NUR 155 Acid Base Imbalances Study
Guide | Galen College of Nursing
SECTION I: Acid-Base Fundamentals & ABG Interpretation
Question 1
A patient's arterial blood gas (ABG) results show: pH 7.31, PaCO₂ 50 mmHg,
HCO₃⁻ 24 mEq/L. The nurse interprets these results as:
A) Metabolic acidosis
B) Metabolic alkalosis
C) Respiratory acidosis
D) Respiratory alkalosis
Correct Answer: C) Respiratory acidosis
Rationale: Respiratory acidosis is characterized by a low pH (< 7.35) and an
elevated PaCO₂ (> 45 mmHg). The HCO₃⁻ is normal (22–26 mEq/L), indicating no
metabolic compensation. This patient's pH of 7.31 (acidosis) and PaCO₂ of 50
mmHg (elevated) indicate respiratory acidosis, likely from hypoventilation.
Metabolic acidosis (A) would show a low pH and low HCO₃⁻. Metabolic alkalosis
(B) would show a high pH and high HCO₃⁻. Respiratory alkalosis (D) would show
a high pH and low PaCO₂.
Question 2
Which acid-base imbalance is most commonly associated with severe diarrhea?
A) Respiratory acidosis
B) Metabolic alkalosis
C) Metabolic acidosis
D) Respiratory alkalosis
Correct Answer: C) Metabolic acidosis
,Rationale: Severe diarrhea causes loss of bicarbonate-rich intestinal fluids,
leading to metabolic acidosis. This is a normal anion gap (hyperchloremic)
metabolic acidosis. Prolonged vomiting (A) would cause metabolic alkalosis from
loss of stomach acid. Respiratory disorders (A, D) are not directly associated with
diarrhea.
Question 3
A nurse is reviewing normal ABG values. Which of the following represents a
normal pH range?
A) 7.25–7.35
B) 7.35–7.45
C) 7.45–7.55
D) 7.30–7.40
Correct Answer: B) 7.35–7.45
Rationale: The normal arterial blood pH range is 7.35–7.45. Values below
7.35 indicate acidemia (acidosis), and values above 7.45 indicate alkalemia
(alkalosis). A pH of 7.30 (option D) would be acidotic.
Question 4
The nurse is teaching a patient about acid-base balance. Which statement by the
patient indicates correct understanding?
A) "A decrease in hydrogen ions causes the pH to decrease."
B) "The pH is inversely proportional to hydrogen ion concentration."
C) "Bases are also called acids."
D) "A pH of 7.0 is considered acidic."
Correct Answer: B) "The pH is inversely proportional to hydrogen ion
concentration."
,Rationale: The pH is inversely proportional to hydrogen ion (H⁺)
concentration. When H⁺ increases, pH decreases (becomes more acidic). When H⁺
decreases, pH increases (becomes more alkaline). A decrease in hydrogen ions (A)
would cause pH to increase, not decrease. Bases are called alkalis (C), not acids. A
pH of 7.0 (D) is neutral.
Question 5
A patient's ABG results are: pH 7.48, PaCO₂ 32 mmHg, HCO₃⁻ 24 mEq/L. The
nurse interprets these results as:
A) Metabolic alkalosis
B) Respiratory alkalosis
C) Metabolic acidosis
D) Respiratory acidosis
Correct Answer: B) Respiratory alkalosis
Rationale: Respiratory alkalosis is identified when pH is above 7.45 and
PaCO₂ is below 35 mmHg. The elevated pH (7.48) indicates alkalosis, and the low
PaCO₂ (32 mmHg) indicates a respiratory cause (hyperventilation). The normal
HCO₃⁻ suggests no metabolic compensation.
Question 6
Which of the following is the primary buffer system in the blood?
A) Phosphate buffer system
B) Protein buffer system
C) Carbonic acid-bicarbonate buffer system
D) Ammonia buffer system
Correct Answer: C) Carbonic acid-bicarbonate buffer system
Rationale: The carbonic acid-bicarbonate buffer system is the primary buffer
system in the blood. It consists of carbonic acid (H₂CO₃) and bicarbonate (HCO₃⁻).
, This system works in conjunction with the respiratory and renal systems to
maintain acid-base balance.
Question 7
The nurse is caring for a patient with an acid-base imbalance. Which compensatory
mechanism responds within minutes?
A) The renal system
B) The respiratory system
C) The buffer systems
D) The cardiovascular system
Correct Answer: B) The respiratory system
Rationale: The respiratory system responds within minutes to correct acid-
base imbalances by adjusting the rate and depth of breathing to retain or eliminate
CO₂. Buffer systems (C) respond within seconds but are the first line of defense.
The renal system (A) takes hours to days to respond. The cardiovascular system
(D) is not a primary compensatory mechanism for acid-base balance.
Question 8
A patient with a history of COPD has an ABG showing: pH 7.36, PaCO₂ 55
mmHg, HCO₃⁻ 30 mEq/L. How should the nurse interpret this?
A) Uncompensated respiratory acidosis
B) Fully compensated respiratory acidosis
C) Metabolic alkalosis
D) Normal ABG
Correct Answer: B) Fully compensated respiratory acidosis
Rationale: In chronic respiratory acidosis, the kidneys compensate by
retaining bicarbonate. The pH is near normal (7.36), indicating compensation. The
elevated PaCO₂ (55 mmHg) indicates the primary disorder is respiratory acidosis.
