Changes in lung function measured by spirometry and the forced oscillation technique in cystic fibrosis patients undergoing treatment for respiratory tract exacerbation

Objective measures of lung function are critical for the treatment and study of lung diseases such as cystic fibrosis (CF). Spirometry is the most widely used and accepted method of pulmonary function testing in CF, but not all patients can perform the maneuvers required to obtain valid results from spirometry. The forced oscillation technique (FOT) requires less cooperation than spirometry. The goals of this study were to determine if FOT could detect changes in lung function in CF patients receiving inpatient treatment of respiratory tract exacerbations (RTEs), and to gather preliminary data on the magnitude of these changes and the variability of FOT data in such patients. We performed a retrospective chart review of CF patients admitted to the hospital for RTEs. We identified 14 patients who had both spirometry and FOT performed at the beginning and end of their treatment course. Their mean age was 15.9 years (range, 8-18). The mean forced expiratory volume in 1 sec (FEV1) on admission was 62.57% predicted. FEV1 increased by 27.1 +/- 33.15% (mean +/- SD, P = 0.008). The absolute value of reactance at 5 Hz (X5) decreased by 22.3 +/- 25.1 % (P = 0.005), while resistance at 5 Hz decreased by 11.6 +/- 17.3% (P = 0.025). There was a significant relationship between changes in FEV1 and X5 (P = 0.003, r(2) = 0.54). Our study demonstrates that FOT can detect significant changes in lung function in CF patients receiving treatment for RTEs. We speculate that FOT can serve as an alternative method to measure lung function in CF patients unable to perform spirometry, such as young children.