Abstract
We measured diffusing capacity (DLCO), alveolar membrane properties (D m), capillary lung volume (V c), and alveolar volume (V A ) in 20 healthy subjects (12 males; age 32.4 ± 13 (SD); BMI 21.7 ± 3; non smokers) at total lung capacity (TLC) and at ∼80, 60, and 40% TLC. In all subjects, D m increased with lung volume, the increase being significantly greater for higher values of D m(TLC): the inter-individual differences can be interpreted by a greater number of alveolar units coupled to a lower thickness of the air–blood barrier (thus a higher alveolar surface to thickness ratio S A/τ). On the average, the volume-dependent increase of D m from ∼40 to 100% TLC is less than expected based on geometrical increase of S A /τ. In fact, up to ∼80% TLC, the increase in D m closely reflects only the increase of S A, suggesting “unfolding” of the septa with no appreciable decrease in τ. Conversely, above 80% TLC, the decrease in τ due to parenchymal stretching becomes the main factor affecting D m. In all subjects, V c decreased with increasing lung volume, in line with an increase in parenchymal stretching; the decrease was significantly larger for higher values of V c (40% TLC). Possibly reflecting differences in alveolar capillary density. No correlation was found between D m(TLC) and V c(40%TLC). The individual specificity in the lung volume dependence of V c and D m can be reasonably described by evaluating the V c/D m ratio at TLC and at ∼40%TLC.
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This research was supported by Fondazione Banca del Monte di Lombardia.
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Miserocchi, G., Messinesi, G., Tana, F. et al. Mechanisms behind inter-individual differences in lung diffusing capacity. Eur J Appl Physiol 102, 561–568 (2008). https://doi.org/10.1007/s00421-007-0625-2
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DOI: https://doi.org/10.1007/s00421-007-0625-2