An elderly couple living in a very cold apament turned on the oven, opened the oven door, and went to sleep. The next morning, the neighbors found the couple dead. The direct mechanism by which death was caused most likely involves which of the following?
Correct Answer: Decreased oxygen-carrying capacity of blood
Description: The scenario described in the question stem is unfounately not at all uncommon. The open oven door is a tip-off that carbon monoxide was involved. Carbon monoxide has a very high affinity for hemoglobin, and binds, nearly irreversibly, to it in such a manner that oxygen cannot bind, drastically decreasing the oxygen-carrying capacity of the blood. Carbon monoxide also causes the oxygen-hemoglobin dissociation curve to shift to the left, making oxygen more difficult to unload. Traditionally, patients with carbon monoxide poisoning have been described as having "cherry red" blood and, consequently, skin, but this change is somewhat unreliable in real life. The 1st and 3rd Choices list secondary changes that are commonly observed in injured cells, no matter what the cause of the injury. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 32. Cardiovascular Regulatory Mechanisms. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.
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