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Paediatric Pulmonology and Allergology
2007 October, Vol. X, No. 2 (3573-3592)
PERIPHERAL AIRWAY FUNCTION ASSESSED BY MULTIPLE-BREATH INERT GAS WASHOUT
Per Gustafsson
Department of Pediatric Clinical Physiology, Queen Silvia Children’s Hospital, Göteborg, Sweden
The importance of the small airways in asthma, cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), and other chronic lung disorders has been underestimated because standard lung function tests are not sensitive to peripheral airway obstruction. Inert gas washout tests for ventilation distribution assessment have been recently been “rediscovered”. In cystic fibrosis (CF) e.g. a simple test of uneven is more sensitive and discriminative than spirometry and correlate better to structural lung damage. Over the last 20 years modeling studies of ventilation distribution in the human lung have resulted in new ways of evaluating inert gas washout tests. New indices derived from conventional multiple-breath inert gas washout (MBW) tests can locate pathological processes to the conducting airways or the acinar zone. In this article inert gas washout procedures and the evaluation of results are described and the theoretical backgrounds to the tests are presented. Findings in clinical studies on asthma, CF, COPD and tobacco smoke exposure using the new analytical approaches are reviewed. Patient friendly and non-hazardous tests can now be undertaken in all age groups allowing for an assessment of the peripheral airways that was only possible with invasive methods or post-mortem previously. It is expected that these new methods will allow for earlier diagnosis and a better understanding of disease processes and that therapeutic interventions hereby may be more successful.