The oxygen uptake efficiency slope in 1411 Caucasian healthy men and women aged 20-60 years: reference values

Abstract

Background: The oxygen uptake efficiency slope (OUES) has been proposed as an independent, reproducible and objective measure of cardiorespiratory function that does not require maximal exercise testing. Existing reference values have been published for healthy paediatric populations and healthy elderly. However, reference ranges and equations for healthy adults of working age are insufficiently documented. The aim of the present study was to establish prediction equations and to describe reference values for healthy men and women aged 20-60 years.

Design: Cross-sectional study.

Methods: One thousand four hundred and eleven (877 men) healthy individuals (mean age 38.6 years; range 20-60) completed a maximal graded cycle exercise test until volitional exhaustion. Subsequently, oxygen uptake was plotted against the logarithm of total ventilation and the OUES was calculated by means of linear regression analysis.

Results: Multivariate regression analyses revealed age, sex and body surface area as statistically significant determinants of the OUES. Following this, sex-specific prediction equations for the OUES were established and cross-validated. Finally, the distribution of the OUES with age was described and reference values were established for men and women separately.

Conclusions: This study established a comprehensive set of reference values and reference equations for the OUES for a healthy population of men and women aged between 20 and 60 years.

Keywords: Cardiopulmonary exercise testing; adults; healthy; oxygen uptake efficiency slope; reference values.