-is also illustrated in disease states. In fibrosis, the diffusion of 02 is restricted because thickening of the alveolar membrane increases diffusion distance. In emphysema, the diffusion of 02 is decreased because the surface area for diffusion of gases is decreased.
- In diffusion-limited exchange, the gas does not equilibrate by the time blood reaches the end of the pulmonary capillary. The partial pressure difference of the gas between alveolar air and pulmonary capillary blood is maintained. Diffusion continues as long as the partial pressure gradient is maintained.
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