arterial blood gas (ABG), the oxygen and carbon dioxide content of arterial blood, measured by various methods to assess the adequacy of ventilation and oxygenation and the acid-base status of the body. Oxygen saturation of hemoglobin is normally 95% or higher. The partial pressure of arterial oxygen, normally 80 to 100 mm Hg, is increased in hyperventilation and decreased in cardiac decompensation, chronic obstructive pulmonary disease, and certain neuromuscular disorders. The partial pressure of carbon dioxide, normally 35 to 45 mm Hg, may be higher in emphysema, chronic obstructive pulmonary disease, and reduced respiratory center function; it may be lower in pregnancy and in the presence of pulmonary emboli and anxiety.
