Lung clearance index in adult respiratory medicine

<bold>Background:</bold> The multiple breath washout (MBW) test measures the efficiency of gas mixing in the lungs enabling earlier detection of lung function impairment and peripheral airway disease compared to spirometry. The lung clearance index (LCI) is the main outcome measure, depicting the number of lung turnovers required to washout an inert gas. Bronchiolectasis in IPF – a morphological correlate of small airways disease – is difficult to detect at spirometry and may be better identified through LCI. This study compares LCI measurements from patients with chronic obstructive airway disease (COPD), asthma, idiopathic lung fibrosis (IPF) and healthy controls in relation to spirometry. <bold>Method:</bold> In addition to body plethysmography and lung diffusion, MBW measurement with EasyOnePro®LAB was performed in patients who presented for routine outpatient and inpatient care with the above-mentioned disease. <bold>Results:</bold> 99 patients undertook MBW (30 IPF, 20 COPD, 20 asthma, 29 healthy) with baseline characteristics and LCI measurements shown in figure 1. COPD patients were the eldest and had the highest LCI whilst healthy controls were significantly younger and had lower LCI. IPF patients had similar LCI as asthma patients. There was no correlation between LCI and FEV1. <fig><object-id>erj;64/suppl_68/PA3053/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> <bold>Conclusion:</bold> LCI is a potential adjunct to standard spirometry. The similar distribution of LCI values for asthma and IPF cohorts suggests a potential role in the detection of small airways disease in IPF.