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Quizzes > Health & Medicine

ABG Interpretation Quiz: Practice Reading Arterial Blood Gases

Quick, free ABG practice questions with instant results and explanations.

Editorial: Review CompletedCreated By: Avinash GuravUpdated Aug 28, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for ABG practice questions quiz on a teal background

This ABG interpretation quiz helps you practice reading arterial blood gases and spot acid-base patterns quickly. Work through pH, PaCO2, HCO3-, and oxygenation with instant results and brief explanations to build confidence for class or clinicals. For more practice, explore pathophysiology practice questions, the emergency medicine quiz, or the critical care nursing quiz.

Given pH 7.28, PaCO2 58 mm Hg, HCO3- 26 mEq/L, which primary disorder is present?
Metabolic alkalosis
Acute respiratory acidosis (Correct. Explanation: Low pH with elevated PaCO2 and near-normal HCO3- indicates primary respiratory acidosis without significant renal compensation)
Metabolic acidosis with respiratory compensation
Chronic respiratory acidosis
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An ABG shows pH 7.52, PaCO2 30 mm Hg, HCO3- 24 mEq/L in an anxious patient. What is the primary disturbance?
Metabolic alkalosis
Respiratory acidosis
Respiratory alkalosis (Correct. Explanation: High pH with low PaCO2 and normal HCO3- indicates primary respiratory alkalosis)
Metabolic acidosis
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Identify the primary disorder: pH 7.60, PaCO2 38 mm Hg, HCO3- 36 mEq/L.
Metabolic alkalosis (Correct. Explanation: Elevated pH with high HCO3- and near-normal PaCO2 indicates metabolic alkalosis)
Combined respiratory alkalosis and metabolic acidosis
Acute respiratory acidosis
Respiratory alkalosis
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A patient with profuse vomiting has pH 7.55, PaCO2 46 mm Hg, HCO3- 38 mEq/L. This pattern indicates which condition?
Metabolic alkalosis with appropriate respiratory compensation (Correct. Explanation: Elevated HCO3- from H+ loss; PaCO2 is elevated as compensatory hypoventilation)
Mixed metabolic acidosis and respiratory acidosis
Primary respiratory alkalosis
Metabolic acidosis
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Which scenario indicates an increased anion gap metabolic acidosis?
Lactic acidosis from shock (Correct. Explanation: Lactate accumulation raises the anion gap)
Diarrhea with HCO3- loss
Vomiting with H+ loss
Renal tubular acidosis type 2
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Calculate the anion gap: Na+ 140, Cl- 100, HCO3- 18 mEq/L (no potassium used).
22 mEq/L (Correct. Explanation: AG = 140 - (100 + 18) = 22 mEq/L)
12 mEq/L
28 mEq/L
18 mEq/L (Correct. Explanation: AG = Na - (Cl + HCO3) = 140 - (100 + 18) = 22; Wait-correct is 22 mEq/L)
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Winter's formula estimates expected PaCO2 in metabolic acidosis. Which is the correct formula?
Expected PaCO2 = 1.5 x HCO3- + 8 +/- 2 (Correct. Explanation: Winter's formula predicts respiratory compensation in metabolic acidosis)
Expected PaCO2 = HCO3- + 15 +/- 3
Expected PaCO2 = 0.7 x HCO3- + 21 +/- 2
Expected PaCO2 = 0.7 x HCO3- + 20 +/- 5
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A COPD patient has pH 7.37, PaCO2 60 mm Hg, HCO3- 34 mEq/L. What best describes the acid-base status?
Metabolic alkalosis
Acute respiratory acidosis
Mixed metabolic acidosis and respiratory alkalosis
Chronic respiratory acidosis with metabolic compensation (Correct. Explanation: Near-normal pH with elevated PaCO2 and elevated HCO3- indicates chronic compensation)
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In diabetic ketoacidosis: pH 7.18, HCO3- 10 mEq/L. Expected PaCO2 by Winter's formula is approximately which value?
12 mm Hg
23 mm Hg (Correct. Explanation: 1.5 x 10 + 8 = 23; +/-2 gives a range 21-25 mm Hg)
30 mm Hg
38 mm Hg
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In acute respiratory acidosis, how much does HCO3- increase per 10 mm Hg rise in PaCO2?
