Prioritising cardiopulmonary exercise testing for adults with cystic fibrosis: a service evaluation

Background: Cystic Fibrosis is an inherited, life-limiting condition causing a range of symptoms including lowered exercise tolerance. Approximately 95% of people with cystic fibrosis in the United Kingdom are now eligible for new genetic modulator therapies. As a result, cystic fibrosis centres are treating older populations in greater numbers. Cardiopulmonary exercise testing measures aerobic capacity, however it is resource intensive. Identifying whether routinely collected clinical measures are associated with reduced aerobic capacity is needed to aid prioritisation of cardiopulmonary exercise testing.

Methods: Maximal cardiopulmonary exercise testing data were collected from July 2022 to January 2024, alongside routine clinical data (spirometry, body mass index, diabetic status, Pseudomonas aeruginosa colonisation status, modulator status, age and sex). Peak oxygen uptake was analysed as a percentage predicted value (VO2peakpp).

Results: Overall aerobic capacity at the centre was low (mean peak oxygen uptake 79.16% predicted). No relationship was identified between body mass index and aerobic capacity (β = 0.23, 95%CI -0.91, 1.37, p = 0.69). When adjusting for other clinical measures, having cystic fibrosis related diabetes (β=-17.56, 95%CI -27.17, -7.95, p < 0.001) and younger age (β = 16.62, 95%CI 4.13, 29.12, p = 0.01) were associated with a reduction in VO2peakpp.

Conclusion: Annual CPET for all pwCF may not be necessary or available. This service evaluation found associations with younger age and CFRD and reduced VO2peak who could be targeted for exercise testing and training intervention in the future.