Validation of the oxygen uptake efficiency slope in children with cystic fibrosis and tetralogy of Fallot

Abstract

Background and Aims: The oxygen uptake efficiency slope (OUES) has been shown to be a valid sub-maximal measure of aerobic capacity and ventilatory efficiency in both adults and children. However, in one study in CF children with mild to moderate disease, OUES had limited discriminatory properties (1). Our aim was to re-examine the validity of OUES in 3 groups of children: CF, TOF and unexplained SOBOE. Methods: We reviewed data from cardiopulmonary exercise tests in children with CF (n=45), TOF (n=30) and patients with unexplained SOBOE (n = 30). All patients had lung function and an incremental exercise test. If the child was tall enough, cycle ergometer was used (n=96) with an appropriately selected ramp ranging from 6.5-25 watts.min-1. Otherwise, a treadmill protocol was used. OUES was calculated over the entire exercise duration. Results: Results are shown in Table 1. The OUES % predicted was lower in TOF, compared to the CF and SOBOE groups (p<0.01). This was also the case for VO2peak % predicted and VO2peak ml.min-1.kg-1 (p<0.01). The OUES showed strong correlations with VO2peak in CF, SOBOE and TOF, r = 0.95, 0.92, 0.89 respectively. Conclusion: The OUES is a valid measure of aerobic capacity and has distinguishing properties in CF and TOF children.