Bone remodelling, the process by which the skeleton adapts to environmental changes, is dependent on the actions of osteoclasts that resorb bone and osteoblasts which make new bone matrix. Aberrant remodelling underpins bone loss in several debilitating skeletal diseases such as osteoporosis, metastatic breast cancer and multiple myeloma. Changes in remodelling activity can also arise as a consequence of therapeutic intervention for instance intravenous bisphosphonate treatment is associated with osteochemonecrosis of the jaw and localised osteoradionecrosis is a common side effect of radiotherapy. Hyperbaric oxygen is often used as an adjunctive therapy in the treatment of these disorders. HBO involves the administration of 100% oxygen at atmospheric pressures greater than one in sealed chambers. The following studies aimed to evaluate the effect of HBO, hyperoxia, and pressure on RANKL-induced osteoclast differentiation and bone resorption from RAW264.7 and human peripheral blood mononuclear cells (PBMC), and osteoblast differentiation in vitro. The study also aimed to further examine the effect of HBO on ex vivo osteoclast formation from peripheral blood monocytes obtained from patients undergoing HBO. Daily exposure to HBO for ninety minutes significantly suppressed osteoclast differentiation and bone resorption in mouse and human monocytes in normoxic and hypoxic conditions in vitro. The suppressive action of HBO on osteoclast formation was associated with a significant reduction in HIF-1α and RANK mRNA expression and HBO also caused a significant reduction in NFATc1 and DC-STAMP expression. This study has for the first time shown that HBO is able to reduce the ability of precursors to form bone resorbing osteoclast. HBO also suppressed the ability of peripheral blood monocytes to develop into RANKL-induced resorptive osteoclasts. In an ex vivo culture system the suppressive effect of HBO was meditated by an action prior to activation of osteoclast differentiation by RANKL and must therefore be an inhibitory effect on the ability of precursors to differentiate along the osteoclastic lineage. HBO also accelerates the rate of osteoblast differentiation and augments early stages of mineralization and has a more pronounced effect than hyperoxia or pressure alone. HBO enhanced bone nodule formation and ALP activity in human osteoblasts. Furthermore HBO promoted the expression of type I collagen and Runx-2 in both normoxic and hypoxic conditions. HBO had a greater effect on these key markers of osteoblast differentiation than hyperoxia or pressure alone. This study suggests that HBO suppresses osteoclast activity and promotes osteoblastic bone formation, which may at least in part mediate its beneficial effects on necrotic bone. This provides evidence supporting the use of HBO as an adjunctive therapy to prevent osteoclast formation in a range of skeletal disorders associated with low oxygen partial pressure. The study also provides further support for the use of HBO in the treatment of skeletal disorders associated with excessive resorption such as osteomyelitis, and also provides a potential mechanism through which short term HBO may help fracture healing.

The aim of this study was to test the application of an in situ–formed synthetic polyethylene glycol (PEG) as a biodegradable membrane with a variety of graft materials and hyperbaric oxygen (HBO) for enhanced bone regeneration. Critical-sized rabbit calvarial defects were created in bilateral parietal bones. Group 1 served as a control with unfilled defects, Group 2 had defects filled with morcelized autogenous bone, and Group 3 had defects filled with biphasic calcium phosphate. One defect was protected PEG membrane and half the animals were subjected to HBOT treatment. The unsupported membrane didn’t produce the desired bone regeneration in the unfilled and bone grafted groups. HBO didn't ameliorate the bone grafted or ceramic filled defects over the 6-week time period. Caution is recommended with the membrane over unsupported defects. Future assessments with HBO should be completed at the 12-week time point.

The aim of this study was to test the application of an in situ–formed synthetic polyethylene glycol (PEG) as a biodegradable membrane with a variety of graft materials and hyperbaric oxygen (HBO) for enhanced bone regeneration. Critical-sized rabbit calvarial defects were created in bilateral parietal bones. Group 1 served as a control with unfilled defects, Group 2 had defects filled with morcelized autogenous bone, and Group 3 had defects filled with biphasic calcium phosphate. One defect was protected PEG membrane and half the animals were subjected to HBOT treatment. The unsupported membrane didn’t produce the desired bone regeneration in the unfilled and bone grafted groups. HBO didn't ameliorate the bone grafted or ceramic filled defects over the 6-week time period. Caution is recommended with the membrane over unsupported defects. Future assessments with HBO should be completed at the 12-week time point.