3 mEq/L
0.2 mEq/L
4 mEq/L
1 mEq/L (Correct. Explanation: Acute renal buffering increases HCO3- ~1 mEq/L per 10 mm Hg PaCO2 rise)
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In chronic respiratory acidosis, the expected HCO3- change per 10 mm Hg rise in PaCO2 is approximately what?
6 mEq/L
0.5 mEq/L
1 mEq/L
3.5 to 4 mEq/L (Correct. Explanation: Renal compensation increases HCO3- by ~3.5-4 mEq/L per chronic 10 mm Hg PaCO2 rise)
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Metabolic alkalosis expected respiratory compensation can be estimated by which relation?
PaCO2 increases by 0.7 mm Hg per 1 mEq/L fall in HCO3-
PaCO2 increases by 0.7 mm Hg per 1 mEq/L rise in HCO3- (Correct. Explanation: Expected PaCO2 = 0.7 x (HCO3- - 24) + 40 +/- 2)
PaCO2 remains unchanged
PaCO2 increases by 1 mm Hg per 1 mEq/L rise in HCO3-
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Which ABG pattern suggests a mixed metabolic acidosis and respiratory alkalosis?
pH 7.40, PaCO2 40, HCO3- 24
pH 7.30, PaCO2 20, HCO3- 10 (Correct. Explanation: Both PaCO2 and HCO3- are low with acidemia; low PaCO2 is lower than expected by Winter's formula)
pH 7.50, PaCO2 30, HCO3- 22
pH 7.48, PaCO2 52, HCO3- 38
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In chronic respiratory alkalosis, expected HCO3- change per 10 mm Hg fall in PaCO2 is approximately:
Increase by 3-4 mEq/L
Decrease by 4-5 mEq/L (Correct. Explanation: Chronic renal compensation lowers HCO3- ~4-5 mEq/L per 10 mm Hg PaCO2 fall)
No change
Decrease by 1-2 mEq/L
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A 65-year-old with severe sepsis: pH 7.32, PaCO2 28, HCO3- 14. Using Winter's formula, is the respiratory compensation appropriate?
No, there is additional respiratory alkalosis
Yes, expected PaCO2 ~29-31 mm Hg (Correct. Explanation: 1.5 x 14 + 8 = 29; measured 28 is appropriate)
Cannot assess without anion gap
No, there is additional respiratory acidosis
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For alveolar-arterial (A-a) gradient assessment, which set of values is required?
SaO2, Hb, lactate
FiO2, PaO2, PaCO2, barometric pressure (Correct. Explanation: A-a gradient uses alveolar gas equation requiring FiO2, PaCO2, PB, and PaO2)
PaCO2, HCO3-, base excess
Blood glucose, creatinine, Na+
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Delta gap analysis: Na 140, Cl 100, HCO3 10. Baseline HCO3 assumed 24. What is delta-delta (delta AG minus delta HCO3)?
0 indicating pure high-gap acidosis
-6 indicating additional metabolic acidosis
+8 indicating additional metabolic alkalosis (Correct. Explanation: AG = 30; delta AG = 30-12=18; delta HCO3 = 24-10=14; delta-delta = 18-14=+4 actually; Correct value +4 indicating mild concurrent metabolic alkalosis)
+4 indicating additional metabolic alkalosis (Correct. Explanation: AG 140-(100+10)=30; delta AG 18; delta HCO3 14; delta-delta +4 suggests concurrent metabolic alkalosis)
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Which combination suggests a mixed respiratory acidosis and metabolic alkalosis?
pH 7.28, PaCO2 20, HCO3- 9
pH 7.42, PaCO2 60, HCO3- 38 (Correct. Explanation: Elevated PaCO2 with elevated HCO3- and normal or slightly high pH indicates opposing disorders)
pH 7.36, PaCO2 40, HCO3- 24
pH 7.50, PaCO2 30, HCO3- 24
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Determine if mixed disorder exists: pH 7.22, HCO3- 12, PaCO2 15.
Simple respiratory alkalosis
Metabolic acidosis with respiratory acidosis
Metabolic acidosis with additional respiratory alkalosis (Correct. Explanation: Winter's expected PaCO2 ~26; measured 15 indicates excessive hyperventilation)
Simple metabolic acidosis with appropriate compensation
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Which ABG indicates a mixed metabolic alkalosis and respiratory alkalosis?
pH 7.55, PaCO2 20, HCO3- 17 (Correct. Explanation: Both PaCO2 and HCO3- are low, yet pH is alkalemic, suggesting dual alkalosis)
pH 7.25, PaCO2 25, HCO3- 10
pH 7.40, PaCO2 40, HCO3- 24
pH 7.30, PaCO2 50, HCO3- 24
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Study Outcomes

