PHSI 208 Lecture Notes - Lecture 5: Pulmonary Edema, Pulmonary Compliance, Partial Pressure
Document Summary
Diffusion is random movement of molecules from a region of high concentration to a region of low concentration. Factors that affect the random movement of gas molecules from a region of high partial pressure to a region of low partial pressure include: concentration gradient, surface area, barrier permeability, diffusion distance, solubility of gas. Surface area, diffusion distance and barrier permeability are constant under normal conditions. In a healthy individual, concentration gradient is variable and the main determinant of diffusion, determined by rate of ventilation. Destruction of alveoli means less surface area for gas exchange. Loss of lung compliance may decrease alveolar ventilation. Fluid in interstitial space between the capillaries and alveoli increases diffusion distance. Arterial pco2 may be normal due to higher co2 solubility in water. This is considered chronic inflammation and results in the bronchioles constricting. Increased diffusion distance. (ex: when the left ventricle of the heart starts to fail).
