Hyperbaric oxygen: its mechanisms and efficacy

Safety of hyperbaric oxygen therapy for management of central airway stenosis after lung transplant

BACKGROUND

Central airway stenosis (CAS) is common after lung transplantation and causes significant post-transplant morbidity. It is often preceded by extensive airway necrosis, related to airway ischemia. Hyperbaric oxygen therapy (HBOT) is useful for ischemic grafts and may reduce the development of CAS.

METHODS

The purpose of this study was to determine whether HBOT could be safely administered to lung transplant patients with extensive necrotic airway plaques. Secondarily, we assessed any effects of HBOT on the incidence and severity of CAS. Patients with extensive necrotic airway plaques within 1-2 months after lung transplantation were treated with HBOT along with standard care. These patients were compared with a contemporaneous reference group with similar plaques who did not receive HBOT.

RESULTS

Ten patients received HBOT for 18.5 (interquartile range, IQR 11-20) sessions, starting at 40.5 (IQR 34-54) days after transplantation. HBOT was well tolerated. Incidence of CAS was similar between HBOT-treated patients and reference patients (70% vs 87%, respectively; P=.34), but fewer stents were required in HBOT patients (10% vs 56%, respectively; P=.03).

CONCLUSIONS

This pilot study is the first to demonstrate HBOT safety in patients who develop necrotic airway plaques after lung transplantation. HBOT may reduce the need for airway stent placement in patients with CAS.

Hyperbaric oxygen preconditioning protects the lung against acute pancreatitis induced injury via attenuating inflammation and oxidative stress in a nitric oxide dependent manner

This study aimed to investigate the protective effects of hyperbaric oxygen preconditioning (HBO-PC) on acute pancreatitis AP associated acute lung injury (ALI) and the potential mechanisms. Rats were randomly divided into sham group, AP group, HBO-PC + AP group and HBO-PC + L-NAME group. Rats in HBO-PC + AP group received HBO-PC once daily for 3 days, and AP was introduced 24 h after last HBO-PC. In HBO-PC + L-NAME group, L-NAME (40 mg/kg) was intraperitoneally injected before each HBO-PC. At 24 h after AP, the blood lipase and amylase activities were measured; the lung and pancreas were harvested for pathological examination; the bronchoalveolar lavage fluid was collected for the detection of lactate dehydrogenase (LDH) and proteins; inflammatory factors, superoxide dismutase (SOD) activity and malonaldehyde content were measured in the lung and blood; the Nrf2, SOD-1 and haem oxygenase-1 (HO-1) protein expression was measured in the lung. The lung nitric oxide (NO) and NO synthase activity increased significantly after HBO-PC. HBO-PC was able to reduce blood lipase and amylase activities, improve lung and pancreatic pathology, decrease LDH and proteins in BALF, inhibit the production of inflammatory factors, reduce malonaldehyde content and increase SOD activity in the lung and blood as well as increase protein expression of Nrf2, SOD-1 and HO-1 in the lung. However, L-NAME before HBO-PC significantly attenuated protective effects of HBO-PC. HBO-PC is able to protect the lung against AP induced injury by attenuating inflammation and oxidative stress in the lung via a NO dependent manner.

Hyperbaric oxygen therapy for traumatic brain injury: bench-to-bedside

Traumatic brain injury (TBI) is a serious public health problem in the United States. Survivors of TBI are often left with significant cognitive, behavioral, and communicative disabilities. So far there is no effective treatment/intervention in the daily clinical practice for TBI patients. The protective effects of hyperbaric oxygen therapy (HBOT) have been proved in stroke; however, its efficiency in TBI remains controversial. In this review, we will summarize the results of HBOT in experimental and clinical TBI, elaborate the mechanisms, and bring out our current understanding and opinions for future studies.

Optical Imaging of Tumor Response to Hyperbaric Oxygen Treatment and Irradiation in an Orthotopic Mouse Model of Head and Neck Squamous Cell Carcinoma

Purpose

Hyperbaric oxygen therapy (HBOT) is used in the treatment of radiation-induced tissue injury but its effect on (residual) tumor tissue is indistinct and therefore investigated in this study.

Procedures

Orthotopic FaDu tumors were established in mice, and the response of the (irradiated) tumors to HBOT was monitored by bioluminescence imaging. Near infrared fluorescence imaging using AngioSense750 and Hypoxisense680 was applied to detect tumor vascular permeability and hypoxia.

Results

HBOT treatment resulted in accelerated growth of non-irradiated tumors, but mouse survival was improved. Tumor vascular leakiness and hypoxia were enhanced after HBOT, whereas histological characteristics, epithelial-to-mesenchymal transition markers, and metastatic incidence were not influenced.

Conclusions

Squamous cell carcinoma responds to HBOT with respect to tumor growth, vascular permeability, and hypoxia, which may have implications for its use in cancer patients. The ability to longitudinally analyze tumor characteristics highlights the versatility and potential of optical imaging methods in oncological research.

Electronic supplementary material

The online version of this article (doi:10.1007/s11307-015-0834-8) contains supplementary material, which is available to authorized users.

Hyperbaric oxygen therapy and osteonecrosis

Osteonecrosis of the jaw may be caused by radiation, medication, or infection. Optimal therapy requires a multimodal approach that combines surgery with adjuvant treatments. This review focuses on the use of adjunctive hyperbaric oxygen therapy for this condition. In addition to evidence regarding the basic and clinical science behind hyperbaric oxygen therapy, controversies in the field and economic implications are discussed.

Thioredoxin Protects Skin Flaps from Ischemia-Reperfusion Injury: A Novel Prognostic and Therapeutic Target

BACKGROUND

Ischemia-reperfusion injury is inevitable during free-tissue transfer, causing oxidative damage and extensive apoptosis. Thioredoxin is an endogenous protein with antioxidant and antiapoptotic activity in a variety of tissues. This study aims to investigate the protective effects of human thioredoxin-1 on ischemia-reperfusion flaps, and its clinical application value.

METHODS

Sixteen clinical specimens of ischemia-reperfusion flaps were collected and assessed for apoptosis and thioredoxin-1 expression. Eighty mice were administered recombinant human thioredoxin-1 or saline intraperitoneally for 5 days before ischemia-reperfusion. Half of the mice were killed 24 hours after reperfusion. The flap tissues were harvested and detected for the changes of morphology, apoptosis, redox condition, and relative protein expression. The flap survival percentage of the remaining mice was consecutively observed within 7 days of reperfusion.

