Hypothesis: Drainage of the peripheral tissue edema by the hyperbaric oxygen therapy because of hyperoxygenation that constricts arterioles and alters the downstream capillary fluid traffic in affected tissues

Hyperbaric oxygen (HBO) therapy still lacks proper interpretations of its many actions. This hypothesis is based on reports of temporarily elevated peripheral vascular resistance (PVR) during HBO sessions. Besides that, during HBO sessions, hyperoxygenated tissues can reduce their perfusion so much that CO₂ can accumulate in them. Tissue perfusion depends on vascular innervation and on the balance between systemic constrictors and local dilators. During an HBO session, increased tissue oxygen levels suppress dilatory mechanisms. Tissue hyperoxygenation increases PVR, suggesting that the HBO action on an edematous tissue may be caused by an oxygen-induced disbalance among Starling capillary forces. The presented hypothesis is that oxygen-caused arteriolar constriction reduces the hydrostatic pressure in downstream capillaries. Thus, more tissue fluid is absorbed in vascular capillaries, under the condition that the plasma colloid osmotic pressure remains unaltered during the HBO session. Among several known mechanisms behind the HBO actions, the vasoconstriction has been listed as a therapeutic modality for the reduction of the tissue edema, for a crush injury, for burns (in an acute phase), and for the compartment syndrome. The Bell's palsy is among often listed indications for the HBO treatment, although evidence is poor and reports of randomized trials are scarce.

Combined Acupuncture-Hyperbaric Oxygen-Steroids Therapy for Idiopathic Sudden Sensorineural Hearing Loss: A Retrospective Observational Study

Objectives: Acupuncture, widely used in Chinese society, has been studied as an adjunct treatment of idiopathic sudden sensorineural hearing loss (ISSNHL). The purpose of this study is to investigate the effectiveness of combined acupuncture and hyperbaric oxygen therapy (HBOT) with conventional steroid therapy for ISSNHL. Methods: This retrospective chart review enrolled 154 patients who met the ISSNHL criteria and were categorized into three groups according to the different treatment regimens. Among these patients, 43 underwent steroid therapy only (S) group, 74 received steroid and HBOT (S-H) group, and the remaining 37 were treated with combined acupuncture-HBOT in addition to steroid therapy (S-H-A) group. The outcome was determined by comparing the differences in pure-tone thresholds and absolute hearing gains after treatment calculated at each audiometric octave frequency or grouped frequencies of audiograms. Hearing recoveries classified into three grades: complete, partial, and poor were also analyzed and compared among different treatment groups. Results: All subjects presented with initial severe hearing loss with averaged hearing thresholds >70 dB. The S-H-A group exhibited good hearing improvement outcomes at each audiometric octave frequency and grouped frequencies of audiograms, with greater hearing gain and had more favorable outcomes in hearing recovery grades compared with the S group and the S-H group. Conclusions: The results obtained in this study revealed a preliminary finding of ISSNHL patients benefiting from combined acupuncture, HBOT, and conventional steroid therapy. Acupuncture is a safe and nonpharmacologic treatment option and can be considered as an initial treatment strategy in such a clinical scenario.

Hyperbaric oxygen therapy improves angiogenesis and bone formation in critical sized diaphyseal defects

Besides the use of autologous bone grafting several osteoconductive and osteoinductive methods have been reported to improve bone healing. However, persistent non-union occurs in a considerable number of cases and compromised angiogenesis is suspected to impede bone regeneration. Hyperbaric oxygen therapy (HBO) improves angiogenesis. This study evaluates the effects of HBO on bone defects treated with autologous bone grafting in a bone defect model in rabbits. Twenty-four New-Zealand White Rabbits were subjected to a unilateral critical sized diaphyseal radius bone defect and treated with autologous cancellous bone transplantation. The study groups were exposed to an additional HBO treatment regimen. Bone regeneration was evaluated radiologically and histologically at 3 and 6 weeks, angiogenesis was assessed by immunohistochemistry at three and six weeks. The additional administration of HBO resulted in a significantly increased new bone formation and angiogenesis compared to the sole treatment with autologous bone grafting. These results were apparent after three and six weeks of treatment. The addition of HBO therapy to autologous bone grafts leads to significantly improved bone regeneration. The increase in angiogenesis observed could play a crucial role for the results observed.