What are the common physiologic causes of hypoxemia?
Answer:
From the shunt equation, arterial oxygen content is related to the change in pulmonary capillary oxygen content, venous oxygen content, and venous admixture. It is easier to classify hypoxemia into the following three categories.
Decreased pulmonary capillary oxygen tension
Hypoventilation
Low FIO2
Ventilation/perfusion mismatch from pulmonary parenchymal change
Diffusion abnormality (rare)
Reduced venous oxygen content
Congestive heart failure—low cardiac output
Increased metabolism—fever, hyperthyroidism, shivering
Decreased arterial oxygen content—anemia
Reference(s):
- Gropper MA, Cohen NH, Eriksson LI, et al, eds. Miller’s Anesthesia. 9th ed. Philadelphia, PA: Elsevier; 2020:354-383, 2592-2593.
- Jameson JL, Fauci AS, Kasper DL, et al, eds. Harrison’s Principles of Internal Medicine. 20th ed. New York: McGraw-Hill; 2018:234-236.