RESULTS

Thioredoxin-1 abundance was negatively correlated with ischemia-reperfusion-induced apoptosis in human samples and animal models. The survival rate of the ischemia-reperfusion flaps in mice increased significantly following recombinant human thioredoxin-1 pretreatment. Mitigated tissue damage, reduced apoptosis, and more antioxidant activity were observed in recombinant human thioredoxin-1-pretreated flaps. Western blot analysis revealed thioredoxin-1 depletion and a significant increase in apoptosis signal-regulating kinase 1, p-p38, and cleaved caspase-3 abundance in the ischemia-reperfusion flaps, whereas supplementation of recombinant human thioredoxin-1 significantly reduced the apoptosis-related protein expression.

CONCLUSIONS

Thioredoxin-1 exerts its flap-protective role through redox regulation of reactive oxygen species scavenging and antiapoptotic signaling. The authors' research provides evidence that thioredoxin-1 may serve as a potential prognostic and therapeutic target for skin flap ischemia-reperfusion injury.

Central Nervous System Oxygen Toxicity and Hyperbaric Oxygen Seizures

INTRODUCTION

The use of hyperbaric oxygen (O2) as a therapeutic agent carries with it the risk of central nervous system (CNS) O2 toxicity.

METHODS

To further the understanding of this risk and the nature of its molecular mechanism, a review was conducted on the literature from various fields.

RESULTS

Numerous physiological changes are produced by increased partial pressures of oxygen (Po2), which may ultimately result in CNS O2 toxicity. The human body has several equilibrated safeguards that minimize effects of reactive species on neural networks, believed to play a primary role in CNS O2 toxicity. Increased partial pressure of oxygen (Po2) appears to saturate protective enzymes and unfavorably shift protective reactions in the direction of neural network overstimulation. Certain regions of the CNS appear more susceptible than others to these effects. Failure to decrease the elevated Po2 can result in a tonic-clonic seizure and death. Randomized, controlled studies in human populations would require a multicenter trial over a long period of time with numerous endpoints used to identify O2 toxicity.

CONCLUSIONS

The mounting scientific evidence and apparent increase in the number of hyperbaric O2 treatments demonstrate a need for further study in the near future.

Hyperbaric oxygen therapy stimulates colonic stem cells and induces mucosal healing in patients with refractory ulcerative colitis: a prospective case series

BACKGROUND

Hyperbaric oxygen (HBO) is used as part of treatment in a variety of clinical conditions. Its use in the treatment of ulcerative colitis has been reported in few clinical reports.

OBJECTIVE

We report the effect of HBO on refractory ulcerative colitis exploring one potential mechanism of action.

DESIGN

A review of records of patients with refractory ulcerative colitis who received HBO was conducted. Clinical and histopathological scoring was utilised to evaluate the response to HBO therapy (HBOT).

RESULTS

All patients manifested clinical improvement by the 40th cycle of HBOT. The median number of stool frequency dropped from seven motions/day (range=3-20) to 1/day (range=0.5-3), which was significant (z=-4.6, p<0.001). None of the patients manifested persistent blood passage after HBOT (z=-3.2, p=0.002). The severity index significantly improved after HBOT (z=-4.97, p<0.001). Histologically, a significant reduction of the scores of activity was recorded accompanied by a significant increase in the proliferating cell nuclear antigen labelling index of the CD44 cells of the colonic mucosa (p=0.001).

CONCLUSIONS

HBOT is effective in the setting of refractory ulcerative colitis. The described protocol is necessary for successful treatment. HBOT stimulates colonic stem cells to promote healing.

Integrative veterinary medical education and consensus guidelines for an integrative veterinary medicine curriculum within veterinary colleges

Integrative veterinary medicine (IVM) describes the combination of complementary and alternative therapies with conventional care and is guided by the best available evidence. Veterinarians frequently encounter questions about complementary and alternative veterinary medicine (CAVM) in practice, and the general public has demonstrated increased interest in these areas for both human and animal health. Consequently, veterinary students should receive adequate exposure to the principles, theories, and current knowledge supporting or refuting such techniques. A proposed curriculum guideline would broadly introduce students to the objective evaluation of new veterinary treatments while increasing their preparation for responding to questions about IVM in clinical practice. Such a course should be evidence-based, unbiased, and unaffiliated with any particular CAVM advocacy or training group. All IVM courses require routine updating as new information becomes available. Controversies regarding IVM and CAVM must be addressed within the course and throughout the entire curriculum. Instructional honesty regarding the uncertainties in this emerging field is critical. Increased training of future veterinary professionals in IVM may produce an openness to new ideas that characterizes the scientific method and a willingness to pursue and incorporate evidence-based medicine in clinical practice with all therapies, including those presently regarded as integrative, complementary, or alternative.

Effects of Hyperoxia on Oxygen-Related Inflammation with a Focus on Obesity

Several studies have shown a pathological oxygenation (hypoxia/hyperoxia) on the adipose tissue in obese subjects. Additionally, the excess of body weight is often accompanied by a state of chronic low-degree inflammation. The inflammation phenomenon is a complex biological response mounted by tissues to combat injurious stimuli in order to maintain cell homeostasis. Furthermore, it is believed that the abnormal oxygen partial pressure occurring in adipose tissue is involved in triggering inflammatory processes. In this context, oxygen is used in modern medicine as a treatment for several diseases with inflammatory components. Thus, hyperbaric oxygenation has demonstrated beneficial effects, apart from improving local tissue oxygenation, on promoting angiogenesis, wound healing, providing neuroprotection, facilitating glucose uptake, appetite, and others. Nevertheless, an excessive hyperoxia exposure can lead to deleterious effects such as oxidative stress, pulmonary edema, and maybe inflammation. Interestingly, some of these favorable outcomes occur under high and low oxygen concentrations. Hereby, we review a potential therapeutic approach to the management of obesity as well as the oxygen-related inflammation accompanying expanded adipose tissue, based on elevated oxygen concentrations. To conclude, we highlight at the end of this review some areas that need further clarification.

