An arterial blood gas (ABG) test is a blood test that measures the acid-base balance (pH) and the levels of oxygen and carbon dioxide in the arterial blood. It is used to assess lung and kidney function, determine how well the lungs are performing gas exchange, and check for acid-base imbalances like acidosis or alkalosis. The sample is typically drawn from an artery in the wrist, groin, or arm.   What it measures pH: Indicates the acidity or alkalinity of the blood.  Partial pressure of oxygen (\(P_{a}O_{2}\)): Measures the amount of oxygen dissolved in the blood.  Partial pressure of carbon dioxide (\(P_{a}CO_{2}\)): Measures the amount of carbon dioxide dissolved in the blood.  Bicarbonate (\(HCO_{3}\)): Measures the metabolic component of the acid-base balance.  How it's performed A blood sample is taken from an artery, most commonly the radial artery in the wrist.  It can also be taken from the femoral artery in the groin or the brachial artery in the arm.  A special procedure called the Allen test may be performed first to ensure the blood flow to the hand is adequate.  For up to 30 minutes before the test, a patient on oxygen therapy may have their oxygen turned off, but this is only done if it is safe to do so.  Why it's performed To check how well the lungs are functioning.  To assess the body's acid-base balance, which is crucial for enzyme function.  To guide the treatment of acute or chronic illnesses. An arterial blood gas (ABG) test is a blood test that measures the acid-base balance (pH) and the levels of oxygen and carbon dioxide in the arterial blood. It is used to assess lung and kidney function, determine how well the lungs are performing gas exchange, and check for acid-base imbalances like acidosis or alkalosis. The sample is typically drawn from an artery in the wrist, groin, or arm.   What it measures pH: Indicates the acidity or alkalinity of the blood.  Partial pressure of oxygen (\(P_{a}O_{2}\)): Measures the amount of oxygen dissolved in the blood.  Partial pressure of carbon dioxide (\(P_{a}CO_{2}\)): Measures the amount of carbon dioxide dissolved in the blood.  Bicarbonate (\(HCO_{3}\)): Measures the metabolic component of the acid-base balance.  How it's performed A blood sample is taken from an artery, most commonly the radial artery in the wrist.  It can also be taken from the femoral artery in the groin or the brachial artery in the arm.  A special procedure called the Allen test may be performed first to ensure the blood flow to the hand is adequate.  For up to 30 minutes before the test, a patient on oxygen therapy may have their oxygen turned off, but this is only done if it is safe to do so.  Why it's performed To check how well the lungs are functioning.  To assess the body's acid-base balance, which is crucial for enzyme function.  To guide the treatment of acute or chronic illnesses. An arterial bl

1. PRESENTED BY:
AYAABD ELRAHMAN ABD ELGHAFAR
UNDER SUPERVISION :
Dr / MONAABO ZAID

2. Outlines
• Definition of Arterial Blood Gases test.
• Measurement in an Arterial Blood Gas test
• Indication of Arterial Blood Gases test.
• Risks to the Arterial Blood Gases test.
• Normal Values of (ABG)
• Technique of Arterial Blood Gases test.
• Arterial Blood Gas interpretation.

3. Definition
• An arterial blood gas (ABG) test is a blood test that requires a
sample from an artery in the body to measure the levels of
oxygen and carbon dioxide in the blood.
• The test also checks the balance of acids and bases, known as the
pH balance, in the blood.

4. Measurement in an Arterial Blood Gas
test
An arterial blood gas test usually includes the following
measurements:
• Oxygen content (O2CT): This measures the amount of oxygen in your
blood.
• Oxygen saturation (O2Sat): This measures how much hemoglobin in
your blood is carrying oxygen. Hemoglobin is a protein in your red
blood cells that carries oxygen from your lungs to the rest of your body.

5. Measurement in an Arterial Blood Gas
test
• Partial pressure of oxygen (PaO2):This measures the pressure of
oxygen dissolved in your blood. It helps show how well oxygen moves
from your lungs to your bloodstream.
• Partial pressure of carbon dioxide (PaCO2): This measures the
amount of carbon dioxide in your blood and how well carbon dioxide
can move out of your body.
• pH: This measures the balance of acids and bases in your blood, known
as your blood pH level. The pH of blood is usually between 7.35 and
7.45. If it’s lower than that, your blood is considered too acidic. If it’s
higher than that range, your blood is considered too basic (alkaline).

6. Measurement in an Arterial Blood Gas
test
• Bicarbonate (HCO3):This is calculated using the measured values of
pH and PaCO2 to determine the amount of the basic compound made
from carbon dioxide (CO2).

7. Indication of Arterial Blood Gases test
Healthcare providers evaluate several conditions using an ABG,
including:
• Acute respiratory distress syndrome (ARDS): This is a life-
threatening lung injury that causes dangerously low oxygen levels in
your blood. It’s caused by sepsis, COVID-19 and other conditions.
• Severe sepsis.
• Septic shock: blood pressure drops to a dangerously low level after an
infection.
• Hypovolemic shock: (severe blood loss or other fluid loss )

8. Indication of Arterial Blood Gases test
• Diabetes-related ketoacidosis (DKA): (mainly Type 1 diabetes) and
those who have undiagnosed Type 1 diabetes. It causes your blood to
become acidic.
• Renal tubular acidosis (RTA): This condition happens when your
kidneys don’t remove acids from your blood into your urine as they
should, causing your blood to become acidic.
• Acute respiratory failure: This happens when fluid builds up in the air
sacs in your lungs.
• Acute heart failure.

