Clinical aspects of asthma
P124 REPRODUCIBILITY OF THE MULTIPLE BREATH NITROGEN WASHOUT TEST IN HEALTHY VOLUNTEERS AND SUBJECTS WITH MILD TO MODERATE ASTHMA
1M. F. Biddiscombe, 2S. Verbanck, 3S. Meah, 3P. J. Barnes, 3O. S. Usmani. 1Nuclear Medicine, Royal Brompton Hospital and National Heart and Lung Institute, Imperial College London, London, UK, 2Respiratory Division, Academic Hospital, Vrije Universiteit, Brussels, Belgium, 3Airways Disease Section, Royal Brompton Hospital and National Heart and Lung Institute, Imperial College London, London, UK
Introduction The multiple breath nitrogen washout (MBNW) test is a non-invasive physiological tool that can be used to assess differences in ventilation heterogeneity arising in the proximal (conducting) from that in the distal (acinar) airway compartments. Abnormalities in the MBNW acinar (Sacin) and conductive (Scond) airway indices have been observed and indicate significant ventilation heterogeneity in patients with asthma and chronic obstructive pulmonary disease (COPD).
Objectives To assess the same-day and day-to-day reproducibility of MBNW parameters (Sacin, Scond) in 24 healthy volunteers (HV, mean forced expiratory volume in 1 s (FEV1) 104%pred; age 22–59 years; males 12) and 12 patients with mild to moderate asthma (A, mean FEV1 92%pred; age 21–54 years; males 8).
Methods Each subject performed two MBNW runs (1 run = 3 MBNW tests) each day, on three separate days. Each MBNW test consisted of consecutive 1-litre oxygen inhalations until expired nitrogen was <2%.
Results Higher Sacin and Scond (greater heterogeneity) values were detected in A vs HV subjects. Functional residual capacity (FRC) calculated from MBNW correlated with that measured using body plethysmography (r = 0.65; p<0.01). No correlation was observed between Sacin and Scond and subject’s FEV1, FVC or FEF25–75 (p>0.10) for both groups. Day-to-day variability of Sacin and Scond were greater than spirometric measures (table 1).
Conclusion Sacin and Scond were significantly higher for asthmatic subjects compared with …