Are superoxide and/or hydrogen peroxide responsible for some of the beneficial effects of hyperbaric oxygen therapy?

The potential of hyperbaric oxygen as a therapy for neurodegenerative diseases

The World Health Organization estimates that by the year 2040, neurodegenerative diseases will be the second leading cause of death in developed countries, overtaking cancer-related deaths and exceeded only by cardiovascular disease-related death. The search for interventions has therefore become paramount to alleviate some of this burden. Based on pathways affected in neurodegenerative diseases, hyperbaric oxygen treatment (HBOT) could be a good candidate. This therapy has been used for the past 50 years for conditions such as decompression sickness and wound healing and has been shown to have promising effects in conditions associated with neurodegeneration and functional impairments. The goal of this review was to explore the history of hyperbaric oxygen therapy, its uses, and benefits, and to evaluate its effectiveness as an intervention in treating neurodegenerative diseases. Additionally, we examined common mechanisms underlying the effects of HBOT in different neurodegenerative diseases, with a special emphasis on epigenetics.

Association between Vitamin D Supplements, Oxidative Stress Biomarkers, and Hyperbaric Therapy in Patients with Sudden Sensorineural Hearing Loss

The effect of vitamin D supplementation to patients with sudden sensorineural hearing loss (SSNHL), treated with hyperbaric oxygen (HBO) therapy, on the markers of the oxidant-antioxidant equilibrium was investigated. Patients were divided into two groups: those who did and did not receive vitamin D (cholecalciferol at 4000 IU/24 h). Concentrations of the following compounds, thiobarbituric acid reactive substances (TBARS), malondialdehyde (MDA), conjugated dienes (CD) in plasma and erythrocytes and activities of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) in erythrocytes, were determined. Haemoglobin (HGB) and haematocrit (HCT) were measured. Blood for analyses was collected from the basilic vein at three time points: before the first HBO procedure, up to 5 min after the first procedure, and after 14 procedures. No statistically significant differences in parameters tested were found between patients who did and did not receive vitamin D. In patients without supplementation, an increase of 53.2% (P ≤ 0.05) in erythrocyte TBARS was observed after the first HBO treatment. In patients receiving vitamin D, a reduction of 27.6% (P ≤ 0.05) was observed in erythrocyte MDA after 14 HBO treatments vs. that after the first treatment. In both groups, a decrease of 33.3% in plasma CD was observed after 14 treatments vs. that after the first treatment (P ≤ 0.05 and P ≤ 0.01, respectively). No statistically significant changes were observed in the erythrocyte SOD, GPx, and CAT activities and in HCT. A reduction of HGB concentration of 10.9% (P ≤ 0.05) was demonstrated in nonsupplemented patients after 14 treatments compared with baseline. The results confirm that the effect of HBO therapy on oxidative stress markers is inconclusive and complex. Repeated HBO procedures can induce adaptive changes which protect against disruption of the oxidant-antioxidant equilibrium. It is possible that vitamin D supplementation inhibits the process of lipid peroxidation in erythrocytes.

Effect of Hyperbaric Oxygen on Proliferation and Gene Expression of Human Chondrocytes: An In Vitro Study

PURPOSE

The present study investigated the effects of hyperbaric oxygen (HBO) on human chondrocyte proliferation and gene expression patterns.

METHODS

Chondrocyte cultures were transferred to a HBO chamber and exposed to 100% oxygen for 7 consecutive days. Within groups, pressure was varied between 1 and 2 atm and duration of HBO administration was varied among 60, 90, and 120 minutes. Cell counts were performed using the WST-1 assay at 1, 3, 5, and 7 days after initiation of HBO treatment to obtain data to plot a growth curve. Gene expression of apoptosis markers PARP and caspase 3, as well as cartilage specific proteins collagen II and COMP, were detected by reverse transcription polymerase chain reaction.

RESULTS

The experiments showed that in vitro administration of HBO inhibit chondrocyte growth. When applied compression was increased up to 2 atm, chondrocyte cell count was reduced by half at days 3 and 7 in association with an upregulation of the apoptosis markers PARP and caspase 3 as well as the cartilage specific proteins collagen II and COMP. No significant differences were monitored from varied duration of daily treatment.

CONCLUSION

Chondrocyte growth was inhibited in vitro by treatment of HBO. This inhibitory effect was even increased by elevating the applied pressure, while molecular testing showed reduced chondrocyte growth. Higher levels of HBO inhibited cell growth even more, but up-regulation of apoptosis specific markers and cartilage specific proteins were seen during administration of high oxygen levels. Thus, it has to be evaluated that there is a critical level of hypo-/hyperoxia required to stimulate or at least maintain chondrocyte cell proliferation.