Perfluorocarbon nanoparticles enhance reactive oxygen levels and tumour growth inhibition in photodynamic therapy

Photodynamic therapy (PDT) kills cancer cells by converting tumour oxygen into reactive singlet oxygen (¹O₂) using a photosensitizer. However, pre-existing hypoxia in tumours and oxygen consumption during PDT can result in an inadequate oxygen supply, which in turn hampers photodynamic efficacy. Here to overcome this problem, we create oxygen self-enriching photodynamic therapy (Oxy-PDT) by loading a photosensitizer into perfluorocarbon nanodroplets. Because of the higher oxygen capacity and longer ¹O₂ lifetime of perfluorocarbon, the photodynamic effect of the loaded photosensitizer is significantly enhanced, as demonstrated by the accelerated generation of ¹O₂ and elevated cytotoxicity. Following direct injection into tumours, in vivo studies reveal tumour growth inhibition in the Oxy-PDT-treated mice. In addition, a single-dose intravenous injection of Oxy-PDT into tumour-bearing mice significantly inhibits tumour growth, whereas traditional PDT has no effect. Oxy-PDT may enable the enhancement of existing clinical PDT and future PDT design.

Photodynamic therapy is used in cancer treatment and generates reactive oxygen species to kill tumour cells but is limited by the availability of oxygen. Here, the authors modify a photodynamic sensitiser so that it produces excess oxygen species and show enhanced tumour cell killing in vitro and in vivo.

Necrotising Soft Tissue Infections: The Effect of Hyperbaric Oxygen on Mortality

In a single-centre, retrospective, case-controlled study of patients attending the Alfred Hospital in Prahran, Victoria, we assessed the effect of hyperbaric oxygen therapy (HBOT) in reducing mortality or morbidity in patients with necrotising fasciitis (NF) over a 13-year period from 2002 to 2014. A total of three hundred and forty-one patients with NF were included in the study, of whom 275 received HBOT and 66 did not. The most commonly involved sites were the perineum (33.7%), lower limb (29.9%) and trunk (18.2%). The commonest predisposing factor was diabetes mellitus (34.8%). Polymicrobial NF (type 1 NF) occurred in 50.7% and Group A streptococcal fasciitis (type 2 NF) occurred in 25.8% of patients. Mortality was 14.4% overall, 12% in those treated with, and 24.3% in those not treated with, HBOT. ICU support was required in 248 (72.7%) patients. Independent factors impacting on mortality included HBOT (odds ratio [OR] 0.42 [0.22 to 0.83], P=0.01), increased age (OR 1.06 [1.03 to 1.08], P=0.001) and immunosuppression (OR 2.6 [1.23 to 5.51], P=0.01). Mortality was linked to illness severity at presentation, however when adjusted for severity score and need for intensive care management, HBOT was associated with significant reduction in mortality.

Is Tracheal Transplantation Possible With Cryopreserved Tracheal Allograft and Hyperbaric Oxygen Therapy? An Experimental Study

BACKGROUND

Allografts have achieved prominence for tracheal reconstruction because of their natural physiologic and anatomic structure, which preserves respiratory tract flexibility and lumen patency. The immunomodulatory effects of cryopreservation prevent tracheal allograft rejection. In addition, hyperbaric oxygen therapy (HBOT) accelerates wound healing by promoting epithelization and neovascularization. This experimental study investigated the early and late effects of HBOT on cryopreserved tracheal allografts (CTAs).

METHODS

The study used 33 outbred Wistar rats weighing 300 to 350 g as allograft transplantation donors and recipients. Among these, 22 recipient rats were randomly assigned to the HBOT (n = 11) and control (n = 11) groups. Rats in the HBOT group were treated with 100% oxygen for 60 minutes at 2.5 atmospheres of absolute pressure for 7 days. Recipient rats in both groups were euthanized at 1 week (n = 5) and 4 weeks (n = 6) after transplantation, defined as the early and late periods, respectively.

RESULTS

In the early period, no significant histopathologic differences were observed between groups (p > 0.05). However, microscopic evaluation of the control group during the late period showed low epithelization of the CTA. In contrast, microscopic evaluation of the HBOT group during this same period revealed epithelium covering the transplanted CTA lumen. Significant epithelization and vascularization and significantly reduced inflammation and fibrosis were found in the HBOT group compared with the control group (p < 0.05).

CONCLUSIONS

HBOT may be effective in tracheal reconstruction by increasing epithelization and neovascularization after extended tracheal resection. HBOT, therefore, should be considered in CTA transplantation.

Microvascular oxygen partial pressure during hyperbaric oxygen in diabetic rat skeletal muscle

Hyperbaric oxygen (HBO) is a major therapeutic treatment for ischemic ulcerations that perforate skin and underlying muscle in diabetic patients. These lesions do not heal effectively, in part, because of the hypoxic microvascular O2 partial pressures (PmvO2 ) resulting from diabetes-induced cardiovascular dysfunction, which alters the dynamic balance between O2 delivery (Q̇o2) and utilization (V̇o2) rates. We tested the hypothesis that HBO in diabetic muscle would exacerbate the hyperoxic PmvO2 dynamics due, in part, to a reduction or slowing of the cardiovascular, sympathetic nervous, and respiratory system responses to acute HBO exposure. Adult male Wistar rats were divided randomly into diabetic (DIA: streptozotocin ip) and healthy (control) groups. A small animal hyperbaric chamber was pressurized with oxygen (100% O2) to 3.0 atmospheres absolute (ATA) at 0.2 ATA/min. Phosphorescence quenching techniques were used to measure PmvO2 in tibialis anterior muscle of anesthetized rats during HBO. Lumbar sympathetic nerve activity (LSNA), heart rate (HR), and respiratory rate (RR) were measured electrophysiologically. During the normobaric hyperoxia and HBO, DIA tibialis anterior PmvO2 increased faster (mean response time, CONT 78 ± 8, DIA 55 ± 8 s, P < 0.05) than CONT. Subsequently, PmvO2 remained elevated at similar levels in CONT and DIA muscles until normobaric normoxic recovery where the DIA PmvO2 retained its hyperoxic level longer than CONT. Sympathetic nervous system and cardiac and respiratory responses to HBO were slower in DIA vs. CONT. Specifically the mean response times for RR (CONT: 6 ± 1 s, DIA: 29 ± 4 s, P < 0.05), HR (CONT: 16 ± 1 s, DIA: 45 ± 5 s, P < 0.05), and LSNA (CONT: 140 ± 16 s, DIA: 247 ± 34 s, P < 0.05) were greater following HBO onset in DIA than CONT. HBO treatment increases tibialis anterior muscle PmvO2 more rapidly and for a longer duration in DIA than CONT, but not to a greater level. Whereas respiratory, cardiovascular, and LSNA responses to HBO are profoundly slowed in DIA, only the cardiovascular arm (via HR) may contribute to the muscle vascular incompetence and these faster PmvO2 kinetics.

