Oxygen Partial Pressure
Oxygen partial pressure (also known as pO2 or PaO2) refers to the pressure exerted by oxygen in a gas mixture, such as the air we breathe or the blood in our lungs. It's a critical indicator of blood oxygenation.
What it is
Oxygen partial pressure is the proportion of the total pressure of a gas mixture that is due to oxygen. In simpler terms, it's the amount of oxygen "pushing" in the air or blood.
Why it matters
It is a crucial factor in determining how well oxygen moves from the lungs into the bloodstream and then from the blood into the tissues.
How it's measured
Oxygen partial pressure is typically measured in millimeters of mercury (mmHg) or kilopascals (kPa).
Normal values
A healthy adult's resting PaO2 (arterial blood oxygen partial pressure) is generally greater than 80 mmHg.
Clinical significance
Measuring oxygen partial pressure is used to:
- Diagnose respiratory failure.
- Monitor supplemental oxygen therapy.
- Assess and monitor patients with respiratory diseases.
Relationship to oxygen saturation
While oxygen partial pressure indicates the pressure of oxygen, oxygen saturation (SaO2) refers to the percentage of hemoglobin molecules in the blood that are carrying oxygen.
Dalton's Law of Partial Pressures
This law states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each individual gas.
Example
In the air we breathe, oxygen makes up about 21% of the total pressure, so the partial pressure of oxygen is about 160 mmHg at sea level.
