Objectives: Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) could be useful clinical parameters in monitoring many conditions including cystic fibrosis (CF). However, current protocols for undertaking the measurements lack standardization including the number of repeated attempts to achieve best values. We aimed to (a) determine the optimum number of attempts to achieve best MIP/MEP values, and (b) evaluate if the number of attempts is consistent across two different test days.
Methods: We analyzed data of a previous randomized controlled trial involving the effect of singing on respiratory muscle strength in 35 children with CF. On two different days (T1, T2) children performed MIP/MEP with at least ten attempts each to achieve < 10% repeatability.
Results: All children achieved repeatable MIP/MEP values within 10–11 attempts with 24 (68.6%) and 26 (74.3%) of these achieving best values of MIP and MEP, respectively, at attempts 6–11. Median values of the pressures by three, five, eight and all attempts significantly increased with more attempts (all p < 0.05). At T2, 56% required fewer attempts to achieve best values, but 32% required more attempts, indicating that the number of attempts required was inconsistent between test days.
Conclusion: It is likely that at least ten attempts (best two within < 10% variability) is required to achieve best and reliable MIP/MEP in children with CF. A larger sample size in children with CF and various conditions is required to consolidate these findings.