Hyperbaric oxygen and aerobic exercise in the long-term treatment of fibromyalgia: A narrative review

Chronic pain is one of the most common clinical presentations in the primary care settings. In the US, Fibromyalgia (FM) affects about 1-3% of adults and commonly occurs in adults between the ages of 40-50 years. FM causes widespread muscular pain and tenderness with hyperalgesia and allodynia and may be associated with other somatic complaints. Hyperbaric oxygen therapy (HBOT) has been utilized and has recently shown promising effects in the management of FM and other chronic pain disorders. In HBOT, the intermittent breathing of 100% oxygen in a pressurized chamber where the pressure is higher than 1 atmosphere absolute (ATA) has been utilized. HBOT exhibits a significant anti-inflammatory effect through reducing production of glial cells and inflammatory mediators which results in pain alleviation in different chronic pain conditions. HBOT can also influence neuroplasticity and affects the mitochondrial mechanisms resulting in functional brain changes. In addition to that, HBOT stimulates nitric oxide (NO) synthesis which helps in alleviating hyperalgesia and NO-dependent release of endogenous opioids which seemed to be the primary HBOT mechanism of antinociception. Moreover, aerobic exercise and meditative movement therapies (MMT) have gained attention for their role in pain alleviation through different anti-inflammatory and antioxidant mechanisms. In this review, we aim to elucidate the different mechanisms of HBOT and aerobic exercise in attenuating pain as adjuvant therapy in the multidisciplinary treatment strategy of chronic pain, and more particularly fibromyalgia.

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.

The effect of hyperbaric oxygen therapy on kidneys in a rat model

Background. Hyperbaric oxygen therapy (HBOT) is used for treating various medical conditions. As far as known yet, HBOT is safe with few major side effects that are easy to avoid using a proper protocol. Renal tubular damage was observed in rats exposed to HBOT in a preliminary study conducted in our institution. Aim. We aim to assess whether HBOT causes renal damage and, if so, whether this is dose dependent. Methods. Thirty-one rats were randomly assigned to three groups. The first group received 10-days HBOT, 100% oxygen at a pressure of 2 atmospheres absolute (2 ATA) for 60 minutes/day, the second received the same treatment for 5 days and the third served as the control. Rat weight, survival, renal function tests, and renal histopathology were analyzed. Results. There were no significant changes in renal function tests in the plasma (cystatin C, urea, creatinine, and electrolytes) between the groups. No significant differences were observed in weight gain or renal histopathological evaluation between all groups. Conclusion. HBOT in this protocol does not cause renal impairment in a rat model, which reinforces the assumption that HBOT is safe in healthy rats, regarding renal function. Further research should be focused on the effect/safety of HBOT on nonhealthy kidneys.

Similarities and differences of hyperbaric oxygen and medical ozone applications

Hyperbaric oxygen (HBO) treatment is based on the principle of having the patient breath 100% oxygen in an environment above atmospheric pressure. Ozone (O(3)) is a colourless gas with a specific odour and consists of three oxygen atoms. The classical scientific understanding is that the world has become a place suitable for life for aerobic organisms with the increasing oxygen in the atmosphere billions of years ago. The formation of ozone after oxygen has then protected aerobic creatures from harmful rays. We now use these two gases for treatment purposes. It is noteworthy that the oxygen and ozone molecules that are formed by the same atom in different numbers are used for similar medical indications. We will try to emphasize the similarities and differences of HBO and medical ozone applications in this article.

Long-term exposure to repetitive hyperbaric oxygen results in cumulative oxidative stress in rat lung tissue

CONTEXT

Despite its known benefits, hyperbaric oxygen (HBO) is also reported to enhance the production of reactive oxygen species and can cause oxidative stress in several tissues. Previous studies had shown that HBO-induced oxidative stress is directly proportional to both its exposure pressure and duration. Nevertheless, these studies were usually performed with single-session HBO exposure but its clinical use commonly depends on long-term exposure periods.

OBJECTIVE

To clarify the oxidative effect of long-term repetitive HBO in the lung tissue of rats.

MATERIALS AND METHODS

Male Sprague-Dawley rats were divided into six study groups exposed to consecutive HBO sessions (2.8 atm/90  min) for 5, 10, 15, 20, 30, and 40 days. Animals were sacrificed 24  h after the last HBO session. An additional control group was set to obtain normal data. Lung malondialdehyde (MDA) and carbonylated protein (PCC) levels were determined as measures of oxidative stress along with the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase.

RESULTS

None of the measured parameters showed any changes among the groups exposed to 5-15 HBO sessions. However, MDA, PCC, and SOD were found to be significantly increased in the 20 to 40 session groups.

DISCUSSION AND CONCLUSION

These results indicate that repetitive treatment with HBO may cause oxidative stress in critical tissues including the lung. Although HBO-mediated free radicals are accepted to be responsible for the benefits of this therapeutic modality, especially in cases with prolonged exposure, possible injurious effects of supranormal values of bio-oxidative products need to be considered.

