CPET in CF Patients With One G551D Mutation Taking VX770

Ivacaftor will restore CFTR function in treated CF patients with the G551D mutation. Improvement in ventilation, salt balance and well-being will contribute to better exercise capacity at all levels of lung function. While potential improvements may be variable across the spectrum of lung function, even small gains at low levels of FEV1 may have significant benefit for some subjects.