Blood Gas Test

Blood Gas Test

Blood Gas Test

What Is a Blood Gas Test?

A blood gas test measures the amount of oxygen and carbon dioxide in the blood. It may also be used to determine the pH of the blood, or how acidic it is. The test is commonly known as a blood gas analysis or arterial blood gas (ABG) test.

Your red blood cells transport oxygen and carbon dioxide throughout your body. These are known as blood gases. As blood passes through your lungs, oxygen flows into the blood while carbon dioxide flows out of the blood into the lungs. The blood gas test can determine how well your lungs are able to move oxygen into the blood and remove carbon dioxide from the blood.

Imbalances in the oxygen, carbon dioxide, and pH levels of your blood can indicate the presence of certain medical conditions. These may include:

  • kidney failure
  • heart failure
  • uncontrolled diabetes
  • hemorrhage
  • chemical poisoning
  • a drug overdose
  • shock

Your doctor may order a blood gas test when you’re showing symptoms of any of these conditions. The test requires the collection of a small amount of blood from an artery. It’s a safe and simple procedure that only takes a few minutes to complete.

Why Is a Blood Gas Test Done?

A blood gas test provides a precise measurement of the oxygen and carbon dioxide levels in your body. This can help your doctor determine how well your lungs and kidneys are working.

This is a test that is most commonly used in the hospital setting to determine the management of acutely ill patients. It does not have a very significant role in the primary care setting, but may be used in a pulmonary function lab or clinic.

Your doctor may order a blood gas test if you’re showing symptoms of an oxygen, carbon dioxide, or pH imbalance. The symptoms can include:

  • shortness of breath
  • difficulty breathing
  • confusion
  • nausea

These symptoms may be signs of certain medical conditions, including asthma and chronic obstructive pulmonary disease (COPD).

Your doctor may also order a blood gas test if they suspect you’re experiencing any of the following conditions:

  • lung disease
  • kidney disease
  • metabolic disease
  • head or neck injuries that affect breathing

Identifying imbalances in your pH and blood gas levels can also help your doctor monitor treatment for certain conditions, such as lung and kidney diseases.

A blood gas test is often ordered along with other tests, such a blood glucose test to check blood sugar levels and a creatinine blood test to evaluate kidney function.

What Are the Risks of a Blood Gas Test?

Since a blood gas test doesn’t require a large sample of blood, it’s considered a low-risk procedure. However, you should always tell your doctor about existing medical conditions that may make you bleed more than expected. You should also tell them if you’re taking any over-the-counter or prescription medications, such as blood thinners, that may affect your bleeding.

Possible side effects associated with the blood gas test include:

  • bleeding or bruising at the puncture site
  • feeling faint
  • blood accumulating under the skin
  • infection at the puncture site

Tell your doctor if you experience unexpected or prolonged side effects.

How Is a Blood Gas Test Performed?

A blood gas test requires the collection of a small sample of blood. Arterial blood can be obtained from an artery in your wrist, arm, or groin, or pre-existing arterial line if you are currently hospitalized. A blood gas sample can also be venous, from a vein or pre-existing IV or capillary, which requires a small prick to the heel.

A technician called a phlebotomist will first sterilize the injection site with an antiseptic. Once they find an artery, they’ll insert a needle into the artery and draw blood. You might feel a slight prick when the needle goes in, but the test itself isn’t painful. After the needle is removed, the technician will put a bandage over the puncture wound.

The blood sample will then be analyzed by a portable machine or in an on-site laboratory. The sample must be analyzed within 10 minutes of the procedure to ensure an accurate test result.

