Lung clearance index using a novel washout device is elevated in premature infants

Abstract

<b>Introduction:</b> Lung clearance index (LCI) is a measure of lung gas mixing, and a sensitive indicator of peripheral airway obstruction. In children born prematurely there have been previous reports of elevated LCI at birth and childhood. LCI in infants is highly challenging, requiring either 100% O2 to washout, or use of 4% SF6. Here we report on a novel method using a portable LCI device in non-sedated premature infants. <b>Methods:</b> LCI measurements were undertaken using 0.1% SF6 and washout on air. Premature infants no longer requiring oxygen were recruited just prior to discharge. Follow up measurements were planned 1 year later. Healthy controls were recruited opportunistically when attending non-thoracic MRI scan under sedation. <b>Results:</b> 13 premature babies (mean 30+6 weeks at birth, 37+6 corrected at measurement) were recruited and successful measurements were achieved on 9 (69%). LCI data are available for 36 healthy controls (mean 62weeks old, range 12-154 weeks). Mean LCI of the premature children (8.4, SD 1.6). was&nbsp;significantly higher than that of the healthy cohort (mean LCI 7.0, SD 0.6), p=&lt;0.001. Median coefficient of variation of ex-premature LCI was 6.6%. Mean(SD) FRC was&nbsp;68.95(47.96)ml (21 ml/kg (SD=3.19)). Only one child attended for a follow-up&nbsp;measurement&nbsp;(study interrupted by COVID pandemic); initial LCI of 7.3 at 38+6 (7 weeks of age) which increased to 8.0 at 61 corrected weeks of age. <b>Conclusion:</b> LCI is elevated in premature infants at time of discharge. This can be measured successfully using a portable device without high concentrations of SF6 or O2, and without sedation. The longitudinal change is still to be determined.