A Systematic Approach to Multiple Breath Nitrogen Washout Test Quality.
BACKGROUND
Accurate estimates of multiple breath washout (MBW) outcomes require correct operation of the device, appropriate distraction of the subject to ensure they breathe in a manner representative of their relaxed tidal breathing pattern, and appropriate interpretation of the acquired data. Based on available recommendations for an acceptable MBW test, we aimed to develop a protocol to systematically evaluate MBW measurements based on these criteria.


METHODS
50 MBW test occasions were systematically reviewed for technical elements and whether the breathing pattern was representative of relaxed tidal breathing by an experienced MBW operator. The impact of qualitative and quantitative criteria on inter-observer agreement was assessed across eight MBW operators (n = 20 test occasions, compared using a Kappa statistic).


RESULTS
Using qualitative criteria, 46/168 trials were rejected: 16.6% were technically unacceptable and 10.7% were excluded due to inappropriate breathing pattern. Reviewer agreement was good using qualitative criteria and further improved with quantitative criteria from (κ = 0.53-0.83%) to (κ 0.73-0.97%), but at the cost of exclusion of further test occasions in this retrospective data analysis.


CONCLUSIONS
The application of the systematic review improved inter-observer agreement but did not affect reported MBW outcomes.
Division of Respiratory Medicine, Hospital for Sick Children, Toronto, Canada.
Renee
R
Jensen
Division of Respiratory Medicine, Hospital for Sick Children, Toronto, Canada.|University of Toronto, Toronto, Canada.
Sanja
S
Stanojevic
Division of Respiratory Medicine, Hospital for Sick Children, Toronto, Canada.
Michelle
M
Klingel
Division of Respiratory Medicine, Hospital for Sick Children, Toronto, Canada.|Pontificia Universidad Católica de Chile, Santiago, Chile.
Maria Ester
ME
Pizarro
Telethon Kids Institute, Perth, Australia.|Centre for Child Health Research, University of Western Australia, Perth, Australia.|School of Physiotherapy and Exercise Science, Curtin University, Perth, Australia.
Graham L
GL
Hall
Telethon Kids Institute, Perth, Australia.|Centre for Child Health Research, University of Western Australia, Perth, Australia.|University of North Carolina at Chapel Hill, Chapel Hill, United States of America.
Kathryn
K
Ramsey
Telethon Kids Institute, Perth, Australia.|Centre for Child Health Research, University of Western Australia, Perth, Australia.
Rachel
R
Foong
Royal Brompton & Harefield NHS Foundation Trust, London, United Kingdom.|Department of Gene Therapy, Imperial College London, London, United Kingdom.
Clare
C
Saunders
Department of Respiratory Medicine, The Children's Hospital at Westmead, Sydney, Australia.|Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia.
Paul D
PD
Robinson
Division of Respiratory Medicine, Hospital for Sick Children, Toronto, Canada.
Hailey
H
Webster
Department of Respiratory Medicine, The Children's Hospital at Westmead, Sydney, Australia.
Kate
K
Hardaker
Division of Respiratory Medicine, Hospital for Sick Children, Toronto, Canada.
Mica
M
Kane
Division of Respiratory Medicine, Hospital for Sick Children, Toronto, Canada.|University of Toronto, Toronto, Canada.
Felix
F
Ratjen
D000293:Adolescent; D001944:Breath Tests / Q000379:methods*; D002648:Child; D003550:Cystic Fibrosis / Q000503:physiopathology; D005260:Female; D006801:Humans; D008176:Lung Volume Measurements / Q000379:methods; D008297:Male; D009584:Nitrogen / Q000032:analysis*; D015203:Reproducibility of Results; D012119:Respiration; D012129:Respiratory Function Tests / Q000379:methods*; D012189:Retrospective Studies; D013990:Tidal Volume
D009584:Nitrogen