Arterial Blood Gas (ABG): Overview, Purpose, Procedure & Levels

Overview

• An Arterial Blood Gas (ABG) test measures:
  • Oxygen and carbon dioxide levels in the blood.
  • pH balance of the blood.
• Blood sample is taken from an artery, typically in emergency situations.
• Key for diagnosing and managing respiratory, circulatory, and metabolic conditions.
• Known as blood gas test, arterial blood gases, ABG, or blood gas analysis.

What is Measured in an ABG Test?

• Oxygen Content (O2CT): Measures oxygen in blood.
• Hemoglobin: Measures hemoglobin, the protein that carries oxygen.
• Oxygen Saturation (O2Sat): Percentage of hemoglobin carrying oxygen.
• Partial Pressure of Oxygen (PaO2): Pressure of dissolved oxygen in blood.
• Partial Pressure of Carbon Dioxide (PaCO2): Amount of carbon dioxide in blood.
• pH: Acid-base balance of blood (normal 7.35-7.45).
• Bicarbonate (HCO3): Amount of bicarbonate, a base compound.

When is an ABG Test Performed?

• Commonly used in:
  • Emergency Medicine: Urgent care for severe conditions.
  • Anesthesiology: Monitoring during surgery and critical care.
  • Pulmonology: Managing respiratory diseases.
• Conditions evaluated include:
  • Acute respiratory distress syndrome (ARDS).
  • Sepsis and septic shock.
  • Hypovolemic shock.
  • Diabetes-related ketoacidosis (DKA).
  • Renal tubular acidosis (RTA).
  • Acute respiratory and heart failure.
  • Cardiac arrest and asthma attacks.
  • Metabolic disorders.
• Used to ensure effective treatment in chronic lung conditions like asthma, COPD, and cystic fibrosis.

Test Details

Who Performs the Test?

• Performed by a respiratory therapist.
• Sample usually taken from an artery in the wrist, arm, or groin.

Procedure

• Before the Test:

  • Allen test may be performed to check blood circulation.
  • Oxygen therapy adjustments may occur (room air test).

• During the Test:

  • Blood sample taken from an artery, often the radial artery.
  • Procedure may cause more discomfort than a venous blood draw.

• After the Test:

  • Bruising and soreness possible.
  • Avoid heavy lifting for 24 hours.

• Risks:

  • Rare but can include fainting, hematomas, excessive bleeding, or infection.

Results

• Quick results; 10-15 minutes using automated analyzers.
• Results indicate:
  • Oxygen and carbon dioxide levels.
  • Blood pH balance.
  • Potential conditions or imbalances requiring further testing.

Normal Values

• pH: 7.35-7.45
• PaO2: 75-100 mmHg
• PaCO2: 35-45 mmHg
• Bicarbonate (HCO3): 22-26 mEq/L
• Oxygen Saturation (O2Sat): 95-100%
• Note: Normal values vary with altitude.

Follow-Up and Care

• Regular monitoring in chronic conditions like COPD.
• Call healthcare provider if symptoms worsen.
• Note from Cleveland Clinic: ABG tests are vital in emergencies and monitoring health conditions.

Cleveland Clinic Services

• Offers primary care and lifelong medical services.
• Schedule appointments and find primary care providers through their services.