Edema

Abstract

Lung edema is defined as an accumulation of fluid within alveoli and small bronchi/bronchioles. Edema fluid enters the peripheral lung from the circulation via the interstitium into alveoli. It can be induced by various causes. The most common form is due to congestion of the pulmonary circulation, most often caused by heart failure either due to infarction, valvular diseases, and the like. In these cases the venous flow into the left atrium is reduced, resistance in the venous part of the circulation increases, and leakage of the pulmonary veins increase. The gaps between the endothelial cells increase in size and serum gets into the interstitium and causes interstitial edema. In this case the composition of proteins and electrolytes are essentially similar to their concentration within the bloodstream. However, large proteins usually are lacking, because their large size prevents transudation in the early phases of edema development. In late phase of edema, this changes and also large proteins can be found within the fluid. Edema impairs respiration. Due to hypoxia patients will start with forced breathing. Air mixes with edema fluid resulting in foamy fluid, which can be easily recognized on patient inspection. Reduced oxygenation of the red blood cells and increased resistance in the peripheral circulation finally causes right ventricular failure and death.