Lung Clearance Index to Detect Early Pulmonary Changes in Children with Sickle Cell Disease

Abstract

<i>Objective:</i> Pulmonary complications including acute chest syndrome, are leading causes of sickle cell disease (SCD) related morbidity and mortality. Prior studies have shown that patients with pulmonary complications have evidence of pulmonary involvement reflected in lung functions trends as early as childhood. Spirometry is the current standard for measuring lung function. Growing evidence suggests that lung clearance index (LCI) which is a commonly reported parameter of multiple breath washout (MBW) tests, is more sensitive than spirometry measurements in the early identification of pulmonary changes in pediatric patients. The aim of our study was to determine if this relationship between LCI and spirometry existed within the pediatric sickle cell population. <i>Study Design: </i>This is a cross-sectional, retrospective study to compare LCI to spirometry measurements in children with SCD. Charts were reviewed of clinic encounters at Phoenix Children’s Hospital from March 1, 2013 – June 30, 2017. Spirometry and MBW measurements were collected from 23 patients between the ages of 5 years – 22 years. The MBW utilized sulfur hexafluoride (SF₆) as the tracer gas. Demographics and SCD variant (e.g. HbSS, HbSC, etc.) for each encounter were also collected. <i>Results: </i>Our results show that LCI correlates to FEV₁% predicted (Spearman’s coefficient -0.44, p = 0.003) and FEF_25-75% (Spearman’s coefficient -0.49, p <0.001) over time. Based on demographics, LCI is affected by weight (p = 0.046) but not age or height. When comparing LCI and FEV₁% predicted, abnormal LCI results were noted to occur even in the presence of normal FEV₁% predicted measurements. <i>Conclusions: </i>Our data support LCI correlating with spirometry measurements, but more studies are necessary to explore whether LCI can be used as a screening test to detect pulmonary changes in young children with SCD. Earlier monitoring of lung function will allow for preventative therapies and delayed progression of pulmonary dysfunction.