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Contributions of Transport Resistance Components to Lung Diffusing Capacity
Author(s) -
Roy Tuhin,
Secomb Timothy
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.787.9
Subject(s) - oxygen transport , hematocrit , capillary action , diffusing capacity , chemistry , oxygen , diffusion , hemoglobin , lung , biophysics , analytical chemistry (journal) , chromatography , materials science , thermodynamics , composite material , medicine , biochemistry , lung function , biology , physics , organic chemistry
A theoretical model of oxygen uptake via the pulmonary capillaries is used to develop explicit expressions for the relative contributions of the various resistances to oxygen transport to lung diffusing capacity as oxygen diffuses from alveoli through the alveolar‐capillary membrane, through the plasma, and into the erythrocytes. This axisymmetric model assumes discrete cylindrical erythrocytes with cell shape and spacing determined by capillary diameter and hematocrit. Analysis of unsteady diffusion due to the passage of the discrete erythrocytes shows that the transport of oxygen through the alveolar‐capillary membrane occurs mainly in the regions adjacent to erythrocytes, and that oxygen transport through regions adjacent to plasma gaps can be neglected. With this assumption, the model demonstrates that diffusing capacity decreases with decreasing hematocrit (increasing cell spacing) as the proportion of vessel length available for oxygen transport decreases, and that diffusing capacity decreases with increasing capillary diameter. Furthermore, the model predicts that oxygen loading onto hemoglobin provides minimal resistance to oxygen transport, and that the relative resistance due to plasma diffusion increases with increasing capillary diameter. Calculations performed for a range of discharge hematocrit and capillary diameter values yield estimates of overall lung diffusing capacity from 60 to 130 mlO 2 min ‐1 mmHg ‐1 , with higher values corresponding to higher hematocrit and lower capillary diameter (i.e. a higher lineal density of erythrocytes). Supported by NIH grant HL070657.