National Physical Therapy Examination (NPTE) Practice Exam

What is the main physiological effect of a rebreather mask on a patient with respiratory alkalosis?

1. Decreases oxygen levels

2. Increases carbon dioxide levels

3. Reduces respiratory rate

4. Corrects metabolic acidosis

The correct answer is: Increases carbon dioxide levels

The main physiological effect of a rebreather mask on a patient with respiratory alkalosis is to increase carbon dioxide levels. In cases of respiratory alkalosis, the patient often hyperventilates, which leads to an excessive loss of carbon dioxide (CO2) from the bloodstream. This drop in CO2 can result in a higher blood pH, leading to alkalosis. When using a rebreather mask, exhaled air is partially recirculated back to the patient. This exhaled air contains higher concentrations of CO2 because it has already been produced by the body and contains less oxygen than fresh air. By rebreathing some of this CO2, the patient can help restore their carbon dioxide levels, effectively working to bring the blood pH back towards normal. The other options do not directly address the primary mechanism of action that a rebreather mask has in this context. While the mask does not specifically aim to decrease oxygen levels or reduce respiratory rate, the primary goal is to stabilize CO2 levels to correct the alkalosis. Correcting metabolic acidosis is also not relevant in this scenario because the focus here is on managing respiratory alkalosis, not metabolic imbalances.