ATI ACID-BASE BALANCE EXAM PREDICTION 2026 QUESTIONS
AND VERIFIED SOLUTIONS
A patient with chronic obstructive pulmonary disease (COPD) presents
with arterial blood gas (ABG) values: pH 7.31, PaCO₂ 50 mmHg, HCO₃⁻
28 mEq/L. Which acid-base disorder is present?
A. Acute respiratory alkalosis
,B. Chronic respiratory acidosis
C. Metabolic acidosis
D. Metabolic alkalosis
Correct Answer: B
Explanation: The low pH (<7.35) indicates acidemia, elevated PaCO₂
(>45 mmHg) indicates respiratory cause, and elevated HCO₃⁻ (>26
mEq/L) shows renal compensation typical of chronic respiratory acidosis
in COPD patients .
Which of the following best describes the primary compensatory
mechanism for metabolic acidosis?
A. Renal retention of bicarbonate
B. Hyperventilation to decrease PaCO₂
C. Renal excretion of hydrogen ions
D. Hypoventilation to increase PaCO₂
Correct Answer: B
Explanation: In metabolic acidosis, the respiratory system compensates
by hyperventilating (Kussmaul respirations) to blow off CO₂, lowering
PaCO₂ and raising pH toward normal .
A patient with diabetic ketoacidosis (DKA) would most likely present
with which ABG pattern?
A. pH 7.50, PaCO₂ 30 mmHg, HCO₃⁻ 24 mEq/L
B. pH 7.25, PaCO₂ 30 mmHg, HCO₃⁻ 12 mEq/L
C. pH 7.35, PaCO₂ 50 mmHg, HCO₃⁻ 30 mEq/L
D. pH 7.48, PaCO₂ 48 mmHg, HCO₃⁻ 35 mEq/L
Correct Answer: B
,Explanation: DKA causes metabolic acidosis with low pH, low HCO₃⁻
from ketone accumulation, and compensatory low PaCO₂ from
hyperventilation .
Which buffer system is the most important extracellular buffer in the
body?
A. Phosphate buffer system
B. Protein buffer system
C. Bicarbonate-carbonic acid buffer system
D. Hemoglobin buffer system
Correct Answer: C
Explanation: The bicarbonate-carbonic acid buffer system is the primary
extracellular buffer, crucial for maintaining blood pH within the narrow
normal range .
A patient with severe diarrhea for 3 days is at highest risk for developing
which acid-base imbalance?
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis
D. Metabolic alkalosis
Correct Answer: C
Explanation: Diarrhea causes loss of bicarbonate-rich intestinal fluids,
leading to non-anion gap metabolic acidosis .
, What is the expected compensatory response in acute respiratory
alkalosis?
A. Increased renal bicarbonate reabsorption
B. Decreased renal bicarbonate reabsorption
C. Increased CO₂ retention
D. No significant compensation occurs acutely
Correct Answer: D
Explanation: In acute respiratory alkalosis, renal compensation takes 24-
48 hours to become significant; initially, there is minimal metabolic
compensation .
Which laboratory value is most critical to monitor in a patient with
metabolic alkalosis?
A. Sodium
B. Potassium
C. Calcium
D. Magnesium
Correct Answer: B
Explanation: Metabolic alkalosis causes intracellular shift of potassium
and renal potassium wasting, leading to hypokalemia which can be life-
threatening .
A patient with salicylate (aspirin) overdose typically presents with which
acid-base disturbance?
A. Pure respiratory acidosis
B. Pure metabolic acidosis
C. Mixed respiratory alkalosis and metabolic acidosis
AND VERIFIED SOLUTIONS
A patient with chronic obstructive pulmonary disease (COPD) presents
with arterial blood gas (ABG) values: pH 7.31, PaCO₂ 50 mmHg, HCO₃⁻
28 mEq/L. Which acid-base disorder is present?
A. Acute respiratory alkalosis
,B. Chronic respiratory acidosis
C. Metabolic acidosis
D. Metabolic alkalosis
Correct Answer: B
Explanation: The low pH (<7.35) indicates acidemia, elevated PaCO₂
(>45 mmHg) indicates respiratory cause, and elevated HCO₃⁻ (>26
mEq/L) shows renal compensation typical of chronic respiratory acidosis
in COPD patients .
Which of the following best describes the primary compensatory
mechanism for metabolic acidosis?
A. Renal retention of bicarbonate
B. Hyperventilation to decrease PaCO₂
C. Renal excretion of hydrogen ions
D. Hypoventilation to increase PaCO₂
Correct Answer: B
Explanation: In metabolic acidosis, the respiratory system compensates
by hyperventilating (Kussmaul respirations) to blow off CO₂, lowering
PaCO₂ and raising pH toward normal .
A patient with diabetic ketoacidosis (DKA) would most likely present
with which ABG pattern?
A. pH 7.50, PaCO₂ 30 mmHg, HCO₃⁻ 24 mEq/L
B. pH 7.25, PaCO₂ 30 mmHg, HCO₃⁻ 12 mEq/L
C. pH 7.35, PaCO₂ 50 mmHg, HCO₃⁻ 30 mEq/L
D. pH 7.48, PaCO₂ 48 mmHg, HCO₃⁻ 35 mEq/L
Correct Answer: B
,Explanation: DKA causes metabolic acidosis with low pH, low HCO₃⁻
from ketone accumulation, and compensatory low PaCO₂ from
hyperventilation .
Which buffer system is the most important extracellular buffer in the
body?
A. Phosphate buffer system
B. Protein buffer system
C. Bicarbonate-carbonic acid buffer system
D. Hemoglobin buffer system
Correct Answer: C
Explanation: The bicarbonate-carbonic acid buffer system is the primary
extracellular buffer, crucial for maintaining blood pH within the narrow
normal range .
A patient with severe diarrhea for 3 days is at highest risk for developing
which acid-base imbalance?
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis
D. Metabolic alkalosis
Correct Answer: C
Explanation: Diarrhea causes loss of bicarbonate-rich intestinal fluids,
leading to non-anion gap metabolic acidosis .
, What is the expected compensatory response in acute respiratory
alkalosis?
A. Increased renal bicarbonate reabsorption
B. Decreased renal bicarbonate reabsorption
C. Increased CO₂ retention
D. No significant compensation occurs acutely
Correct Answer: D
Explanation: In acute respiratory alkalosis, renal compensation takes 24-
48 hours to become significant; initially, there is minimal metabolic
compensation .
Which laboratory value is most critical to monitor in a patient with
metabolic alkalosis?
A. Sodium
B. Potassium
C. Calcium
D. Magnesium
Correct Answer: B
Explanation: Metabolic alkalosis causes intracellular shift of potassium
and renal potassium wasting, leading to hypokalemia which can be life-
threatening .
A patient with salicylate (aspirin) overdose typically presents with which
acid-base disturbance?
A. Pure respiratory acidosis
B. Pure metabolic acidosis
C. Mixed respiratory alkalosis and metabolic acidosis
