Summary. Background: Although lung clearance index (LCI) is a sensitive indicator of mild cystic fibrosis (CF) lung disease, it is rarely measured due to lengthy protocols and the commercial unavailability of multiple-breath washout (MBW) setups and tracer gases. We used a newly validated, commercially available nitrogen (N 2 ) MBW setup to assess success rate, duration, and variability of LCI within a 20 min timeframe, during clinical routine. We also evaluated the relationship between LCI and other clinical markers of CF lung disease. Methods: One hundred thirty six children (83 with CF) between 4 and 16 years were studied in a pediatric CF outpatient setting. One hundred eighteen out of 136 children were naïve to MBW. Within 20 min, each child was trained, N 2 MBW was performed, and LCI was analyzed. We assessed intra-and between-test reproducibility in a subgroup of children. Results: At least one LCI was feasible in 123 (90%) children, with a mean (range) of 3.3 (1.2-6.4) min per test. Two or more measurements were feasible in 56 (41%) children. Comparing LCI in CF versus controls, LCI mean (SD) was 12.0 (3.9) versus 6.1 (0.9), and the intra-and inter-test coefficient of repeatability was 1.00 versus 0.81 and 0.96 versus 0.62, respectively. LCI was correlated with spirometry, blood gases, and Pseudomonas aeruginosa infection. Conclusions: Using available N 2 MBW equipment, LCI measurements are practical and fast in children. LCI is correlated with markers of CF lung disease. Longer timeframes would be required for triplicate N 2 MBW tests in inexperienced children.

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BackgroundThe multiple breath nitrogen washout (N2MBW) technique is increasingly used to assess the degree of ventilation inhomogeneity in school-aged children with lung disease. However, reference values for healthy children are currently not available. The aim of this study was to generate reference values for N2MBW outcomes in a cohort of healthy Caucasian school-aged children.MethodsN2MBW data from healthy Caucasian school-age children between 6 and 18 years old were collected from four experienced centres. Measurements were performed using an ultrasonic flowmeter (Exhalyzer D, Eco Medics AG, Duernten, Switzerland) and were analysed with commercial software (Spiroware version 3.2.1, Eco Medics AG). Normative values and upper limits of normal (ULN) were generated for lung clearance index (LCI) at 2.5% (LCI2.5%) and at 5% (LCI5%) of the initial nitrogen concentration and for moment ratios (M1/M0 and M2/M0). A prediction equation was generated for functional residual capacity (FRC).ResultsAnalysis used 485 trials from 180 healthy Caucasian children aged from 6 to 18 years old. While LCI increased with age, this increase was negligible (0.04 units·year–1 for LCI2.5%) and therefore fixed ULN were defined for this age group. These limits were 7.91 for LCI2.5%, 5.73 for LCI5%, 1.75 for M1/M0 and 6.15 for M2/M0, respectively. Height and weight were found to be independent predictors of FRC.ConclusionWe report reference values for N2MBW outcomes measured on a commercially available ultrasonic flowmeter device (Exhalyzer D, Eco Medics AG) in healthy school-aged children to allow accurate interpretation of ventilation distribution outcomes and FRC in children with lung disease.

Pulmonary exacerbations are important clinical events for cystic fibrosis (CF) patients. Studies assessing the ability of the lung clearance index (LCI) to detect treatment response for pulmonary exacerbations have yielded heterogeneous results. Here, we conduct a retrospective analysis of pooled LCI data to assess treatment with intravenous antibiotics for pulmonary exacerbations and to understand factors explaining the heterogeneous response.A systematic literature search was performed to identify prospective observational studies. Factors predicting the relative change in LCI and spirometry were evaluated while adjusting for within-study clustering.Six previously reported studies and one unpublished study, which included 176 pulmonary exacerbations in both paediatric and adult patients, were included. Overall, LCI significantly decreased by 0.40 units (95% CI −0.60-−0.19, p=0.004) or 2.5% following treatment. The relative change in LCI was significantly correlated with the relative change in forced expiratory volume in 1 s (FEV1), but results were discordant in 42.5% of subjects (80 out of 188). Higher (worse) baseline LCI was associated with a greater improvement in LCI (slope: −0.9%, 95% CI −1.0-−0.4%).LCI response to therapy for pulmonary exacerbations is heterogeneous in CF patients; the overall effect size is small and results are often discordant with FEV1. @ERSpublications Lung clearance index response to therapy for pulmonary exacerbations is heterogeneous in cystic fibrosis patients http://ow.ly/Mnvtd

We recommend the use of the manual modus for the analysis of MBW outcomes in infants in order to obtain more accurate results. This will allow appropriate use of infant lung function results for clinical and scientific purposes.

RationaleWhile lung clearance index (LCI) is a sensitive marker of small airway disease in individuals with cystic fibrosis (CF), less is known about longitudinal changes in LCI during routine clinical surveillance.ObjectivesTo describe the longitudinal course of LCI in children with CF during routine clinical surveillance and assess influencing factors.MethodsChildren with CF aged 3–18 years performed LCI measurements every 3 months as part of routine clinical care between 2011 and 2018. We recorded clinical data at every visit. We used a multilevel mixed-effect model to determine changes in LCI over time and identify clinical factors that influence LCI course.Measurements and Main ResultsWe collected LCI from 1204 visits (3603 trials) in 78 participants, of which 907 visits had acceptable LCI data. The average unadjusted increase in LCI for the entire population was 0.29 LCI units·year−1 (95% CI 0.20–0.38). The increase in LCI was more pronounced in adolescence, with 0.41 units·year−1 (95% CI 0.27–0.54). Colonisation with either Pseudomonas aeruginosa or Aspergillus fumigatus, pulmonary exacerbations, CF-related diabetes, and bronchopulmonary aspergillosis were associated with a higher increase in LCI over time. Adjusting for clinical risk factors reduced the increase in LCI over time to 0.24 LCI units·year−1 (95% CI 0.16–0.33).ConclusionLCI measured during routine clinical surveillance is associated with underlying disease progression in children with CF. An increased change in LCI over time should prompt further diagnostic intervention.

Prematurity is the most common disruptor of lung development. The aim of our study was to examine the function of the more vulnerable peripheral airways in former preterm children by multiplebreath washout (MBW) measurements.86 school-aged children, born between 24 and 35 weeks of gestation and 49 term-born children performed nitrogen MBW. Lung clearance index (LCI), and slope III-derived Scond and Sacin were assessed as markers for global, convection-dependent and diffusion-convection-dependent ventilation inhomogeneity, respectively.We analysed the data of 77 former preterm (mean (range) age 9.5 (7.2-12.8) years) and 46 term-born children (mean age 9.9 (6.0-15.9) years). LCI and Sacin did not differ between preterm and term-born children. Scond was significantly elevated in preterm compared to term-born participants (mean difference z-score 1.74, 95% CI 1.17-2.30; p<0.001), with 54% of former preterm children showing elevated Scond. In multivariable regression analysis Scond was significantly related only to gestational age (R 2 =0.37). Normal Sacin provides evidence for a functionally normal alveolar compartment, while elevated Scond indicates impaired function of more proximal conducting airways. Together, our findings support the concept of continued alveolarisation, albeit with "dysanaptic" lung growth in former preterm children. @ERSpublications Evidence for a prematurity-related dysanaptic lung growth in former preterm children

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