Spinal cord injury (SCI) is a physically and mentally devastating condition for which there is no curative treatment. It involves primary trauma from the impact and secondary damage in the form of biochemical cascades that threaten the integrity of functional tissue. Therapeutic interventions can only prevent secondary damages, given the irreversibility of the primary laceration. Experimental therapies for SCI can aim to promote neuronal growth and/or regeneration, promote neuroplasticity in surviving neurons and networks, and enhance neuroprotection, or the survival of spared neurons. Surgical decompression and hypothermia are neuroprotective strategies that usually precede rehabilitational strategies in SCI. Hyperbaric oxygen (HBO) treatment constitutes another promising therapy that can increase the amount of oxygen dissolved in the blood, and therefore, the amount delivered to tissues. Both pre-clinical and clinical studies have illustrated that HBO therapy can enhance motor recovery and exert neurological improvements after SCI. A plethora of pre-clinical studies have elucidated several aspects of its function in SCI; HBO seems to suppress apoptosis, edema, and inflammation, as well as mitigate oxidizing conditions. It can also promote angiogenesis, enhance nerve conduction, and inhibit neural degeneration. The limited number of clinical studies and the heterogeneity of protocols allow for fewer conclusions on the roles of HBO in human SCI: motor benefits are hinted in several clinical trials, while neuroprotective effects include increases in blood oxygen, and suppression of inflammatory responses. However, the number and variety of pre-clinical studies suggest that HBO can exert additional neuroprotective benefits in human SCI, which remain to be explored in the future.

Hyperbaric oxygen (HBO) therapy is the intermittent inhalation of 100% oxygen at a pressure greater than one atmosphere absolute. It is an effective treatment for various inflammatory conditions, including chronic wounds which are characterized by an excessive influx of neutrophils and their prolonged persistence at the wound site. Neutrophil apoptosis and clearance have been shown to be required for resolution of inflammation. The mechanisms by which HBO aids wound healing are well documented, but its effects on cellular inflammatory response are not well understood particularly with respect to neutrophils. The hypothesis presented in this thesis is that increased oxygenation via HBO assists chronic wound healing by enhancing non-inflammatory neutrophil defences and cell death through apoptosis. An investigation was carried out into the effects of HBO on neutrophil antimicrobial function and apoptosis using differentiated HL-60 cells as an in vitro neutrophil model. The data clearly showed that a single HBO treatment for 90 min caused an increase in the oxidative burst activity of neutrophil-like cells as shown by increased NBT staining, superoxide (cytochrome c reduction) and H2O2 production (Kruskal-Wallis, P < 0.05), and phagocytosis of Staphylococcus aureus. HBO treatment displayed a pro-apoptotic effect, enhancing caspase 3/7 activity both in the presence and absence of a TNF-α stimulus (Kruskal-Wallis, P < 0.05) and causing morphological changes (observed using Giemsa and SYBR® Safe staining) associated with apoptosis. Although no consistent pattern was observed, both hyperoxia and pressure alone seemed to contribute to both the increase in antimicrobial activity and the increase in apoptosis induced by HBO in these neutrophil-like cells (Chapters 4 and 5). HBO-enhanced neutrophil clearance by macrophages was investigated using bovine neutrophils and monocyte-derived macrophages (MDMФ). A single 90 min HBO exposure significantly increased the clearance of fresh and 22 h-aged neutrophils by MDMФ (two-way ANOVA, P < 0.05), suggesting an increase in phosphatidylserine (PS) exposure in apoptotic neutrophils after HBO treatment (Chapter 6). Importantly, a long-term repetitive exposure to HBO in patients with chronic wounds caused a significant decrease in the antioxidant enzyme defence system (one-way repeated measures ANOVA, P < 0.05), plasma TNF-α and IL-1β after 30 HBO sessions, with down regulation of expression of the anti-apoptotic factors, NF-B and Bcl-2 (Chapter 7). These findings may go some way towards explaining the effectiveness of HBO treatment not only for chronic wounds but also for other inflammatory conditions that may be affected by this treatment.

