A 49-year-old farmer develops headache and becomes dizzy after working on a tractor in his barn. His wife suspects carbon monoxide poisoning and brings him to the emergency department where he complains of dizziness, lightheadedness, headache, and nausea. The patient's skin is red, he does not appear to be in respiratory distress, and denies dyspnea. Blood levels of carboxyhemoglobin are elevated. Which of the following best explains the absence of respiratory signs and symptoms associated with carbon monoxide poisoning?
a. Blood flow to the carotid body is decreased
b. Arterial oxygen content is normal
c. Cerebrospinal fluid (CSF) pH is normal
d. Central chemoreceptors are depressed
e. Arterial oxygen tension is normal