Respiratory System MCAT Practice Question
A 24-year-old woman with type 1 diabetes mellitus presents to the emergency department with a 2-day history of polyuria, polydipsia, and progressive dyspnea. Vital signs show respiratory rate 32/min with deep, regular breathing. Laboratory values are: pH: 7.18
pCO2: 26 mmHg
HCO3−: 10 mEq/L
Glucose: 520 mg/dL
Serum beta-hydroxybutyrate: elevated The patient's arterial blood gas and clinical presentation are most consistent with diabetic ketoacidosis (DKA). Which of the following best explains the physiological mechanism underlying the patient's respiratory pattern?
Answer choices
- AHyperventilation driven by acidemia acts as a compensatory mechanism to eliminate CO2 and minimize the pH decreaseCorrect answer
- BHypoventilation allows accumulation of CO2, which buffers the excess hydrogen ions and raises pH
- CRapid breathing increases minute ventilation to generate additional bicarbonate through increased alveolar gas exchange
- DThe respiratory pattern is an independent response to elevated blood glucose and is unrelated to acid-base balance
- EDecreased ventilation preserves CO2 to drive the bicarbonate buffer system toward HCO3− regeneration
- FTachypnea is a compensatory response to hypoxemia and has no direct relationship to the metabolic acidosis
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