Hyperbaric Oxygen Therapy (HBOT) is an old technology which has acquired value in chronic wound care. HBOT is known to promote local and systemic healing effects by improving the oxygenation of the wound tissue. The increased tissue oxygenation hastens removal of the bacterial bioburden, which allows resolution of inflammation and facilitates matrix production, cell division, and ultimately wound closure. Staphylococcus aureus is the most frequently isolated organism from Diabetic Foot Infections (DFI). Therefore, our lab chose to use the treatment paradigm of HBOT to initially look at the single species level as to how HBOT affects S. aureus. DFI are primarily polymicrobial, so the responses of bacterial communities to this therapy were also considered. Previous research focused solely on host response to HBOT, but our pilot testing indicates that HBOT also exhibits a bacterial response. Initial testing with S. aureus indicated that HBOT can create growth defects in bacteria in vitro. In preliminary experiments, our lab discovered that bacterial culture on solid medium is greatly altered under the pressure of hyperbaric oxygen. Normal robust growth and pigmentation are seen in S. aureus cultured in ambient conditions. However, when the same strain is cultured under HBOT conditions, there is a marked decrease in pigmentation and colony size. When other species were exposed to HBOT conditions, growth on solid media was significantly diminished. Interestingly, K. pneumoniae is able to grow normally under HBOT conditions. Normal air mixtures at the increased pressure do not have any discernable effect on bacterial growth, and the limiting effects of oxygen are not seen unless used at the increased pressure. In a broth macrodilution MIC assay, various antibiotics show an increase in susceptibility after exposure to HBOT. Lastly, biofilm formation is altered under HBOT conditions, further supporting a bacterial adjustment to HBOT and an altered mode of growth. In order to better understand the effects of a high pressure high oxygen environment on the bacterial bioburden, this study investigates the effects of HBOT on bacterial species comprising a chronic wound. Primary data has suggested that HBOT increases susceptibility of antibiotics, and can alter bacterial transcription to hinder growth of many organisms. We hypothesize that Hyperbaric Oxygen Therapy affects diabetic foot infections by changing the healing process via transcriptional alteration of bacterial species in the wound. Furthermore, we hypothesize that HBOT alters the efficacy of some antibiotics as well as affecting the biofilm capacity of many bacterial species.

Thesis (MScMedSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A survey was conducted between 3 August and 5 October 2011 to test and evaluate the knowledge and attitudes of the military and civilian medical practitioners at the royal medical Service in the kingdom of Bahrain with regards to the clinical application of hyperbaric oxygen therapy. The survey consisted of a questionnaire and a semi-structured interview in which a total of 93 (out of a possible 302) medical practitioners were included (13 participated in the interviews). Similar to findings of previous studies, the knowledge of medical practitioners in Bahrain regarding hyperbaric oxygen therapy was low. Several practitioners were able to mention at least one indication for the therapy. No single factor had a statistically significant association with knowledge or the lack thereof. A large proportion of the participants had a positive attitude towards the use of hyperbaric oxygen therapy, felt that it is a valid treatment modality and they would refer their patients for such treatment. They would like to receive more information on hyperbaric oxygen therapy. Educational interventions to address the knowledge gap would likely be effective, since most participants have a positive attitude towards the therapy and believe that it is cost-effective.