9. Indication of Arterial Blood Gases test
• Cardiac arrest.
• Asthma attack.
• Inborn errors of metabolism: These are rare genetic (inherited) conditions
in which your body can’t properly turn food into energy due to a lack of
specific proteins (enzymes) that help break down parts of food.
• To make sure your treatment is working properly in the following cases:
• Asthma.
• Chronic obstructive pulmonary disease (COPD).
• Cystic fibrosis.
• Heart disease

10. Risks to the Arterial Blood Gases test
• There’s little risk associated with getting an arterial blood gas test when
the procedure performed correctly.
• Risks associated with having an arterial blood gas blood draw are rare,
but may include:
• Fainting or feeling lightheaded.
• Multiple punctures to locate your artery.
• Hematoma (blood building up under your skin).
• Excessive bleeding.
• Infection (a slight risk any time your skin is punctured or cut).

11. Normal Values of (ABG)

12. Technique of Arterial Blood Gases test
Equipment:
• A blue (23 G) needle.
• 2ml syringe with heparin.
• A cap for the syringe.
• A plastic bung.
• Local anesthetic (plus needle and syringe for giving).
• Alcohol gel.
• Gauze.
• Gloves.
• A sharps bin.

13. Steps:
Technique no
Wash your hands
. 1
Introduce yourself to the patient and clarify their identity 2
Explain what you would like to do and obtain consent. This is a slightly uncomfortable
procedure so you should let the patient know this 3
Gather the necessary equipment 4
Position the patient’s arm with the wrist extended
. 5
Locate the radial artery with your index and middle fingers
. 6
Perform Allen’s test where you compress both the radial and ulnar arteries at the same time
. 7
Put on your gloves and attach the needle to the heparinized syringe
. 8
Prepare your local anesthetic and give a small amount over the palpable radial artery
. 9
Let the patient know you are about to proceed and to expect a sharp scratch
. 10
Insert the needle at 30 degrees to the skin at the point
of maximum pulsation of the radial artery 11
Advance the needle until arterial blood flushes into the syringe. The arterial pressure will cause
the blood to fill the syringe
. 12

14. Steps:
Technique no
Remove the needle/syringe placing the needle into the bung
. 13
Press firmly over the puncture site with the gauze to halt the bleeding.( Remain pressed for 5
minutes)
. 14
Remove the needle and discard safely in the sharps bin. 15
Cap the syringe 16
push out any air within it
. 17
Send immediately for analysis ensuring that the sample is packed in ice
. 18
Remove your gloves and dispose them in the clinical waste bin
. 19
Wash your hands and thank the patient
. 20

16. Arterial Blood Gas interpretation
• Before attempting to interpret the results, you should know whether the patient
was on room air or on oxygen when the sample was taken, and if on oxygen,
what concentration.
• It is also useful to know whether the patient has a temperature or not, and this
should be clearly written on the sample.
• Results
• The following information shows the changes in pH, CO2 and bicarbonate
concentrations in different situations:
• Metabolic Acidosis
• pH: ↓
• pCO2: ↔
• Bicarbonate: ↓

17. Arterial Blood Gas interpretation
• Respiratory Acidosis
• pH: ↓
• pCO2: ↑
• Bicarbonate: ↔
• Results Metabolic Alkalosis
• pH: ↑
• pCO2: ↔
• Bicarbonate: ↑
• Respiratory Alkalosis
• pH: ↑
• pCO2: ↓
• Bicarbonate: ↔

18. Respiratory acidosis
• Respiratory acidosis occurs when exhalation of carbon dioxide is
inhibited, creating a carbonic acid excess in the body. As a result, the pH
of the blood falls below 7.35, if not compensated.
• Hypoventilation is its general cause. Two major conditions that cause
hypoventilation are central nervous system depression and obstructive
lung disease.
• Respiratory acidosis is associated with airway obstruction such as occurs
with asthmatic bronchial spasm, bronchitis and pulmonary diseases such
as severe pneumonia and pulmonary fibrosis; thoracic conditions such as
multiple broken ribs.

19. Respiratory alkalosis
• Respiratory alkalosis occurs when exhalation of carbon dioxide is
excessive, resulting in a carbonic acid deficit. As a result, the blood pH
rises above 7.45. The root cause is hyperventilation, which can occur as
a result of fever, anxiety, or pulmonary infections
• Respiratory alkalosis may be caused by hyperventilation psychologically
induced (anxiety), by drugs that stimulate the respiratory center,
excessive ventilation therapy.

20. Metabolic acidosis
• Metabolic acidosis occurs when levels of base bicarbonate are low in
relation to carbonic acid blood levels.
• The kidneys normally retain bicarbonate (HC03-) or excrete hydrogen
ions (H+) in response to altered blood pH.
• Prolonged diarrhea can decrease bicarbonate. Common causes of
metabolic acidosis are diabetes mellitus, alcoholism, lactic acidosis
(associated with hypoxia), acid poisoning, renal failure

21. Metabolic alkalosis
• Metabolic alkalosis occurs when the level of base bicarbonate is high.
Metabolic alkalosis may be due to excess intake of baking
soda .Prolonged vomiting causes the body to lose hydrogen (H+) ions
• Metabolic alkalosis can be caused by mineral-corticoid excess (e.g.
Cushing's syndromes), which promotes increased acid excretion and
bicarbonate retention by the kidney. Other causes are diuretic therapy,
vomiting, severe dehydration, hypokalemia (low blood potassium), and
hypoparathyroidism .

22. References
• Arterial Blood Gas (ABG): What It Is, Purpose, Procedure & Levels
(clevelandclinic.org)
• Arterial Blood Gases (ABG) — Medistudents