Wilderness Medical Society practice guidelines for the prevention and treatment of frostbite: 2014 update

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for the prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the original guidelines published in Wilderness & Environmental Medicine 2011;22(2):156-166.

Effects of hyperbaric oxygen on Pseudomonas aeruginosa susceptibility to imipenem and macrophages

BACKGROUND

The seriousness to treat burn wounds infected with Pseudomonas aeruginosa led us to examine whether the effect of the carbapenem antibiotic imipenem is enhanced by hyperbaric oxygen (HBO).

MATERIALS & METHODS

The effects of HBO (100% O2, 3 ATA, 5 h) in combination with imipenen on bacterial counts of six isolates of P. aeruginosa and bacterial ultrastructure were investigated. Infected macrophages were exposed to HBO (100% O2, 3 ATA, 90 min) and the production of reactive oxygen species monitored.

RESULTS

HBO enhanced the effects of imipenen. HBO increased superoxide anion production by macrophages and likely kills bacteria by oxidative mechanisms.

CONCLUSION

HBO in combination with imipenem can be used to kill P. aeruginosa in vitro and such treatment may be beneficial for the patients with injuries containing the P. aeruginosa.

Beneficial effects of hyperbaric oxygen on edema in rat hippocampus following traumatic brain injury

Hyperbaric oxygen (HBO) therapy helps alleviate secondary injury following brain trauma [traumatic brain injury (TBI)], although the mechanisms remain unclear. In this study, we assessed recovery of post-TBI spatial learning and memory in rats using the Morris water maze (MWM) and measured changes in apparent diffusion coefficient in the hippocampus by diffusion-weighted imaging (DWI) to evaluate possible therapeutic effects of HBO on TBI-associated brain edema. DWIs were obtained 8, 24, 48 h, 7 days, and 14 days post-TBI. Daily HBO therapy significantly improved post-TBI MWM performance and reduced edema in the ipsilateral hippocampus, suggesting that the therapeutic efficacy of HBO is mediated, at least in part, by a reduction in brain edema.

Hyperbaric oxygen therapy attenuates central sensitization induced by a thermal injury in humans

BACKGROUND

Hyperbaric oxygen (HBO2 ) treatment has in animal experiments demonstrated antinociceptive effects. It was hypothesized that these effects would attenuate secondary hyperalgesia areas (SHAs), an expression of central sensitization, after a first-degree thermal injury in humans.

METHODS

Seventeen healthy volunteers were examined during two sessions using a randomized crossover design. Volunteers were studied during control conditions (ambient pressure, FI O2  = 0.21) and during HBO2 (2.4 standard atmosphere, FI O2  = 1.0, 90 min) conditions in a pressure chamber. Quantitative sensory testing, including assessment of SHAs was performed.

RESULTS

A statistically significant overall attenuation of SHAs was seen during the HBO2 sessions compared with the control-sessions (P = 0.011). In the eight volunteers starting with the HBO2 session, no difference in SHAs compared with control was demonstrated. However, in the nine volunteers starting with the control session, a statistical significant attenuation of SHAs was demonstrated in the HBO2 session (P = 0.004).

CONCLUSIONS

The results indicate that HBO2 therapy in humans attenuates central sensitization induced by a thermal skin injury, compared with control. These new and original findings in humans corroborate animal experimental data. The thermal injury model may give impetus to future human neurophysiological studies exploring the central effects of hyperbaric oxygen treatment.

Non-Toxic Metabolic Management of Metastatic Cancer in VM Mice: Novel Combination of Ketogenic Diet, Ketone Supplementation, and Hyperbaric Oxygen Therapy

The Warburg effect and tumor hypoxia underlie a unique cancer metabolic phenotype characterized by glucose dependency and aerobic fermentation. We previously showed that two non-toxic metabolic therapies - the ketogenic diet with concurrent hyperbaric oxygen (KD+HBOT) and dietary ketone supplementation - could increase survival time in the VM-M3 mouse model of metastatic cancer. We hypothesized that combining these therapies could provide an even greater therapeutic benefit in this model. Mice receiving the combination therapy demonstrated a marked reduction in tumor growth rate and metastatic spread, and lived twice as long as control animals. To further understand the effects of these metabolic therapies, we characterized the effects of high glucose (control), low glucose (LG), ketone supplementation (βHB), hyperbaric oxygen (HBOT), or combination therapy (LG+βHB+HBOT) on VM-M3 cells. Individually and combined, these metabolic therapies significantly decreased VM-M3 cell proliferation and viability. HBOT, alone or in combination with LG and βHB, increased ROS production in VM-M3 cells. This study strongly supports further investigation into this metabolic therapy as a potential non-toxic treatment for late-stage metastatic cancers.

Hyperbaric oxygen for patients with above-knee amputations, persistent ischemia, and nonreconstructable vascular disease

We describe four patients with above-knee amputations whose stump wounds failed to heal. After numerous revascularization attempts, these patients were diagnosed with nonreconstructable pelvic and groin vascular disease and were facing hip disarticulation. With the addition of hyperbaric oxygen treatment to vigilant wound care and negative pressure therapy, these patients healed their amputation stumps and were fit with prostheses. At their most recent follow-up, all patients were ambulating and using their prostheses.

Effect of hyperbaric oxygen preconditioning on peri-hemorrhagic focal edema and aquaporin-4 expression

The aim of the present study was to investigate the effect of hyperbaric oxygen preconditioning (HBO-PC) on peri-hemorrhagic focal edema and aquaporin-4 (AQP-4) expression in an experimental intracerebral hemorrhage (ICH) rat model. Sixty-six Sprague Dawley® rats were divided into three groups: The sham-surgery group (SHG; n=6); the control group (A-ICH; n=30), in which the rats were injected with autologous blood; and the experimental HBO-PC group (P-HBO; n=30). The rats underwent brain edema and AQP-4 detection at 5 postoperative time-points (24, 48 and 72 h and 5 and 7 days). The water content in the brain tissues of the A-ICH animals was higher than that in the brain tissues of the SHG rats at each time-point (P<0.05), and the edema in the P-HBO was significantly more severe 24 and 48 h postoperatively than that at 7 days postoperatively (P<0.05). The difference between the P-HBO and A-ICH was significant at 48 and 72 h postoperatively (P<0.05). AQP-4 was expressed in the post-hemorrhagic rat brains of all groups; the SHG animals exhibited low expression, while the A-ICH animals exhibited an increased expression 24 h postoperatively. In the A-ICH, expression peaked at 48 h postoperatively and began to decrease gradually after 72 h. At the 7-day time-point, the expression level in the A-ICH was closer to but still higher than that of the SHG animals (P<0.05). The differences between the P-HBO and A-ICH animals at the postoperative 24-h, 48-h and 7-day time-points were statistically significant (P<0.05). In conclusion, HBO-PC may downregulate AQP-4 expression to reduce the intracerebral edema, thus strengthening tolerance to ICH and protecting the nerves.

