Abstract
Background: Gas washout measurements are used to detect ventilation inhomogeneity (VI) in patients with lung disease. Our aim was to assess whether washout tests can help to define physiological phenotypes in children with different lung diseases.
Method: 80 school age children performed three different gas washout measurements, nitrogen multiple and single breath washout (N2-MBW and N2-SBW) and double-tracer gas single breath washout (DTG-SBW). We included each 20 children with cystic fibrosis, with primary ciliary dyskinesia, who were former preterm and healthy controls. Outcome parameters to represent global VI were lung clearance index (LCI) derived from the N2-MBW and Slope III of the N2-SBW. Specific VI were Scond (diffusion and convection dependent) and Sacin of the N2-MBW, SIII-CO2-DTG and SIII-DTG of the DTG-SBW (acinar VI). Z-scores were calculated based on healthy controls. Clustering of different gas washout indices was performed using hierarchical ward clustering.
Results: Mean values of all indices were elevated in PCD and CF, whereas in former preterm only SIII-CO2-DTG was significantly elevated on a group level (0.6 z-scores). In CF especially LCI and Scond (4.4, 3.4 z-scores) were increased. In PCD beside LCI and Scond also Sacin (1.4 z-scores) was increased. We focused on four to six clusters carrying different characteristics of the respective groups, partly independent of lung disease.
Conclusion: The combination of different indices fromgas washout tests can be used to define physiological phenotypes. Longitudinal data using larger numbers will show whether the clusters are disease course-specific or can identify physiological phenotypes independent of age or disease condition.
- Copyright ©ERS 2015