This document provides an overview of arterial blood gas interpretation including: - Definitions of normal values and the tic-tac-toe method for analysis using pH, PaCO2, and HCO3 levels - Explanations of respiratory acidosis, respiratory alkalosis, metabolic acidosis, and metabolic alkalosis - Risk factors, signs/symptoms, and management approaches for each acid-base imbalance - Examples of interpreting arterial blood gas results using the tic-tac-toe method and identifying the acid-base imbalance and compensation status.

1. Arterial Blood Gas Interpretation
Prepared by
Dr/ Noha Mohammed Ibrahim

2. Outlines
• Definition
• Normal Values in Arterial Blood Gas
• Steps in ABG analysis using the tic-tac-toe
method
• Acid-Base Balance and Imbalances
Respiratory acidosis
Respiratory alkalosis
Metabolic acidosis
Metabolic alkalosis
• ABG Interpretation Quiz

3. Arterial Blood Gas Interpretation
• Interpretation of arterial blood gases
(ABGs) is a crucial skill that a lot of
student nurses and medical practitioners
need to learn. In this guide, we’ll help you
understand the concepts behind arterial
blood gas and teach you the easiest and
most fun way to interpret ABGs using the
tic-tac-toe method.

4. Normal Values in Arterial Blood Gas
, the normal range is 7.35 to 7.45
, the normal range is 35 to 45 mmHg
(respiratory determinant)
, the normal range is 75 to 100 mmHg
, the normal range is 22 to 26 mEq/L
(metabolic determinant)
, the normal range is 94–100%
, the normal range is –2 to +2 mmol/L

5. Steps in ABG analysis using
the tic-tac-toe method

6. 1. Memorize the normal values.

7. 2. Create your tic-tac-toe grid.

8. 3. Determine if pH is under NORMAL,
ACIDOSIS, or ALKALOSIS.
• The third step of this technique is to determine the acidity
or alkalinity of the blood with the given value of the pH as
our determining factor.
• If the blood pH is between 7.35 to 7.39, the interpretation
is NORMAL but SLIGHTLY ACIDOSIS, place it under
the NORMAL column.
• If the blood pH is between 7.41 to 7.45, interpretation is
NORMAL but SLIGHTLY ALKALOSIS, place it under
the NORMAL column.

9. • Any blood pH below 7.35 (7.34, 7.33, 7.32, and so on…)
is ACIDOSIS, place it under the ACIDOSIS column.
• Any blood pH above 7.45 (7.46, 7.47, 7.48, and so on…)
is ALKALOSIS, place it under the ALKALOSIS column.

11. 4. Determine if PaCO2 is under NORMAL,
ACIDOSIS, or ALKALOSIS.

12. 5. Determine if HCO3 is under NORMAL,
ACIDOSIS, or ALKALOSIS.

13. 6. Solve for goal #1: ACIDOSIS or
ALKALOSIS.

14. 7. Solve for goal #2: METABOLIC or
RESPIRATORY.

15. 8. Solve for goal #3: COMPENSATION.

16. • It is FULLY COMPENSATED if pH is normal.
• It is PARTIALLY COMPENSATED if all three (3)
values are abnormal.
• It is UNCOMPENSATED if PaCO2 or HCO3 is
normal and the other is abnormal.

17. Practice Problem #1: pH=7.26 | PaCO2=32 | HCO3=18
• Remember the normal values.
• pH of 7.26 ABNORMAL and under ACIDOSIS, so we
place pH under ACIDOSIS.
• PaCO2 of 32 is ABNORMAL and under ALKALOSIS, so
we place PaCO2 under ALKALOSIS.
• HCO3 of 18 is ABNORMAL and under ACIDOSIS, so
we place HCO3 under ACIDOSIS.
• pH is under ACIDOSIS, therefore solving for goal #1, we
have ACIDOSIS.
• pH is on the same column as HCO3, therefore solving for
goal #2, we have METABOLIC.
• All three values are ABNORMAL, therefore solving for
goal #3, we have a PARTIALLY COMPENSATED ABG.

