Practice Question
A nurse is planning care for a patient with COPD. The nurse knows that this patient will have difficulty regulating their acid-base balance due to what:
Answer Choices:
Correct Answer:
The lungs control the concentration of carbon dioxide in the blood by changing rate and depth in response to fluctuations in Ph
Rationale:
🔵 In COPD, the primary problem is impaired ventilation, which affects how well the lungs can eliminate carbon dioxide (CO₂).
🔵 The lungs regulate acid–base balance mainly by changing the rate and depth of breathing to alter the amount of CO₂ (a respiratory acid) in the blood.
🔵 When blood becomes more acidic (↓pH, ↑CO₂), healthy lungs respond with increased ventilation to blow off CO₂ and raise the pH toward normal.
🔵 In COPD, this compensatory mechanism is impaired, so patients have difficulty regulating CO₂ levels and pH, leading to chronic respiratory acidosis with possible metabolic compensation.
🔵 This option correctly identifies the lung’s role in acid–base control as being through CO₂ concentration changes, not bicarbonate or electrolyte reabsorption.
“The lungs buffer acids through electrolyte changes.”
🔵 Electrolyte changes (like shifts in bicarbonate, potassium, chloride) are primarily regulated by the kidneys and intracellular buffering systems, not the lungs.
🔵 The lungs’ main acid–base function is ventilation of CO₂, not direct manipulation of electrolyte levels in the blood.
🔵 Saying the lungs “buffer acids through electrolyte changes” misrepresents the actual physiology of respiratory regulation.
🔵 Electrolyte-based buffering is a slower metabolic process compared to the rapid respiratory adjustments of CO₂.
🔵 Because of this, this statement is incorrect as an explanation of why COPD affects acid–base balance.
“They control the level of bicarbonate in the blood to maintain a stable pH.”
🔵 Bicarbonate (HCO₃⁻) levels are primarily controlled by the kidneys, which reabsorb or excrete bicarbonate to compensate for acid–base disturbances.
🔵 The lungs do not directly regulate bicarbonate; they regulate CO₂, which pairs with water to form carbonic acid.
🔵 Attributing bicarbonate control to the lungs confuses respiratory and metabolic roles in acid–base balance.
🔵 In chronic COPD, kidneys may increase bicarbonate retention to compensate for sustained CO₂ retention, but this is a renal response, not a lung function.
🔵 Therefore, this option is incorrect because it assigns a renal function to the lungs.
“The lungs regulate and reabsorb carbonic acid to change and maintain pH.”
🔵 The lungs do not reabsorb carbonic acid; they excrete CO₂ (a component of carbonic acid) through ventilation.
🔵 Carbonic acid (H₂CO₃) is formed in the blood from CO₂ + H₂O, and its levels change when the lungs alter CO₂ elimination, not by reabsorption.
🔵 The concept of “reabsorbing carbonic acid” is physiologically inaccurate; reabsorption of acids and bases is primarily a renal function.
🔵 The lungs’ contribution to pH control is exhalation of CO₂, which indirectly reduces carbonic acid and raises blood pH.
🔵 Because the wording suggests a mechanism that lungs do not perform, this option is incorrect.
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This question is from SDAP FALL 25 EXAM2 which contains 34 questions.
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Question Details
- Category: RN Nursing Exam(s)
- Subcategory: Examplify Exam(s)
- Domain: Medical-Surgical
- Answer Choices: 4