Usmle Pretest Physiology 14th Edition Questions Study Guide Rated A+

217. The answer is e. (Kaufman, p 272. Levitzky, pp 153-154, 183.) The decrease in arterial oxygen saturation caused by carbon monoxide poisoning reduces the oxyhemoglobin and thus total arterial oxygen contents but does not reduce the amount of oxygen dissolved in the plasma, which determines the arterial oxygen tension. Carbon monoxide is odorless and tasteless, and dyspnea and respiratory distress are late signs, which is the reason why it is so important to install carbon monoxide detectors in homes and businesses. Respiratory distress becomes manifest with severe tissue hypoxia and anaerobic glycolysis, which leads to lactic acidosis. The decrease in arterial pH stimulates ventilation via the peripheral chemoreceptors. The resultant hyperventilation decreases arterial (and CSF) PCO2, causing CSF pH to rise. Carboxyhemoglobin has a cherry-red color. {Ans: 217. 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