18. Practice Problem #2: pH=7.44 | PaCO2=30 | HCO3=21
• Remember the normal values.
• pH of 7.44 is NORMAL but slightly leaning towards
ALKALOSIS, so we place pH under the NORMAL column with
an arrow pointing towards the ALKALOSIS column.
• PaCO2 of 30 is ABNORMAL and ALKALOSIS, so we place
PaCO2 under the ALKALOSIS column.
• HCO3 of 21 is ABNORMAL and ACIDOSIS, so we place
HCO3 under the ACIDOSIS column.
• pH of 7.44 is NORMAL but leaning towards ALKALOSIS,
therefore solving for goal #1, we have ALKALOSIS.
• pH is NORMAL but is leaning towards ALKALOSIS, therefore
under the same column as PaCO2. Solving for goal #2, we
have RESPIRATORY.
• pH is NORMAL, therefore solving for goal #3, we have a
FULLY COMPENSATED ABG.

19. Practice Problem #3: pH=7.1 | PaCO2=40 | HCO3=18
• Remember the normal values.
• pH of 7.1 is ABNORMAL and ACIDOSIS, therefore, we place
pH under the ACIDOSIS column in the tic-tac-toe grid.
• PaCO2 of 40 is NORMAL, therefore, place it under the
NORMAL column.
• HCO3 of 18 is ABNORMAL and ACIDOSIS, so we place
HCO3 under the ACIDOSIS column.
• pH of 7.1 is ACIDOSIS, therefore, solving for goal #1, we have
ACIDOSIS.
• pH is under the same column as HCO3, therefore, solving for
goal #2, we have determined that it is METABOLIC.
• pH is ABNORMAL so as HCO3, but PaCO3 is under the
NORMAL column. Solving for goal #3, we can interpret it as
UNCOMPENSATED.

20. Acid-Base Balance and Imbalances
• Acidosis where in the blood is relatively too
acidic (low pH).There are two types of acidosis:
respiratory acidosis and metabolic acidosis.
• Alkalosis is a condition where in the blood is
relatively too basic (high pH), there are also two
types of alkalosis: respiratory alkalosis and
metabolic alkalosis.

21. • When acid-base imbalances occur, the body
activates its compensatory mechanisms (the
lungs and kidneys) to help normalize the blood
pH. The kidneys compensate for respiratory
acid-base imbalances while the respiratory
system compensates for metabolic acid-base
imbalances.

22. Respiratory Acidosis
• Respiratory acidosis occurs
causing
PaCO2 or respiratory acid builds up. The
,
causing a state of acidosis — a common
occurrence in emphysema. The kidneys activate
its compensatory process (albeit slow, often 24
hours or more) by increasing the excretion of
metabolic acids through urination, which
increases blood bicarbonate.

23. Types of Respiratory Acidosis
• Acute respiratory acidosis. This form of
respiratory acidosis occurs immediately. Left
untreated, symptoms will get progressively
worse. It’s a medical emergency and can
become life-threatening.
• Chronic respiratory acidosis. This form of
respiratory acidosis develops through time. It
doesn’t cause symptoms. Instead, the body
adapts to the increased acidity.

24. Risk Factors
• Hypoventilation.
• Chronic Obstructive Pulmonary Disease (COPD).
• Respiratory Conditions. (pneumothorax, pneumonia)
• Drug Intake. Overdose of an opiate or opioid, such
as morphine, tramadol, heroin, fentanyl, or
magnesium sulfate .

25. Signs and Symptoms
• Altered level of consciousness.
• Confusion.
• Disorientation.
• Coma.
• Tremors.
• Asterixis: An inability to maintain the posture of
part of the body.

26. Management of Respiratory Acidosis
• Medications. Bronchodilator medicines and
corticosteroids .
• Weight loss.
• Provide mechanical ventilation through O2 therapy.
• Manage hyperkalemia through the use of Kayexalate.
Kayexalate increases fecal potassium excretion
through the binding of potassium in the lumen of the
gastrointestinal tract.
• Maintain adequate hydration.

27. Respiratory Alkalosis
• Respiratory alkalosis can result from
hyperventilation since the lungs excrete too
much carbonic acid which increases pH.

28. Risk Factors
• Panic.
• Hyperthermia.
• Brainstem damage.
• Metabolic acidosis.
• Diabetic ketoacidosis (DKA).
• Pregnancy. Progesterone levels are increased
during pregnancy. Progesterone causes
stimulation of the respiratory center, which
can lead to respiratory alkalosis

29. Signs and Symptoms
• Numbness.
• Tingling sensation.
• Palpitations.
• Tetany.
• Convulsions.
• Signs and symptoms of hypokalemia and
hypocalcemia.

30. Management of Respiratory Alkalosis
• Breathe into a paper bag.
• Treat underlying condition:
 Medications. Administering an opioid pain reliever
or anti-anxiety medication to reduce
hyperventilation.
 Relaxation techniques.
 Safety.
 Lavage.
 Correction of hypokalemia and hypocalcemia.
 Oxygenation as indicated.