  1. Analyze ABG Components -

    Break down key parameters such as pH, PaCO₂, and HCO₃❻ using targeted abg practice questions to understand their physiological significance.

  2. Interpret Acid-Base Imbalances -

    Use arterial blood gases practice questions to identify and classify respiratory versus metabolic acidosis and alkalosis.

  3. Differentiate Compensation Mechanisms -

    Apply concepts of renal and respiratory compensation when working through practice abgs questions to predict patient responses.

  4. Evaluate Clinical Scenarios -

    Leverage real-world arterial blood gas practice questions to sharpen critical thinking and diagnostic reasoning skills.

  5. Apply Systematic ABG Analysis -

    Develop a step-by-step approach to abg interpretation practice, ensuring consistent and accurate evaluations under pressure.

  6. Enhance NCLEX Readiness -

    Reinforce test-taking strategies and confidence by practicing with focused abg practice questions aligned to exam-style formats.

Cheat Sheet

  1. Normal ABG reference ranges & ROME mnemonic -

    Familiarize yourself with standard arterial blood gas values (pH 7.35 - 7.45, PaCO2 35 - 45 mmHg, HCO3− 22 - 26 mEq/L) before diving into abg practice questions. Use the ROME mnemonic ("Respiratory → Opposite, Metabolic → Equal") to quickly recall that pH and PaCO2 move in opposite directions in respiratory disorders and in the same direction in metabolic ones.

  2. Stepwise ABG interpretation approach -

    Adopt a structured method: first assess pH (acidosis vs. alkalosis), then determine if the primary disturbance is respiratory (PaCO2) or metabolic (HCO3−), and finally evaluate compensation. This systematic analysis is essential for success in arterial blood gas practice questions and abg interpretation practice.

  3. Henderson - Hasselbalch equation & pH regulation -

    Remember the Henderson - Hasselbalch formula (pH = 6.1 + log([HCO3−]/(0.03×PaCO2))), which underpins the chemical relationship between bicarbonate and carbon dioxide in buffers. Understanding this equation enhances your ability to predict pH changes during acid - base imbalances and sharpen your metabolic vs. respiratory distinctions in abg interpretation practice.

  4. Compensation rules & Winter's formula -

    Learn expected compensation: for metabolic acidosis use Winter's formula (Expected PaCO2 = 1.5×HCO3− + 8 ±2) to detect mixed disorders when actual PaCO2 deviates. Similar equations exist for metabolic alkalosis and respiratory compensations, helping you flag complex imbalances in practice abgs questions confidently.

  5. Clinical correlations & key scenarios -

    Associate ABG patterns with common clinical conditions: COPD exacerbations yield respiratory acidosis, DKA causes metabolic acidosis, and persistent vomiting produces metabolic alkalosis. Practice with real-world arterial blood gases practice questions to strengthen your diagnostic speed and accuracy ahead of exams.

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