Effect of long-term normobaric hyperoxia on oxidative stress in mitochondria of the guinea pig brain

Normobaric hyperoxia (NBO) is applied for treatment of various clinical conditions related to hypoxia, but it can potentially also induce generation of reactive oxygen species, causing cellular damage. In this study, we examined the effects of 60 h NBO treatment on lipid and protein oxidative damage and activity of superoxide dismutase (Mn-SOD) in brain mitochondria of guinea pigs. Despite significant stimulation of Mn-SOD expression and activity the NBO treatment resulted in accumulation of markers of oxidative lesions, including lipid peroxidation (conjugated dienes, thiobarbituric acid reactive substances) and protein modification (bityrosines, adducts with lipid peroxidation products, oxidized thiols). When inhaled O(2) was enriched with oxygen cation, O (2) (•+) , the Mn-SOD expression and activity were stimulated to similar extend, but lipid peroxidation and protein oxidation were prevented. These results suggest that long-term NBO treatment causes oxidative stress, but enrichment of inhaled oxygen by oxygen cation can protect the brain again adverse effects of hyperoxia.

Ozone therapy and hyperbaric oxygen treatment in lung injury in septic rats

Various therapeutic protocols were used for the management of sepsis including hyperbaric oxygen (HBO) therapy. It has been shown that ozone therapy (OT) reduced inflammation in several entities and exhibits some similarity with HBO in regard to mechanisms of action. We designed a study to evaluate the efficacy of OT in an experimental rat model of sepsis to compare with HBO. Male Wistar rats were divided into sham, sepsis+cefepime, sepsis+cefepime+HBO, and sepsis+cefepime+OT groups. Sepsis was induced by an intraperitoneal injection of Escherichia coli; HBO was administered twice daily; OT was set as intraperitoneal injections once a day. The treatments were continued for 5 days after the induction of sepsis. At the end of experiment, the lung tissues and blood samples were harvested for biochemical and histological analysis. Myeloperoxidase activities and oxidative stress parameters, and serum proinflammatory cytokine levels, IL-1β and TNF-α, were found to be ameliorated by the adjuvant use of HBO and OT in the lung tissue when compared with the antibiotherapy only group. Histologic evaluation of the lung tissue samples confirmed the biochemical outcome. Our data presented that both HBO and OT reduced inflammation and injury in the septic rats' lungs; a greater benefit was obtained for OT. The current study demonstrated that the administration of OT as well as HBO as adjuvant therapy may support antibiotherapy in protecting the lung against septic injury. HBO and OT reduced tissue oxidative stress, regulated the systemic inflammatory response, and abated cellular infiltration to the lung demonstrated by findings of MPO activity and histopathologic examination. These findings indicated that OT tended to be more effective than HBO, in particular regarding serum IL-1β, lung GSH-Px and histologic outcome.

Efficacy of hyperbaric oxygen therapy and medical ozone therapy in experimental acute necrotizing pancreatitis

OBJECTIVES

Our aims were to evaluate the efficacy of ozone therapy (OT) in an experimental rat model of acute necrotizing pancreatitis (ANP) and to compare its effects with hyperbaric oxygen (HBO) therapy in this entity.

METHODS

Forty Sprague-Dawley rats were divided into sham-operated, ANP, ANP + HBO, and ANP + OT groups. Acute necrotizing pancreatitis was induced by infusing 1-mL/kg 3% sodium taurocholate into the common biliopancreatic duct. Hyperbaric oxygen was administered twice daily at a 2.8-atm pressure for 90 minutes. Ozone therapy was set as daily intraperitoneal injections of 0.7-mg/kg ozone/oxygen gas mixture. Hyperbaric oxygen and OT were continued for 3 days after the induction of ANP. The surviving animals were killed at the fourth day, and their pancreases were harvested for biochemical, microbiological, and histopathologic analyses.

RESULTS

Serum amylase/lipase and neopterin levels and tissue oxidative stress parameters were similar to sham's values in both the ANP + HBO and the ANP + OT groups. Histopathologic injury scores were significantly lower in the treatments groups than in the ANP group. When compared with the ANP group, the number of infected rats was significantly lesser in the ANP + HBO and the ANP + OT groups.

CONCLUSIONS

Hyperbaric oxygen and OT reduce the severity and the mortality in the experimental rat model of ANP, and a greater benefit was received for OT comparing with HBO.

Hyperbaric oxygen prevents early death caused by experimental cerebral malaria

Background

Cerebral malaria (CM) is a syndrome characterized by neurological signs, seizures and coma. Despite the fact that CM presents similarities with cerebral stroke, few studies have focused on new supportive therapies for the disease. Hyperbaric oxygen (HBO) therapy has been successfully used in patients with numerous brain disorders such as stroke, migraine and atherosclerosis.