31. Metabolic Acidosis
• Metabolic acidosis is when there is a
decrease in bicarbonates and a buildup of
lactic acid occurs. This happens in
diarrhea, ketosis, and kidney disorders. It
has three main root causes: increased
acid production, loss of bicarbonate, and a
reduced ability of the kidneys to excrete
excess acids.

32. Risk Factors
• Diabetic Ketoacidosis (DKA).
• Chronic Renal Failure (CRF).
• Chronic Hypoxia.
• Obesity.
• Diarrhea.
• Dehydration.
• Aspirin Toxicity.

33. Signs and Symptoms
• Altered level of consciousness
• Confusion
• Disorientation
• Lack of appetite
• Coma
• Jaundice

34. Management of Metabolic Acidosis
• Sodium bicarbonate
• Treat the underlying condition.
• Hydration for diabetic ketoacidosis.
• Dialysis for chronic renal failure.
• Use of diuretics.
• Initiate safety measures.
• Kayexalate.

35. Metabolic Alkalosis
• Metabolic alkalosis occurs when
bicarbonate ion concentration increases,
causing an elevation in blood pH. This can
occur in excessive vomiting, dehydration,
or endocrine disorders

36. Risk Factors
• Vomiting.
• Sodium bicarbonate overdose.
• Hypokalemia.
• Nasogastric suction.

37. Signs and Symptoms
• Numbness
• Vomiting
• Diarrhea
• Swelling in the lower legs (peripheral edema)
• Fatigue
• Tingling sensation
• Agitation
• Disorientation
• Seizures
• Coma

38. Management of Metabolic Alkalosis
• Antiemetic.
• Ammonium chloride.
• Acetazolamide (Diamox).

39. ABG Interpretation Quiz
Measurement of arterial blood gas shows pH 7.0,
PaO2 90 mm Hg, PaCO2 23 mm Hg, and HCO3
12 mmol/L; other results are Na+ 126 mmol/L, K+
5 mmol/L, and Cl- 95 mmol/L. What is your
assessment?
A. Respiratory Acidosis, Uncompensated
B. Respiratory Acidosis, Partially Compensated
C. Metabolic Alkalosis, Uncompensated
D. Metabolic Acidosis, Partially, Compensated

40. • Measurement of arterial blood gas reveals pH
7.6, PaO2 120 mm Hg, PaCO2 31 mm Hg, and
HCO3 25 mmol/L. What does this mean?
• A. Respiratory Alkalosis, Uncompensated
• B. Respiratory Acidosis, Partially Compensated
• C. Metabolic Alkalosis, Uncompensated
• D. Metabolic Alkalosis, Partially Compensated

41. A 12- year- old boy was brought to the
Emergency respiratory arrest due to drowning.
Cardiac resuscitation what is the major
complication that might happen if treated after
drowning quickly?
A. Sepsis
B. Alkalosis
C. Acidosis
D. Hypothermia

42. • Gastric suction can cause :
A.Metabolic acidosis
B. Respiratory acidosis
C. Metabolic alkalosis
D. Respiratory alkalosis.

43. ABG reading was low PH ,HIGH PCO2 ,
NORMAL Hco3 what the interpretation ?
A. Compensated respiratory acidosis
B. Uncompensated respiratory acidosis
C. Metabolic acidosis
D. Metabolic alkalosis

44. The nurse assesses a client with an ileostomy
for possible development of which of the
following acid-base imbalances?
A.Respiratory acidosis
B.Metabolic acidosis
C. Metabolic alkalosis
D. Respiratory alkalosis

45. • The nurse is assigned to care for the
patient with Cushing syndrome on adrenal
corticoid hormones syndrome. Which of
the following condition should nurse
expect to patient ?
A. Respiratory alkalosis
B. Respiratory acidosis
C. Metabolic alkalosis
D. Metabolic acidosis

46. A nurse reviewed a chart of a 42 year-old
man whose ABG analysis report is shown PH
7.20 PCO2 35 HCO3 20. Which of the
following is the most likely interpretation of
the findings in the report?
A. Respiratory alkalosis
B. Metabolic acidosis
C. Respiratory acidosis
D. Metabolic acidosis

47. • A 20 year old woman, a case of panic
attacks, comes to the emergency
department. An arterial blood gas analysis
is done PH 7.53 , HCO3 22 and , PCO2 27
what is most likely?
A. Metabolic acidosis
B. Metabolic alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis