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Quizzes > Health & Medicine

ABG Practice Questions: NCLEX-Style Arterial Blood Gas Quiz

Quick, free ABG NCLEX questions to check your understanding. Instant results.

Editorial: Review CompletedCreated By: Sam StevensUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration showing arterial blood gas quiz with stethoscope pencil notepad graphs on dark blue background

This quiz helps you practice arterial blood gas (ABG) interpretation and tackle NCLEX-style questions. For extra review, try the abg interpretation quiz or build confidence with the rn respiratory practice quiz. You can also explore respiratory therapy practice questions to strengthen respiratory concepts ahead of test day.

What is the normal pH range for arterial blood gas?
7.30 to 7.50
7.45 to 7.55
7.35 to 7.45
7.25 to 7.35
The normal arterial blood pH range is tightly regulated between 7.35 and 7.45. Values below 7.35 indicate acidemia, while those above 7.45 indicate alkalemia. Maintaining this range is critical for enzyme function and cellular metabolism.
Which arterial blood gas component primarily reflects respiratory acid-base status?
PaO2
PaCO2
HCO3?
pH
PaCO2 reflects the partial pressure of carbon dioxide and is directly related to respiratory function. An increase in PaCO2 causes respiratory acidosis, while a decrease causes respiratory alkalosis. It is the key parameter for assessing ventilatory status.
Which parameter indicates the metabolic component in an ABG?
pH
HCO3?
PaO2
PaCO2
Bicarbonate (HCO3?) is regulated by the kidneys and represents the metabolic component of acid-base balance. Changes in HCO3? indicate metabolic acidosis or alkalosis. The kidneys adjust bicarbonate reabsorption or excretion for compensation.
What is the normal range for arterial PaO2?
80 to 100 mmHg
35 to 45 mmHg
4.5 to 5.5 mmol/L
20 to 30 mmHg
The normal arterial partial pressure of oxygen (PaO2) ranges from 80 to 100 mmHg. Values below this range suggest hypoxemia, while values above may occur with supplemental oxygen. PaO2 helps assess oxygenation status.
An ABG shows pH 7.25, PaCO2 55 mmHg, HCO3? 24 mEq/L. What is the primary acid-base disturbance?
Respiratory acidosis
Metabolic acidosis
Metabolic alkalosis
Respiratory alkalosis
A pH of 7.25 indicates acidemia. The elevated PaCO2 of 55 mmHg points to a respiratory origin for the acidosis. Bicarbonate is normal, so primary compensation has not occurred.
An ABG shows pH 7.50, PaCO2 30 mmHg, HCO3? 24 mEq/L. What is the acid-base disturbance?
Metabolic alkalosis
Respiratory alkalosis
Metabolic acidosis
Respiratory acidosis
A pH of 7.50 indicates alkalemia. The PaCO2 is low at 30 mmHg, consistent with respiratory alkalosis. Bicarbonate remains normal, indicating there has been no metabolic compensation.
An ABG shows pH 7.30, PaCO2 40 mmHg, HCO3? 18 mEq/L. What is the primary disturbance?
Respiratory alkalosis
Respiratory acidosis
Metabolic acidosis
Metabolic alkalosis
With a pH of 7.30 and normal PaCO2, the disturbance is metabolic. The reduced bicarbonate of 18 mEq/L signifies metabolic acidosis. Respiratory parameters are unchanged, indicating no primary respiratory disorder.
A patient's ABG shows pH 7.50, PaCO2 48 mmHg, HCO3? 33 mEq/L. What best describes this disturbance?
Respiratory acidosis
Metabolic acidosis
Metabolic alkalosis with respiratory compensation
Respiratory alkalosis
The pH is elevated, indicating alkalemia. The high bicarbonate shows a metabolic alkalosis. The PaCO2 is slightly elevated, reflecting respiratory compensation via hypoventilation.
An ABG reads pH 7.20, PaCO2 28 mmHg, HCO3? 12 mEq/L. What best characterizes this ABG?
Pure metabolic acidosis
Mixed metabolic acidosis and respiratory alkalosis
Metabolic alkalosis
Pure respiratory alkalosis
The low pH indicates acidemia. Both bicarbonate and PaCO2 are decreased - low HCO3? points to metabolic acidosis, low PaCO2 points to respiratory alkalosis. This pattern is characteristic of a mixed disorder.
An ABG shows pH 7.52, PaCO2 50 mmHg, HCO3? 40 mEq/L. What is the most likely disorder?
Combined metabolic alkalosis and respiratory acidosis
Acute respiratory acidosis
Compensated metabolic alkalosis
Mixed metabolic alkalosis and respiratory alkalosis
Alkalemia with elevated bicarbonate indicates metabolic alkalosis. The high PaCO2 indicates a superimposed respiratory acidosis. This combined pattern is seen in mixed disorders.
An ABG shows pH 7.32, PaCO2 47 mmHg, HCO3? 24 mEq/L. What is the primary disturbance?
Acute respiratory acidosis
Chronic respiratory acidosis
Metabolic alkalosis
Metabolic acidosis
The pH is low, indicating acidemia, and the PaCO2 is elevated, indicating respiratory origin. Because bicarbonate is normal, renal compensation has not occurred, signifying an acute process.
A chronic COPD patient's ABG returns pH 7.38, PaCO2 52 mmHg, HCO3? 30 mEq/L. How would you interpret these values?
Normal ABG
Compensated respiratory acidosis
Compensated metabolic alkalosis
Uncompensated respiratory acidosis
The pH is near normal despite an elevated PaCO2, which indicates chronic retention of CO2. The increased bicarbonate shows renal compensation. This pattern is typical of compensated respiratory acidosis in chronic COPD.
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Study Outcomes

