Abstract
Background: During Multiple Breath Washout (MBW) subjects are to maintain quiet, tidal breathing and avoid sighs. Most children naturally breathe at 8-13mL/kg of ideal body weight (IBW; Horton et al. 2017 Abstract) and breathing far outside this range may impact MBW results (Yammine et al. J Cyst Fibros 2014).
Objective: To identify the distribution of tidal volumes during MBW testing in children and to assess whether natural deviations from the ideal range affect MBW results.
Methods: 7100 MBW trials from two multicentre clinical studies without leaks and meeting end of test criteria were analyzed (43% male, median 8.1 years, range 2.2-15.3). Comparisons were made within-test, between trials in and outside the ideal range. IBW was calculated from sex and height using equations derived from CDC growth charts.
Results: Median tidal volume was 11.97mL/kg IBW (IQR 10.65-13.45). 2248 trials (32%) fell above 13mL/kg IBW by a median of 1.2mL/kg IBW (IQR 0.56-2.4), and 131 (2%) fell below 8mL/kg IBW by a median of 0.40 mL/kg IBW (IQR 0.17-0.69). Breathing above 13mL/kg IBW had no impact on LCI (0.26%, 95% CI -0.45-0.98, p=0.47), but increased FRC by 2.97% (95% CI 2.28-3.68, n=910, P<0.01). Breathing below 8mL/kg IBW did not impact either LCI (p=0.24) or FRC (p=0.54). Trials with one or more sighs (defined as 150% of the mean tidal volume) were associated with an increase in LCI of 1.03% (95% CI 0.5-1.5, n=1862, p<0.01) and FRC of 2.31% (95% CI 1.87-2.75, n=1862, p<0.01).
Conclusion: Within the range of tidal volumes observed, minor deviations from ideal tidal volume range, and sighs that do not impact end-tidal nitrogen concentration, had small effects on FRC and LCI that are unlikely to be clinically relevant.
Footnotes
Cite this article as: European Respiratory Journal 2018 52: Suppl. 62, OA4987.
This is an ERS International Congress abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only).
- Copyright ©the authors 2018