Hyperbaric Oxygen Therapy: A New Treatment for Chronic Pain?

BACKGROUND AND OBJECTIVE

Hyperbaric oxygen therapy (HBOT) is a treatment providing 100% oxygen at a pressure greater than that at sea level. HBOT is becoming increasingly recognized as a potential treatment modality for a broad range of ailments, including chronic pain. In this narrative review, we discuss the current understanding of pathophysiology of nociceptive, inflammatory and neuropathic pain, and the body of animal studies addressing mechanisms by which HBOT may ameliorate these different types of pain. Finally, we review clinical studies suggesting that HBOT may be useful in treating chronic pain syndromes, including chronic headache, fibromyalgia, complex regional pain syndrome, and trigeminal neuralgia.

DATABASE AND DATA TREATMENT

A comprehensive search through MEDLINE, EMBASE, Scopus, and Web of Science for studies relating to HBOT and pain was performed using the following keywords: hyperbaric oxygen therapy or hyperbaric oxygen treatment (HBOT), nociceptive pain, inflammatory pain, neuropathic pain, HBOT AND pain, HBOT AND headache, HBOT AND fibromyalgia, HBOT AND complex regional pain syndrome, and HBOT AND trigeminal neuralgia.

RESULTS

Twenty-five studies examining the role of HBOT in animal models of pain and human clinical trials were found and reviewed for this narrative review.

CONCLUSIONS

HBOT has been shown to reduce pain using animal models. Early clinical research indicates HBOT may also be useful in modulating human pain; however, further studies are required to determine whether HBOT is a safe and efficacious treatment modality for chronic pain conditions.

Does hyperbaric oxygen therapy prevent airway anastomosis from breakdown?

Ischemia with subsequent necrosis of anastomoses, after central airway resection and reconstruction, remains a feared complication for thoracic surgeons and their patients. To date, there is no evidence to support the use of hyperbaric oxygen in the prevention of necrosis of airway reconstructions in humans. We present a patient who underwent central airway surgery with postoperative ischemia of an end-to-side anastomosis. Repeat visit to a hyperbaric oxygen chamber seemed to prevent the anastomosis from subsequent necrosis and dehiscence with complete healing as a result. In conclusion, hyperbaric oxygen treatment can be considered when ischemia or necrosis is observed in central airway anastomoses during postoperative bronchoscopic surveillance.

Intra-arterial injection of sclerosants: Report of three cases treated with systemic steroids

Intra-arterial injection of sclerosants is a significant but uncommon complication of sclerotherapy that may result in extensive tissue necrosis and in rare cases digit or limb amputation. We have managed three cases in the past 10 years. One patient was referred for immediate treatment following intra-arterial injection of liquid polidocanol. The other two had undergone foam sclerotherapy with polidocanol and sodium tetradecyl sulphate, respectively. All patients were treated with a combination of oral steroids (prednisone 0.5–1 mg/kg) and systemic anticoagulants (enoxaparin 1.5 mg/kg daily subcutaneous injection). One case progressed to skin ulceration where prednisone was started five days after the adverse event and prematurely stopped after four weeks. The other cases did not progress to necrosis or other long-term sequelae. In these patients, prednisone was commenced immediately and slowly reduced over the following 12 weeks. The inflammation that follows ischemia plays a significant role in tissue necrosis and the immediate management of this adverse event may benefit from anti-inflammatory measures and in particular systemic steroid therapy unless contraindicated.

Photosynthetic biomaterials: a pathway towards autotrophic tissue engineering

Engineered tissues are highly limited by poor vascularization in vivo, leading to hypoxia. In order to overcome this challenge, we propose the use of photosynthetic biomaterials to provide oxygen. Since photosynthesis is the original source of oxygen for living organisms, we suggest that this could be a novel approach to provide a constant source of oxygen supply independently of blood perfusion. In this study we demonstrate that bioartificial scaffolds can be loaded with a solution containing the photosynthetic microalgae Chlamydomonas reinhardtii, showing high biocompatibility and photosynthetic activity in vitro. Furthermore, when photosynthetic biomaterials were engrafted in a mouse full skin defect, we observed that the presence of the microalgae did not trigger a native immune response in the host. Moreover, the analyses showed that the algae survived for at least 5 days in vivo, generating chimeric tissues comprised of algae and murine cells. The results of this study represent a crucial step towards the establishment of autotrophic tissue engineering approaches and suggest the use of photosynthetic cells to treat a broad spectrum of hypoxic conditions.

Literature review on the management of diabetic foot ulcer

Diabetic foot ulcer (DFU) is the most costly and devastating complication of diabetes mellitus, which affect 15% of diabetic patients during their lifetime. Based on National Institute for Health and Clinical Excellence strategies, early effective management of DFU can reduce the severity of complications such as preventable amputations and possible mortality, and also can improve overall quality of life. The management of DFU should be optimized by using a multidisciplinary team, due to a holistic approach to wound management is required. Based on studies, blood sugar control, wound debridement, advanced dressings and offloading modalities should always be a part of DFU management. Furthermore, surgery to heal chronic ulcer and prevent recurrence should be considered as an essential component of management in some cases. Also, hyperbaric oxygen therapy, electrical stimulation, negative pressure wound therapy, bio-engineered skin and growth factors could be used as adjunct therapies for rapid healing of DFU. So, it’s suggested that with appropriate patient education encourages them to regular foot care in order to prevent DFU and its complications.

Postoperative Hyperoxia (60%) Worsens Hepatic Injury in Mice

Background:

Liver damage by ischemia and reperfusion injury is a risk factor for morbidity and mortality after liver surgery. Postoperative oxygen treatment is routinely applied in the postanesthesia and intensive care unit after liver surgery. The risks of aggravating the injury by increasing inspiratory oxygen from 21 to 60% in the postoperative period were investigated in mice.