  1. Interpret ABG Values -

    Learn to accurately read and interpret arterial blood gas results, including pH, PaCO2, and HCO3− levels.

  2. Differentiate Acid-Base Imbalances -

    Analyze and distinguish between respiratory and metabolic acidosis and alkalosis based on ABG parameters.

  3. Evaluate Oxygenation Status -

    Assess oxygenation by interpreting PaO2 and SaO2 values to determine hypoxemia and adequacy of gas exchange.

  4. Apply Compensation Mechanisms -

    Recognize and apply physiological compensation mechanisms to correct primary acid-base disturbances.

  5. Tackle NCLEX-Style ABG Questions -

    Build confidence in answering ABG NCLEX questions by practicing a variety of scenario-based test items.

Cheat Sheet

  1. Know Your Normal ABG Values -

    Start by memorizing the standard ABG norms - pH 7.35 - 7.45, PaCO2 35 - 45 mmHg, HCO3− 22 - 26 mEq/L, PaO2 80 - 100 mmHg, and SaO2 95% - 100%. A handy trick is "7:35 to 7:45, 35 - 45 rocks the hive" which anchors pH and PaCO2. Mastering these baselines is critical for nailing any abgs quiz or abg test questions.

  2. Henderson-Hasselbalch Equation Essentials -

    The Henderson-Hasselbalch equation (pH = pKa + log [HCO3−]/(0.03 × PaCO2)) explains the interplay between bicarbonate and carbon dioxide (American Thoracic Society). Use this formula to predict pH shifts when tackling abg nclex questions and solidify your calculations. It's your go-to tool for precise acid - base disturbance analysis on the abgs quiz.

  3. Apply the ROME Mnemonic -

    Use ROME (Respiratory Opposite, Metabolic Equal) to quickly classify imbalances: in respiratory disorders pH and PaCO2 change in opposite directions, while in metabolic issues pH and HCO3− move together. This mnemonic, endorsed in critical care curricula, streamlines interpretation under exam time pressure. Practicing ROME on nclex questions on abgs boosts both speed and accuracy.

  4. Differentiate Compensation Patterns -

    Recognize partial versus complete compensation: in acute respiratory acidosis HCO3− rises ~1 mEq/L per 10 mmHg CO2 increase, while chronic cases see ~4 mEq/L (UpToDate guidelines). Likewise, metabolic acidosis drives CO2 down ~1.2 mmHg per 1 mEq/L HCO3− drop. Spotting these patterns is a must for any abg nclex questions or abg test questions you'll face.

  5. Assess Oxygenation and A - a Gradient -

    Beyond pH and buffers, check PaO2 and calculate the A - a gradient (A - a = [150 - PaCO2/0.8] - PaO2) to evaluate diffusion defects (Pulmonary Physiology textbook). A normal gradient is 5 - 15 mmHg; higher values signal V/Q mismatch or shunt. Integrating this step rounds out your ABG interpretation for the abgs quiz and clinical readiness.

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