PaO2
Summary
PaO2 is the partial pressure of oxygen dissolved in arterial plasma, normally 80-100 mmHg on room air at sea level. Indicates adequacy of lung oxygenation.
Detail
PaO2 depends on alveolar oxygen pressure calculated by the alveolar gas equation. The A-a gradient (PAO2 - PaO2, normally <15 mmHg) helps classify hypoxemia: normal A-a with low PaO2 suggests hypoventilation; elevated A-a indicates V/Q mismatch, diffusion limitation, or shunt. PaO2 is crucial for tissue oxygenation; combined with SaO2 and hemoglobin, it determines oxygen content. Clinical decisions regarding supplemental oxygen target PaO2 >=60 mmHg for SaO2 >=90%.
Sources
- First Aid for the USMLE Step 1
- West's Respiratory Physiology
- Harrison's Principles of Internal Medicine
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