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measures the acidity (pH) and the levels

of oxygen and carbon dioxide in the

blood from an artery. This test is used tocheck how well your lungs are able to

move oxygen into the blood and

remove carbon dioxide from the blood.

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As blood passes through your lungs,

oxygen moves into the blood while

carbon dioxide moves out of the bloodinto the lungs. An ABG test uses blood

drawn from an artery, where the oxygen

and carbon dioxide levels can be

measured before they enter bodytissues.

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An ABG measures:

Partial pressure of oxygen (PaO2). Thismeasures the pressure of oxygen dissolvedin the blood and how well oxygen is able tomove from the airspace of the lungs intothe blood.

Partial pressure of carbon dioxide(PaCO2). This measures how much carbondioxide is dissolved in the blood and howwell carbon dioxide is able to move out ofthe body.

pH. The pH measures hydrogen ions (H+) inblood. The pH of blood is usually between7.35 and 7.45. A pH of less than 7.0 is calledacid and a pH greater than 7.0 is calledbasic (alkaline). So blood is slightly basic.

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Bicarbonate (HCO3). Bicarbonate is achemical (buffer) that keeps the pH of

blood from becoming too acidic or toobasic.

Oxygen content (O2CT) and oxygensaturation (O2Sat) values. O2 content

measures the amount of oxygen in theblood. Oxygen saturation measures howmuch of the hemoglobin in the redblood cells is carrying oxygen (O2).

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Blood for an ABG test is taken from an

artery. Most other blood tests are done

on a sample of blood taken from a vein,after the blood has already passed

through the body's tissues where the

oxygen is used up and carbon dioxide is

produced.

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An arterial blood gas (ABG) test is done to: Check for severe breathing problems and lung

diseases, such as asthma, cystic fibrosis, or chronicobstructive pulmonary disease (COPD).

See how well treatment for lung diseases is working. Find out if you need extra oxygen or help withbreathing (mechanical ventilation).

Find out if you are receiving the right amount ofoxygen when you are using oxygen in the hospital.

Measure the acid-base level in the blood of peoplewho have heart failure, kidney failure,uncontrolled diabetes, sleep disorders, severeinfections, or after a drug overdose.

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Ask the patient if he/she Have had bleeding problems or take blood thinners,

such as aspirin or warfarin(Coumadin).

is taking any medicines. is allergic to any medicines, such as those used to

numb the skin(anesthetics).If the patient is on oxygen therapy, the oxygen may beturned off for20 minutes before the blood test. This is

called a "room air" test. If he/she cannot breathewithout the oxygen, the oxygen will not be turned off..

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A sample of blood from an artery isusually taken from the inside of the wrist(radial artery), but it can also becollected from an artery in the groin(femoral artery) or on the inside of thearm above the elbow crease (brachialartery). You will be seated with your armextended and your wrist resting on asmall pillow. The health professionaldrawing the blood may rotate your handback and forth and feel for a pulse inyour wrist.

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To prevent the possibility of damaging

the artery of the wrist when the blood

sample is taken, a procedure calledthe Allen test may be done to ensure

that blood flow to your hand is normal.

An arterial blood gas (ABG) test will not

be done on an arm used for dialysis or ifthere is an infection or inflammation in

the area of the puncture site.

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Clean the needle site with alcohol. You maybe given an injection of local anesthetic tonumb that area.

Put the needle into the artery. More than oneneedle stick may be needed.

Allow the blood to fill the syringe. Be sure tobreathe normally while your blood is beingcollected.

Put a gauze pad or cotton ball over the needlesite as the needle is removed.

Put a bandage over the puncture site andapply firm pressure for 5 to 10 minutes (possiblylonger if you take blood-thinning medicine orhave bleeding problems).

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Collecting blood from an artery is more painfulthan collecting it from a vein because the arteriesare deeper and are protected by nerves.

Most people feel a brief, sharp pain as the needleto collect the blood sample enters the artery. If youare given a local anesthetic, you may feel nothingat all from the needle puncture, or you may feel a

brief sting or pinch as the needle goes through the

skin. You may feel more pain if the person drawing your

blood has a hard time finding your artery, your

artery is narrowed, or if you are very sensitive to

pain.

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There is little chance of a problem fromhaving blood sample taken from an artery.

You may get a small bruise at the site. Youcan lower the chance of bruising by

keeping pressure on the site for at least 10minutes after the needle is removed (longerif you have bleeding problems or takeblood thinners).

You may feel lightheaded, faint, dizzy, ornauseated while the blood is being drawnfrom your artery.

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Ongoing bleeding can be a problem for

people with bleeding disorders. Aspirin,warfarin (Coumadin), and other blood-thinning medicines can make bleeding morelikely. If you have bleeding or clottingproblems, or if you take blood-thinning

medicine, tell your doctor before your bloodsample is taken.

On rare occasions, the needle may damagea nerve or the artery, causing the artery tobecome blocked.

Though problems are rare, be careful withthe arm or leg that had the blood draw. Donot lift or carry objects for about 24 hoursafter you have had blood drawn from anartery

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Parameter Arterial Blood Mixed Venous

pH 7.35-7.45 7.33-7.41

PaCO2 35-45 mm Hg 41-51 mm Hg

Po2 80-100 mm Hg 35-40 mm Hg

HCO3 22-26 mEq/L 22-26 mEq/L

Base Excess/ deficit + 2 mEq/L + 2 mEq/LOxygen Saturation >94% 75%

Normal Values

RESULTSArterial blood gas (ABG) test measures the acidity (pH) and levels of

oxygen and carbon dioxide in the blood.

The concentration of oxygen being breathed, called the fraction ofinhaled oxygen (FiO2), is also usually reported. This is only useful ifyou are receiving oxygen therapy from a tank or are on a ventilator.

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Disorder Initial Event

Respiratory Acidosis pH, or normal HCO3, PaCO3

Respiratory Alkalosis pH, or normal HCO3, PaCO3

Metabolic Acidosis pH, HCO3, or normal PaCO3

Metabolic Alkalosis pH, HCO3, or normal PaCO3

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Normal

Normal

HCO3HCO3

Normal

Normal

Metabolic Alkalosis

Uncompensated

Partly Compensated

Compensated

Normal

Normal

Metabolic Acidosis

Uncompensated

Partly Compensated

Compensated

Normal

Respiratory Alkalosis

Uncompensated

Partly CompensatedCompensated

Normal

Respiratory Acidosis

Uncompensated

Partly Compensated

Compensated

PCO2PCO2pHpHCONDITIONCONDITION

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Diabetes.

Drug or alcohol overdose.

Kidney failure. Lung diseases, such as chronic lung disease,

a blood clot in the lungs, or pneumonia.

Severe dehydration from severeburns, vomiting, diarrhea, or taking waterpills (diuretics).

Severe infection (sepsis).

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Reasons you may not be able to have the testor why the results may not be helpful includethe following:

You have a fever or an abnormally low bodytemperature (hypothermia).

You have a disease that affects how muchoxygen is carried in your blood, such assevere anemia or polycythemia.

You smoke just before the test orbreathe secondhand smoke, carbonmonoxide, or certain paint or varnish removersin closed or poorly ventilated areas.

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PCO2= 46 alkaline

HCO3=28 acid

pH= 7.45 alkaline 7.4

Respiratory Alkalosis, Fully Compensated