Hypoxia, Hypoxemia, and Ischemia Mechanisms
Detailing mechanisms of oxygen deprivation, oxygen-hemoglobin dissociation, the alveolar gas equation, and ventilation-perfusion mismatch. Mechanisms of Oxygen Deprivation Hypoxia Definition : Reduced oxygen delivery to tissues. Causes : Decreased cardiac output Hypoxemia Anemia Carbon monoxide poisoning Hypoxemia Definition : Reduced partial pressure of oxygen in the blood. Mechanisms : Normal A-a gradient : Low FiO2 (e.g., high altitudes) Hypoventilation Increased A-a gradient : V/Q mismatch Right-to-left shunt Diffusion limitation Ischemia Definition : Reduced blood flow to tissues. Causes : Impaired arterial flow Decreased venous drainage Oxygen-Hemoglobin Dissociation Curve Rightward Shift : Decreased affinity of hemoglobin (Hb) for oxygen Facilitates oxygen unloading to tissues Causes : ↓pH (↑H+), ↑CO2, exercise, ↑temperature, ↑2,3-BPG, altitude Oxygen Content of Blood : Anemia: ↓[Hb], reduced O2 carrying capacity Carbon monoxide poisoning: CO binds Hb, shifts curve left, reduces...