Methodology/Principal Findings

C57BL/6 mice infected with Plasmodium berghei ANKA (PbA) were exposed to daily doses of HBO (100% O₂, 3.0 ATA, 1–2 h per day) in conditions well-tolerated by humans and animals, before or after parasite establishment. Cumulative survival analyses demonstrated that HBO therapy protected 50% of PbA-infected mice and delayed CM-specific neurological signs when administrated after patent parasitemia. Pressurized oxygen therapy reduced peripheral parasitemia, expression of TNF-α, IFN-γ and IL-10 mRNA levels and percentage of γδ and αβ CD4⁺ and CD8⁺ T lymphocytes sequestered in mice brains, thus resulting in a reduction of blood-brain barrier (BBB) dysfunction and hypothermia.

Conclusions/Significance

The data presented here is the first indication that HBO treatment could be used as supportive therapy, perhaps in association with neuroprotective drugs, to prevent CM clinical outcomes, including death.

Effects of different doses of hyperbaric oxygen on cisplatin-induced nephrotoxicity

Cisplatin, an effective antineoplastic agent, frequently induces acute renal failure in animals and humans. Hyperbaric oxygen (HBO) has been shown to prevent cisplatin-induced nephrotoxicity in rats. This study investigated the effect of two different HBO regimes on renal functions, oxidative stress, and histopathological changes in rat kidneys after cisplatin treatment. Wistar rats were divided into five groups: control, HBO, cisplatin, cisplatin plus once daily HBO, and cisplatin plus twice daily HBO. Cisplatin was given as a single intraperitoneal dose of 6 mg/kg, and HBO was applied for 60 min at 2.5 atm for six days. HBO alone did not alter any biochemical parameters or histopathological findings compared with the control group. Cisplatin increased serum urea and creatinine levels and caused severe histopathological injury. In addition, cisplatin increased lipid peroxidation and impaired superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in kidney tissue. Once daily HBO after cisplatin treatment slightly reduced serum urea and creatinine levels and attenuated histopathological injury. HBO also reduced lipid peroxidation and increased SOD and GSH-Px activities significantly. Although twice daily HBO was determined to be more effective than once daily HBO on oxidative stress parameters, it increased serum creatinine levels and histopathological injury compared with the cisplatin group. It was concluded that HBO alone does not induce nephrotoxicity and oxidative stress in rat kidneys; once daily HBO may prevent cisplatin-induced nephrotoxicity, an effect that is partially mediated by the modification of oxidant/antioxidant systems in the kidneys; and twice daily HBO potentiates cisplatin nephrotoxicity by a ROS-independent mechanism.

The effect of hyperbaric oxygen on regional brain and spinal cord levels of nitric oxide metabolites in rat

Hyperbaric oxygen (HBO(2)) therapy is reported to be beneficial in transient brain ischemia. The present study was conducted to determine the influence of HBO(2) on metabolites of nitric oxide (NO) in brain and spinal cord of rats. Rats were exposed to room air (RA), normobaric air (NBA), normobaric oxygen (NBO(2)), hyperbaric air (HBA) or HBO(2), the last two conditions at 2.5ATA (atmosphere absolute) for 60 min. The results demonstrate that, compared to the NBA control, oxygen alone generally reduced tissue levels of NO(x)(-) (nitrite plus nitrate). On the other hand, 2.5ATA alone tended to have a slight, if any, effect on tissue levels of NO(x)(-). The combination of oxygen and pressure (i.e., HBO(2)) generally led to an increase in tissue levels of NO(x)(-). Based on these findings, it is concluded that HBO(2) appears to markedly increase NO function most notably in the corpus striatum, brainstem, cerebellum and spinal cord.

Exposure time related oxidative action of hyperbaric oxygen in rat brain

Hyperbaric oxygen (HBO) is known to cause oxidative stress in several organs and tissues. Due to its high rate of blood flow and oxygen consumption, the brain is one of the most sensitive organs to this effect. The present study was performed to elucidate the relation of HBO exposure time to its oxidative effects in rats' brain cortex tissue. For this purpose, 49 rats were randomly divided into five groups. Except the control group, study groups were subjected to three atmospheres HBO for 30, 60, 90, and 120 min. Their cerebral cortex layer was taken immediately after exposure and used for analysis. Thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and nitrate-nitrite (NOX) levels were determined. TBARS and SOD levels were found to increase in a time-dependent manner. GSH-Px activity reflected an inconsistent course. NOX levels were found to be increased only in the 120 min exposed group. The results of this study suggests that HBO induced oxidative effects are strongly related with exposure time.

