.5 in the second decade to 33.7 in the eighth decade in women. In the overall group, correlations with baseline characteristics and the (V) over dot(E)/(V) over dot(CO2) slope were statistically significant (P < .05) although generally weak, particularly for age and body mass index. Conclusion: The results of the current study establish reference values for the (V) over dot(E)/(V) over dot(CO2) slope when treadmill testing is performed, and all exercise data are used for the slope calculation. These results may prove useful in enhancing the interpretation of CPX results when assessing CRF.

Automated summary

The study aimed to establish reference standards for the (V) over dot(E)/(V) over dot(CO2) slope in healthy men and women from CPX laboratories in the United States, showing an increase with age regardless of gender, with weak correlations particularly for age and body mass index.