Macromolecule transport across the pulmonary microvessel walls.

In summary, it has been difficult to assess the permeability properties of the pulmonary capillary membrane. However, new mathematical and experimental techniques have recently been developed which are of sufficient sensitivity and specificity to begin to evaluate the complex mechanisms responsible for many forms of lung pathology. While future work will undoubtedly need to address problems associated with heterogeneity of pulmonary blood flow, and with an equally heterogeneous population of vascular permeability and fluid formation sites, we currently need to focus on using the correct experimental approaches for assessing vascular permeability. The appropriate techniques are described in the text and indicate that the measurements of reflection coefficients using lymph obtained at high vascular pressures, filtration coefficients obtained from both isolated and intact lungs, and two-pore models are useful in assessing vascular permeability.