Methods:

Parameters of liver injury were compared after induction of hepatic ischemia–reperfusion injury, by clamping the left liver lobe for 45 min, and reperfusion for 24 h either under normoxic (21% oxygen) or hyperoxic (60% oxygen) conditions (n = 22 per group). The extent of tissue injury and oxidative responses was analyzed in the presence or absence of polymorphonuclear leukocytes, functional Kupffer cells, and the p47phox unit of the nicotinamide adenine dinucleotide phosphate oxidase (n = 6 to 11 per group).

Results:

Compared with postoperative normoxic conditions, hyperoxia increased cell damage (glutamate-pyruvate transaminase: 1,870 [±968 SD] vs. 60% 2,981 [±1,038 SD], 21 vs. 60% oxygen, in U/l as mean ± SD; P &lt; 0.01), liver weights (341 ± 52 vs. 383 ± 44, 21 vs. 60% oxygen, in mg as mean ± SD; P = 0.02), damage scores (1.9 ± 0.8 vs. 3.1 ± 1.0, 21 vs. 60% oxygen, score as mean ± SD; P = 0.02), and reactive oxygen species (15.0 ± 12.0 vs. 30.4 ± 19.2, 21 vs. 60% oxygen, in μmol/l as mean ± SD; P &lt; 0.05). The aggravation of the tissue damaging effects as a result of hyperoxia was not seen in mice with depletions of polymorphonuclear leukocytes or Kupffer cells, or with nonfunctioning nicotinamide adenine dinucleotide phosphate oxidase.

Conclusion:

Liver injury after ischemia was significantly aggravated by hyperoxia as a consequence of immune cell-mediated oxidative burst. Further studies are needed to elucidate whether routine delivery of high inspirational oxygen concentrations postoperatively should be limited.

Correlation between intraluminal oxygen gradient and radial partitioning of intestinal microbiota

BACKGROUND & AIMS

The gut microbiota is a complex and densely populated community in a dynamic environment determined by host physiology. We investigated how intestinal oxygen levels affect the composition of the fecal and mucosally adherent microbiota.

METHODS

We used the phosphorescence quenching method and a specially designed intraluminal oxygen probe to dynamically quantify gut luminal oxygen levels in mice. 16S ribosomal RNA gene sequencing was used to characterize the microbiota in intestines of mice exposed to hyperbaric oxygen, human rectal biopsy and mucosal swab samples, and paired human stool samples.

RESULTS

Average Po2 values in the lumen of the cecum were extremely low (<1 mm Hg). In altering oxygenation of mouse intestines, we observed that oxygen diffused from intestinal tissue and established a radial gradient that extended from the tissue interface into the lumen. Increasing tissue oxygenation with hyperbaric oxygen altered the composition of the gut microbiota in mice. In human beings, 16S ribosomal RNA gene analyses showed an increased proportion of oxygen-tolerant organisms of the Proteobacteria and Actinobacteria phyla associated with rectal mucosa, compared with feces. A consortium of asaccharolytic bacteria of the Firmicute and Bacteroidetes phyla, which primarily metabolize peptones and amino acids, was associated primarily with mucus. This could be owing to the presence of proteinaceous substrates provided by mucus and the shedding of the intestinal epithelium.

CONCLUSIONS

In an analysis of intestinal microbiota of mice and human beings, we observed a radial gradient of microbes linked to the distribution of oxygen and nutrients provided by host tissue.

Hyperbaric oxygen therapy as salvage treatment for sudden sensorineural hearing loss: a prospective controlled study

The most commonly used treatment for sensorineural sudden hearing loss (SSHL) in clinical practice is the administration of steroids; however, a favorable result is not always obtained. We studied 58 patients who failed to recover after primary treatment with IV steroids, 44 of these met our inclusion criteria (mean age 50.7, 27 males, range 30-74). We treated 23 patients (mean age 47.3, 16 males, age range 22-74) with hyperbaric oxygen therapy (HBO) (2.5 ATA for 60 min for 15 treatments), while 21 (mean age 54.5, 11 males, age range 22-71) patients refused to be treated and served as a non-randomized control group. Patients treated with HBO had a mean improvement of 15.6 dB (SD ± 15.3), with 1 of them completely healed, 5 with a good recovery, 10 with a fair recovery and 7 unchanged. Patients who were not treated had a spontaneous mean improvement of 5.0 dB (SD ± 11.4) with 3 patients with a good recovery, 1 patient with a fair recovery and 17 patients unchanged. Mean improvement was significantly better in patients treated with HBO compared to controls (p = 0.0133). Patients with worst hearing had the greater degree of improvement whether or not they were treated in the first 10 days after the onset of the hearing loss or between 11 and 30 days. In conclusion, hyperbaric oxygen therapy can lead to significant improvement of pure tone hearing thresholds in patients with SSHL who failed primary corticosteroid treatment and are within 4 weeks of the onset of deafness.

Hyperbaric oxygen therapy to treat diabetes impaired wound healing in rats

Wound healing in diabetes is frequently impaired and its treatment remains a challenge. Hyperbaric oxygen therapy (HBOT) receives a wide attendance and is often used as a last resort treatment option, however, its effectiveness for many conditions is unproven. We tested the effect of HBOT on healing of diabetic ulcers in an animal experimental setting. Experimental diabetes was induced by intraperitoneal injection of streptozotocin. Four weeks after diabetes induction, rats were ulcerated by clamping a pair of magnet disks on the dorsal skin for 16 h. After magnet removal, the animals received HBOT, daily on weekdays, for 4 weeks. To examine the effect of HBOT on diabetes impaired wound healing, the degree of wound tissue perfusion, inflammation, angiogenesis, and tissue breaking strength were evaluated. HBOT effects on the degree of inflammation and number of blood vessels could not be observed. HBOT improved the tissue breaking strength of the wound, however, this did not reach statistical significance. Twenty hours after ending the HBOT, a significantly improved oxygen saturation of the hemoglobin at the venous end of the capillaries and the quantity of hemoglobin in the micro-blood vessels was measured.

