Pulmonary Circulation Fluid Dynamics

It’s been almost 140 years from a report that brought a great and surprising insight into pulmonary fluid dynamics. 25L of warm water were poured down the trachea of a horse over a period of 6 h. No effects other than deepening of respiration were observed and no excess fluid could be found in the lungs at autopsy (Colin, 1873). It became obvious that a constant tendency for water and solutes to equilibrate between the barriers separating pulmonary vessels, pulmonary interstitium and air spaces comprises an important part of respiratory physiology. Barrier permeability in normal, physiological situation is governed by the opposing activity of transvascular hydrostatic pressure and transvascular oncotic pressure (Starling, 1896). Fluid and solutes constantly equilibrate between physiological compartments to achieve neutral pressure gradient. Loss of barrier functions and changes in compartmental pressures due to a disease or a physiological adaptation (i.e. exercise) change lung fluid dynamics. Lung fluid dynamics can be monitored by quantification of pulmonary circulation transvascular fluid fluxes, which can be defined using blood volume changes across the lung and the cardiac output (Vengust et al. 2006). […]