Measurement of lung clearance index (LCI2.5) by nitrogen multiple breath washout (N2-MBW) is feasible and well‍-‍tolerated by adults and children with cystic fibrosis.

BACKGROUND

Lung clearance index (LCI2.5), measured by nitrogen-multiple breath washout (N2-MBW), is a sensitive measure of ventilatory inhomogeneity that can be performed awake/unsedated from aged 3 years. However, concerns have been raised about the feasibility of LCI2.5 measurement by N2-MBW in adults with cystic fibrosis (CF), especially those with advanced lung disease, due to prolonged test durations. We assessed the feasibility, technical acceptability and patient perception of N2-MBW in adults and children/adolescents with CF within the exercise as an airway clearance technique-CF feasibility trial.

METHODS

N2-MBW (Exhalyzer-D, EcoMedics, Switzerland) was performed on two separate occasions, by multidisciplinary trial staff. Data were centrally over-read (European Cystic Fibrosis Society LCI Core Facility). Outcomes included the proportion of technically acceptable tests, numbers of trials per test, times per trial and total time to perform N2-MBW. Comparisons were made according to age group and forced expiratory volume in 1 s (FEV1) category (>70% vs <70% predicted). Participants also completed a questionnaire assessing acceptability and willingness to repeat testing.

RESULTS

49 participants (21 female; age: 10-55 years, FEV1: 38%-113% predicted) completed N2-MBW. Median (IQR) test durations were similar for adults (42 (27-55) min) and children (37 (26-44) min) with CF. Technically acceptable LCI2.5 results were obtained for 90/94 (95.8%) tests. Most participants rated the test easy to perform (87%) and comfortable (93%), with none reporting unwillingness to repeat N2-MBW testing.

CONCLUSIONS

N2-MBW testing is feasible, technically acceptable and well-tolerated in people with CF across a wide age and disease severity spectrum. With appropriate standardised training and over-reading, LCI2.5 represents a robust outcome measure for consideration in CF clinical trials.

TRIAL REGISTRATION NUMBER: NCT05482048.