Which type of hypoxia is caused by reduced PO2 in the lungs (high altitude)?

Which type of hypoxia is caused by reduced PO2 in the lungs (high altitude)?

• A. Hypoxic Hypoxia
• B. Hypemic Hypoxia
• C. Stagnant Hypoxia
• D. Histotoxic Hypoxia

Answer: (A)

When inspired PO2 is reduced, as happens at high altitude due to lower barometric pressure, the alveolar PO2 and consequently arterial PO2 fall. Even with normal hemoglobin and good perfusion, less oxygen is loaded into blood and delivered to tissues, producing hypoxic hypoxia. In this scenario the key issue is the low oxygen tension in the lungs and blood, not a problem with how much hemoglobin is available or how well blood flows. If the oxygen-carrying capacity is reduced (as in anemia or carbon monoxide poisoning), or if blood flow to tissues is impeded (stagnant hypoxia), or if cells cannot use oxygen (histotoxic hypoxia), the underlying cause is different though the result—tissue hypoxia—can look the same. Hypemic hypoxia involves normal PO2 but reduced oxygen content in blood; stagnant hypoxia involves adequate PO2 but insufficient delivery due to poor circulation; histotoxic hypoxia involves toxins preventing cellular use of oxygen.

When inspired PO2 is reduced, as happens at high altitude due to lower barometric pressure, the alveolar PO2 and consequently arterial PO2 fall. Even with normal hemoglobin and good perfusion, less oxygen is loaded into blood and delivered to tissues, producing hypoxic hypoxia. In this scenario the key issue is the low oxygen tension in the lungs and blood, not a problem with how much hemoglobin is available or how well blood flows.

If the oxygen-carrying capacity is reduced (as in anemia or carbon monoxide poisoning), or if blood flow to tissues is impeded (stagnant hypoxia), or if cells cannot use oxygen (histotoxic hypoxia), the underlying cause is different though the result—tissue hypoxia—can look the same. Hypemic hypoxia involves normal PO2 but reduced oxygen content in blood; stagnant hypoxia involves adequate PO2 but insufficient delivery due to poor circulation; histotoxic hypoxia involves toxins preventing cellular use of oxygen.