Short‐term effects of positive expiratory pressure mask on ventilation inhomogeneity in children with cystic fibrosis: A randomized, sham‐controlled crossover study

Background: Can physiotherapy with a positive expiratory pressure (PEP) mask improve peripheral ventilation inhomogeneity, a typical feature of children with cystic fibrosis (cwCF)? To answer this question, we used the nitrogen multiple-breath washout (N2 MBW) test to measure diffusion-convection-dependent inhomogeneity arising within the intracinar compartment (Sacin *VT). Methods: For this randomized, sham-controlled crossover trial, two N2 MBW tests were performed near the hospital discharge date: one before and the other after PEP mask therapy (1 min of breathing through a flow-dependent PEP device attached to a face mask, followed by three huffs and one cough repeated 10 times) by either a standard (10-15 cmH2 0) or a sham (<5 cmH2 0) procedure on two consecutive mornings. Deception entailed misinforming the subjects about the nature of the study; also the N2 MBW operators were blinded to treatment allocation. Study outcomes were assessed with mixed-effect models. Results: The study sample was 19 cwCF (ten girls), aged 11.4 (2.7) years. The adjusted Sacin *VT mean difference between the standard and the sham procedure was -0.015 (90% confidence interval [CI]: -∞ to 0.025) L-1 . There was no statistically significant difference in Scond *VT and lung clearance index between the two procedures: -0.005 (95% CI: -0.019 to 0.01) L-1 and 0.49 (95% CI: -0.05 to 1.03) turnovers, respectively. Conclusion: Our findings do not support evidence for an immediate effect of PEP mask physiotherapy on Sacin *VT with pressure range 10-15 cmH2 0. Measurement with the N2 MBW and the crossover design were found to be time-consuming and unsuitable for a short-term study of airway clearance techniques.