Which statement about respiration is true?

Which statement about respiration is true?

• A. Depress medullary respiratory centers, cause cough suppression, slow respiration, and apnea can occur before unconsciousness; chest wall rigidity can occur
• B. They depress medullary respiratory centers and cause apnea only after unconsciousness
• C. They increase hypoxic drive
• D. They never cause chest wall rigidity

Answer: (C)

Respiratory control relies on two main drives: the central CO2 response from the medullary centers and the peripheral hypoxic drive from the carotid bodies. Many anesthetic drugs blunt the medullary response to CO2, which slows ventilation and can lead to apnea or shallow breathing. However, the hypoxic drive is relatively preserved and can become more influential when the CO2 drive is suppressed. This means that, even when central drive is reduced, a fall in oxygen levels can still stimulate ventilation, effectively increasing the importance of hypoxic drive. So the statement that they increase hypoxic drive captures this preserved peripheral response and its relatively greater role when central chemoreceptor stimulation is diminished.

Respiratory control relies on two main drives: the central CO2 response from the medullary centers and the peripheral hypoxic drive from the carotid bodies. Many anesthetic drugs blunt the medullary response to CO2, which slows ventilation and can lead to apnea or shallow breathing. However, the hypoxic drive is relatively preserved and can become more influential when the CO2 drive is suppressed. This means that, even when central drive is reduced, a fall in oxygen levels can still stimulate ventilation, effectively increasing the importance of hypoxic drive. So the statement that they increase hypoxic drive captures this preserved peripheral response and its relatively greater role when central chemoreceptor stimulation is diminished.