One of my readers recently asked a very important question about ventilating a patient with a bag-valve-mask device: “Is there an outlet for the expired air of the patient?” The answer is yes. When ventilating a patient we are concentrating, and rightfully so, on watching the lungs expand and verifying that we hear breath sounds. It is just as important to verify that your patient can exhale. All ventilation devices have a built in pressure relief valve, also called a pop-off valve, which allows you to balance the force needed to expand the lungs with the ability to the patient to passively exhale. Failure to allow exhalation can lead to patient injury from barotrauma.