EFFECTS OF VENTILATION AND PLEURAL EFFUSION ON MEASUREMENTS OF AIRWAYTHERMAL VOLUME AND BLOOD-FLOW IN DOG LUNGS

We studied the effects of ventilation and pleural effusion on measurem ents of airway thermal volume (ATV) and pulmonary blood flow (PBF) by using the airway gas thermometry method of V. B. Serikov, M. S. Rumm, K. Kambara, M. I. Bootomo, A. R. Osmack, and N. C. Staub (J. Appl. Phy siol. 72: 944-953, 1992) in 39 anesthetized dogs with or without lung edema or pleural effusion. To examine the differential effects of incr eased-pressure and increased-permeability lung edema on accuracy and s ensitivity of ATV and PBF, two models of lung edema were induced by in travenous infusion of a Dextran 70 solution and alloxan monohydrate, r espectively Dogs were hyperventilated for 3 min by using a wide range of minute ventilation (VE) to produce two steady-state conditions of a irway temperature. Higher levels of VE increased an estimated amount o f ATV. The ATV produced by hyperventilation at VE values of 559, 158, and 72 . ml . min(-1) kg(-1) was consistent with the gravimetric total lung mass, the blood-free wet lung weight, and the extravascular lung water volume, respectively. The coefficient of lung thermal conductiv ity, a practical index of the rate of heat conduction through tissue f rom lung vessels, was related to the ratio of the decrease in expired air temperature to VE, and estimated PBF was consistent with the therm odilution cardiac output. Pleural effusion had little effect on measur ements of ATV and PBF. However, ATV and PBF showed increased variation in dogs with dextran-induced lung edema.