I.E. similar mechanism to bed sores. Pressure caused necrosis of epithelium and together with possible infectious agents caused inflammation in the exposed tissue. Enzymes and free radicals from inflammatory leukocytes caused additional tissue injury and deepening of ulcer. Although it is possible that the irritating substances caused acute inflammation with an exudate that organized, it is also possible that the substances caused low grade insidious chronic inflammation with eventual build up of fibrous connective tissue in alveolar septae. Destruction of septae decreases surface area.
Fibrosis decreases elasticity of the lung.