When using a rescue mask with a one-way valve, what does it do?

• A. Allows air from the rescuer to reach the patient while preventing air from the patient from entering the rescuer's mouth.
• B. Delivers a shock
• C. Measures heart rate
• D. Records oxygen saturation

Answer: (A)

This question is about how a rescue mask with a one-way valve functions during ventilation. The one-way valve is designed to let air move from you to the patient, so each rescue breath reaches the patient’s lungs, while preventing the patient’s air from flowing back toward you. This direction of airflow helps deliver effective breaths and protects you by blocking backflow of the patient’s air and potential pathogens. The mask doesn’t deliver a shock, measure heart rate, or record oxygen saturation—those tasks belong to a defibrillator, a heart-rate monitor, and a pulse oximeter, respectively. So the primary purpose is to direct airflow to the patient and prevent backflow toward you.