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.
Your doctor will use a medical instrument called a stethoscope to listen for normal breath sounds. A normal breath sound is similar to the sound of air. Your doctor can hear normal breath sounds by placing the stethoscope on your: chest; back; collarbone; rib cage; Your doctor can also use a stethoscope to hear abnormal breathing sounds, which may include: rhonchi, which are low-pitched sounds; crackles, which are high-pitched sounds