Table of ContentsView AllTable of ContentsWhat It IsTest PurposeRisks and ContraindicationsBefore the TestDuring the TestAfter the TestInterpreting Results
Table of ContentsView All
View All
Table of Contents
What It Is
Test Purpose
Risks and Contraindications
Before the Test
During the Test
After the Test
Interpreting Results
The PaO2 is one of the components measured in an arterial blood gas (ABG) test, which also reports oxygen (O2) saturation, bicarbonate (HCO3), the partial pressure of carbon dioxide (CO2), and the pH level in red blood cells.
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What Is Partial Pressure of Oxygen?
Oxygenation of tissues occurs when pressure pushes oxygen from your membranes into your tissues. In medicine, the term “partial pressure of oxygen” describes how well oxygen moves from your lungs to your bloodstream.
Purpose of PaO2 Test
The PaO2 test measures the pressure of oxygen in your blood. The measurement is taken during anarterial blood gas (ABG) test.
The PaO2 test can be used to assess the effects of breathing problems on oxygen supply, especially in a hospital setting or during an episode of severe respiratory distress. The results are often used to determine whether emergency treatment—such asoxygen supplementationormechanical breathing support—are needed.
PaO2 values can also be used (along with other tests) to help diagnose a number of chronic medical conditions or events like:
In some situations, such as when oxygen therapy or ventilation (mechanical breathing support) has been started, a repeat PaO2 test is used to assess whether a respiratory condition is improving or worsening and whether the treatment should be adjusted.
Breathing problems can disrupt the natural exchange between oxygen and carbon dioxide. A PaO2 test can shed light on why.
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A PaO2 test has very few risks associated with it. Because the test uses blood obtained with an arterial puncture instead of blood drawn from a vein, there is a slightly higher risk of bleeding or bruising.
If you’re taking ablood thinneror have ableeding disorder, your medical team may take special precautions while you undergo this test, such as monitoring for bleeding from your puncture site for a longer period of time.
Before the PaO2 Test
A PaO2 test as part of an outpatient diagnostic evaluation requires an appointment. However, the test can be done urgently during a respiratory emergency.
Often, the test is administered during a hospital stay or to monitor treatment or the progression of an illness.
Timing
Drawing blood for this test takes about five minutes, but you should allot about an hour if you’re having the test done in an outpatient setting. This will give you time to register, wait for your turn, and ensure that the puncture site isn’t bleeding.
Location
Outpatient PaO2 tests are done at a healthcare provider’s office or at a clinic or lab where blood draws are performed. If you have this test in a hospital or during an emergency, you will be able to remain in a hospital bed during the arterial blood draw.
What to Wear
Dress comfortably for a PaO2 test. Often, blood is drawn from theradial artery, which runs along the inner surface of the wrist. So it’s a good idea to wear either a short-sleeve shirt or a shirt with sleeves that are easy to pull up.
Food and Drink
You can eat and drink whatever you want prior to this test because your diet will not affect the results.
Cost and Health Insurance
Check with your healthcare provider or health insurer about whether your plan will cover the cost of the test and, if relevant, the cost of your co-pay.
If you have time, you may wish to shop around and compare prices. They can vary considerably.
During a PaO2 Test
Pre-Test
First, you’ll have your arterial pulse checked. While blood is usually drawn from the radial artery in your wrist, this is not always ideal. If your pulse is weak due to severe illness or blood loss, thefemoral arteryin your groin may be used instead.
Puncture Could Be SparedSometimes, a catheter (tube) is placed in an artery during surgery or during a prolonged illness. In this case, your PaO2 can be checked without a needle puncture.
Puncture Could Be Spared
Sometimes, a catheter (tube) is placed in an artery during surgery or during a prolonged illness. In this case, your PaO2 can be checked without a needle puncture.
Throughout the Test
The skin around the intended puncture site will be cleaned, usually with an alcohol pad. A small needle, which is attached to a tube, will then be inserted into the artery in your wrist.
The pressure or pain is a bit uncomfortable—more uncomfortable than the pain felt when you have blood drawn from a vein.However, most people consider the pain bearable.
Typically, blood pumps rapidly through the arteries. This is why the volume of blood needed for your test can be collected quickly. Once the blood is collected, the needle is removed and cotton or gauze is placed over the puncture site.
After the PaO2 Test
After your PaO2 test, you will have a bandage placed over your puncture wound. You might also need to have gauze wrapped around your wrist for a few hours. Your wrist may feel a bit sore for several days after the test.
Many people are able to resume normal activities soon after having a PaO2 test. Still, it’s best to avoid heavy lifting with the arm used for the blood draw until a few days after your procedure. Ask your healthcare provider to be sure.
