A method for increasing circulation and providing oxygen to a patient in cardiac arrest includes the step of coupling an interface to the patient's airway, the interface providing access to the patient's respiratory system. A valve system is operably attached to the interface. Oxygen is delivered through the interface a rate of between about 1.0 to about 10.0 L/min to provide a continuous supply of oxygen to the patient. While supplying the oxygen, a body structure of the patient is manipulated to increase the magnitude and duration of the patient's negative intrathoracic pressure. During the manipulation, the valve system prevents additional respiratory gases from entering the lungs until a negative intrathoracic pressure level in the range from about −1 cm H2O to about −15 cm H2O, the valve system assisting in increasing the magnitude and duration of negative intrathoracic pressure thereby enhancing the amount of blood flow in the heart and lungs and lowering intracranial pressure, therein further increasing blood flow to the brain.