BLOOD GAS ANALYSIS

OBJECTIVES

• What is blood gas analysis?• Purpose?• Procedure, preparation,

aftercare?• Normal and abnormal results?

WHAT

?

BLOOD GAS ANALYSIS

• Known as arterial blood gas (ABG) analysis.

• A procedure to measure the partial pressure of Oxygen (O2 ) and

• the carbon dioxide gases (CO2 ) and• the pH(Hyrdrogen ion concentration)

in arterial blood.

PURPOSE

• Evaluates how effectively the lungs are delivering O2 to the blood and

• How effectively they are eliminating CO2 from it.

• The test also indicates how well the lungs and kidneys are interacting to maintain normal blood pH(acid-base balance).

Procedure

• The blood sample is obtained by arterial puncture(usually in the wrist,although it could be in the groin arm

• Or from an arterial line already in place.

• If a puncture is needed,the skin over the artery is cleaned with antiseptic.

• A technician then collects the blood with a small sterile needle attached to a disposable syringe.

• The patient may feel a brief throbbing or cramping at the site of the puncture.• After the blood is drawn,the sample must be transported to the laboratory as soon as posible for analysis.

Preparation

• There are NO special preparations.

• Patients have NO restrictions on DRINKING or EATING before the test.

• If,the patient is receiving oxygen,the oxygen concentration must remain the same for 20 mins before the test;

• if the test is to be taken without oxygen ,the gas must be turn off for 20 mins before the test is taken.

• The patient also should breath normally during the test.

Aftercare

• After the blood has been taken,• the technian or the patient applies

pressure to be puncture site 10 – 15 mins to stop the bleeding,and

• Then places a dressing over the puncture site.

• Health care workers will observe the patient for signs of bleeding or circulation problems.

RISKS

• Risks are very low when the test is done correctly.

• Risks include bleeding or bruising at the site,

• Or delayed delayed bleeding from the site.

• Very rarely,there may be a problem with circulation in the puncture area.

Results>NORMAL

>ABNORMAL

Result Normal range Abnormal Description

Partial pressure of oxygen

75-100 mm Hg Other results

that differ the normal range.

A low PO2 indicates that the patient is not oxygenating properly, and is hypoxemic. (Note that a low PO2 is not required for the patient to have hypoxia.) At a PO2 of less than 60 mm Hg, supplemental oxygen should be administered. At a PO2 of less than 26 mmHg, the patient is at risk of death and must be oxygenated immediately.

Partial pressure of carbon dioxide

35-45 mm Hg

the carbon dioxide partial pressure (PCO2) is an indicator of CO2 production and elimination: for a constant metabolic rate, the PCO2 is determined entirely by its elimination through ventilation. A high PCO2(respiratory acidosis, alternatively hypercapnia) indicates underventilation (or, more rarely, a hypermetabolic disorder), a low PCO2 (respiratory alkalosis, alternatively hypocapnia) hyper- or overventilation.

Result Normal range

Abnormal Description

Oxygen content(O2CT)

15-23%

Other results

that differ the normal

range.

This is the sum of oxygen dissolved in plasma and chemically bound to hemoglobin .

Oxygen saturation(SaO2)

94-100%

Measures how much of the hemoglobin in the red blood cells is carrying oxygen (O2).

Bicarbonate(HCO3)

22-26 mEq/L

The HCO3− ion indicates

whether a metabolic problem is present (Eg:ketoacidosis). A low HCO3

−indicates metabolic acidosis, a high HCO3

− indicates metabolic alkalosis.

pH 7.35- 7.47

The pH or H+ indicates if a patient is acidemic or alkalemic.