The oxygen uptake efficiency slope is not a valid surrogate of aerobic fitness in cystic fibrosis

Williams, Craig A., Tomlinson, Owen W., Chubbock, Lucy V., Stevens, Daniel, Saynor, Zoe L., Oades, Patrick J. and Barker, Alan R. (2017) The oxygen uptake efficiency slope is not a valid surrogate of aerobic fitness in cystic fibrosis. Pediatric Pulmonology, 53 (1), 36-42. (doi:10.1002/ppul.23896).

Abstract

Background: maximal cardiopulmonary exercise testing is recommended on an annual basis for children with cystic fibrosis (CF), due to a clinically useful prognostic information provided by maximal oxygen uptake (O2max). However, not all patients are able, or willing, to reach O2max, and therefore submaximal alternatives are required. This study explored the validity of the oxygen uptake efficiency slope (OUES) as a submaximal measure of O2max in children and adolescents with CF.

Methods: data were collated from 72 cardiopulmonary exercise tests (36 CF, 36 controls), with OUES determined relative to maximal and submaximal parameters of exercise intensity, time and individual metabolic thresholds. Pearson’s correlation coefficients, independent t-tests and factorial ANOVAs were used to determine validity.

Results: significant (p < 0.05) correlations with O2max were observed for most expressions of OUES, but were consistently weaker in CF (r = 0.30 – 0.47) when compared to CON (r = 0.58 – 0.89). Mean differences for all OUES parameters between groups were not significant (p > 0.05). When split by O2max tertiles, minimal significant differences were found between, and within, groups for OUES, indicating poor discrimination of O2max.

Conclusions: the OUES is not a valid (sub)maximal measure of O2max in children and adolescents with mild-to-moderate CF. Clinicians should continue to use maximal markers (i.e. O2max) of exercise capacity.

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Contributors

Author: Zoe L. Saynor

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