Cardiopulmonary exercise testing with supramaximal verification produces a safe and valid assessment of V̇o_2max in people with cystic fibrosis: a retrospective analysis

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. 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 men] who completed a routine ramp-incremental cycling test to determine peak oxygen uptake (V̇o_2peak) was studied. Maximal oxygen uptake (V̇o_2max) was subsequently confirmed by S_max at 110% of peak power output. 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%. Adults ( n = 9) 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 only S_max. S_max did not significantly worsen perceived breathing effort, chest tightness, throat narrowing, or exertion compared with ramp-incremental testing. 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. NEW & NOTEWORTHY Incorporating supramaximal verification into cardiopulmonary exercise testing protocols did not increase the frequency of adverse events or perceived discomfort versus a single-phase incremental exercise test in people with mild-to-severe cystic fibrosis. Furthermore, a valid measure of maximal oxygen uptake (V̇o_2max) was obtained from 85.7% of pediatric and 96.4% of adult exercise tests, whereas peak oxygen uptake underestimated aerobic fitness in comparison with V̇o_2max in 21.4% of cases (by up to 24.4%).