The development of normative values of LCI in healthy school-children using the SF6 (Innocor) Multiple Breath Washout technique

Abstract

Background
Some respiratory diseases are believed to start early in life, yet manifest later as lung damage progresses. Early pathological changes are usually missed on traditional methods of lung function assessment. Therefore, multiple breath washout (MBW) may be of value in clinical practice as it is known to be more sensitive for early airway changes. This study aims to identify normative MBW outcome measures, particularly the lung clearance index (LCI), for the SF6-based Innocor MBW device as well as explore the effect of demographic and environmental factors on MBW measures in the paediatric population.

Methods
A cross-sectional study was carried out on a sample of healthy children (aged 9-15 years; n=64) recruited from two schools in Stoke-on-Trent. Three runs of MBW testing were performed on each child in one sitting using the SF6-based Innocor device. A questionnaire was filled prior to testing by each child’s parent/guardian to assess the demographic and environmental factors of the study population.

Results
Sixty-two out of the 64 recruited subjects had valid measures, which were further analysed. The mean LCI was found to be 6.18 (SD=0.3). Gender, BMI, activity level, social deprivation, pollution level, and age were not found to have a significant effect on the outcome measures. The 95% limits of agreement was 0.96 and this equate to 15.5% of the normative value. The mean time for the three measurements was 17 minutes and 36 seconds (min = 13 minutes and 20 seconds and max = 26 minutes).

Conclusion
This study has suggested a normative LCI value for healthy individuals, particularly those aged 5 to 40 years. It also demonstrated the possibility of taking MBW testing from the research to the community setting using the portable Innocor MBW device. LCI may prove to be a valuable lung function assessment measure in the future as it is reliable, repeatable, sensitive, stable across age groups, and shows low variability among healthy individuals.