Chest physiotherapy can affect the lung clearance index in cystic fibrosis patients

OBJECTIVES The lung clearance index (LCI) is determined by multiple‐breath washout lung function (MBW). It is increasingly used as an endpoint in clinical trials. Chest physiotherapy (CP) is part of routine cystic fibrosis (CF) care. Whether the LCI is useful in detecting short‐term treatment effects of CP has not been sufficiently investigated. We assessed the short‐term influence of CP with highly standardized high‐frequency chest wall oscillation (HFCWO) on the LCI in CF patients. METHODS In this randomized controlled study, the LCI was obtained in 20 CF patients (7‐34 years) hospitalized for infective pulmonary exacerbation prior to and immediately after a single treatment of HFCWO. Twenty‐one control group CF patients (7‐51 years) received no treatment. We calculated the coefficient of repeatability (CR) to estimate the clinical relevance of possible treatment effects. RESULTS HFCWO improved (ie, decreased) the LCI by a median of 0.9 (range −0.45; 3.47; P = 0.002); the LCI decreased in 15 of 20 intervention group patients. In five patients the decrease in LCI exceeded the CR (2.15), indicating a clinically relevant treatment effect; in five patients the LCI increased but did not exceed the CR. The LCI did not change significantly in the control group patients. CONCLUSIONS HFCWO can have a short‐term decreasing effect on the LCI, but the treatment response is heterogeneous. In future trials using LCI as an endpoint, the timing of CP in relation to MBW should be considered a possible bias.