If you are a nursing student trying to master arterial blood gas interpretation, you are in the right place. ABG practice questions are one of the most effective ways to build confidence before clinicals, NCLEX, or your next exam. In this post, you will work through 10 ABG practice questions nursing students encounter most often, Read More
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If you are a nursing student trying to master arterial blood gas interpretation, you are in the right place. ABG practice questions are one of the most effective ways to build confidence before clinicals, NCLEX, or your next exam.
In this post, you will work through 10 ABG practice questions nursing students encounter most often, complete with step-by-step solutions so you can see exactly how to arrive at the correct answer, not just memorize it.
| What you will find in this post:
– A quick ABG interpretation refresher (the 4-step method) – 10 ABG practice questions with detailed answers – Nursing tips for each question
|
Before jumping into ABG practice questions for nursing, let’s quickly revisit the framework every nurse uses:
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| Parameter | Normal Range | Acidosis | Alkalosis |
| pH | 7.35 – 7.45 | < 7.35 | > 7.45 |
| PaCO2 | 35 – 45 mmHg | > 45 (respiratory) | < 35 (respiratory) |
| HCO3 | 22 – 26 mEq/L | < 22 (metabolic) | > 26 (metabolic) |
| PaO2 | 80 – 100 mmHg | — | — |
| SpO2 | 95 – 100% | — | — |
Work through each question before reading the answer. These reflect common scenarios tested in nursing school and on the NCLEX.
| Question 1: Post-operative patient, day 1
pH: 7.28 | PaCO2: 55 mmHg | HCO3: 24 mEq/L | PaO2: 82 mmHg What is the acid-base disturbance? |
| Answer: Respiratory Acidosis — Uncompensated
Step 1: pH 7.28 = acidosis Step 2: PaCO2 55 = elevated → respiratory cause confirmed Step 3: HCO3 24 = normal → no metabolic compensation yet Step 4: Conclusion: Uncompensated respiratory acidosis |
| Nursing Tip: Common post-op cause: residual anesthesia, pain splinting, or opioid sedation reducing respiratory drive. Assess airway and encourage deep breathing. |
| Question 2: Anxious patient hyperventilating in triage
pH: 7.52 | PaCO2: 28 mmHg | HCO3: 23 mEq/L | PaO2: 98 mmHg What is the acid-base disturbance? |
| Answer: Respiratory Alkalosis — Uncompensated
Step 1: pH 7.52 = alkalosis Step 2: PaCO2 28 = low → CO2 is being blown off → respiratory cause Step 3: HCO3 23 = normal → kidneys have not compensated Step 4: Conclusion: Uncompensated respiratory alkalosis |
| Nursing Tip: Classic presentation: panic attack, pain, or early sepsis. Calm the patient, treat the underlying cause. Do not simply rebreathe into a paper bag without physician order. |
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| Question 3: Patient with prolonged vomiting
pH: 7.49 | PaCO2: 44 mmHg | HCO3: 30 mEq/L | PaO2: 88 mmHg What is the acid-base disturbance? |
| Answer: Metabolic Alkalosis — Uncompensated
Step 1: pH 7.49 = alkalosis Step 2: PaCO2 44 = normal → respiratory system not the cause Step 3: HCO3 30 = elevated → metabolic cause confirmed Step 4: Conclusion: Uncompensated metabolic alkalosis |
| Nursing Tip: Loss of gastric acid (HCl) through vomiting depletes chloride and hydrogen ions, raising HCO3. Expect hypokalemia alongside. Monitor electrolytes. |
| Question 4: Diabetic patient with fruity breath
pH: 7.22 | PaCO2: 30 mmHg | HCO3: 12 mEq/L | PaO2: 90 mmHg What is the acid-base disturbance? |
| Answer: Metabolic Acidosis — Partially Compensated
Step 1: pH 7.22 = acidosis Step 2: HCO3 12 = low → metabolic cause confirmed Step 3: PaCO2 30 = low → lungs compensating by blowing off CO2 Step 4: pH still acidotic → compensation is partial, not complete Step 5: Conclusion: Partially compensated metabolic acidosis (likely DKA) |
| Nursing Tip: Kussmaul respirations are the body’s attempt to blow off CO2 and raise pH. This is a medical emergency — start insulin, fluids, and electrolyte replacement per protocol. |
| Question 5: COPD patient with worsening shortness of breath
pH: 7.33 | PaCO2: 60 mmHg | HCO3: 30 mEq/L | PaO2: 58 mmHg What is the acid-base disturbance? |
| Answer: Respiratory Acidosis — Partially Compensated
Step 1: pH 7.33 = acidosis Step 2: PaCO2 60 = elevated → respiratory cause Step 3: HCO3 30 = elevated → kidneys retaining bicarb to buffer Step 4: pH still below 7.35 → partial compensation only Step 5: Conclusion: Partially compensated respiratory acidosis |
| Nursing Tip: In COPD, the kidneys chronically retain HCO3 to compensate for CO2 retention. A ‘normal’ ABG for a COPD patient may look abnormal. Always compare to the patient’s baseline. |
| Question 6: Patient on long-term diuretics
pH: 7.46 | PaCO2: 48 mmHg | HCO3: 32 mEq/L | PaO2: 85 mmHg What is the acid-base disturbance? |
| Answer: Metabolic Alkalosis — Partially Compensated
