Long-term exercise capacity in paediatric cystic fibrosis: a modern era perspective.

Background: Maintaining good cardiopulmonary fitness is crucial for global health in cystic fibrosis (CF), but there is limited knowledge about the longitudinal evolution of fitness measures at young ages, particularly with recent therapeutic advances. We investigated trends in exercise test outcomes in young people with CF and how they are influenced by elexacaftor, tezacaftor and ivacaftor (ETI) and the coronavirus disease 2019 (COVID-19) pandemic.

Methods: 70 young people with CF (12-20 years old) were included in this retrospective observational single-centre study. We reviewed 177 symptom-limited surveillance cardiopulmonary exercise tests (CPETs) conducted on a cycle ergometer between 2010 and 2024. Longitudinal trends in peak oxygen uptake (V'_{O2 peak}), maximal workload and ventilation were analysed using linear mixed models, separately for periods before and after the COVID-19 pandemic onset and ETI introduction.

Results: In ETI-naive people with CF, V'_{O2 peak} was lower, and the increase from 12 to 20 years was smaller than predicted by validated reference data (p<0.001). 40 people with CF started ETI during the observational period with 46 of 103 tests performed under ETI (median therapy duration 1.6 years, range 0.4-3.9). After ETI introduction, V'_{O2 peak} improved significantly, whereas ventilation and maximal workload were not relevantly affected. ETI approval coincided with the COVID-19 pandemic, during which a steeper decline of V'_{O2 peak} in ETI-naive people with CF was observed. However, this potential confounder did not significantly impact the overall longitudinal improvement in V'_{O2 peak} trajectory following ETI introduction (p<0.05).

Conclusion: The longitudinal trend in V'_{O2 peak} progression from adolescence to young adulthood is impaired in people with CF, but the initiation of ETI can have a positive impact on this trajectory.