Final answer:
A decrease in blood pH and an increased partial pressure of carbon dioxide (PCO₂) would both cause a decrease in the percent saturation of hemoglobin, as they reduce hemoglobin's affinity for oxygen.
Step-by-step explanation:
The question is asking which factors would be expected to cause a decrease in the percent saturation of hemoglobin, which refers to the extent to which hemoglobin is bound with oxygen. The factors that can affect this include:
- a decrease in blood pH, which can arise from an increase in carbon dioxide concentration in the blood, making the blood more acidic and thereby reducing hemoglobin's affinity for oxygen.
- a decrease in temperature, since lower temperatures typically increase hemoglobin's affinity for oxygen, thus increasing the percent saturation.
- an increase in the partial pressure of carbon dioxide (PCO₂), which leads to lowered pH and shifts the oxygen-hemoglobin dissociation curve to the right, reducing hemoglobin's affinity for oxygen.
Consequently, the options that would cause a decrease in the percent saturation of hemoglobin are a decrease in blood pH (b), and an increase in PCO₂ (c). A decrease in PO₂ (a) would directly lower the percent saturation because there would be less oxygen available to bind with hemoglobin. A decrease in temperature (d) would typically increase the affinity for oxygen and therefore is not expected to decrease the percent saturation. Therefore, the correct answers that would decrease the percent saturation of hemoglobin are a decrease in blood pH (b) and an increased partial pressure of carbon dioxide (PCO₂) (c).