Certified Pulmonary Function Technologist (CPFT) Practice Exam

What is the effect of decreased blood temperature on PO2, PCO2, and pH?

1. Increase PO2, Decrease PCO2, Decrease pH

2. Decrease PO2, Decrease PCO2, Increase pH

3. Decrease PO2, Increase PCO2, Decrease pH

4. No effect on indicators

The correct answer is: Decrease PO2, Decrease PCO2, Increase pH

Decreased blood temperature can significantly impact the partial pressures of oxygen (PO2) and carbon dioxide (PCO2) and the acidity of blood (pH). As blood temperature drops, the solubility of gases in the blood increases. This leads to an increase in PO2 because colder blood can hold more dissolved oxygen. Additionally, lower temperatures favor the binding of oxygen to hemoglobin, which can result in a greater oxygen saturation. At the same time, as temperature decreases, there is often a decrease in metabolic activity, leading to lower carbon dioxide production. Less carbon dioxide in the blood corresponds to a decrease in PCO2. Moreover, with reduced PCO2, there is a shift in the acid-base equilibrium, often resulting in an increase in pH (making the blood less acidic). This interrelationship between temperature, gas solubility, and gas exchange emphasizes how a decrease in blood temperature can result in a decrease in carbon dioxide levels, subsequently increasing the pH due to reduced carbonic acid formation. The combination of these effects leads to the observation encapsulated in the selected answer, highlighting the physiological responses to changes in temperature in a clinical context.