Effects of Hyperbaric Oxygen (HBO) on Blood Count Recovery After Autologous Hematopoietic Stem Cell (HSPC) Transplant for Multiple Myeloma

Inclusion Criteria: * Voluntary written informed consent. * Multiple myeloma diagnosis applying the latest criteria by International Working Group. Patients should have received myeloma-directed induction therapy with appropriate response (partial response or better) in newly diagnosed myeloma patients. Multiple myeloma patients who relapse following induction therapy or following prior autologous hematopoietic stem cell transplant are also eligible as far as remission following their first autologous hematopoietic stem cell transplant lasted 12 months or more. * Patients who are considered for high-dose therapy and autologous transplantation at the bone marrow transplant clinic at Wilmot Cancer Institute will be screened for eligibility to enroll in this study and if eligible will be approached to participate. Eligible patients will have the chance to tour the hyperbaric oxygen facility prior to signing the consent form. * Subjects must be ≥ 18 years old and ≤ 75 years old. * Karnofsky performance status (KPS) of ≥ 70%. * Adequate hepatic, cardiac and pulmonary function to be eligible for transplant. Minimum criteria include: * \- Alanine aminotransferase (ALT), aspartate aminotransferase (AST): \< 4x institutional upper limit of normal (IULN) * \- Total bilirubin: ≤ 2.0 mg/dL * \- Ejection fraction (EF) measured by two-dimensional echocardiography (2D-ECHO) or multigated acquisition (MUGA) scan of ≥ 45% * \- Forced expiratory volume at one second (FEV1), forced vital capacity (FVC), and diffusing capacity of lung for carbon monoxide (DLCO) ≥ 50% of predicted value (corrected to serum hemoglobin) * \- Electrocardiogram (EKG) with no clinically significant arrhythmia. * Patients should have New York Heart Association (NYHA) Functional Classification, class I or II (No or mild limitation during ordinary activity). * Patients should be evaluated for fitness for hyperbaric oxygen therapy by a hyperbaric oxygen trained medical professional who is not part of the study team prior to starting preparative regimen. * Women of child-bearing potential should have a negative urine pregnancy test within 4 weeks of starting preparative regimen. * Women of child-bearing potential and men with partners of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry, for the duration of study participation, and for 30 days following completion of therapy. Should a woman or partner become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician and the investigator immediately. * A woman of child-bearing potential is any female (regardless of sexual orientation, having undergone a tubal ligation, or remaining celibate by choice) who meets the following criteria: * \- Has not undergone a hysterectomy or bilateral oophorectomy; or * \- Has not been naturally postmenopausal for at least 12 consecutive months (i.e., has had menses at any time in the preceding 12 consecutive months) Exclusion Criteria: * Pregnant or breastfeeding * Severe chronic obstructive pulmonary disease requiring oxygen supplementation * History of spontaneous pneumothorax * Active ear/sinus infection * History of sinus or ear surgery, excluding myringotomy or ear tubes * Claustrophobia * History of seizures * Evidence of pneumothorax or significant pulmonary fibrosis on chest imaging * Prior chest surgery or irradiation * Patients who had intrathecal chemotherapy within 2 weeks of starting preparative regimen or cranial irradiation within 4 weeks of starting preparative regimen * Active infection (viral, fungal, and/or bacterial) * Positive screening for Hepatitis A, B, or C indicating an ongoing infection