Background: CFTR modulators have transformed Cystic Fibrosis (CF) care. However, there is limited knowledge on impact of modulators on exercise capacity. Reduced VO2 at peak exercise and ventilatory limitation indicated by low breathing reserve < 15% are common abnormalities in CF patients.
Aims: To study the impact of Kaftrio on exercise capacity in CF children.
Methods: Observational cohort study. Cardiopulmonary exercise testing (CPET) was performed at baseline and after 6-8 months of Kaftrio treatment.
Results : 7 children participated in this study (3 males, mean age 11.24 years +/- 1.4). Significant improvement was noted in FEV1% predicted and BMI. There were however no changes in VO2 peak. 4 patients had ventilatory limitation at baseline, this persisted in 3 patients on Kaftrio. There was significant improvement in breathing reserve for the whole cohort. Improvements in FEV1 % predicted was not associated with changes in breathing reserve (Table).
Table - Clinical and CPET parameters for the patient cohort
| Pre-Kaftrio | After 6 months | p-value | |
| FEV1%predicted | 84.1 +/- 16.37 | 98.63+/- 21.34 | 0.018 |
| BMI | 17.86 +/- 1.57 | 18.43 +/- 1.62 | 0.046 |
| VO2 ( ml/min/kg) | 39 +/- 9.3 | 38.37 +/- 7.47 | 1 |
|
VO2 at AT ( % of VO2 peak) |
60 +/- 17.15 | 61.86 +/- 10.7 | 0.612 |
|
Breathing reserve ( %) |
16.29 +/- 15.83 | 30.29 +/- 19.52 | 0.018 |
|
Maximal workload ( % predicted) |
82 +/- 20.1 | 90.14 +/- 9.35 | 0.108 |
Conclusion: Patients on Kaftrio had improved FEV1 and BMI but no improvement in VO2 peak. Improvement in ventilatory limitation was not associated with improvement in FEV1. Longitudinal studies with CPET in CF children are needed to evaluate impact of CFTR modulators on exercise capacity.