Magnetopneumographic Study of Human Alveolar Clearance in Health and Disease

Magnetopneumography (MPG) was used to determine the influence of cigarette smoking and pulmonary disease on the alveolar clearance of an inhaled magnetic tracer in 14 cigarette smokers, 15 nonsmokers, 8 patients of similar age with cystic fibrosis, and 4 older patients with emphysema. Alveolar clearance half-times, based upon a single exponential fit, increased with post-inhalation observation time. For nonsmokers, half-times were 65 ± 10 days (mean ± s.d.) to 5 months, 81 ± 18 days to 8 months, and 113 ± 41 days to 12 months. Half-times for smokers were significantly longer at all times, being 108 ± 28 days to 5 months, 126 ± 29 to 8 months, and 172 ± 60 to 12 months. The 8 patients with cystic fibrosis had an alveolar clearance half-time to 5 months of 92 ± 23, which was intermediate to nonsmokers and smokers. Lung clearance measurements of the 4 patients with emphysema showed wide inter-subject variation and overlapped the normal range. When looking at regional clearance, we observed that deeper regions of the thorax cleared dust more slowly than superficial regions, a finding compatable with centripetal translocation of particles. In smokers and in cystics, translocation was slower than in the nonsmokers. Magnetic relaxation rates were also studied and some differences between groups were seen. We conclude that MPG is suitable for evaluating alveolar clearance and translocation of inhaled particles.