Practicability of nitrogen multiple‐breath washout measurements in a pediatric cystic fibrosis outpatient setting

Abstract

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.

Multiple-Breath Washout as a Lung Function Test in Cystic Fibrosis. A Cystic Fibrosis Foundation Workshop Report

“…The majority of studies performed in subjects with CF are cross-sectional, where LCI is related to other measures of lung function (26,32), imaging (28,(33)(34)(35), or clinical status (36)(37)(38). These studies consistently demonstrate that, compared with healthy control subjects, LCI is abnormal in a significant proportion of preschool children with CF and in the majority of school-aged children and adults (32,33,35,39).…”

“…Cross-sectional data in infants and children suggest that those with evidence of bacterial infection are more likely to have abnormal LCI (36,38,40). In a preschool crosssectional study, children who had "ever cultured" Pseudomonas aeruginosa from airway secretions had higher LCI than those who had not (32).…”

“…At these centers, MBW is performed on at least an annual basis; however, MBW may be performed more often if the physician is unclear about symptomatology and/or if symptoms are being reported by the patient or parents (weight deviation, loss of appetite, fatigue, irritability). Currently, an increase of 1 unit in the LCI value is considered a sign of deterioration in these centers (36,37). The medical history coupled with the LCI values is used as part of the clinical decision making for these patients.…”

Is Lung Clearance Index (LCI) Affected by the Severity of Lung Disease in CF?

“…MBW measurements were performed according to ATS/ERS standards [45] using a validated ultrasonic flow measuring system for measuring flow, volume and molecular mass (EXHALYZER D, Ecomedics, Switzerland) [46]. The duration of a MBW test is on average 2-5 min per maneuver in a healthy subject, but longer in subjects with airway obstruction [47], while LCI success rate ranges between 70% to 85% in CF patients [48].…”

Functional evidence for continued alveolarisation in former preterms at school age?

“…Nitrogen multiple-breath washout All children performed nitrogen MBW (N 2 MBW) according to current consensus [25] using a previously described setup [26,27] (Exhalyzer D; Eco Medics AG). The application of 100% oxygen washes out the lung-resident nitrogen.…”