Hyperoxygenation attenuated a murine model of atopic dermatitis through raising skin level of ROS

Atopic dermatitis (AD) is a chronic inflammatory skin disease resulting from excessive stimulation of immune cells. Traditionally, reactive oxygen species (ROS) have been implicated in the progression of inflammatory diseases, but several opposing observations suggest the protective role of ROS in inflammatory disease. Recently, we demonstrated ROS prevented imiquimod-induced psoriatic dermatitis through enhancing regulatory T cell function. Thus, we hypothesized AD might also be attenuated in elevated levels of ROS through tissue hyperoxygenation, such as by hyperbaric oxygen therapy (HBOT) or applying an oxygen-carrying chemical, perfluorodecalin (PFD). Elevated levels of ROS in the skin have been demonstrated directly by staining with dihydroethidum as well as indirectly by immunohistochemistry (IHC) for indoleamine 2,3-dioxygenase (IDO). A murine model of AD was developed by repeated application of a chemical irritant (1% 2,4-dinitrochlorobenzene) and house dust mite (Dermatophagoide farinae) extract on one ear of BALB/c mice. The results showed treatment with HBOT or PFD significantly attenuated AD, comparably with 0.1% prednicarbate without any signs of side effects, such as telangiectasia. The expressions of interleukin-17A and interferon-γ were also decreased in the AD lesions by treatment with HBOT or PFD. Enhanced expression of IDO and reduced level of hypoxia-inducible factor-1α, in association with increased frequency of FoxP3⁺ regulatory T cells in the AD lesions, might be involved in the underlying mechanism of oxygen therapy. Taken together, it was suggested that tissue hyperoxygenation, by HBOT or treatment with PFD, might attenuate AD through enhancing skin ROS level.

Angiogenesis contributes to the neuroprotection induced by hyperbaric oxygen preconditioning against focal cerebral ischemia in rats

Ischemic stroke is one of the leading causes of mortality and disability worldwide. Previous studies have indicated that hyperbaric oxygen preconditioning (HBO-PC) can induce neuroprotection against focal cerebral ischemia. However, the underlying mechanisms are still not fully understood, and the optimal regimen for preconditioning must be confirmed. In the present study, we designed eight preconditioning regimens and compared their neuroprotective effects. Hyperbaric oxygen preconditioning every other day for there sessions exhibited the best neuroprotective effect; the infarct volume was reduced by almost 50% at 48 h after middle cerebral artery occlusion. We also found that HBO-PC significantly increased the microvessel density and the CD31-positive cells in the penumbra at 72 h after stroke. These results indicate that angiogenesis is involved in the neuroprotection induced by HBO-PC. Moreover, we explored the roles of HIF-1α and angiogenic factors in the angiogenesis process induced by HBO-PC. The results from western blotting demonstrated that protein expression of Ang-2 in the HBO-PC group was significantly increased. In conclusion, HBO-PC reduced brain injury and improved neurological function after focal cerebral ischemia, as partly mediated by the increased microvessel density in the penumbra, and this effect may result from the upregulation of Ang-2.

Hyperbaric oxygen therapy improves cognitive functioning after brain injury

Hyperbaric oxygen therapy has been widely applied and recognized in the treatment of brain injury; however, the correlation between the protective effect of hyperbaric oxygen therapy and changes of metabolites in the brain remains unclear. To investigate the effect and potential mechanism of hyperbaric oxygen therapy on cognitive functioning in rats, we established traumatic brain injury models using Feeney's free falling method. We treated rat models with hyperbaric oxygen therapy at 0.2 MPa for 60 minutes per day. The Morris water maze test for spatial navigation showed that the average escape latency was significantly prolonged and cognitive function decreased in rats with brain injury. After treatment with hyperbaric oxygen therapy for 1 and 2 weeks, the rats’ spatial learning and memory abilities were improved. Hydrogen proton magnetic resonance spectroscopy analysis showed that the N-acetylaspartate/creatine ratio in the hippocampal CA3 region was significantly increased at 1 week, and the N-acetylaspartate/choline ratio was significantly increased at 2 weeks after hyperbaric oxygen therapy. Nissl staining and immunohistochemical staining showed that the number of nerve cells and Nissl bodies in the hippocampal CA3 region was significantly increased, and glial fibrillary acidic protein positive cells were decreased after a 2-week hyperbaric oxygen therapy treatment. Our findings indicate that hyperbaric oxygen therapy significantly improves cognitive functioning in rats with traumatic brain injury, and the potential mechanism is mediated by metabolic changes and nerve cell restoration in the hippocampal CA3 region.

Tanshinone IIA pretreatment protects free flaps against hypoxic injury by upregulating stem cell-related biomarkers in epithelial skin cells

Background

Partial or total flap necrosis after flap transplantation is sometimes encountered in reconstructive surgery, often as a result of a period of hypoxia that exceeds the tolerance of the flap tissue. The purpose of this study was to determine whether Tanshinone IIA (TSA) pretreatment can protect flap tissue against hypoxic injury and improve its viability.

Methods

Primary epithelial cells isolated from the dorsal skin of mice were pretreated with TSA for 2 weeks. Cell Counting Kit-8 and Trypan Blue assays were carried out to examine the proliferation of TSA-pretreated cells after exposure to cobalt chloride. Polymerase chain reaction and western blot analysis were used to assess the expression of β-catenin, vascular endothelial growth factor (VEGF), sex determining region Y-box 2 (SOX2), OCT4 (also known as POU domain class 5 transcription factor 1), Nanog, and glycogen synthase kinase-3 beta (GSK-3β) in TSA-treated cells. In other experiments, after mice were pretreated with TSA for 2 weeks, a reproducible ischemic flap model was implemented, and the area of surviving tissue in the transplanted flaps was measured. Immunohistochemistry was conducted to examine Wnt signaling as well as stem cell- and angiogenesis-related biomarkers in epithelial tissue in vivo.

Results

Epidermal cells, pretreated with TSA, showed enhanced resistance to hypoxia. Activation of the Wnt signaling pathway in TSA-pretreated cells was characterized by the upregulation of β-catenin and the downregulation of GSK-3β. The expression of SOX2, Nanog, and OCT4 were also higher in TSA-pretreated epithelial cells than in control cells. In the reproducible ischemic flap model, pretreatment with TSA enhanced resistance to hypoxia and increased the area of surviving tissue in transplanted flaps. The expression of Wnt signaling pathway components, stem-cell related biomarkers, and VEGF and CD34, which are involved in the regeneration of blood vessels, was also upregulated in TSA-pretreated flap tissue.

Conclusions

TSA pretreatment protects free flaps against hypoxic injury and increases the area of surviving tissue by activating Wnt signaling and upregulating stem cell-related biomarkers.

