Briefly discuss how each of the following respiratory problems will affect the rate of diffusion of O2 from the air in the lungs into the blood. Will O2 diffuse into the blood faster, slower, or with no change? In each case, identify which variable in Fi

Fick's law of diffusion states that the rate of diffusion of a gas is directly proportional to the surface area available for diffusion and the difference in partial pressure of the gas, and inversely proportional to the thickness of the membrane through which it diffuses. The formula can be expressed as: \[ J = \frac{DA(P1 - P2)}{d} \] Where: - \( J \) = rate of diffusion - \( D \) = diffusion coefficient - \( A \) = surface area available for diffusion - \( P1 - P2 \) = difference in partial pressure (concentration difference) - \( d \) = thickness of the membrane ### Emphysema: **Effect on O2 diffusion:** Slower **Variable in Fick’s law changing:** Surface area (A) **Discussion:** In emphysema, the walls of the alveoli break down and merge, leading to a reduction in the overall surface area available for gas exchange. While the large alveolus may allow for some air exchange, the diminished surface area results in a slower rate of diffusion of O2 from the air into the blood. The reduced surface area means there are fewer sites for diffusion, which hinders the efficiency of O2 uptake. ### Cystic Fibrosis: **Effect on O2 diffusion:** Slower **Variable in Fick’s law changing:** Thickness of the membrane (d) **Discussion:** In cystic fibrosis, thick mucus builds up in the airways, which can obstruct airflow and lead to an increase in the thickness of the barrier that O2 must cross (i.e., the mucus layer). This increased thickness decreases the rate of diffusion according to Fick's law. With more thickness to traverse, O2 diffusion from the alveolar air into the blood is hindered, leading to a slower uptake of O2. In summary, both conditions lead to a slower diffusion rate of O2 into the blood, but they do so through changes in different factors as described by Fick’s law: surface area in emphysema and membrane thickness in cystic fibrosis.