Physiology & Biochemistry · single question
The patient's hyperventilation could be a result of:
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Correct answer: B. Hypercapnia (elevated CO2 in blood)
- A. Hypocapnia is the RESULT of hyperventilation — not the cause. CO2 falls after hyperventilation begins.
- B. HYPERCAPNIA (elevated PaCO2) is the primary physiologic stimulus for INCREASED respiratory drive, which can manifest as hyperventilation. When CO2 rises, chemoreceptors (central and peripheral) detect the change and stimulate deeper, faster breathing to eliminate the excess CO2. In the dental office, anxiety can also trigger hyperventilation, but physiologically, hypercapnia is the primary driver.
- C. Anemia causes increased respiratory rate to compensate for reduced oxygen-carrying capacity, but this is tachypnea — not the primary mechanism of hyperventilation.
- D. Metabolic alkalosis actually SUPPRESSES respiratory drive (compensatory hypoventilation to retain CO2) — it is not a cause of hyperventilation.
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