ABG (Arterial Blood Gas) is a diagnostic blood test that measures the levels of oxygen (O₂), carbon dioxide (CO₂), and the pH (acidity) of arterial blood. It provides crucial information about how well a patient’s lungs and kidneys are functioning, especially in critical care and emergency settings.
🫁 Purpose of ABG Test
- Assess respiratory function
- Monitor oxygenation and ventilation
- Evaluate acid-base balance
- Guide treatment in:
- Respiratory failure
- Shock
- Kidney failure
- Metabolic disorders
- Sepsis or poisoning
🩸 What ABG Measures
Parameter | Normal Range | What It Indicates |
pH | 7.35 – 7.45 | Blood acidity/alkalinity |
PaO₂ | 75 – 100 mmHg | Oxygen level in arterial blood |
PaCO₂ | 35 – 45 mmHg | CO₂ level; indicator of respiratory function |
HCO₃⁻ (Bicarbonate) | 22 – 26 mEq/L | Buffer system; reflects metabolic activity |
O₂ Saturation (SaO₂) | 94 – 100% | Percentage of hemoglobin saturated with O₂ |
Base Excess | –2 to +2 mEq/L | Indicates metabolic acid-base disturbances |
🏥 Procedure
- Blood is drawn from an artery (usually the radial artery at the wrist).
- Sample is analyzed quickly (within minutes) using a blood gas analyzer.
- Results guide immediate treatment decisions.
🧑⚕️ Indications for ABG
- Shortness of breath or difficulty breathing
- COPD, asthma, pneumonia, or ARDS
- Post-surgery monitoring
- Mechanical ventilation management
- Diabetic ketoacidosis or renal failure
⚠️ Abnormal ABG Results
Condition | ABG Pattern |
Respiratory Acidosis | ↓ pH, ↑ PaCO₂ |
Respiratory Alkalosis | ↑ pH, ↓ PaCO₂ |
Metabolic Acidosis | ↓ pH, ↓ HCO₃⁻ |
Metabolic Alkalosis | ↑ pH, ↑ HCO₃⁻ |
Hypoxemia | ↓ PaO₂, ↓ SaO₂ |
✅ Advantages
- Fast, real-time analysis
- Critical in emergency and ICU settings
- Offers detailed insight into respiratory and metabolic status
🛑 Risks/Discomforts
- Arterial puncture can be painful
- Risk of bruising, bleeding, or arterial injury
- Requires trained personnel to perform
