Predictive value of impulse oscillometry and multiple breath washout parameters in pediatric patients with cystic fibrosis pulmonary exacerbation

Background Pulmonary exacerbations (PE) tend to complicate the course of cystic fibrosis (CF) and worsen the disease prognosis. One of the diagnostic criteria for an exacerbation is the forced expiratory volume in the first second (FEV1) decline. Not all children, however, are able to perform spirometry. Therefore, the aim of this study was to evaluate alternative lung function tests in the diagnosis of PE. Methods We assessed retrospectively the results of impulse oscillometry (IOS) and lung clearance index in multiple breath washout (MBW) during 259 visits in 47 CF paediatric patients. The differences in the results were compared between patients diagnosed with PE (Delta PE) and those in stable condition (Delta S). Results Among the whole group of patients, we found significant differences between the changes during exacerbation (Delta PEs) and stable condition (Delta Ss) values for lung clearance index (LCI), S-acin, R5Hz, R5-20Hz, X10Hz, AX, and Fres. The predictive values of Fres and X10Hz in IOS (AUC(ROC) 0.71 both parameters) were higher than those of LCI (AUC(ROC) 0.67). There was no difference in the predictive values (AUC(ROC)) of Delta LCI and IOS parameters in the subgroups of patients stratified based on FEV1 z-score cut-off value of -1.64. In both groups of patients, predictive values of LCI were slightly lower than of IOS parameters (AUC 0.66 for LCI vs. 0.69 for both Delta X10Hz z-score and Delta Fres z-score in patients with FEV1 z-score >=-1.64 and AUC 0.67 for LCI vs 0.69 for both Delta X10Hz zscore and Delta Fres zscore in patients with FEV1<1.64. Conclusions Both IOS and MBW measurements are useful in the assessment of pediatric CF patients with PE. LCI has a similar predictive value to IOS in children with CF independently of their FEV1 value.