Time lag between pulmonary congestion and pulmonary edema in dogs.

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Abstract
The time course of pulmonary congestion and pulmonary edema was examined using a gravimetric method in 19 open-chest anesthetized dogs. Balloon catheters in the left atrium (LA) were inflated to elevate LA pressure more than 25 mmHg. The dogs were divided into 4 groups (G) according to the duration of the elevated LA pressure: G.1 (n = 6) as control; G.2 (n = 4) for 15 minutes; G.3 (n = 4) for 30 minutes; and G.4 (n = 5) for 60 minutes. Although no significant increase of extravascular lung water content (an indicator of pulmonary edema) was observed in G.2 (4.97 .+-. 0.85 g/kg) and G.3 (4.46 .+-. 0.96) compared with G.1 (4.02 .+-. 0.88), a significant increase was observed in G.4 (6.81 .+-. 1.21, P < 0.05). Residual pulmonary blood content (an indicator of pulmonary congestion) was significantly increased in G.2, 3 and 4 compared with G.1. By light and electron microscopes, pulmonary congestion was revealed in G.2, whereas interstitial pulmonary edema was demonstrated only in G.4. Thus, it was concluded that pulmonary congestion occurred within 15 minutes, but pulmonary edema occurred 30 to 60 minutes after left atrial pressure was elevated more than 25 mmHg. This time lag may be an important factor in explaining the discrepancy between the elevated left atrial pressure and the clinical manifestation of pulmonary edema.