Blood oxygen levels (arterial oxygen) indicate the oxygen levels present in the blood that flows through the arteries of the body. An ABG test uses blood drawn from an artery, where the oxygen and carbon dioxide levels can be measured before they enter body tissues. The blood will be put in an ABG machine (blood gas analyzer) that provides your blood oxygen levels in the form of the partial pressure of oxygen (PaO2).
- Hyperoxemia is generally detected using ABG testing and is defined as blood oxygen levels above 120 mmHg.
- Normal arterial oxygen pressure (PaO2) measured using the arterial blood gas (ABG) test is approximately 75 to 100 millimeters of mercury (75-100 mmHg).
- When the level goes below 75 mmHg, the condition is generally termed as hypoxemia.
- Levels under 60 mmHg are considered very low and indicate the need for supplemental oxygen. Supplemental oxygen is provided through an oxygen cylinder that is connected to the nose via a tube, with or without a mask.
What should oxygen levels be?
Blood oxygen levels can also be measured using an instrument known as a pulse oximeter.
- The normal oxygen levels in a pulse oximeter usually range from 95% to 100%.
- Blood oxygen levels below 90% are considered low (hypoxemia).
Hyperoxemia is generally detected using ABG testing and is defined as blood oxygen levels above 120 mmHg. This is mostly seen in hospitals when patients are exposed to high pressures of supplemental oxygen for prolonged periods (3 to more than 10 hours).
What causes blood oxygen levels to become low?
Blood oxygen levels can get low due to any of the problems that include:
- Low air oxygen levels: Atmospheric oxygen becomes extremely low at high altitudes such as mountainous regions.
- Decreased capacity of the body to take in oxygen: This can be caused by lung conditions that include:
- Asthma
- Emphysema (damage of the air sacs in the lung)
- Bronchitis
- Pneumonia
- Pneumothorax (leaking of air in the space between the lung and chest wall)
- Acute respiratory distress syndrome (ARDS)
- Pulmonary edema (the lung swells due to build-up of fluid)
- Pulmonary fibrosis (scarring of the lungs)
- Interstitial lung disease (a large group of lung disorders that generally cause progressive scarring of the lungs)
- Viral infections such as COVID-19
- Other conditions include:
- Anemia
- Sleep apnea (temporary cessation of breathing during sleep)
- Smoking
- Decreased capacity of the heart to supply the oxygenated blood back to the lungs: The most common causes are congenital heart diseases (heart defects present by birth).
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