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Quizzes > Health & Medicine

ABG Interpretation Quiz: Practice Acid-Base Analysis

Quick, free arterial blood gas quiz with instant results.

Editorial: Review CompletedCreated By: Aaa AaaUpdated Aug 24, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art stethoscope lungs test tubes on golden yellow backdrop ABG quiz challenge acid base skills, instant feedback

This ABG interpretation quiz helps you practice reading blood gases, spot acidosis and alkalosis patterns, and get instant feedback. After you finish, build speed with abg practice questions, review respiratory cases with a med surg respiratory quiz, or strengthen the chemistry behind it using acid base buffer problems.

What is the normal arterial pH range in adults?
7.20-7.30
7.45-7.55
7.25-7.35
7.35-7.45
The normal arterial pH is tightly regulated between 7.35 and 7.45 by respiratory and renal mechanisms. Values below or above this range indicate acidosis or alkalosis respectively. Maintaining pH within this range is essential for optimal enzyme function and cellular activity.
What is the normal arterial PaCO2 range in mm Hg?
35-45 mm Hg
45-55 mm Hg
25-35 mm Hg
20-30 mm Hg
Arterial PaCO2 reflects respiratory ventilation and normally ranges from 35 to 45 mm Hg. Values above indicate hypoventilation, while values below indicate hyperventilation. This range is used clinically to assess respiratory acid-base status.
What is the normal arterial bicarbonate (HCO3-) concentration?
14-18 mEq/L
22-26 mEq/L
26-30 mEq/L
18-22 mEq/L
Normal serum bicarbonate is maintained by renal function and buffering systems at approximately 22 to 26 mEq/L. Deviations reflect metabolic acid-base disturbances. This value helps distinguish metabolic from respiratory disorders.
A measured arterial pH of 7.25 indicates which primary disturbance?
Normal acid-base status
Acidosis
Mixed acid-base disorder
Alkalosis
A pH below 7.35 indicates acidemia, meaning the blood is too acidic. Acidosis may be respiratory (elevated PaCO2) or metabolic (low HCO3-). Further ABG values are needed to subtype the disturbance.
An increased PaCO2 on an ABG most directly causes which disturbance?
Respiratory alkalosis
Respiratory acidosis
Metabolic alkalosis
Metabolic acidosis
Elevated PaCO2 reflects hypoventilation leading to CO2 retention and respiratory acidosis. The pH falls due to increased carbonic acid. Compensation occurs over hours to days via renal retention of bicarbonate.
An arterial blood gas shows pH 7.30, PaCO2 50 mm Hg, HCO3- 24 mEq/L. What is the primary acid-base disturbance?
Metabolic alkalosis
Respiratory acidosis
Metabolic acidosis
Respiratory alkalosis
The low pH and elevated PaCO2 with normal bicarbonate indicate primary respiratory acidosis. The kidneys have not yet compensated.
An ABG reveals pH 7.50, PaCO2 30 mm Hg, HCO3- 22 mEq/L. The most likely disturbance is:
Metabolic alkalosis
Respiratory alkalosis
Respiratory acidosis
Metabolic acidosis
A high pH with low PaCO2 indicates primary respiratory alkalosis. The kidneys may reduce bicarbonate over time to compensate.
ABG: pH 7.25, PaCO2 30 mm Hg, HCO3- 14 mEq/L. What is the acid-base disorder?
Respiratory acidosis with compensation
Respiratory alkalosis
Metabolic acidosis with respiratory compensation
Metabolic alkalosis
Low pH and low bicarbonate indicate metabolic acidosis. The PaCO2 is appropriately reduced (respiratory compensation).
Calculate the anion gap for Na+ 140, Cl- 100, HCO3- 24 (mEq/L).
10 mEq/L
8 mEq/L
16 mEq/L
20 mEq/L
Anion gap = Na+ - (Cl- + HCO3-) = 140 - (100 + 24) = 16 mEq/L. Normal is ~8 - 12 mEq/L. Elevated gap suggests unmeasured anions.
Which formula represents Winter's formula for expected PaCO2 in metabolic acidosis?
2.0 × HCO3-
0.7 × HCO3- + 20
Equal to HCO3-
1.5 × HCO3- + 8 ± 2
Winter's formula predicts respiratory compensation in metabolic acidosis: expected PaCO2 = 1.5 × [HCO3-] + 8 ± 2 mm Hg. Deviation suggests mixed disorders.
A patient has pH 7.40, PaCO2 50 mm Hg, HCO3- 32 mEq/L. Which best describes this ABG?
Mixed respiratory acidosis and metabolic alkalosis
Compensated respiratory acidosis
Normal acid-base status
Compensated metabolic alkalosis
A normal pH with both elevated PaCO2 and elevated HCO3- indicates two primary processes in opposite directions: respiratory acidosis plus metabolic alkalosis.
Calculate the delta ratio for Na+ 140, Cl- 100, HCO3- 12 mEq/L (normal AG = 12 mEq/L).
1.3, suggesting a mixed anion-gap and non-gap acidosis
1.0, suggesting pure gap acidosis
0.6, suggesting pure non-gap acidosis
2.5, suggesting pure gap acidosis
AG = 140 - (100+12) = 28; ?AG = 28 - 12 = 16; ?HCO3- = 24 - 12 = 12; delta ratio = 16/12 ?1.3, indicating a mixed anion-gap and non-gap metabolic acidosis.
ABG: pH 7.30, PaCO2 20 mm Hg, HCO3- 10 mEq/L. What does this indicate?
Pure metabolic acidosis
Mixed metabolic acidosis and respiratory alkalosis
Mixed metabolic alkalosis and respiratory acidosis
Pure respiratory alkalosis
Low pH and low HCO3- indicate metabolic acidosis, but PaCO2 is lower than expected compensation, so there is a concurrent respiratory alkalosis.
Which formula predicts respiratory compensation in metabolic alkalosis?
Expected PaCO2 = 1.5 × HCO3- + 8
Expected PaCO2 = HCO3- + 40
Expected PaCO2 = 2 × HCO3-
Expected PaCO2 = 0.7 × HCO3- + 20
In metabolic alkalosis, the expected respiratory compensation is PaCO2 = 0.7 × [HCO3-] + 20 mm Hg. This helps confirm pure metabolic alkalosis.
An ABG shows pH 7.45, PaCO2 55 mm Hg, HCO3- 36 mEq/L. What is the most accurate interpretation?
Mixed respiratory acidosis and metabolic alkalosis
Normal acid-base status
Compensated respiratory acidosis
Compensated metabolic alkalosis
A near-normal-high pH with elevated PaCO2 and elevated HCO3- signals two primary processes: respiratory acidosis and metabolic alkalosis. The pH balance masks the mixed disorder.
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Study Outcomes

