Noninvasive measurement of small-solute pulmonary microvascular permeability using a multicompartment indicator dilution-diffusion model

Measurement of pulmonary capillary permeability with small solutes in the intact organism has traditionally required multiple indicators. To enable measurement of permeability (as permeability-surface area product, PS), we developed a mathematical model based on indicator dilution and diffusion that has PS as a parameter, and which can be it to time-activity curves of a radioactively labeled small solute. Experimental validation of the technique in an experimental canine model of hydrostatic and permeability pulmonary edema resulted in PS measurements that here comparable to previously reported values, and were able to discriminate permeability pulmonary edema from normal and hydrostatic pulmonary edema.