Hyperbaric oxygen therapy in acute ischemic stroke: a review

Stroke, also known as cerebrovascular disease, is a common and serious neurological disease, which is also the fourth leading cause of death in the United States so far. Hyperbaric medicine, as an emerging interdisciplinary subject, has been applied in the treatment of cerebral vascular diseases since the 1960s. Now it is widely used to treat a variety of clinical disorders, especially hypoxia-induced disorders. However, owing to the complex mechanisms of hyperbaric oxygen (HBO) treatment, the therapeutic time window and the undefined dose as well as some common clinical side effects (such as middle ear barotrauma), the widespread promotion and application of HBO was hindered, slowing down the hyperbaric medicine development. In August 2013, the US Food and Drug Administration declared artery occlusion as one of the 13 specific indications for HBO therapy. This provides opportunities, to some extent, for the further development of hyperbaric medicine. Currently, the mechanisms of HBO therapy for ischemic stroke are still not very clear. This review focuses on the potential mechanisms of HBO therapy in acute ischemic stroke as well as the time window.

Nrf2 activation in astrocytes contributes to spinal cord ischemic tolerance induced by hyperbaric oxygen preconditioning

In this study, we investigated whether nuclear factor erythroid 2-related factor 2 (Nrf2) activation in astrocytes contributes to the neuroprotection induced by a single hyperbaric oxygen preconditioning (HBO-PC) against spinal cord ischemia/reperfusion (SCIR) injury. In vivo: At 24 h after a single HBO-PC at 2.5 atmospheres absolute for 90 min, the male ICR mice underwent SCIR injury by aortic cross-clamping surgery and observed for 48 h. HBO-PC significantly improved hindlimb motor function, reduced secondary spinal cord edema, ameliorated the reactivity of spinal motor-evoked potentials, and slowed down the process of apoptosis to exert neuroprotective effects against SCIR injury. At 12 h or 24 h after HBO-PC without aortic cross-clamping surgery, Western blot, enzyme-linked immunosorbent assay, realtime-polymerase chain reaction and double-immunofluorescence staining were used to detect the Nrf2 activity of spinal cord tissue, such as mRNA level, protein content, DNA binding activity, and the expression of downstream gene, such as glutamate-cysteine ligase, γ-glutamyltransferase, multidrug resistance protein 1, which are key proteins for intracellular glutathione synthesis and transit. The Nrf2 activity and downstream genes expression were all enhanced in normal spinal cord with HBO-PC. Glutathione content of spinal cord tissue with HBO-PC significantly increased at all time points after SCIR injury. Moreover, Nrf2 overexpression mainly occurs in astrocytes. In vitro: At 24 h after HBO-PC, the primary spinal astrocyte-neuron co-cultures from ICR mouse pups were subjected to oxygen-glucose deprivation (OGD) for 90 min to simulate the ischemia-reperfusion injury. HBO-PC significantly increased the survival rate of neurons and the glutathione content in culture medium, which was mainly released from asctrocytes. Moreover, the Nrf2 activity and downstream genes expression induced by HBO-PC were mainly enhanced in astrocytes, but not in neurons. In conclusion, our findings demonstrated that spinal cord ischemic tolerance induced by HBO-PC may be mainly related to Nrf2 activation in astrocytes.

Successful bilateral composite ear reattachment

Summary:

A successful bilateral ear composite graft nonmicrosurgical reattachment is presented. In cases where suitable vessels are unavailable for microsurgical revascularization, the reconstructive challenge can be formidable for salvaging the unique anatomic and aesthetic structure of the ear. The case is presented of an 18-year-old woman who was a victim of an assault wherein both of her ears were intentionally amputated by her attacker. She underwent successful surgical reattachment followed by a postoperative regimen of hyperbaric oxygen, cooling, and meticulous wound care. The patient achieved 100% survival of her left ear graft and 95% survival of her right ear graft. Clinical photographs at 18 months are presented, along with a discussion of the possible implications for other reconstructive applications.

A novel technique for increasing skin oxygenation

OBJECTIVE

To develop a novel technique for increasing skin oxygenation based on diffusion principles and Fick's laws of diffusion.

METHODS

A device that allows the creation of an oxygen-depleted environment immediately to the skin while simultaneously allowing measurement of the transcutaneous oxygen tension (TcPo2) levels was created. This device forms an oxygen gradient from the capillary bed of the subcutaneous tissue, through the skin's semipermeable membrane, and toward the oxygen-depleted enclosed environment. A healthy adult subject was fitted with the device. Once baseline TcPo2 levels were recorded, the oxygen concentration within the device was lowered, and TcPo2 levels were monitored. Effects were also studied when subjects breathed 100% oxygen for 5 minutes.

RESULTS

Oxygen levels in the device decreased in accordance with increases in skin TcPo2 levels measured within the device.

CONCLUSIONS

The application of this technique results in an increase in oxygen concentration in the skin and subcutaneous tissue in healthy subjects with normal, well-perfused skin. Whether this novel technique produces an increase in the skin oxygenation of subjects with inappropriate tissue oxygenation and chronic wounds requires further study.

Systematic review: The safety and efficacy of hyperbaric oxygen therapy for inflammatory bowel disease

BACKGROUND

Hyperbaric oxygen therapy (HBOT) provides 100% oxygen under pressure, which increases tissue oxygen levels, relieves hypoxia and alters inflammatory pathways. Although there is experience using HBOT in Crohn's disease and ulcerative colitis, the safety and overall efficacy of HBOT in inflammatory bowel disease (IBD) is unknown.

AIM

To quantify the safety and efficacy of HBOT for Crohn's disease (CD) and ulcerative colitis (UC). The rate of adverse events with HBOT for IBD was compared to the expected rate of adverse events with HBOT.

METHODS

MEDLINE, EMBASE, Cochrane Collaboration and Web of Knowledge were systematically searched using the PRISMA standards for systematic reviews. Seventeen studies involving 613 patients (286 CD, 327 UC) were included.

RESULTS

The overall response rate was 86% (85% CD, 88% UC). The overall response rate for perineal CD was 88% (18/40 complete healing, 17/40 partial healing). Of the 40 UC patients with endoscopic follow-up reported, the overall response rate to HBOT was 100%. During the 8924 treatments, there were a total of nine adverse events, six of which were serious. The rate of adverse events with HBOT in IBD is lower than that seen when utilising HBOT for other indications (P < 0.01). The risk of bias across studies was high.

CONCLUSIONS

Hyperbaric oxygen therapy is a relatively safe and potentially efficacious treatment option for IBD patients. To understand the true benefit of HBOT in IBD, well-controlled, blinded, randomised trials are needed for both Crohn's disease and ulcerative colitis.