Answer: With pneumonia, if the lungs become edematous, the thickness of the exchange membrane may increase dramatically, restricting gas exchange, and body tissues begin to suffer from hypoxia. With emphysema, the lungs become progressively less elastic and more fibrous, which hinders both inspiration and expiration. Gas exchange remains adequate initially, but muscular activity must be enlisted to expire. Additionally, a symptom of emphysema is fusion of alveoli, resulting in less surface area for gas exchange.
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