The present research sought to understand patient experiences during Hyperbaric Oxygen Therapy (HBOT) by using 24 HBOT patients (17 men, 7 women) to examine the relationship between individual variables and anxiety, and providing One Session Exposure Therapy (OSET; Öst, 1989) if necessary. Pre-HBOT participants completed the following measures: State-Trait Anxiety Inventory (STAI; Spielberger, 1983), Claustrophobia Questionnaire (CLQ; Radomsky, Rachman, Thordarson, McIsaac, & Teachman, 2001), Anxiety Sensitivity Index (ASI; Reiss, Peterson, Gursky, & McNally, 1986), and Treatment Credibility/Expectancy Questionnaire (CEQ; Devilly & Borkovec, 2000). State Anxiety was assessed pre-HBOT and at the tenth and last sessions. Findings suggest Dispositional Anxiety (STAI-Trait + ASI), Expectancy of symptom improvement (CEQ), and gender were significantly predictive of State Anxiety before and during HBOT. Limitations and directions for future research are discussed.

As investigações sobre os efeitos da oxigenoterapia hiperbárica (OHB) em lesão por ruído são escassas e apontam para diferentes efeitos em função do momento de intervenção. Dentre os trabalhos já descritos foi observado efeito lesivo da OHB quando aplicada imediatamente ao trauma acústico, contudo, efeito positivo foi observado quando aplicada após 2 e 6 horas. Com relação aos tratamentos usados para trauma acústico, alguns estudos descrevem o uso de corticoides como melhor alternativa, mas recentemente estudos apontam para a sua combinação com OHB como a terapêutica com maior beneficio nas lesões por ruído. O presente estudo teve como objetivos avaliar o momento da intervenção pela OHB após 2, 4 e 6 horas de repouso auditivo após exposição ao ruído e avaliar a associação terapêutica entre a OHB e corticoterapia (CT). Cobaias albinas foram expostas a um ruído branco na faixa de 4 kHz com intensidade igual a 110dB NPS por 72h e divididas em cinco grupos terapêuticos: OHB com início após 2, 4 e 6h de repouso auditivo após exposição ao ruído, CT isolada e OHB após 6 horas de repouso associada a CT. O tratamento durou 5 dias, sendo uma sessão terapêutica por dia. Todos os animais tiveram a função auditiva avaliada pelo Potencial Evocado Auditivo de Tronco Encefálico (PEATE) e pelas Emissões Otoacústicas Produtos de Distorção (EOAPD) em três momentos: pré-ruído, pós-ruído e pós-tratamento. Após a eutanásia dos animais e preparação dos espécimes cocleares, todas as cócleas foram analisadas através de Microscopia Eletrônica de Varredura (MEV). Não houve diferença estatística significativa entre os momentos de intervenção pela OHB após 2, 4 e 6 horas, contudo, os dados de MEV demonstraram que uma maior otoproteção ocorreu quando a intervenção foi realizada após um maior repouso auditivo. Apesar da não diferença estatística significativa, os achados anatômicos e funcionais permitiram concluir que a associação terapêutica entre a OHB e a corticoterapia desempenhou um melhor efeito otoprotetor e terapêutico se comparada a essas mesmas terapias isoladas. / Investigations on the effects of hyperbaric oxygen therapy (HBOT) in noise injury are scarce and point to different effects depending on the time of intervention. Among the work already described has been observed damaging effect of HBOT when applied immediately after the acoustic trauma, however, positive effect was observed when applied after 2 and 6 hours of rest after the trauma. Studies describe the use of corticosteroids as the best alternative to treat acoustic trauma, but recent studies point to their combination with HBOT as the major benefit in lesions by noise. This study aimed to evaluate the time of intervention by HBOT after 2, 4 and 6 hours of rest after hearing noise exposure and to evaluate the association between HBOT and corticoid. Female guinea pigs were exposed to a white noise on 4kHz at 110dB SPL during 72 hours and divided into five treatment groups: HBOT after 2, 4 and 6 hours of rest after the noise exposure, corticosteroid therapy and HBOT combined with corticoid. The treatment lasted five days, being a therapy session per day. All animals were exposed to Distortion Product Otoacoustic Emissions (DPOAE) and Auditory Brainstem evoked Response (ABR) in three moments: before and after exposure to the noise and after the treatment. All cochleae were examined by scanning electron microscopy (SEM). There was no statistically significant difference between the moments of intervention by HBOT after 2, 4 and 6 hours, however, the SEM data showed that a greater otoprotection occurred when the intervention was performed after a higher auditory rest. Although not statistically significant, the anatomical and functional findings concluded that the association between HBOT and corticosteroid therapy played a better otoprotective and therapeutic effect compared to those same therapies alone.

