Control of Respiration

A 72-year-old woman with a history of stroke 6 months ago is admitted with acute pneumonia. On examination, she has a respiratory rate of 28 breaths/min, but her breathing pattern is irregular with periods of apnea lasting 10–15 seconds followed by rapid, deep breaths. Arterial blood gas shows: pH 7.38, PaCO₂ 38 mmHg, HCO₃⁻ 22 mEq/L, PaO₂ 72 mmHg. CT head is unchanged from prior imaging. Which respiratory control abnormality best explains this breathing pattern?

Which of the following chemoreceptors is responsible for detecting changes in arterial PaCO₂ and pH, and is located on the ventrolateral surface of the medulla?

The Hering-Breuer reflex is mediated by which cranial nerve, and what is its primary physiological effect?

A 58-year-old man with chronic obstructive pulmonary disease (COPD) presents to the emergency department with acute dyspnea. Arterial blood gas analysis shows: pH 7.32, PaCO₂ 65 mmHg, HCO₃⁻ 32 mEq/L, PaO₂ 48 mmHg. His respiratory rate is 18 breaths/min. He is given supplemental oxygen at 4 L/min via nasal cannula. Two hours later, his respiratory rate drops to 12 breaths/min and he becomes increasingly drowsy. Repeat ABG shows: pH 7.28, PaCO₂ 78 mmHg, HCO₃⁻ 34 mEq/L, PaO₂ 65 mmHg. Which of the following best explains the deterioration in his respiratory drive?