Introduction Convection Dependent Inhomogeneity (CDI, a measure of ventilation inequality among larger lung units) quantified by Scond cannot be assessed in subjects with severe ventilation inhomogeneity (VI) as assumptions underlying the calculation are invalid; an alternate index that has been suggested is Scond.1
Aim To compare these two methods of CDI assessment in CF children
Methods Children with cystic fibrosis (CF; 67) and healthy controls (61) performed multiple breath washout with sulphur hexaflouride measured using mass spectrometry. Scond was calculated from 1.5 to 6 turnovers and Scond* from breath 2 to 3 turnovers.
Results All measures of VI were significantly higher for CF vs control, mean difference: LCI 4.0, Scond 0.054, Scond* 0.081.
In CF, LCI correlated better with Scond* than Scond (See figure: correlation coefficient LCI vs. Scond* 0.75; LCI vs. Scond 0.42). If children with moderate-severe VI (LCI > 11) were excluded there was an improved correlation for both relationships (correlation coefficient LCI vs. Scond 0.83; LCI vs. Scond* 0.86).
An asymptote for the Scond vs LCI relationship was at Scond 0.07 and Scond* 0.13.
Conclusion Scond* quantifies the mechanism of VI in moderate to severe lung disease, but it may reach asymptote in very severe VI.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.