RespiratoryPulmonology

Arterial Blood Gas (ABG)

Normal Range
pH: 7.35-7.45, pO2: 80-100 mmHg, pCO2: 35-45 mmHg
Sample Type
Whole Blood (Arterial)
Fasting
No
Unit
mmHg

Function

An Arterial Blood Gas (ABG) test measures the levels of oxygen and carbon dioxide in the blood, as well as the blood's pH (acidity). Unlike most blood tests which use venous blood, the ABG uses blood from an artery, providing a real-time snapshot of how efficiently the lungs are moving oxygen into the blood and removing carbon dioxide from it. It also assesses the kidneys' ability to maintain a balanced pH.

Why it is Ordered

Physicians order an ABG for patients experiencing respiratory distress, shortness of breath, or suspected metabolic imbalances. It is a critical tool in emergency rooms and intensive care units (ICUs) for monitoring patients on ventilators, diagnosing acid-base disorders, and evaluating lung diseases like COPD, asthma, or cystic fibrosis.

Associated Conditions

  • Respiratory Acidosis: Often caused by hypoventilation (COPD, pneumonia).
  • Respiratory Alkalosis: Caused by hyperventilation, anxiety, or high altitudes.
  • Metabolic Acidosis: Seen in diabetic ketoacidosis (DKA) or kidney failure.
  • Hypoxemia: Low blood oxygen levels which can lead to organ failure if untreated.

Panel Components

This test is a profile comprising the following specific markers:

Partial Pressure of Oxygen (pO2)
mmHg
Partial Pressure of Carbon Dioxide (pCO2)
mmHg
pH
pH units
Bicarbonate (HCO3)
mEq/L
Base Excess (BE)
mEq/L
Oxygen Saturation (SaO2)
%

Why Context Matters

The results of an ABG are highly sensitive to the patient's immediate state. Factors such as hyperventilation due to the pain of the arterial puncture (which is more painful than a standard draw), the exact percentage of oxygen the patient is breathing (FiO2) at the time of the draw, and even the presence of air bubbles in the syringe can significantly skew results. A second opinion or repeat test may be necessary if the patient's clinical presentation does not match the rapid changes shown on the lab report.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for Arterial Blood Gas (ABG):

Research & Guidelines

Related Indicators

Pulmonary Function Test

View Range

Forced Vital Capacity (FVC)

View Range

Forced Expiratory Volume (1s) (FEV1)

View Range
DR

Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

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