A ventilator circuit is provided for use with a ventilator and a low pressure low flow oxygen source to provide a hyper-oxygenated mixture of air and oxygen at the onset of inspiration. The ventilator circuit achieves this result by using its inspiratory limb to store oxygen between breaths. As a result, the oxygen content of dead space gas is increased before delivery to the distal alveoli of the patient. Accordingly, the ventilator circuit achieves an efficient use of available oxygen and requires less oxygen to a desired oxyhemoglobin percentage at the patient.
