Arterial Blood Gases. Test Overview. An arterial blood gas (ABG) test measures the acidity (pH) and the levels of oxygen and carbon dioxide in the blood from an artery. This test is used to check how well your lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.
How Often the Test Is Done During Your Pregnancy. Your doctor may use the Doppler often to listen to your baby's heartbeat during routine checkups, starting at about 8 to 10 weeks. Handheld Dopplers will not work quite this early.
A pacemaker is a small but very sophisticated electronic device that is implanted under the skin to help regulate the heart beat. Pacemakers are used to keep a person's heart rate from going too slowly, and to help coordinate the beating of the cardiac chambers -- the atria and ventricles.