Multiple breath inert gas washout as a measure of ventilation distribution in children with cystic fibrosis
- 1Portex Anaesthesia, Intensive Therapy and Respiratory Medicine Unit, Institute of Child Health, London, UK
- 2Cardiorespiratory and Critical Care Division, Great Ormond Street Hospital for Children, London, UK
- 3Queen Silvia Children’s Hospital, Sahlgrenska University Hospital, Göteborg, Sweden
- 4Department of Paediatric Respiratory Medicine, Royal Brompton Hospital, London, UK
- Correspondence to:
Dr P Aurora
Portex Anaesthesia, Intensive Therapy and Respiratory Medicine Unit, Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK;
- Received 4 February 2004
- Accepted 24 June 2004
Background: Multiple breath inert gas washout (MBW) has been suggested as a tool for detecting early cystic fibrosis (CF) lung disease. A study was undertaken to compare the relative sensitivity of MBW and spirometry for detecting abnormal lung function in school age children with CF and to compare MBW results obtained from healthy children in the UK with those recently reported from Sweden.
Methods: Forced expiratory volume in 1 second (FEV1) and maximal expiratory flow when 25% of forced vital capacity remains to be expired (MEF25) were compared with the lung clearance index (LCI) derived from sulphur hexafluoride MBW in 22 children with CF aged 6–16 years and in 33 healthy controls.
Results: LCI was higher in children with CF than in healthy controls (mean difference 5.1 (95% CI of difference 4.1 to 6.1) and FEV1 and MEF25 z-scores were lower (mean difference −2.3 (95% CI −2.9 to −1.7) and −1.8 (95% CI −2.4 to −1.3), respectively; p<0.001 for all). There was a significant negative correlation between LCI and FEV1 (r2 = 0.62) and MEF25 (r2 = 0.46). However, while normal (⩾−1.96 z-scores) FEV1 and MEF25 results were seen in 11 (50%) and 12 (53%) children with CF, respectively, all but one of these children had an abnormally increased LCI. LCI was repeatable in both groups (within subject CV for three measurements 6% for CF and 5% for healthy children). In healthy subjects LCI was independent of age and virtually identical in the British and Swedish children (mean difference 0.1 (95% CI −0.1 to 0.4), p = 0.38)
Conclusions: MBW is reproducible between laboratories, generates normal ranges which are constant over childhood, and is more frequently abnormal than spirometry in children with CF.
- FEV1, forced expiratory volume in 1 second
- FRC, functional residual capacity
- FVC, forced vital capacity
- LCI, lung clearance index
- MEF25, maximal expiratory flow when 25% of FVC remains to be expired
- MBW, multiple breath inert gas washout
- SF6, sulfur hexafluoride
Funding: Dunhill Medical Trust, British Lung Foundation, Swedish Heart Lung Foundation. Research at the Institute of Child Health and Great Ormond Street Hospital for Children benefits from R&D funding provided by the NHS Executive.