Is impulse oscillometry (IOS) better than spirometry for monitoring treatment outcomes in adult cystic fibrosis (CF) pulmonary exacerbations? A pilot study

Introduction: Spirometry is the gold standard for detecting and monitoring lung function decline in CF exacerbation. IOS is a newer diagnostic tool that detects airway resistance. The aim of this study is to compare IOS and spirometry in evaluating the effectiveness of intravenous antibiotic treatment for CF exacerbation. Methods: CF patients commencing intravenous antibiotic treatment for pulmonary exacerbations were prospectively recruited into the study. IOS and spirometry were performed prior to and weekly during antibiotic treatment. Results: Eleven patients aged 31.9±8.1 years(mean±SD) have completed the study to date. Mean pre-exacerbation FEV1 and FVC were 2.9±1.0L(71.2±22.8% predicted) and 4.2±1.3L(85.6±19.1% predicted). Subjects received antibiotics for mean 17.2 days(median 14 to 28 days). Paired t-tests were used to determine statistical significance pre and post antibiotic treatment. Significant improvement in spirometry was seen but not in the IOS parameters(Figure 1). Using linear mixed-effects model controlling for repeated measurements over time, correlations were seen between spirometry and IOS resistance values. Conclusion: Although we have not shown a significant change in IOS parameters post treatment, modelling demonstrates a significant correlation between spirometry and IOS resistance values over time, suggesting that with increased patient numbers we will also demonstrate significant change in IOS parameters.