Acute effects of combined exercise and oscillatory positive expiratory pressure therapy on sputum properties and lung diffusing capacity in cystic fibrosis: a randomized, controlled, crossover trial

BACKGROUND: Regular airway clearance by chest physiotherapy and/or exercise is critical to lung health in cystic fibrosis (CF). Combination of cycling exercise and chest physiotherapy using the Flutter® device on sputum properties has not yet been investigated. METHODS: This prospective, randomized crossover study compared a single bout of continuous cycling exercise at moderate intensity (experiment A, control condition) vs a combination of interval cycling exercise plus Flutter® (experiment B). Sputum properties (viscoelasticity, yield stress, solids content, spinnability, and ease of sputum expectoration), pulmonary diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO) were assessed at rest, directly and 45 min post-exercise (recovery) at 2 consecutive visits. Primary outcome was change in sputum viscoelasticity (G’, storage modulus; G”, loss modulus) over a broad frequency range (0.1–100 rad.s(− 1)). RESULTS: 15 adults with CF (FEV(1)range 24–94% predicted) completed all experiments. No consistent differences between experiments were observed for G’ and G” and other sputum properties, except for ease of sputum expectoration during recovery favoring experiment A. DLNO, DLCO, alveolar volume (V(A)) and pulmonary capillary blood volume (V(cap)) increased during experiment A, while DLCO and V(cap) increased during experiment B (all P < 0.05). We found no differences in absolute changes in pulmonary diffusing capacity and its components between experiments, except a higher V(A) immediately post-exercise favoring experiment A (P = 0.032). CONCLUSIONS: The additional use of the Flutter® to moderate intensity interval cycling exercise has no measurable effect on the viscoelastic properties of sputum compared to moderate intensity continuous cycling alone. Elevations in diffusing capacity represent an acute exercise-induced effect not sustained post-exercise. TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT02750722; URL: clinical.trials.gov; Registration date: April 25th, 2016. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12890-018-0661-1) contains supplementary material, which is available to authorized users.