title: Repeatability of airway resistance measurements made using the interrupter technique.
abstract: BACKGROUND
  To be able to interpret any measurement, its repeatability should be known. This study reports the repeatability of airway resistance measurements using the interrupter technique (Rint) in children with and without respiratory symptoms.
  
  
  METHODS
  Children aged 2-10 years who were healthy, had persistent isolated cough, or who had previous wheeze were studied. On the same occasion, three Rint measurements were made 15 minutes apart, before and after placebo and salbutamol given in random order. Results from those given placebo first were analysed for within-occasion repeatability. Between-occasion repeatability measurements were made 2-20 weeks apart (median 3 weeks).
  
  
  RESULTS
  For 85 pairs of measurements before and after placebo the limits of agreement were 20% expected resistance and were unaffected by age or health status. The change in resistance following bronchodilator in one of 18 healthy children, 12 of 28 with cough, and 22 of 39 with wheeze exceeded this threshold. For between-occasion measurements the limits of agreement were 32% in 72 healthy subjects, 49% in 57 with cough, and 53% in 95 with previous wheeze.
  
  
  CONCLUSIONS
  The measurement of airways resistance by the interrupter technique is clinically meaningful when change following an intervention such as the administration of bronchodilator is greater than its within-occasion repeatability. Between-occasion repeatability is too poor to judge change confidently.
authors.affiliation: Department of Respiratory Paediatrics, Fielden House, The Royal London Hospital, Barts, London E1 1BB, UK.
authors.forename: E Y
authors.initials: EY
authors.lastname: Chan
authors.forename: P D
authors.initials: PD
authors.lastname: Bridge
authors.forename: I
authors.initials: I
authors.lastname: Dundas
authors.forename: C S
authors.initials: CS
authors.lastname: Pao
authors.forename: M J R
authors.initials: MJ
authors.lastname: Healy
authors.forename: S A
authors.initials: SA
authors.lastname: McKenzie
mesh_terms: D000403:Airway Resistance / Q000502:physiology*; D000420:Albuterol; D001985:Bronchial Provocation Tests; D001993:Bronchodilator Agents; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease; D003371:Cough / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D011897:Random Allocation; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D012135:Respiratory Sounds / Q000503:physiopathology*
chemical_list: D001993:Bronchodilator Agents; D000420:Albuterol