This is a prospective study in a human model examining treatment of patients who have sustained damage to salivary glands following head and neck radiation, subsequent xerostomia, and who are currently indicated for hyperbaric oxygen therapy for treatment of osteoradionecrosis. Salivary flow rates, pH and buffering capacity before and after hyperbaric oxygen treatments will be collected using GC America (Alsip, Illinois) Saliva-Check BUFFER Kit and results will be recorded. The 6 tests take 10 minutes to complete per patient. According to GC America, these tests are simple, demonstrate salivary dysfunction, help identify factors affecting salivary dysfunction, and assist in the diagnosis of xerostomia. Salivary testing and data collection will occur on 8 independent visits over the course of hyperbaric oxygen treatment and during follow-up. Stimulated saliva samples will be used to measure proteins that are involved in salivary gland revascularization and repair. Saliva samples will be stored at less than or equal to -20C for up to 1 year. Measurements of salivary VEGF-A, IGF-1, and Thrombospondin-1 will be quantified using R\&D Systems (Minneapolis, MN) ELISA kits and results will be recorded. Salivary Alpha-Amylase will be measured using Rocky Mountain Diagnostics, Inc (Colorado Springs, CO) Alpha-Amylase Saliva kit. Protein analysis will be done on stimulated saliva samples collected at 4 independent visits: first week, fourth week, eighth week, sixteenth week.

The medical, surgical, and health histories of each participant will be reviewed. Each participant will complete the EORTC quality of life core questionnaire (QLQ - C30 v3.0), including head and neck cancer module, at the start and completion of the trial. A blood sample from each participant will be drawn, and analyzed for A1c levels and albumin levels. During the first, fourth, eighth, and sixteenth week, following Saliva-Check BUFFER Kit testing done before HBO therapy, additional saliva will be collected to ensure that a minimum of 2 mL of saliva can be stored at less than or equal to -20 oC for protein analysis.

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.

Collected data will be compared to two independent control groups. The Positive Control Group will include 26 individuals who fit the inclusion and exclusion criteria: participants for whom hyperbaric oxygen treatment is indicated, but who have not had radiation therapy for head or neck cancer. The Negative Control Group will include the first 26 individuals who fit the inclusion and exclusion criteria: participants who have previously had head and neck radiation therapy, but for whom hyperbaric oxygen treatment is not indicated. Salivary data for the Positive Control Group will be collected in such as way as to parallel data collected for the Treatment Group. Salivary data will be collected in the same way for the Negative Control Group with the following modifications: salivary flow rate testing will only be performed once during each visit and salivary testing will be spaced on the basis of time in days in contrast to number of hyperbaric oxygen treatment sessions.