As investigações sobre os efeitos da oxigenoterapia hiperbárica (OHB) em lesão por ruído são escassas e apontam para diferentes efeitos em função do momento de intervenção. Dentre os trabalhos já descritos foi observado efeito lesivo da OHB quando aplicada imediatamente ao trauma acústico, contudo, efeito positivo foi observado quando aplicada após 2 e 6 horas. Com relação aos tratamentos usados para trauma acústico, alguns estudos descrevem o uso de corticoides como melhor alternativa, mas recentemente estudos apontam para a sua combinação com OHB como a terapêutica com maior beneficio nas lesões por ruído. O presente estudo teve como objetivos avaliar o momento da intervenção pela OHB após 2, 4 e 6 horas de repouso auditivo após exposição ao ruído e avaliar a associação terapêutica entre a OHB e corticoterapia (CT). Cobaias albinas foram expostas a um ruído branco na faixa de 4 kHz com intensidade igual a 110dB NPS por 72h e divididas em cinco grupos terapêuticos: OHB com início após 2, 4 e 6h de repouso auditivo após exposição ao ruído, CT isolada e OHB após 6 horas de repouso associada a CT. O tratamento durou 5 dias, sendo uma sessão terapêutica por dia. Todos os animais tiveram a função auditiva avaliada pelo Potencial Evocado Auditivo de Tronco Encefálico (PEATE) e pelas Emissões Otoacústicas Produtos de Distorção (EOAPD) em três momentos: pré-ruído, pós-ruído e pós-tratamento. Após a eutanásia dos animais e preparação dos espécimes cocleares, todas as cócleas foram analisadas através de Microscopia Eletrônica de Varredura (MEV). Não houve diferença estatística significativa entre os momentos de intervenção pela OHB após 2, 4 e 6 horas, contudo, os dados de MEV demonstraram que uma maior otoproteção ocorreu quando a intervenção foi realizada após um maior repouso auditivo. Apesar da não diferença estatística significativa, os achados anatômicos e funcionais permitiram concluir que a associação terapêutica entre a OHB e a corticoterapia desempenhou um melhor efeito otoprotetor e terapêutico se comparada a essas mesmas terapias isoladas. / Investigations on the effects of hyperbaric oxygen therapy (HBOT) in noise injury are scarce and point to different effects depending on the time of intervention. Among the work already described has been observed damaging effect of HBOT when applied immediately after the acoustic trauma, however, positive effect was observed when applied after 2 and 6 hours of rest after the trauma. Studies describe the use of corticosteroids as the best alternative to treat acoustic trauma, but recent studies point to their combination with HBOT as the major benefit in lesions by noise. This study aimed to evaluate the time of intervention by HBOT after 2, 4 and 6 hours of rest after hearing noise exposure and to evaluate the association between HBOT and corticoid. Female guinea pigs were exposed to a white noise on 4kHz at 110dB SPL during 72 hours and divided into five treatment groups: HBOT after 2, 4 and 6 hours of rest after the noise exposure, corticosteroid therapy and HBOT combined with corticoid. The treatment lasted five days, being a therapy session per day. All animals were exposed to Distortion Product Otoacoustic Emissions (DPOAE) and Auditory Brainstem evoked Response (ABR) in three moments: before and after exposure to the noise and after the treatment. All cochleae were examined by scanning electron microscopy (SEM). There was no statistically significant difference between the moments of intervention by HBOT after 2, 4 and 6 hours, however, the SEM data showed that a greater otoprotection occurred when the intervention was performed after a higher auditory rest. Although not statistically significant, the anatomical and functional findings concluded that the association between HBOT and corticosteroid therapy played a better otoprotective and therapeutic effect compared to those same therapies alone.