Interpreting the Results of a Blood Gas Test

The results of a blood gas test can help your doctor diagnose various diseases or determine how well treatments are working for certain conditions, including lung diseases. It also shows whether or not your body is compensating for the imbalance. Due to the potential for compensation in some values that will cause the correction of other values, it is essential that the person interpreting the result is a trained healthcare provider, with experience in blood gas interpretation. The test measures:

  • Arterial blood pH measures the amount of hydrogen ions in blood. A pH of less than 7.0 is called acidic, and a pH greater than 7.0 is called basic, or alkaline. A lower blood pH may indicate that your blood is more acidic and has higher carbon dioxide levels. A higher blood pH may indicate that your blood is more basic and has a higher bicarbonate level.
  • Bicarbonate is a chemical that helps prevent the pH of blood from becoming too acidic or too basic.
  • Partial pressure of oxygen is a measure of the pressure of oxygen dissolved in the blood. It determines how well oxygen is able to flow from the lungs into the blood.
  • Partial pressure of carbon dioxide is a measure of the pressure of carbon dioxide dissolved in the blood. It determines how well carbon dioxide is able to flow out of the body.
  • Oxygen saturation is a measure of the amount of oxygen being carried by the hemoglobin in the red blood cells.
    In general, normal values include:
  • arterial blood pH: 7.38 to 7.42
  • bicarbonate: 22 to 28 milliequivalents per liter
  • partial pressure of oxygen: 75 to 100 mm Hg
  • partial pressure of carbon dioxide: 38 to 42 mm Hg
  • oxygen saturation: 94 to 100 percent

Your blood oxygen levels may be lower if you live above sea level.

The normal values will have a slightly different reference range if they are from a venous or capillary sample.

Abnormal results can be signs of certain medical conditions, including the ones in following table:

Blood pHBicarbonatePartial pressure of carbon dioxideConditionCommon causes
Less than 7.4LowLowMetabolic acidosisKidney failure, shock, diabetic ketoacidosis
Greater than 7.4HighHighMetabolic alkalosisChronic vomiting, low blood potassium
Less than 7.4HighHighRespiratory acidosisLung diseases, including pneumonia or COPD
Greater than 7.4LowLowRespiratory alkalosisBreathing too fast, pain, or anxiety
 Normal and abnormal ranges can vary depending on the lab because some use different measurements or methods to analyze blood samples. You should always meet with your doctor to discuss your test results in more detail. They’ll be able to tell you if you need more testing and if you’ll need any treatment.

Source: Click This Link



What is Blood?

Blood is a constantly circulating fluid providing the body with nutrition, oxygen, and waste removal. Blood is mostly liquid, with numerous cells and proteins suspended in it, making blood "thicker" than pure water. The average person has about 5 liters (more than a gallon) of blood.

About Blood Donation

A blood donation occurs when a person voluntarily has blood drawn and used for transfusions and/or made into biopharmaceutical medications by a process called fractionation (separation of whole-blood components). Donation may be of whole blood (WB), or of specific components directly (the latter called apheresis). Blood banks often participate in the collection process as well as the procedures that follow it.

More Facts

A liquid called plasma makes up about half of the content of blood. Plasma contains proteins that help blood to clot, transport substances through the blood, and perform other functions. Blood plasma also contains glucose and other dissolved nutrients.

About half of blood volume is composed of blood cells:

• Red blood cells, which carry oxygen to the tissues
• White blood cells, which fight infections
• Platelets, smaller cells that help blood to clot

Blood is conducted through blood vessels (arteries and veins). Blood is prevented from clotting in the blood vessels by their smoothness, and the finely tuned balance of clotting factors.

Blood Conditions

Hemorrhage (bleeding): Blood leaking out of blood vessels may be obvious, as from a wound penetrating the skin. Internal bleeding (such as into the intestines, or after a car accident) may not be immediately apparent.

Hematoma: A collection of blood inside the body tissues. Internal bleeding often causes a hematoma.

Leukemia: A form of blood cancer, in which white blood cells multiply abnormally and circulate through the blood. The abnormal white blood cells make getting sick from infections easier than normal.

Multiple myeloma: A form of blood cancer of plasma cells similar to leukemia. Anemia, kidney failure and high blood calcium levels are common in multiple myeloma.

Lymphoma: A form of blood cancer, in which white blood cells multiply abnormally inside lymph nodes and other tissues. The enlarging tissues, and disruption of blood's functions, can eventually cause organ failure.

Anemia: An abnormally low number of red blood cells in the blood. Fatigue and breathlessness can result, although anemia often causes no noticeable symptoms.

Hemolytic anemia: Anemia caused by rapid bursting of large numbers of red blood cells (hemolysis). An immune system malfunction is one cause.

