Arterial Blood Gas Make an Appointment Ask a Question Refer Patient Reviewed by George Zeman BS, RRT, CPFT (December 01, 2014) An arterial blood gas is a blood sample test ordered by your physician to evaluate measurements of oxygen, carbon dioxide, and several other parameters. Generally, it is indicated when your physician needs to evaluate the effectiveness of your breathing. This sample is drawn at the pulse site at the wrist. The technologist will apply a local anesthetic at the site if indicated. An oximeter clip will be placed on your finger to correlate with the blood values if further oxygen testing is indicated Pressure will be held at the site for several minutes to ensure that there is no bleeding.