Effects of emboli, positive-pressure ventilation, and airway water on lung water measurements

We tested the effects of microemboli, continuous positive-pressure ventilation (CPPV), and aspirated airway water on measurements of extravascular lung water by use of the technique of thermal indicator dilution (ETVL). A control group of dogs and a group of dogs in which dextran was infused created all levels of pulmonary edema. In an emboli group 0.125 g/kg of starch microemboli (63-74 micron diam) were infused. In groups with emboli and CPPV, starch emboli were infused and CPPV was then applied at 15 cmH2O. In an airway saline group measured amounts of saline were poured into the airway. In all groups postmortem pulmonary extravascular tissue weight (PETW) was determined and compared with the last ETVL. Emboli created an increased scatter when the last ETVL is compared with PETW because 1) blood trapped distal to emboli was included in the ETVL measurement, and/or 2) diffusion limitations for the thermal indicator were exceeded. Emboli and CPPV decreased ETVL/PETW. Airway saline (80 +/- 5%) was measured by ETVL. In conclusion, the ETVL technique is reliable in well-perfused lungs but loses accuracy in measuring lung water after emboli of any size or with large amounts of airway fluid.