Guide | Galen College of Nursing
SECTION I: Acid-Base Fundamentals & ABG Interpretation
Question 1
A patient's arterial blood gas (ABG) results show: pH 7.31, PaCO₂ 50 mmHg,
HCO₃⁻ 24 mEq/L. The nurse interprets these results as:
A) Metabolic acidosis
B) Metabolic alkalosis
C) Respiratory acidosis
D) Respiratory alkalosis
Correct Answer: C) Respiratory acidosis
Rationale: Respiratory acidosis is characterized by a low pH (< 7.35) and an
elevated PaCO₂ (> 45 mmHg). The HCO₃⁻ is normal (22–26 mEq/L), indicating no
metabolic compensation. This patient's pH of 7.31 (acidosis) and PaCO₂ of 50
mmHg (elevated) indicate respiratory acidosis, likely from hypoventilation.
Metabolic acidosis (A) would show a low pH and low HCO₃⁻. Metabolic alkalosis
(B) would show a high pH and high HCO₃⁻. Respiratory alkalosis (D) would show
a high pH and low PaCO₂.
Question 2
Which acid-base imbalance is most commonly associated with severe diarrhea?
A) Respiratory acidosis
B) Metabolic alkalosis
C) Metabolic acidosis
D) Respiratory alkalosis
Correct Answer: C) Metabolic acidosis
,Rationale: Severe diarrhea causes loss of bicarbonate-rich intestinal fluids,
leading to metabolic acidosis. This is a normal anion gap (hyperchloremic)
metabolic acidosis. Prolonged vomiting (A) would cause metabolic alkalosis from
loss of stomach acid. Respiratory disorders (A, D) are not directly associated with
diarrhea.
Question 3
A nurse is reviewing normal ABG values. Which of the following represents a
normal pH range?
A) 7.25–7.35
B) 7.35–7.45
C) 7.45–7.55
D) 7.30–7.40
Correct Answer: B) 7.35–7.45
Rationale: The normal arterial blood pH range is 7.35–7.45. Values below
7.35 indicate acidemia (acidosis), and values above 7.45 indicate alkalemia
(alkalosis). A pH of 7.30 (option D) would be acidotic.
Question 4
The nurse is teaching a patient about acid-base balance. Which statement by the
patient indicates correct understanding?
A) "A decrease in hydrogen ions causes the pH to decrease."
B) "The pH is inversely proportional to hydrogen ion concentration."
C) "Bases are also called acids."
D) "A pH of 7.0 is considered acidic."
Correct Answer: B) "The pH is inversely proportional to hydrogen ion
concentration."
,Rationale: The pH is inversely proportional to hydrogen ion (H⁺)
concentration. When H⁺ increases, pH decreases (becomes more acidic). When H⁺
decreases, pH increases (becomes more alkaline). A decrease in hydrogen ions (A)
would cause pH to increase, not decrease. Bases are called alkalis (C), not acids. A
pH of 7.0 (D) is neutral.
Question 5
A patient's ABG results are: pH 7.48, PaCO₂ 32 mmHg, HCO₃⁻ 24 mEq/L. The
nurse interprets these results as:
A) Metabolic alkalosis
B) Respiratory alkalosis
C) Metabolic acidosis
D) Respiratory acidosis
Correct Answer: B) Respiratory alkalosis
Rationale: Respiratory alkalosis is identified when pH is above 7.45 and
PaCO₂ is below 35 mmHg. The elevated pH (7.48) indicates alkalosis, and the low
PaCO₂ (32 mmHg) indicates a respiratory cause (hyperventilation). The normal
HCO₃⁻ suggests no metabolic compensation.
Question 6
Which of the following is the primary buffer system in the blood?
A) Phosphate buffer system
B) Protein buffer system
C) Carbonic acid-bicarbonate buffer system
D) Ammonia buffer system
Correct Answer: C) Carbonic acid-bicarbonate buffer system
Rationale: The carbonic acid-bicarbonate buffer system is the primary buffer
system in the blood. It consists of carbonic acid (H₂CO₃) and bicarbonate (HCO₃⁻).
, This system works in conjunction with the respiratory and renal systems to
maintain acid-base balance.
Question 7
The nurse is caring for a patient with an acid-base imbalance. Which compensatory
mechanism responds within minutes?
A) The renal system
B) The respiratory system
C) The buffer systems
D) The cardiovascular system
Correct Answer: B) The respiratory system
Rationale: The respiratory system responds within minutes to correct acid-
base imbalances by adjusting the rate and depth of breathing to retain or eliminate
CO₂. Buffer systems (C) respond within seconds but are the first line of defense.
The renal system (A) takes hours to days to respond. The cardiovascular system
(D) is not a primary compensatory mechanism for acid-base balance.
Question 8
A patient with a history of COPD has an ABG showing: pH 7.36, PaCO₂ 55
mmHg, HCO₃⁻ 30 mEq/L. How should the nurse interpret this?
A) Uncompensated respiratory acidosis
B) Fully compensated respiratory acidosis
C) Metabolic alkalosis
D) Normal ABG
Correct Answer: B) Fully compensated respiratory acidosis
Rationale: In chronic respiratory acidosis, the kidneys compensate by
retaining bicarbonate. The pH is near normal (7.36), indicating compensation. The
elevated PaCO₂ (55 mmHg) indicates the primary disorder is respiratory acidosis.
