An arterial blood gas (ABG) is a test that measures the blood levels of oxygen and carbon dioxide as well the level of acid-base (ph) in the body. An ABG test is used to check how well lungs move oxygen into different body parts and how efficient it eliminates carbon dioxide.
Normally, healthy lungs move oxygen into the blood and push carbon dioxide out efficiently during inhalation and exhalation (called gas exchange). With this process, our body receives energy while making sure to eliminate waste. However if someone have breathing problems or a disease that affects your lung function, so the ABG result can be abnormal that’s why a doctor may order this test.
ABGs Normal Values:
• PH: 7.35 to 7.45
• PCO2: 35 to 45 mm Hg
• HCO3: 22 to 27 mEq/L
• PO2: 80 to 100 mm Hg
• O2 saturation: 96% to 100%
• Oxyhemoglobin dissociation curve: No shift
The 6 Easy Steps to ABG Analysis:
• Is the pH normal?
• Is the CO2 normal?
• Is the HCO3 normal?
• Match the CO2 or the HCO3 with the pH
• Does the CO2 or the HCO3 go the opposite direction of thepH?
• Are the pO2 and the O saturation normal?
Steps for analyzing Arterial Blood Gas results:
If you can remember the following Pyramid Points and Pyramid Steps, you will be able to analyze any blood gas report.
• In acidosis, the pH is decreased.
• In alkalosis, the pH is elevated.
• The respiratory function indicator is the PCO2.
• The metabolic function indicator is the bicarbonate ion (HCO3
4 Pyramid Steps:
Pyramid Step 1
• Look at the blood gas report. Look at the pH. Is the pH elevated or decreased? If the pH is elevated, it reflects alkalosis. If the pH is decreased, it reflects acidosis.
Pyramid Step 2
• Look at the PCO2. Is the PCO2 elevated or decreased? If the PCO2 reflects an opposite relationship to the pH, then the condition is a respiratory imbalance. If the PCO2 does not reflect an opposite relationship to the pH, go to Pyramid Step 3.
Pyramid Step 3
• Look at the HCO3
• Does the HCO3 reflect acorresponding relationship with the pH? If it does, then the condition is a metabolic imbalance.
Pyramid Step 4
• Compensation has occurred if the pH is in a normal range of 7.35 to 7.45. If the pH is not within normal range, look at the respiratory or metabolic function indicators. If the condition is a respiratory imbalance, look at the HCO3 to determine the state of compensation. If the condition is a metabolic imbalance, look at the PCO2 to determine the state of compensation.
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