Managing Side Effects
If you feel sore, you can place an ice pack on your wrist. Ask your healthcare provider if you can use mild pain relievers for soreness and pain. Be careful with respect to medications that are alsoblood thinners(likeaspirinor ibuprofen) as they can trigger additional bleeding.
When to Call Your Healthcare Provider
If you experience any of the following, be sure to let your healthcare provider know immediately:
Blood Draw Sites VaryIn addition to having blood drawn from the radial artery in the wrist, it can be taken from the femoral artery in the groin or the brachial artery in the arm.
Blood Draw Sites Vary
In addition to having blood drawn from the radial artery in the wrist, it can be taken from the femoral artery in the groin or the brachial artery in the arm.
Each breath delivers air to thealveoliin your lungs. There, oxygen and carbon dioxide are transferred between the lungs and the blood. Because oxygen pressure is higher in the alveoli than it is in the adjacent capillaries (tiny blood vessels), itflows into the capillaries.
When the body is functioning normally, the normal range for partial pressure of oxygen is between 75 and 100 mmHg (at sea level).A result in this range means a sufficient amount of oxygen is flowing from the alveoli to the blood. If your PaO2 is below the normal range, that is not the case.
Lung diseases and breathing problems can increase the risk of developing low PaO2. Talk to your healthcare provider for their interpretation of the results.
Factors Affecting PaO2 Levels
A number of factors can lower your PaO2 levels, including:
You may need to have a follow up PaO2 test, especially if your symptoms don’t improve. You may also need a follow-up test when it’s time to change your oxygen supply or ventilation assistance.
Often, when respiratory support is decreased due to improvement, PaO2 is rechecked to confirm that breathing and oxygenation remain at optimal levels, even with less support.
Summary
The PaO2 test is used to evaluate respiratory diseases and conditions that affect the lungs. The results are often used to determine whether emergency treatment—such asoxygen supplementationormechanical breathing support—is needed.
The test can also shed light on the body’s lung and kidney function and its general metabolic state, meaning the physical and chemical processes in the body that use or convert energy.
If oxygen therapy is being used, the PaO2 can tell a physician how well it seems to be working. Like other lab tests, the PaO2 test is over in no time.
11 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Carlino MV, Guarino M, Izzo A, et al.Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma.Respir Physiol Neurobiol. 2020;274:103363. doi:10.1016/j.resp.2019.103363National Library of Medicine.Arterial blood gas (ABG) test.Robalo MM, Araújo IM, Domingues RM, Viana Pereira M, Esperança S.Heart failure: From typical clinical manifestations to the surprising final diagnosis.Cureus. 2022;14(7):e26870. doi:10.7759/cureus.26870Lius EE, Syafaah I.Hyperoxia in the management of respiratory failure: A literature review.Ann Med Surg (Lond). 2022;81:104393. doi:10.1016/j.amsu.2022.104393University of Rochester Medical Center.Arterial blood gas (ABG).Dukić L, Kopčinović LM, Dorotić A, Baršić I.Blood gas testing and related measurements: National recommendations on behalf of the Croatian Society of Medical Biochemistry and Laboratory Medicine.Biochem Med (Zagreb). 2016;26(3):318-336. doi:10.11613/BM.2016.036.Northwestern Medicine.Arterial blood gas test.UCSF Health.Blood gases.Forrer A, Gaisl T, Sevik A, et al.Partial pressure of arterial oxygen in healthy adults at high altitudes: A systematic review and meta-analysis.JAMA Netw Open. 2023;6(6):e2318036. doi:10.1001/jamanetworkopen.2023.18036Song Y, Liu S, Qiu W, Liu K, Zhang HL.Prediction of mechanical ventilation in Guillain-Barré syndrome at admission: Construction of a nomogram and comparison with the EGRIS model.Heliyon. 2024;10(9):e30524. doi:10.1016/j.heliyon.2024.e30524Littleton SW, Tulaimat A.The effects of obesity on lung volumes and oxygenation.Respir Med. 2017;124:15-20. doi:10.1016/j.rmed.2017.01.004
