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An ABG is a blood test that measures the acidity, or pH, and the levels of oxygen (O2) and carbon dioxide (CO2) from an artery. The test is used to check the function of the patient’s lungs and how well they are able to move oxygen and remove carbon dioxide. This test is commonly performed in the ICU and ER setting; however, ABGs can be drawn on any patient on any floor depending on their diagnosis.
How Is An ABG Drawn?
The radial artery is most commonly used to obtain the sample. However, the femoral artery and bronchial artery can be used if necessary. If the patient already has a pre-existing arterial line, this can be used to obtain the sample.
An Arterial Blood Gas requires the nurse to collect a small sample of blood – generally a minimum of 0.5 ml, but a full 1 ml is preferred. Blood can be drawn via an arterial stick from the wrist, groin, or forearm.
Key Components
There are five key components to an ABG. They include:
- pH
- Partial pressure of oxygen (PaO2)
- Partial pressure of carbon dioxide (PaCO2)
- Bicarbonate (HCO3)
- Oxygen saturation (O2 Sat) .
Blood gases can also measure hemoglobin and hematocrit as well as electrolyte values such as potassium, calcium, and sodium. If a clinician wishes to obtain these values, a SuperGas is run.
The aforementioned five components all have different normal values and represent different aspects of the blood gas. According to the National Institute of Health, typical normal values are:
- pH: 7.35-7.45
- Partial pressure of oxygen (PaO2): 75 to 100 mmHg
- Partial pressure of carbon dioxide (PaCO2): 35-45 mmHg
- Bicarbonate (HCO3): 22-26 mEq/L
- Oxygen saturation (O2 Sat): 94-100%
How to Interpret an ABG?
The first value a nurse should look at is the pH to determine if the patient is in normal range, above, or below. If a patient’s pH > 7.45, the patient is alkalotic. If the pH < 7.35, then the patient is acidotic.
Next, examine the PaCO2. This will determine if the changes in the blood gas are due to the respiratory system or metabolically driven. In combination with the HCO3, the nurse will be able to fully comprehend the blood gas.
Below is a chart that contains the different values and determining if the patient is suffering from a respiratory or a metabolic component. This will enable the medical team to treat the patient adequately.
| pH | CO2 | HCO3 | |
| Respiratory acidosis | ↓ | ↑ | Normal |
| Respiratory alkalosis | ↑ | ↓ | Normal |
| Respiratory acidosis with metabolic compensation | ↓ | ↑ | ↑ |
| Respiratory alkalosis with metabolic compensation | ↑ | ↓ | ↓ |
The acronym ROME is used to help nurses remember the relationship between pH and CO2.
Respiratory Opposite
Metabolic Equal
Zainab musa
Am really sick Dr over one year I have sinus tachycardia always and we don’t know the reason I can’t even walk straight unless I bend pls need ur advice sir
Dr Mohamed Ibrahim (Alfaruki)
zainab you need to visit hospital especially cardiologist .
becouse the reason is abnormal heart rate that is why you feel sinus tachycardia.
please reduce amount of salt that you used because increase the problem .
rest is the best way that you reduce complications unless you go a hospital because your condition is emergence .
we must prevent complication ,met the doctor on the spot .
Zainab musa
Good day sir, I do went to the hospital these week I have an ECG test again its shows normal result, one the Dr I meet prescribed tab isordil 5mg bd and metoprolol xl 50mg once daily but I still have those pains in my left hand palpitations and chest pain and I don’t have blood pressure, but to be sincere I always think I have artery disease pls Dr is there any advice u can give me
Zainab musa
Am 21yrs old sir