Step 1: pH 7.46 = alkalosis Step 2: HCO3 32 = elevated → metabolic cause Step 3: PaCO2 48 = elevated → lungs retaining CO2 to compensate Step 4: pH near normal but still > 7.45 → partial compensation Step 5: Conclusion: Partially compensated metabolic alkalosis |
| Nursing Tip: Loop diuretics cause potassium and chloride loss, which leads to metabolic alkalosis. Check potassium levels and replace electrolytes as ordered. |
| Question 7: Salicylate overdose patient
pH: 7.42 | PaCO2: 28 mmHg | HCO3: 18 mEq/L | PaO2: 95 mmHg What is the acid-base disturbance? |
| Answer: Mixed Disturbance: Respiratory Alkalosis + Metabolic Acidosis
Step 1: pH 7.42 = appears normal Step 2: PaCO2 28 = low → respiratory alkalosis component Step 3: HCO3 18 = low → metabolic acidosis component Step 4: Both systems distorted in OPPOSITE directions — mixed disturbance Step 5: Conclusion: Mixed respiratory alkalosis and metabolic acidosis (classic salicylate toxicity) |
| Nursing Tip: When pH is normal but both PaCO2 and HCO3 are abnormal, always suspect a mixed disturbance. Salicylate toxicity is a classic NCLEX scenario for this pattern. |
| Question 8: Mechanically ventilated patient, rate set too high
pH: 7.54 | PaCO2: 26 mmHg | HCO3: 25 mEq/L | PaO2: 100 mmHg What is the acid-base disturbance? |
| Answer: Respiratory Alkalosis — Uncompensated
Step 1: pH 7.54 = alkalosis Step 2: PaCO2 26 = low → CO2 blown off by over-ventilation Step 3: HCO3 25 = normal → metabolic system not yet compensating Step 4: Conclusion: Uncompensated respiratory alkalosis (iatrogenic cause) |
| Nursing Tip: Always verify vent settings when you see respiratory alkalosis in an intubated patient. Notify the provider immediately — over-ventilation can cause cerebral vasoconstriction and seizures. |
| Question 9: Patient with acute kidney injury
pH: 7.29 | PaCO2: 32 mmHg | HCO3: 14 mEq/L | PaO2: 84 mmHg What is the acid-base disturbance? |
| Answer: Metabolic Acidosis — Partially Compensated
Step 1: pH 7.29 = acidosis Step 2: HCO3 14 = low → metabolic acidosis Step 3: PaCO2 32 = low → respiratory compensation occurring Step 4: pH still < 7.35 → partial compensation Step 5: Conclusion: Partially compensated metabolic acidosis (AKI/uremia) |
| Nursing Tip: Failing kidneys cannot excrete hydrogen ions or regenerate bicarbonate. Monitor for peaked T-waves on ECG — hyperkalemia often accompanies metabolic acidosis in AKI. |
| Question 10: Elderly patient with pneumonia, 3 days in
pH: 7.38 | PaCO2: 50 mmHg | HCO3: 28 mEq/L | PaO2: 72 mmHg What is the acid-base disturbance? |
| Answer: Respiratory Acidosis — Fully Compensated
Step 1: pH 7.38 = normal (within range) Step 2: PaCO2 50 = elevated → respiratory acidosis Step 3: HCO3 28 = elevated → metabolic compensation Step 4: pH back to normal → full compensation achieved Step 5: Conclusion: Fully compensated respiratory acidosis |
| Nursing Tip: A normal pH does NOT mean no problem. The underlying respiratory acidosis is still present — the kidneys have simply compensated. Address the pneumonia and monitor oxygenation; PaO2 of 72 warrants supplemental oxygen. |
Use this pattern recognition table when working through ABG practice questions in nursing school or clinical rotations:
| Condition | pH | PaCO2 | HCO3 |
| Respiratory Acidosis | Low | High | Normal/High |
| Respiratory Alkalosis | High | Low | Normal/Low |
| Metabolic Acidosis | Low | Normal/Low | Low |
| Metabolic Alkalosis | High | Normal/High | High |
Download free flashcard questions Nursing_Flashcards_Printable
The NCLEX does not specify an exact number, but ABG interpretation is a high-yield topic. You can expect 2 to 5 questions directly testing ABG analysis, with additional questions where ABG knowledge supports clinical reasoning.
Use the ROME mnemonic: Respiratory Opposite, Metabolic Equal. In respiratory disorders, the pH and PaCO2 move in opposite directions. In metabolic disorders, the pH and HCO3 move in the same direction.
Yes. Normal values are the foundation of every ABG question. Memorize: pH 7.35-7.45, PaCO2 35-45, HCO3 22-26, PaO2 80-100. Everything else is interpretation built on these anchors.
If the pH has returned to normal (7.35-7.45), compensation is full. If the compensating system has moved but pH is still outside normal range, compensation is partial.
| Want More ABG Practice?
These 10 questions are just the beginning. Our full ABG practice pack includes 50 questions with answers, covering simple, partially compensated, fully compensated, and mixed disturbances — plus a printable reference card. >> Order for Nursing Assignment << |
Download free ABG_Practice_Questions_Ebook
ABG interpretation is a skill that improves with repetition. The 10 ABG practice questions above cover the most commonly tested scenarios in nursing school and on the NCLEX from simple uncompensated disorders to mixed disturbances.
Bookmark this page and work through the questions regularly. When you are ready to level up, download the full 50-question pack and put your interpretation skills to the real test.
Evan John