Time-dependent course of hyperbaric oxygen-induced oxidative effects in rat lung and erythrocytes

1. The oxygen toxicity of hyperbaric oxygen (HBO) treatment has long been of interest. There is an extensive amount of information regarding the role oxidative stress plays after HBO exposure in different tissues, but the question of the persistence of this oxidative effect has not been thoroughly elucidated. 2. The present study was performed to elucidate the persistence of the oxidative effects of HBO on rat lungs and erythrocytes after they had been subjected to 100% oxygen exposure. 3. Rats were divided into five groups. All animals, except those in the control group, were subjected to 100% oxygen for 2 h at 3 ATA ( identical with 300 kPa). Rats were killed at 30, 60, 90 or 120 min after exposure and thiobarbituric acid-reactive substances (TBARS) levels and the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were determined. 4. Thiobarbituric acid-reactive substances levels and SOD and GPx levels were found to be significantly increased in lung tissue up to 60 min after exposure. Superoxide dismutase activity persisted at significantly high values for 90 min after exposure in erythrocytes and the lung. The TBARS levels in erythrocytes were also significantly higher for 60 min, whereas increased GPx activity was observed to persist for only 30 min. 5. The oxidative effect of HBO exposure declines to physiological levels within 90 min at most for erythrocytes and in lung tissue in rats. Further studies should focus on the molecular mechanisms that can be activated during this time interval.

Effects of methylprednisolone and hyperbaric oxygen on oxidative status after experimental spinal cord injury: a comparative study in rats

The effects of hyperbaric oxygen (HBO) therapy or methylprednisolone on the oxidative status were evaluated in experimental spinal cord injury. Clip compression method was used to produce acute spinal cord injury rats. Hyperbaric oxygen was administered twice daily for a total of eight 90 min-sessions at 2.8 atmospheres. Methylprednisolone was first injected with a bolus of 30 mg/kg followed with an infusion rate of 5.4 mg/kg/h for 24 h. Five days after clip application animals were sacrificed and their traumatized spinal cord segment were excised. Tissue levels of thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were evaluated to reflect oxidant/antioxidant status. Non-treated clip-operated animals reflected significantly higher SOD, GSH-Px and TBARS levels that were found to be significantly higher than the sham-operated. Methylprednisolone was not able to lower these levels. HBO administration diminished all measured parameters significantly; however, their levels appeared already to be high when compared with sham animals. According to these results obtained on the 5th day after induction, HBO, but not methylprednisolone, seems to procure prevention against oxidative spinal cord injury.

Hyperbaric oxygen treatment augments the efficacy of a losartan regime in an experimental nephrotic syndrome model

BACKGROUND/AIMS

Proteinuria is associated with oxidant stress and inflammation. Hyperbaric oxygen (HBO) treatment has anti-inflammatory and anti-oxidant effects. The aim of the study was to investigate the benefits of HBO treatment on an experimental nephrotic syndrome model.

METHODS

50 male Sprague-Dawley rats weighing 255 +/- 39 g were housed. Forty rats were injected 6 mg/kg adriamycin into tail veins under anesthesia to induce nephrosis, while 10 rats were spared as sham control. After the stabilization of proteinuria at the sixth week, the rats were treated for 6 weeks by losartan (n = 10, 30 mg/kg/day), HBO (n = 10, 2.8 atmosphere absolute, 90 min/day), HBO + losartan (n = 10) and vehicle (n = 10). Protein carbonyl (PCO), superoxide dismutase (SOD) and glutathione peroxidase (GPx) were analyzed from tissue specimens. Biochemical markers were studied from venous samples and 24-hour urine was collected for proteinuria. The surviving animals at 12 weeks (vehicle group (n = 6), HBO (n = 6), losartan (n = 8), HBO + losartan (n = 10) were sacrificed. Glomerular sclerosis, tubulointerstitial and blood vessel changes were determined by semiquantitative scoring.

RESULTS

The PCO levels increased (p < 0.001), and the GPx and SOD levels decreased (p < 0.001 for both) in the nephrotic rats. In losartan and HBO groups GPx levels increased (p = 0.001, p = 0.002 respectively), but PCO and SOD levels did not change. The combination of HBO with losartan significantly increased the GPx and SOD levels (p = 0.001 for both) and decreased PCO levels (p = 0.005). HBO but not losartan significantly reduced proteinuria (p < 0.001). The combination of HBO and losartan reduced proteinuria better than the single losartan regime (p < 0.001). The effect of the combination was also noticed on the histological examination of the kidneys. The activities, appetites, weight gains, and improvement of edema were better in the HBO combined with losartan regime.

CONCLUSIONS

These results indicate that the addition of HBO therapy to a conventional regime, angiotensin receptor blockers, has significant benefits in the management of proteinuria. Future clinical studies are needed to elucidate the role of HBO and other antioxidant strategies in the treatment of proteinuria.

