After salivary testing, each patient will enter a hyperbaric oxygen chamber located at Loma Linda University Medical Center. The patient will gradually be elevated to therapeutic oxygen levels over an 8-12 minute period. At this time, 100% oxygen will be administered at 2.0 ATA or 2.5 ATA, at the discretion of the treating physician, for 90 minutes. A 10-minute air-break will be given after the first 45 minutes if the patients are on the 2.5 ATA protocol. At the conclusion of the oxygen treatment, the oxygen and pressure levels are gradually decreased over 8-12 minutes to return to a depth of 1 ATA. After exiting the hyperbaric oxygen chamber, salivary testing will once again be performed on each patient.