Hemochromatosis: A disorder causing excessive levels of iron in the blood. The iron deposits in the liver, pancreas and other organs, causing liver problems and diabetes.

Sickle cell disease: A genetic condition in which red blood cells periodically lose their proper shape (appearing like sickles, rather than discs). The deformed blood cells deposit in tissues, causing pain and organ damage.

Bacteremia: Bacterial infection of the blood. Blood infections are serious, and often require hospitalization and continuous antibiotic infusion into the veins.

Malaria: Infection of red blood cells by Plasmodium, a parasite transmitted by mosquitos. Malaria causes episodic fevers, chills, and potentially organ damage.

Thrombocytopenia: Abnormally low numbers of platelets in the blood. Severe thrombocytopenia may lead to bleeding.

Leukopenia: Abnormally low numbers of white blood cells in the blood. Leukopenia can result in difficulty fighting infections.

Disseminated intravascular coagulation (DIC): An uncontrolled process of simultaneous bleeding and clotting in very small blood vessels. DIC usually results from severe infections or cancer.

Hemophilia: An inherited (genetic) deficiency of certain blood clotting proteins. Frequent or uncontrolled bleeding can result from hemophilia.

Hypercoaguable state: Numerous conditions can result in the blood being prone to clotting. A heart attack, stroke, or blood clots in the legs or lungs can result.

Polycythemia: Abnormally high numbers of red blood cells in the blood. Polycythemia can result from low blood oxygen levels, or may occur as a cancer-like condition.

Deep venous thrombosis (DVT): A blood clot in a deep vein, usually in the leg. DVTs are dangerous because they may become dislodged and travel to the lungs, causing a pulmonary embolism (PE).

Myocardial infarction (MI): Commonly called a heart attack, a myocardial infarction occurs when a sudden blood clot develops in one of the coronary arteries, which supply blood to the heart.

Source: WebMD

Today in the developed world, most blood donors are unpaid volunteers who donate blood for a community supply. In some countries, established supplies are limited and donors usually give blood when family or friends need a transfusion (directed donation). Many donors donate as an act of charity, but in countries that allow paid donation some donors are paid, and in some cases there are incentives other than money such as paid time off from work. Donors can also have blood drawn for their own future use (autologous donation). Donating is relatively safe, but some donors have bruising where the needle is inserted or may feel faint.

Potential donors are evaluated for anything that might make their blood unsafe to use. The screening includes testing for diseases that can be transmitted by a blood transfusion, including HIV and viral hepatitis. The donor must also answer questions about medical history and take a short physical examination to make sure the donation is not hazardous to his or her health. How often a donor can donate varies from days to months based on what component they donate and the laws of the country where the donation takes place. For example, in the United States, donors must wait eight weeks (56 days) between whole blood donations but only seven days between plateletpheresis donations and twice per seven-day period in plasmapheresis.

The amount of blood drawn and the methods vary. The collection can be done manually or with automated equipment that takes only specific components of the blood. Most of the components of blood used for transfusions have a short shelf life, and maintaining a constant supply is a persistent problem. This has led to some increased interest in autotransfusion, whereby a patient's blood is salvaged during surgery for continuous reinfusion—or alternatively, is "self-donated" prior to when it will be needed. (Generally, the notion of "donation" does not refer to giving to one's self, though in this context it has become somewhat acceptably idiomatic.)

Who can give blood

Most people can give blood. You can give blood if you:

  • are fit and healthy
  • weigh between 7 stone 12 lbs and 25 stone, or 50kg and 160kg
  • are aged between 17 and 66 (or 70 if you have given blood before)
  • are over 70 and have given blood in the last two years

How often can I give blood?

Men can give blood every 12 weeks and women can give blood every 16 weeks. Find out more about what happens on the day of your donation.

Check you are able to give blood

You can check some of the most common eligibility questions we receive from blood donors.

You can register here as a blood donor.

The common reasons donors should check if they can give blood are:

  • if you are receiving medical or hospital treatment
  • if you are taking medication
  • during and after pregnancy
  • if you feel ill
  • if you have cancer
  • after receiving blood, blood products or organs.

Women under 20 - check if you can give blood.

X