Blood Gas Testing

When a person breathes, air passes through the airways into tiny air sacs called alveoli. These alveoli are where the oxygen we breathe passes into the blood. This is also where carbon dioxide (a waste gas from our cells) leaves the blood so we can breathe it out.  

Children with chILD may have more trouble taking in oxygen and getting rid of carbon dioxide. A blood gas is a test that measures the levels of acid, carbon dioxide, and oxygen in the blood. The name of the blood gas depends on which type of blood is used. 

• Venous Blood Gas (VBG) – Blood is drawn from one of the veins (usually in the arm). This blood is also used for other common lab tests. A VBG gives us information about the levels of acid and carbon dioxide in the blood. 
• Capillary Blood Gas (CBG) – Blood is drawn using a needle into a finger or toe. This “finger stick” can be used for other types of labs as well. A CBG gives us information about the levels of acid and carbon dioxide in the blood. 
• Arterial Blood Gas (ABG) – Blood is drawn from an artery. Some teams may use this test regularly. Others may only use it in older children or when children are very sick in the intensive care unit. An ABG gives us the best information about levels of acid, carbon dioxide, and oxygen in the blood. This is the only blood gas that really can be used to measure oxygen levels. 

The medical team may use blood gasses to follow how well the lungs are working over time. If the carbon dioxide levels are too high, it may mean that the child needs more help with their breathing.