Oxygenation and mechanisms of hypoxemia
- Arthur C Theodore, MD
Arthur C Theodore, MD
- Associate Professor of Medicine
- Boston University School of Medicine
The process of taking oxygen from the inspired air and using it to sustain aerobic cellular metabolism throughout the body can be conceptualized as having three steps:
●Oxygenation is the process of oxygen diffusing passively from the alveolus to the pulmonary capillary, where it binds to hemoglobin in red blood cells or dissolves into the plasma. Insufficient oxygenation is termed hypoxemia. This is to be differentiated from hypoxia, which is an abnormally low oxygen content in a tissue or organ.
●Oxygen delivery is the rate of oxygen transport from the lungs to the peripheral tissues.
●Oxygen consumption is the rate at which oxygen is removed from the blood for use by the tissues.
●Hypoxemia is defined as an abnormally low level of oxygen in the blood (ie, low partial oxygen tension).
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- MEASURES OF OXYGENATION
- Arterial oxygen saturation (SaO2)
- Arterial oxygen tension (PaO2)
- A-a oxygen gradient
- PaO2/FiO2 ratio
- a-A oxygen ratio
- Oxygenation index
- MECHANISMS OF HYPOXEMIA
- V/Q mismatch
- Right-to-left shunt
- Diffusion limitation
- Reduced inspired oxygen tension
- EFFECTS OF HYPOXEMIA
- SUMMARY AND RECOMMENDATIONS