Measurement of airway mucosal perfusion and water volume with an inert soluble gas.

The purpose of this study was to develop and validate a new in vivo technique for the measurement of tracheal mucosal blood flow (Qtr) and tissue water volume (VH2O) with an inert soluble gas. The technique was based on the notion that the uptake of dimethyl ether (VDME) from an isolated tracheal segment is governed by VH2O (transient state) and Qtr (steady state). In lightly anesthetized sheep, an endotracheal tube with two cuffs placed 14.5-16.5 cm apart was placed to create a chamber into which dimethyl ether was introduced and from which VDMME into the mucosa was determined with a sensitive pneumotachograph. Mean Qtr was 1.20 ml/min (range 0.87-1.73), and mean VH2O was 1.67 ml (range 1.27-2.26). Qtr correlated with cardiac output but not with body weight or tracheal mucosal surface area determined by He dilution. VH2O did not show a correlation with any of these parameters. The response to selected pharmacological agents suggested that the measurements of Qtr and VH2O are independent of each other and from changes in tracheal diameter. Mean Qtr was 80% of mean tracheal mucosal blood flow measured with radiolabeled microspheres. We concluded that the inert soluble gas method is capable of measuring in vivo the perfusion and a water compartment of the intact tracheal mucosa.