Hyperbaric oxygen therapy may improve symptoms in autistic children

Autism is a neurodevelopmental disorder that currently affects as many as 1 out of 166 children in the United States. Recent research has discovered that some autistic individuals have decreased cerebral perfusion, evidence of neuroinflammation, and increased markers of oxidative stress. Multiple independent single photon emission computed tomography (SPECT) and positron emission tomography (PET) research studies have revealed hypoperfusion to several areas of the autistic brain, most notably the temporal regions and areas specifically related to language comprehension and auditory processing. Several studies show that diminished blood flow to these areas correlates with many of the clinical features associated with autism including repetitive, self-stimulatory and stereotypical behaviors, and impairments in communication, sensory perception, and social interaction. Hyperbaric oxygen therapy (HBOT) has been used with clinical success in several cerebral hypoperfusion syndromes including cerebral palsy, fetal alcohol syndrome, closed head injury, and stroke. HBOT can compensate for decreased blood flow by increasing the oxygen content of plasma and body tissues and can even normalize oxygen levels in ischemic tissue. In addition, animal studies have shown that HBOT has potent anti-inflammatory effects and reduces oxidative stress. Furthermore, recent evidence demonstrates that HBOT mobilizes stem cells from human bone marrow, which may aid recovery in neurodegenerative diseases. Based upon these findings, it is hypothesized that HBOT will improve symptoms in autistic individuals. A retrospective case series is presented that supports this hypothesis.

Extension of brain tolerance to hyperbaric O2 by intermittent air breaks is related to the time of CBF increase

Intermittent air breaks during hyperbaric oxygen (HBO2) exposures protect against pulmonary and central nervous system (CNS) toxicity. The mechanisms of this beneficial effect from intermittency are not known. In this study, we examined if release of vasoconstriction during HBO2 exposure indicates a threshold for toxic dose of HBO2 and how it may be related to tolerance by intermittency. Awake rats instrumented for EEG and cerebral blood flow (CBF) measurement were exposed to 100% O2 at 6 ATA (absolute pressure). Air breaks of 3 or 10 min were given at different times after CBF increase. Following the air break, animals were exposed to 100% O2 until seizure and total O2 time was used to calculate benefit/toxicity. The most beneficial schedule was then used to assess the role of the multiple air breaks in extension of HBO2 tolerance. A significant increase in seizure latency was observed in animals with a single 3- or 10 min air break given 5-10 min after CBF increase. No change in seizure latency was observed when air breaks were given beyond (>10 and <5 min) this window. The duration of total O2 time to seizures was doubled with multiple 3 min air breaks, and quadrupled with 10 min air breaks compared with continuous HBO2 exposures. With more time spent on O2, the duration of air breaks was not sufficient for recovery from O2 toxicity and for CBF to return to baseline. Results show that an "optimal window" of HBO2 exposure is required for benefits by intermittent exposure to air.

Investigation of the Effect of Hyperbaric Oxygen on Experimental Cyclosporine Nephrotoxicity

Hyperbaric oxygen interacts with drugs which patients use concurrently with hyperbaric oxygen treatment, which may cause in potentiation or inhibition of both therapeutic and toxic effects. We examined the effect of hyperbaric oxygen therapy on experimental cyclosporine A nephrotoxicity. The study comprised four groups of rats: a control group, a cyclosporine A group (25 mg/kg/day intraperitoneally for four days), a hyperbaric oxygen group (60 min. every day for four days at 2.5 atmospheric pressure), and a cyclosporine A+hyperbaric oxygen group (CsA 25 mg/kg/day intraperitoneally for four days+hyperbaric oxygen for 60 min. every day for four days at 2.5 atmospheric pressure). Hyperbaric oxygen did not alter biochemical parameters. Cyclosporine A increased serum urea and serum creatinine levels and decreased creatinine clearance. In the cyclosporine A+hyperbaric oxygen group serum urea level increased more than in the cyclosporine A group. Cyclosporine A increased tubular epithelial cell apoptosis and necrosis score values. The numbers of apoptotic cells in proximal tubule epithelial cells in the cyclosporine A+hyperbaric oxygen group were significantly higher than those of the cyclosporine A group. We recommend that renal functions of the patients receiving cyclosporine A should be monitored during hyperbaric oxygen therapy.

Correlation between hyperbaric oxygen exposure pressures and oxidative parameters in rat lung, brain, and erythrocytes

OBJECTIVES

The oxygen toxicity risk of hyperbaric oxygen (HBO) treatment has long been of interest. However, there are no comprehensive articles describing the relationship between HBO protocols and oxidative parameters used clinically. The purpose of this study was to determine the effects of various HBO pressure modalities on the oxidative values of rat lung, brain, and erythrocytes.

