Cardiopulmonary exercise testing with supramaximal verification produces a safe and valid assessment of V̇O_2max in people with cystic fibrosis

Introduction - The validity and safety of using supramaximal verification (S_max) to confirm a maximal effort during cardiopulmonary exercise testing (CPET) in people with cystic fibrosis (CF) and/or those with severe disease has been questioned. Therefore, this study aimed to investigate these concerns in children, adolescents and adults with mild-to-severe CF lung disease. 

Methods - Retrospective analysis of 17 pediatric and 28 adult participants with CF (age range: 9.2-62.9 y; forced expiratory volume in 1 s: 66.7% [range: 29.9-102.3%]; 30 males) who completed a routine ramp incremental cycling test to determine peak oxygen uptake (V̇O_2peak). Maximal oxygen uptake (V̇O_2max) was subsequently confirmed by S_max at 110% of peak power output. 

Results - All participants satisfied the criteria to verify a maximal effort during CPET. However, S_max-V̇O_2peak exceeded ramp-V̇O_2peak in 3/14 (21.4%) of pediatric and 6/28 (21.4%) adult exercise tests. A valid measurement of V̇O_2max was attained in 85.7% of pediatric and 96.4% of adult exercise tests, as S_max-V̇O_2peak did not exceed ramp-V̇O_2peak by > 9%. Nine adults experienced a ≥ 5% reduction in arterial O₂ saturation during CPET; 4 during both the ramp and S_max, 3 during only the ramp and 2 during S_max only. S_max did not significantly worsen perceived breathing effort, chest tightness, throat narrowing or exertion compared with ramp incremental testing. 

Conclusions - Given the clinical importance of aerobic fitness in people with CF, incorporating S_max is recommended to provide a safe and valid measure of V̇O_2max in children, adolescents and adults who span the spectrum of CF disease severity.