Lung clearance index: assessment and utility in children with asthma

Abstract

There is increasing evidence that ventilation heterogeneity and small airway disease are significant factors in asthma, with evidence suggesting that the small airways are involved from an early stage in childhood asthma. Spirometry is commonly used to monitor lung function in asthmatics; however, it is not sensitive to small airway disease. There has been renewed interest in multibreath washout (MBW) tests, with recognition of the lung clearance index (LCI) as a global index of abnormality in gas mixing of the lungs that therefore also reflects small airway disease. This review summarises the technical and practical aspects of the MBW/LCI in children, and the differences between commercially available equipment. Children with severe asthma are more likely to have an abnormal LCI, whereas most children with mild-to-moderate asthma have an LCI within the normal range, but slightly higher than age-matched healthy controls. Monitoring children with asthma with MBW alongside standard spirometry may provide useful additional information.

Clinical and lung function outcomes in a cohort of children with severe asthma

“…However, for the majority of patients, LCI remained in the abnormal range (83%) even after a personalised asthma intervention. Abnormal LCI measurements have been demonstrated in children with normal spirometry [32]. More studies are required to elucidate the precise mechanisms underpinning the occurrence of lung ventilation inhomogeneities in SA and the clinical relevance of its persistence.…”

Pulmonary Function Testing in Asthmatic Children. Tests to Assess Outpatients During the Covid-19 Pandemic

“…Small airways dysfunction in asthma is now widely recognized (9)(10)(11). Spirometric variables such as FEV 1 are affected by flow resistance at the large airways.…”

“…Small airway dysfunction and ventilation heterogeneity are relevant in asthma (11,18,(35)(36)(37). Uneven ventilation can be assessed through inert gas dilution during tidal breathing: washout of the resident nitrogen with 100% oxygen, or initial wash-in of an exogenous gas (e.g., sulfur hexafluoride, SF 6 ), and washout thereafter.…”

“…Young children usually cooperate with the test; they need coaching to breath normally while seated, wearing a mouthpiece with in-line microbial filter. Gas leaks should be avoided during the process (11,38).…”

“…Children with severe asthma have elevated LCI values as compared to those with a mild-to-moderate disease or healthy controls. However, many patients with severe disease yield LCI values within the normal range (11,36).…”