An
arterial blood gas (
ABG) test is a
blood gas test of
blood from an
artery; it is thus a
blood test that measures the amounts of certain
gases (such as
oxygen and
carbon dioxide) dissolved in arterial blood. An ABG test involves puncturing an artery with a thin
needle and
syringe and drawing a small volume of blood. The most common puncture site is the
radial artery at the
wrist, but sometimes the
femoral artery in the groin or other sites are used. The blood can also be drawn from an
arterial catheter. An ABG test measures the
blood gas tension values of arterial oxygen tension (Pa
O2), arterial carbon dioxide tension (Pa
CO2), and acidity (
pH). In addition, arterial
oxygen saturation (Sa
O2) can be determined. Such information is vital when caring for patients with critical illness or respiratory disease. Therefore, the ABG test is one of the most common tests performed on patients in
intensive care units (ICUs). In other
levels of care,
pulse oximetry plus transcutaneous carbon dioxide measurement is an alternative method of obtaining similar information less invasively.