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.