P91 Cardiopulmonary exercise testing in CF adolescents after starting Tezacaftor/Ivacaftor

Background Aerobic exercise capacity, as assessed by Cardiopulmonary exercise testing (CPET) is an independent predictor of mortality and morbidity in cystic fibrosis (CF). There is limited evidence on the change in exercise tolerance for patients treated with CFTR modulators. The aim of our study was to review the impact of Tezacaftor/Ivacaftor (Tez/Iva) on exercise capacity in our cohort of CF adolescents. Method Eligible CF adolescents performed CPET testing immediately before initiating Tez/Iva combination therapy with repeat testing at 7 to 8 months after commencing treatment. Results Four adolescents (Three males, mean age 16.3 years) participated in this study to date. All of them performed technically acceptable CPET, the results are shown in table 1. Peak VO2 decreased slightly in 3 of our 4 patients. In these 3 patients, the mean peak VO2% predicted reduced by 15%, 4% and 4% respectively; it improved by 22% predicted in the fourth patient. A low mean anaerobic threshold at the beginning of the study suggested some element of deconditioning. The VO2 values at anaerobic thresholds improved in all four patients by 4%, 14%, 19% and 79% respectively. The mean anaerobic threshold (calculated as VO2 AT/VO2max predicted), improved by 3%, 7% and 23% in three of our patients, there was no change noted in the fourth patient. Three children had an increase in their BMI. Conclusion Tez/Iva treatment improved the anaerobic threshold in our patients. Larger and longitudinal studies are required to ascertain the impact of these treatments on cardiopulmonary fitness in CF patients. Reference Hulzebos EH, Bomhof-Roordink H, van de Weert-van Leeuwen PB, et al. Prediction of mortality in adolescents with cystic fibrosis. Med Sci Sports Exerc 2014;46(11):2047–2052.