alveolar gas equation calculates oxygen content of alveoli

• related: pathophysiology of hypoxia and hypoxemia
• tags: #permanent #pulmonology

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Oxygen content of alveoli is dependent on oxygen content of inspired air and mixing of $CO_2$ gas exchange.

$$P_{AO_2}=P_{IO_2}-\frac{P{aCO_2}}{R} = 150-\frac{P_{aCO_2}}{0.8}$$

• $P_{IO_2}$: inspired air O2 content
• $P_{AO_2}$: alveolar O2 content is lower because of gas exchange
• $P_{aO_2}$: arterial blood content is lower because of shunt
• $S_{aO_2}$: oxygen saturation is directly dependent on arterial oxygen content. Oxygen saturation is percentage of hemoglobin site that’s bound with oxygen molecule.

Links to this note

• pathophysiology of hypoxia and hypoxemia

  • alveolar gas equation calculates oxygen content of alveoli

• using Aa gradient to determine reason for hypoxemia

  • Hypoxemia is decreased $O\_2$ saturation, which is directly affected by $P\_{aO\_2}$ (alveolar gas equation calculates oxygen content of alveoli).