Guide to arterial blood gas analysis

At Advocate Health Care, we use every diagnostic tool available to deliver expert care to get you back to feeling your best.

One of those tools is an arterial blood gas (ABG) analysis, where blood is drawn to check the balance of oxygen and carbon dioxide in your blood. It also provides valuable insights into acid-base balance (pH levels).

Your arterial blood gas test helps your Advocate doctor to diagnose and manage conditions that affect your lungs, heart and metabolism.

Understanding pH levels in an ABG analysis

A primary element of the ABG analysis process is evaluating pH levels in your blood. Acids and bases in your body play a crucial role in how your body functions. Your body compensates for changes in acid levels with hemoglobin, a protein in red blood cells, and by breathing, which regulates oxygen and carbon dioxide levels.

Assessing respiratory status

Breathing provides oxygen to your cells and eliminates carbon dioxide, a waste product of your metabolism.

In arterial blood gases analysis, partial pressure of carbon dioxide is measured to gauge how much carbon dioxide is removed.

Interpreting oxygenation levels

Delivering oxygen from your lungs to your blood is critical for many of your body’s functions. In ABG interpretation guidelines, two key parameters assess how much oxygen is being delivered to your cells.

• Partial pressure of oxygen: This reveals the amount of oxygen dissolved in blood in the arteries.
• Oxygen saturation: This highlights the percentage of available hemoglobin bound to oxygen.

Analyzing metabolic imbalances in arterial blood gases

While your respiratory system can adjust to maintain pH levels, the metabolic process also plays a crucial role. An ABG analysis also checks for bicarbonate levels in the blood.

Bicarbonate is a byproduct of your body’s metabolism. Your blood carries bicarbonate to your lungs, where it’s exhaled as carbon dioxide. Your kidneys also remove bicarbonate from your body.

Low bicarbonate levels might suggest metabolic acidosis, a condition where the body either produces too much acid or fails to excrete it.

Clinical significance of ABG parameters in diagnoses

Arterial blood gas tests are a valuable tool to diagnose disease or conditions related to metabolic disorders, lung and respiratory conditions and the risk of heart disease. ABG analysis is often used in the emergency department to diagnose several life-threatening conditions including:

• Acute respiratory distress syndrome (ARDS): A life-threatening lung injury that causes dangerously low oxygen levels in your blood.
• Severe sepsis: Sepsis is a medical emergency caused by your body's response to an infection and can be life-threatening.
• Septic shock: A life-threatening condition that happens when your blood pressure drops to a dangerously low level after an infection.
• Diabetes-related ketoacidosis (DKA): A life-threatening complication that affects people with diabetes, mainly type 1 diabetes.
• Renal tubular acidosis (RTA): This condition happens when your kidneys don’t remove acids from your blood as they should, causing your blood to become acidic.
• Cardiac arrest: This happens when your heart suddenly stops beating. It can happen to individuals who may or may not have heart disease and requires immediate medical attention.
• Asthma attack: A sudden worsening of asthma symptoms caused by the tightening of muscles around your airways.

When to get a arterial blood gas test

If you have COPD (chronic obstructive pulmonary disease) or asthma, your Advocate doctor may regularly order an ABG analysis to check for changes in oxygen and pH levels or evaluate the effectiveness of treatment. If you have symptoms or a chronic lung condition, schedule an appointment with your doctor.