A new double-tracer gas single-breath washout to assess early cystic fibrosis lung disease

摘要

In cystic fibrosis (CF), tests for ventilation inhomogeneity are sensitive but not established for clinical routine. We assessed feasibility of a new double-tracer gas single-breath washout (SBW) in school-aged children with CF and control subjects, and compared SBW between groups and with multiple-breath nitrogen washout (MBNW). Three SBW and MBNW were performed in 118 children (66 with CF) using a side-stream ultrasonic flowmeter setup. The double-tracer gas containing 5% sulfur hexafluoride and 26.3% helium was applied during one tidal breath. Outcomes were SBW phase III slope (SIIIDTG), MBNWderived lung clearance index (LCI), and indices of acinar (Sacin) and conductive (Scond) ventilation inhomogeneity. SBW took significantly less time to perform than MBNW. SBW and MBNW were feasible in 109 (92.4%) and 98 (83.0%) children, respectively. SIIIDTG differed between children with CF and controls, mean±SD was -456.7±492.8 and -88.4±129.1 μg.mol.L-1, respectively. Abnormal SIIIDTG was present in 36 (59%) children with CF. SIIIDTG was associated with LCI (r= -0.58) and Sacin (r= -0.58), but not with Scond. In CF, steeply sloping SIIIDTG potentially reflects ventilation inhomogeneity near the acinus entrance. This tidal SBW is a promising test to assess ventilation inhomogeneity in an easy and fast way.