DESIGN AND METHODS

A total of 64 male Sprague-Dawley rats was randomly divided into 7 groups. Group A was used as a control. Groups C to G were subjected to 100% oxygen at a pressure of 1, 1.5, 2, 2.5, and 3 ATA (atmosphere absolute), respectively, for 2 h. Group B was exposed to normal atmospheric air at 3 ATA for the same duration. The rat's lung, brain, and blood were taken immediately after the exposure and thiobarbituric acid reactive substances (TBARS) and superoxide dismutase (SOD) levels were determined.

RESULTS

Both TBARS levels and SOD activity increased concordantly with the pressure increase. Although a statistically significant change in TBARS levels started from 100% oxygen exposure at 1 ATA (normobaric), SOD activity was affected after 2 ATA. A significant correlation exists between exposure pressure and the aforementioned parameters. Ambient air exposure at 3 ATA did not affect any parameters besides the brain TBARS levels.

CONCLUSIONS

It is clear that HBO exposure causes oxidative stress. The main reason for this effect seems to be exposure to pure oxygen, since pure high pressure has no significant effect on the aforementioned parameters. However, clinicians should use as low pressures as possible since all oxidative parameters appear to be directly proportional to the extent of HBO exposure.

Protective effects of exogenously administered or endogenously produced melatonin on hyperbaric oxygen-induced oxidative stress in the rat brain

1. Hyperbaric oxygen (HBO) is a widely used treatment modality in many diseases. A known side-effect of HBO is the production of reactive oxygen species (ROS). Many anti-oxidants, such as vitamins C and E, riboflavin and selenium, have been used successfully to scavenge the ROS produced by HBO administration. 2. The aim of the present study was to determine whether melatonin, a newly discovered anti-oxidant, has a protective effect against the overproduction of ROS produced by HBO in rat brain tissue. 3. Seventy male Sprague-Dawley rats were divided into seven groups as follows: 1, daytime control; 2, daytime HBO; 3, melatonin; 4, daytime HBO plus melatonin; 5, night-time control; 6, night-time HBO; and 7, night-time HBO under light exposure. 4. Hyperbaric oxygen was administered at 303 kPa for 120 min. Melatonin was injected at a dose of 10 mg/kg, i.p. Brain malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GPx) levels were measured to elucidate oxidant status. 4. The MDA and SOD levels of groups 2 and 7 increased significantly. Exogenous (group 4) and endogenous (group 6) melatonin protected against HBO-induced lipid peroxidation. Exogenously administered melatonin (groups 3 and 4) had increased levels of the anti-oxidant enzymes SOD and GPx. 5. In conclusion, HBO caused oxidative stress and melatonin exhibited protective effects. Both endogenously produced and exogenously administered melatonin were found to be effective.

Hyperbaric oxygen therapy of cerebral ischemia

BACKGROUND

Hyperbaric oxygen (HBO) therapy of cerebral ischemia has been evaluated in a number of human and animal studies; however, there is presently no consensus on its efficacy.

METHODS

We present a review of animal and human studies on HBO therapy of cerebral ischemia as well as present potential mechanisms of action of HBO.

RESULTS

Animal studies of HBO have shown promise by reducing infarct size and improving neurologic outcome. HBO has also been shown to inhibit inflammation and apoptosis after cerebral ischemia. Early reports in humans also suggested benefit in stroke patients treated with HBO. Recent randomized, controlled human studies, however, have not shown benefit, although all were limited by small sample size. Important differences between animal and human studies suggest HBO might be more effective in stroke within the first few hours and at a pressure of 2-3 ATA.

CONCLUSIONS

The clinical usefulness of HBO in the treatment of cerebral ischemia is not yet certain. Attention to emerging pathophysiologic data should be taken into consideration in design of any future clinical trials of HBO in acute ischemic stroke.

Effects of hyperbaric oxygen treatment on liver functions, oxidative status and histology in septic rats

OBJECTIVE

The liver is thought to be responsible for multiple organ failure during sepsis. Increase in tissue oxygen consumption is a major component of the septic response. Hyperbaric oxygen (HBO) therapy provides more oxygenation in the whole body. This study examined the effect of HBO alone or in combination with cefepime (CEF) on the liver in septic rats.

DESIGN AND INTERVENTIONS

We divided 90 male rats into six groups; control, HBO, sepsis (SEP), SEP+HBO, SEP+CEF, and SEP+CEF+HBO. Sepsis was induced with an intraperitoneal injection of Escherichia coli (2.1 x 10(9) cfu). A total of six HBO sessions were performed at 2 atm absolute for 90 min at 6-h intervals. CEF was administered intraperitoneally at a dose of 50 mg/kg twice daily. Animals were killed 48 h after sepsis induction. Their liver and blood were removed for biochemical and histopathological analysis.

