Acute Post-Radiation Hyperbaric Oxygen (HBO2) for Breast Cancer Patients Who Have Recently Completed Radiation Therapy

Inclusion Criteria: * \> 18 years of age * Patient is currently undergoing treatment for breast cancer and is on one of two pathways: * Pathway 1 involves lumpectomy with radiation therapy, recurrence years later, mastectomy and tissue expander with further radiation therapy * Pathway 2 involves mastectomy and tissue expander, 6 weeks of radiation therapy, and an implant in 6 months * Undergone mastectomy with expander or implant reconstruction \> 2 weeks before starting radiation therapy * Completed chest wall irradiation in the past 3 days * Willing to stop herbal medications as directed by provider * Willing to stop daily use of supplemental vitamin E (Multivitamin with vitamin E component is acceptable, vitamin E cream is also acceptable) * Willing to have photographs of chest area taken for research purposes only * Therapeutic PT-INR for participants taking Coumadin * If tissue expanders remain intact during radiation, plan for conversion to the final implants must occur \> 4 months after completing radiation * Willing to travel to a Legacy Health facility for study related visits * Agree to attend study visits outside of standard of care visits, if needed * Willing to engage in pre/post testing and survey/phone calls * Willing to attend all 6 weeks of HBOT if randomized to that group Exclusion Criteria: * \< 18 years of age * Pregnant or lactating * Have final implant placed \< 2 weeks before start of radiation therapy * Plan to place final impacts \< 4 months from the completion of radiation therapy, if tissue expanders are intact during radiation therapy * Have evidence of ongoing infection or implant exposure before start of radiation therapy * Radiation completed more than 3 days prior to study start * Unable to comply with protocol * Unable to provide written informed consent * Unwilling or unable to stop oral supplemental Vitamin E * PT-INR outside of acceptable range for participants taking Coumadin * Any delay in radiation treatment greater than 14 days * Investigator does not believe study participation is in the best interest of the patient * History of a seizure within the last 5 years