Protein composition of lung fluids in anesthetized dogs with acute cardiogenic edema

Abstract

We measured the protein composition of plasma and lung fluids from nine dogs with cardiogenic edema. To produce the edema, we increased left atrial pressure an average of 36 cmH2O by inflating a balloon catheter in the left atrium, infusing norepinephrine, and infusing large volumes of saline or saline-diluted blood. Blood samples were collected every 15 min, and airway fluid was collected from five dogs that developed severe edema. Terminally, the chest was opened and the lungs were removed. Samples of alveolar fluid were taken from the excised lung by direct pleural puncture with micropipettes. The lungs were frozen in liquid nitrogen and samples of free interstitial fluid were taken from the perivascular and peribronchial cuffs. Plasma and lung fluids were analyzed for total protein by the Lowry method and for albumin-globulin fractions by cellulose acetate electrophoresis. The average total protein concentrations (g/100 ml) were--plasma, 2.65; free interstitial fluid, 1.05; alveolar fluid, 1.23; and airway fluid, 1.29. The average albumin fraction of plasma was 0.40; of alveolar fluid, 0.43; and of airway fluid, 0.43. The protein concentrations in the three lung fluids were nearly identical to each other, but were less than half that of plasma. We conclude that in high-pressure pulmonary edema with alveolar flooding, the capillary endothelium retains the ability to restrict protein relative to fluid filtration, but the alveolar epithelium becomes freely permeable to protein.

Alveolar epithelial damage. A critical difference between high pressure and oleic acid-induced low pressure pulmonary edema.

“…Previous studies (18) have shown that it is difficult to produce alveolar flooding in dogs by simply raising the pulmonary vascular pressures. Vreim et al (3) showed that in high pressure pulmonary edema, with the extravascular lung water-to-dry weight ratio ranging from 6.6 to 15.7, the alveolar flooding was less obvious. However, they had much less difficulty producing alveolar flooding in low pressure pulmonary edema (2).…”

Pulmonary Vascular Effects of Fat Emulsion Infusion in Unanesthetized Sheep

“…Lymph collected this way is largely from the lungs (8,9). Also, lymph protein concentration appears to reflect protein concentration in the lung perimicrovascular space (10,11). Under steady-state conditions, we assume that lymph flow is proportional to the net volume of fluid filtered from lung exchanging vessels.…”

High permeability pulmonary edema (ARDS) during tocolytic therapy — a case report

“…Animal studies in which alveolar fluid was obtained by direct alveolar micropuncture have shown that the protein concentration of alveolar fluid is similar to that of fluid in the airways in both cardiac and permeability types of pulmonary edema [19,20]. Clinical studies have shown that the analysis of edema protein relative to plasma protein concentrations is useful in separating these two types of pulmonary edema.…”