  1. Analyze ABG Components -

    Break down pH, PaCO₂, and HCO₃❻ values to determine each parameter's role in acid-base balance.

  2. Interpret Acid-Base Imbalances -

    Use ABG interpretation techniques to identify respiratory and metabolic acidosis or alkalosis patterns.

  3. Apply Compensation Mechanisms -

    Assess how respiratory and renal systems respond to primary imbalances to restore homeostasis.

  4. Differentiate Mixed Disorders -

    Distinguish when concurrent acid-base disturbances are present and evaluate their combined effects.

  5. Evaluate Clinical Scenarios -

    Use real-world case questions to test your speed and accuracy in diagnosing acid-base disorders with instant feedback.

Cheat Sheet

  1. Know Normal ABG Ranges -

    Familiarize yourself with standard pH (7.35 - 7.45), PaCO2 (35 - 45 mmHg) and HCO3 - (22 - 26 mEq/L) ranges before tackling any abg interpretation quiz. A handy mnemonic is "ROME" (Respiratory Opposite, Metabolic Equal) to recall primary acid-base disturbances quickly. Quizzes from institutions like the American Thoracic Society often emphasize these values as the first step.

  2. Apply the Henderson - Hasselbalch Equation -

    Use pH = pKa + log ([HCO3 - ]/(0.03×PaCO2)) to understand how bicarbonate and CO2 drive pH changes and predict shifts in abg interpretation questions. This formula, widely taught in medical school curricula, helps you see exactly how manipulating HCO3 - or PaCO2 affects hydrogen ion concentration. Having this mathematical insight boosts confidence on quiz day.

  3. Differentiate Primary Disorders -

    Check the direction of pH versus PaCO2 to classify the disorder: if they move oppositely, suspect respiratory; if they move together, think metabolic. This simple pattern recognition, validated by research published in the New England Journal of Medicine, streamlines your decision tree in any abg interpretation quiz with answers. Practice with clinical vignettes to lock this in.

  4. Calculate Expected Compensation -

    Use Winter's formula (PaCO2expected = 1.5×HCO3 - + 8 ±2) for metabolic acidosis or the rule of thumb for metabolic alkalosis (PaCO2increase ≈ 0.6×ΔHCO3 - ) to evaluate whether compensation is appropriate. The Mayo Clinic highlights that checking expected vs. actual PaCO2 reveals mixed disorders and refines your analysis. Knowing these formulas inside out makes abg quiz with answers a lot less scary.

  5. Spot Mixed Acid - Base Disorders -

    Calculate the anion gap (AG = Na+ - (Cl - + HCO3 - )) and adjust for albumin to uncover hidden metabolic disturbances; a normal AG is roughly 8 - 12 mEq/L. Compare measured values with predicted compensations - discrepancies often indicate a mixed disorder, a tip emphasized in UpToDate's acid - base chapter. This strategy will elevate your performance on advanced abg interpretation quiz scenarios.

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