WS9.2 Modified shuttle test performance in CF children and adolescents with different severity of lung disease

Abstract

Objectives: Despite considerable progress and improved survival in CF, patients still suffer from loss of lung function, malnutrition and reduced exercise capacity. Previous studies have revealed an association between oxygen uptake and lung function. The objective of this study was to examine whether a lung function measurement can predict oxygen uptake in children and adults with CF. Methods: An analytical cross-sectional study based on registry data from 78 patients aged 9−42. The lung function was measured by spirometry, and oxygen uptake was estimated based on the Watt-max test. Results: FEV1 can predict VO2max, with a prediction interval (PI) of 1.47 l/min (R2 = 0.65), and FEV1% can predict VO2max/kg (PI=30ml/kg/min; R 2 = 0.22). Furthermore, FEF25−75 can predict VO2max (PI=2.06 l/min) and FEF25−75% can predict VO2max/kg (PI=32ml/kg/min). All p< 0.001. Stratified analysis showed that the association between FEV1% and VO2max/kg is comparatively stronger in patients with reduced lung function (FEV1% <85; PI=24ml/kg/min and R2 = 0.36), than in patients with normal lung function (FEV1% 85), where no association was found (R2 = −0.02), p< 0.05. Although significant, all PI’s were too wide for any clinical relevance; for any FEV1% predicted VO2max/kg ranged from very low to very high for age and gender. Conclusion: The model of predicting oxygen uptake solely based on lung function does not seem to be useful in clinical practice. The estimated prediction intervals are too wide caused by substantial individual variation in oxygen uptake, even in patients with reduced lung function. Exercise capacity can only be determined by testing it independently.