Arterial Blood Gas Studies:
Purpose
1)  A measurement of partial pressure of oxygen and carbon dioxide  in arterial blood, as well as the pH  of  the blood. 

2) The Partial pressure of oxygen, together with hemoglobin,  is a measurement of the amount of oxygen in the arterial blood.
3)  Provide a means of assessing the adequacy oxygenation and ventilation (i.e., the lungs supplying oxygen to the body and removing carbon dioxide.)
4)  Help assess the acid-base  status of the body-whether acidosis or alkalosis is present and to what  degree.

Clinical Uses of Arterial Blood Gas Studies:

1)  Unexplained tachypnea, dyspnea,(especially  in patients with  cardiovascular or pulmonary disease).
2)  Unexplained restlessness, anxiety, drowsiness, or confusion in patients at risk  for respiratory insufficiency br respiratory failure.
3)  Assessment of preoperative pulmonary status.
4)  Assessment before and  during long-term oxygen therapy and during mechanical ventilator support.
5)  Potential or actual impairment in acid-base balance.
6)  Assessment of disease progression or reversibility