MEASUREMENTS AND RESULTS

Liver thiobarbituric acid reactive substances as well as serum alanine transaminase, aspartate transaminase and alkaline phosphatase levels increased while the activity of the antioxidant enzymes superoxide dismutase and catalase decreased significantly in septic rats. These parameters returned to nearly control levels in the SEP+CEF+HBO group. Histological observations supported these findings: Hepatocellular degeneration was observed and intensive polymorphonuclear cell infiltration appeared in all fields of septic animal livers. HBO alone could not sufficiently reverse these histopathological changes, but most liver sections presented normal histology when it was combined with CEF.

CONCLUSIONS

HBO may be a useful adjuvant therapy modality to improve the efficacy of sepsis treatment.

Effects of hyperbaric oxygen on Leishmania amazonensis promastigotes and amastigotes

In the present study, we evaluated the effects of hyperbaric oxygen (HBO) exposure in both Leishmania amazonensis life stages (promastigotes and amastigotes) and on macrophage cultures infected with the parasite. HBO treatment protocols, which can be tolerated by humans and animals, induced irreversible metabolic damage and affected parasite morphology, growth and ability to transform. The observation that the antioxidant N-acetylcysteine (NAC) prevents some of these deleterious effects indicated an involvement of oxidative stress during parasite HBO exposure. In addition, HBO exposed L. amazonensis-infected macrophage cultures showed reduction of the percentage of infected cells and of the number of intracellular parasites per cell. Thus, the demonstration that HBO, a therapy used in the management of different diseases, is toxic for both L. amazonensis life stages and can alter macrophage susceptibility to the infection encourages further studies of this therapy in animal models of Leishmania infection.

Investigation of the role of hyperbaric oxygen therapy in cisplatin-induced nephrotoxicity in rats

Cisplatin (CP) is an effective chemotherapeutic agent used in the treatment of a variety of solid tumours. The most frequently observed side-effect of the use of CP is nephrotoxicity. Recently, evidence has been demonstrated that reactive oxygen species forming in the tubular epithelium play an important role in CP-linked nephrotoxicity. The aim of the study was to observe the effect of hyperbaric oxygen (HBO) therapy on CP nephrotoxicity, a subject which has not been studied previously. Wistar rats were treated with CP (a single intraperitoneal (IP) dose of 0.6 mg/100 g) alone and in combination with HBO (60 min every day for seven days at 2.5 x atmospheric pressure). Effects of the treatment on renal function and histology were determined. In analyses at the end of the study it was observed that serum urea, creatinine, and daily urinary protein excretion levels of the CP group were higher than at the start of the study, and that the creatinine clearance level had fallen (P < 0.05). There was no significant difference between the CP+HBO group and HBO group serum urea, creatinine, creatinine clearance, and daily urinary protein excretion levels at the beginning and end of the study (P > 0.05). Histopathological examination showed that the necrosis score in the proximal tubule epithelial cells and average apoptitic cell numbers in the CP group were higher than those in the CP+HBO and HBO groups (P < 0.05). There was no statistical difference between the CP+HBO group and the HBO group in terms of necrosis score in the proximal tubule epithelial cells and the percentage of distal tubules containing hyaline casts in the lumen. In conclusion, in this study it was observed that in experimental study of CP nephrotoxicity the synchronous application of HBO therapy with CP prevents kidney damage.

Exogenously administered and endogenously produced melatonin reduce hyperbaric oxygen-induced oxidative stress in rat lung

Hyperbaric oxygen (HBO) is a widely used treatment modality in many diseases. A known side effect of HBO is the production of reactive oxygen species. Many antioxidants such as vitamins C and E, riboflavin and selenium have been used successfully to scavenge the reactive oxygen species caused by HBO administration. In this study, we aimed to see if melatonin, a newly discovered antioxidant, has a protective effect against the overproduction of reactive oxygen species produced by HBO in rat lung tissue. Sixty male Sprague-Dawley rats were divided into 5 groups as follows: control, daytime HBO (3 ATA, 120 min), daytime HBO plus melatonin (10 mg/kg), nighttime HBO and nighttime HBO (under light exposure). The MDA, SOD and CAT levels of daytime and nighttime HBO (under light exposure) increased significantly. This significance was not found in the daytime HBO plus melatonin and nighttime HBO groups when compared with the control. In this study, HBO caused oxidant stress, and melatonin decreased the levels of MDA, SOD and CAT. Moreover, endogenous melatonin was found to be a more effective antioxidant than exogenous 10 mg/kg melatonin.

The endotracheal tube in situ as a foreign body: the master key to general anesthesia, its mechanism and inherent (though not peculiar) complications and to effective 'life support'

Next to the discovery of general anesthesia, the most important advance was the development of endotracheal intubation by Irish Sir I.W. Magill with Dr. E.C. Rowbotham and other British colleagues in London. The endotracheal tube not alone enhanced the value, safety, and applicability of general anesthesia, it also demonstrates the mechanism of the phenomenon, and provides a monitor for the reactions and condition of the anesthetized patient.