Five minutes prior to completion of treatment the nitrous oxide flow is terminated and 100% oxygen is administered to the patient. Because nitrous oxide is highly insoluble and is not readily absorbed by the blood, when the flow of nitrous oxide is terminated it is rapidly removed through the lungs. During this process, nitrous oxide exits faster than the atmospheric nitrogen that replaces it, thereby, diluting the supply of oxygen and reducing the oxygen blood saturation. This condition is referred to as diffusion hypoxia and in some patients can lead to post-treatment dizziness (vertigo), headache, lethargy and nausea. The administration of 100% oxygen for five minutes before termination of the procedures may prevent or minimize these symptoms.