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Carlino MV, Guarino M, Izzo A, et al.Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma.Respir Physiol Neurobiol. 2020;274:103363. doi:10.1016/j.resp.2019.103363National Library of Medicine.Arterial blood gas (ABG) test.Robalo MM, Araújo IM, Domingues RM, Viana Pereira M, Esperança S.Heart failure: From typical clinical manifestations to the surprising final diagnosis.Cureus. 2022;14(7):e26870. doi:10.7759/cureus.26870Lius EE, Syafaah I.Hyperoxia in the management of respiratory failure: A literature review.Ann Med Surg (Lond). 2022;81:104393. doi:10.1016/j.amsu.2022.104393University of Rochester Medical Center.Arterial blood gas (ABG).Dukić L, Kopčinović LM, Dorotić A, Baršić I.Blood gas testing and related measurements: National recommendations on behalf of the Croatian Society of Medical Biochemistry and Laboratory Medicine.Biochem Med (Zagreb). 2016;26(3):318-336. doi:10.11613/BM.2016.036.Northwestern Medicine.Arterial blood gas test.UCSF Health.Blood gases.Forrer A, Gaisl T, Sevik A, et al.Partial pressure of arterial oxygen in healthy adults at high altitudes: A systematic review and meta-analysis.JAMA Netw Open. 2023;6(6):e2318036. doi:10.1001/jamanetworkopen.2023.18036Song Y, Liu S, Qiu W, Liu K, Zhang HL.Prediction of mechanical ventilation in Guillain-Barré syndrome at admission: Construction of a nomogram and comparison with the EGRIS model.Heliyon. 2024;10(9):e30524. doi:10.1016/j.heliyon.2024.e30524Littleton SW, Tulaimat A.The effects of obesity on lung volumes and oxygenation.Respir Med. 2017;124:15-20. doi:10.1016/j.rmed.2017.01.004
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Carlino MV, Guarino M, Izzo A, et al.Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma.Respir Physiol Neurobiol. 2020;274:103363. doi:10.1016/j.resp.2019.103363National Library of Medicine.Arterial blood gas (ABG) test.Robalo MM, Araújo IM, Domingues RM, Viana Pereira M, Esperança S.Heart failure: From typical clinical manifestations to the surprising final diagnosis.Cureus. 2022;14(7):e26870. doi:10.7759/cureus.26870Lius EE, Syafaah I.Hyperoxia in the management of respiratory failure: A literature review.Ann Med Surg (Lond). 2022;81:104393. doi:10.1016/j.amsu.2022.104393University of Rochester Medical Center.Arterial blood gas (ABG).Dukić L, Kopčinović LM, Dorotić A, Baršić I.Blood gas testing and related measurements: National recommendations on behalf of the Croatian Society of Medical Biochemistry and Laboratory Medicine.Biochem Med (Zagreb). 2016;26(3):318-336. doi:10.11613/BM.2016.036.Northwestern Medicine.Arterial blood gas test.UCSF Health.Blood gases.Forrer A, Gaisl T, Sevik A, et al.Partial pressure of arterial oxygen in healthy adults at high altitudes: A systematic review and meta-analysis.JAMA Netw Open. 2023;6(6):e2318036. doi:10.1001/jamanetworkopen.2023.18036Song Y, Liu S, Qiu W, Liu K, Zhang HL.Prediction of mechanical ventilation in Guillain-Barré syndrome at admission: Construction of a nomogram and comparison with the EGRIS model.Heliyon. 2024;10(9):e30524. doi:10.1016/j.heliyon.2024.e30524Littleton SW, Tulaimat A.The effects of obesity on lung volumes and oxygenation.Respir Med. 2017;124:15-20. doi:10.1016/j.rmed.2017.01.004
Carlino MV, Guarino M, Izzo A, et al.Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma.Respir Physiol Neurobiol. 2020;274:103363. doi:10.1016/j.resp.2019.103363
National Library of Medicine.Arterial blood gas (ABG) test.
Robalo MM, Araújo IM, Domingues RM, Viana Pereira M, Esperança S.Heart failure: From typical clinical manifestations to the surprising final diagnosis.Cureus. 2022;14(7):e26870. doi:10.7759/cureus.26870
Lius EE, Syafaah I.Hyperoxia in the management of respiratory failure: A literature review.Ann Med Surg (Lond). 2022;81:104393. doi:10.1016/j.amsu.2022.104393
University of Rochester Medical Center.Arterial blood gas (ABG).
Dukić L, Kopčinović LM, Dorotić A, Baršić I.Blood gas testing and related measurements: National recommendations on behalf of the Croatian Society of Medical Biochemistry and Laboratory Medicine.Biochem Med (Zagreb). 2016;26(3):318-336. doi:10.11613/BM.2016.036.
Northwestern Medicine.Arterial blood gas test.
UCSF Health.Blood gases.
Forrer A, Gaisl T, Sevik A, et al.Partial pressure of arterial oxygen in healthy adults at high altitudes: A systematic review and meta-analysis.JAMA Netw Open. 2023;6(6):e2318036. doi:10.1001/jamanetworkopen.2023.18036
Song Y, Liu S, Qiu W, Liu K, Zhang HL.Prediction of mechanical ventilation in Guillain-Barré syndrome at admission: Construction of a nomogram and comparison with the EGRIS model.Heliyon. 2024;10(9):e30524. doi:10.1016/j.heliyon.2024.e30524
Littleton SW, Tulaimat A.The effects of obesity on lung volumes and oxygenation.Respir Med. 2017;124:15-20. doi:10.1016/j.rmed.2017.01.004
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