Abstract

Lung clearance index (LCI), a measure of ventilation inhomogeneity derived from the multiple-breath inert gas washout (MBW) technique has been shown to detect abnormal lung function more readily than spirometry in preschool children with Cystic Fibrosis (CF), but whether this holds true during infancy is unknown.

Objectives: We compared the extent to which parameters derived from the MBW and the raised volume (RVRTC) technique identify diminished airway function in infants with CF when compared with healthy controls.

Methods: Measurements were performed during quiet sleep with the tidal breathing MBW technique being performed prior to forced expiratory manoeuvres.

Results: Measurements were obtained in 39 infants with CF (mean[SD] age: 41.4[22.0]w) and 21 controls (37.0 [15.1] w). CF subjects had significantly higher respiratory rate (38 [10] vs. 32[5] bpm) and LCI (8.4 [1.5] vs. 7.2[0.3]), and significantly lower values for all forced expiratory flow-volume parameters compared with controls. Girls with CF had significantly lower FEV_0.5 and FEF_25-75 than boys (mean [95% CI girls - boys] - 1.2[-2.1, -0.3] for FEV_0.5 Z-score; FEFFEF_25-75: -1.2[- 2.2, -0.15]). When using both the MBW and RVRTC techniques, abnormalities were detected in 72% of infants with CF, with abnormalities detected in 41% on both techniques and a further 15% by each of the two tests performed.

Conclusions: These findings support the view that inflammatory and/or structural changes in the airways of children with CF start early in life, and have important implications regarding early detection and interventions. Monitoring of early lung disease and functional status in infants and young children with CF may be enhanced by using both the MBW and the RVRTC.