Hyperbaric oxygen and cerebral physiology

Intervention modalities for brain fog caused by long-COVID: systematic review of the literature

Individuals suffering from long-COVID can present with "brain fog", which is characterized by a range of cognitive impairments, such as confusion, short-term memory loss, and difficulty concentrating. To date, several potential interventions for brain fog have been considered. Notably, no systematic review has comprehensively discussed the impact of each intervention type on brain fog symptoms. We included studies on adult (aged > 18 years) individuals with proven long- COVID brain-fog symptoms from PubMed, MEDLINE, Central, Scopus, and Embase. A search limit was set for articles published between 01/2020 and 31/12/2023. We excluded studies lacking an objective assessment of brain fog symptoms and patients with preexisting neurological diseases that affected cognition before COVID-19 infection. This review provided relevant information from 17 studies. The rehabilitation studies utilized diverse approaches, leading to a range of outcomes in terms of the effectiveness of the interventions. Six studies described noninvasive brain stimulation, and all showed improvement in cognitive ability. Three studies described hyperbaric oxygen therapy, all of which showed improvements in cognitive assessment tests and brain perfusion. Two studies showed that the use of Palmitoylethanolamide and Luteolin (PEA-LUT) improved cognitive impairment. Noninvasive brain stimulation and hyperbaric oxygen therapy showed promising results in the treatment of brain fog symptoms caused by long-COVID, with improved perfusion and cortical excitability. Furthermore, both rehabilitation strategies and PEA-LUT administration have been associated with improvements in symptoms of brain fog. Future studies should explore combinations of interventions and include longer follow-up periods to assess the long-term effects of these treatments.

Hyperbaric Oxygen Therapy Attenuated the Motor Coordination and Cognitive Impairment of Polyglutamine Spinocerebellar Ataxia SCA17 Mice

Spinocerebellar ataxias (SCAs) are a large and diverse group of autosomal-dominant neurodegenerative diseases. No drugs have been approved for these relentlessly progressive and fatal SCAs. Our previous studies indicate that oxidative stress, neuroinflammation, and neuronal apoptosis are elevated in the SCA17 mice, which are the main therapeutic targets of hyperbaric oxygen treatment (HBOT). HBOT is considered to be an alternative and less invasive therapy for SCAs. In this study, we evaluated the HBOT (2.2 ATA for 14 days) effect and the persistence for the management of SCA17 mice and their wild-type littermates. We found HBOT attenuated the motor coordination and cognitive impairment of SCA17 mice and which persisted for about 1 month after the treatment. The results of several biochemistry and liver/kidney hematoxylin and eosin staining show the HBOT condition has no obvious toxicity in the mice. Immunostaining analyses show that the neuroprotective effect of HBOT could be through the promotion of BDNF production and the amelioration of neuroinflammation. Surprisingly, HBOT executes different effects on the male and female SCA17 mice, including the reduction of neuroinflammation and activation of CaMKII and ERK. This study suggests HBOT is a potential alternative therapeutic treatment for SCA17. Accumulated findings have revealed the similarity in disease pathomechanisms and possible therapeutic strategies in polyQ diseases; therefore, HBOT could be an optional treatment as well as the other polyQ diseases.

Hyperbaric Oxygen Therapy Alleviates Memory and Motor Impairments Following Traumatic Brain Injury via the Modulation of Mitochondrial-Dysfunction-Induced Neuronal Apoptosis in Rats

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in young adults, characterized by primary and secondary injury. Primary injury is the immediate mechanical damage, while secondary injury results from delayed neuronal death, often linked to mitochondrial damage accumulation. Hyperbaric oxygen therapy (HBOT) has been proposed as a potential treatment for modulating secondary post-traumatic neuronal death. However, the specific molecular mechanism by which HBOT modulates secondary brain damage through mitochondrial protection remains unclear. Spatial learning, reference memory, and motor performance were measured in rats before and after Controlled Cortical Impact (CCI) injury. The HBOT (2.5 ATA) was performed 4 h following the CCI and twice daily (12 h intervals) for four consecutive days. Mitochondrial functions were assessed via high-resolution respirometry on day 5 following CCI. Moreover, IHC was performed at the end of the experiment to evaluate cortical apoptosis, neuronal survival, and glial activation. The current result indicates that HBOT exhibits a multi-level neuroprotective effect. Thus, we found that HBOT prevents cortical neuronal loss, reduces the apoptosis marker (cleaved-Caspase3), and modulates glial cell proliferation. Furthermore, HBO treatment prevents the reduction in mitochondrial respiration, including non-phosphorylation state, oxidative phosphorylation, and electron transfer capacity. Additionally, a superior motor and spatial learning performance level was observed in the CCI group treated with HBO compared to the CCI group. In conclusion, our findings demonstrate that HBOT during the critical period following the TBI improves cognitive and motor damage via regulating glial proliferation apoptosis and protecting mitochondrial function, consequently preventing cortex neuronal loss.

Synergistic neuroprotective effects of hyperbaric oxygen and methylprednisolone following contusive spinal cord injury in rat

OBJECTIVE

Recent studies revealed the neuroprotective effects of hyperbaric oxygen (HBO) on spinal cord injury (SCI). Meanwhile, the use of methylprednisolone (MP) is one of the current protocols with limited effects in SCI patients. Accordingly, the aim of the present study was to investigate the effect of combined HBO and MP treatment on SCI.

DESIGN

The present study was conducted on five groups of rats each as follows: Sham group (underwent laminectomy alone at T9 level vertebra); SCI group (underwent moderate contusive SCI); MP group (underwent SCI and received MP); HBO group (underwent SCI and received HBO); HBO + MP group (underwent SCI and simultaneously received MP and HBO). Blood serum and Spinal cord tissue samples were taken 48 h after SCI for analysis of serum ferric reducing antioxidant power (FRAP) and tissue malodialdehyde (MDA) levels as well as immunohistochemistry of caspase-3 and tumor necrosis factor-alpha (TNF-α). Neurological function was evaluated by the Basso-Beattie-Bresnehan (BBB) locomotion scores until the end of experiments. Additionally, histopathology was assessed at the end of the study.

SETTING

Mazandaran University of Medical Sciences, Sari, Iran.

RESULTS

Combination therapy with HBO and MP in the HBO + MP group significantly decreased MDA as well as increased FRAP levels compared to other treatment groups. Meanwhile, attenuated TNF-α and Caspase-3 expression could be significantly detected in the HBO + MP group. At the end of treatment, the neurological outcome was significantly improved and the extent of injured spinal tissue was also significantly reduced in the HBO + MP compared to other treatment groups.

CONCLUSION

The results suggest that combined therapy with MP and HBO has synergistic effects on SCI treatment.

Hyperbaric oxygen therapy in children with post-concussion syndrome improves cognitive and behavioral function: a randomized controlled trial

Persistent post-concussion syndrome (PPCS) is a common and significant morbidity among children following traumatic brain injury (TBI) and the evidence for effective PPCS treatments remains limited. Recent studies have shown the beneficial effects of hyperbaric oxygen therapy (HBOT) in PPCS adult patients. This randomized, sham-control, double blind trial evaluated the effect of hyperbaric oxygen therapy (HBOT) on children (age 8–15) suffering from PPCS from mild-moderate TBI events six months to 10 years prior. Twenty-five children were randomized to receive 60 daily sessions of HBOT (n = 15) or sham (n = 10) treatments. Following HBOT, there was a significant increase in cognitive function including the general cognitive score (d = 0.598, p = 0.01), memory (d = 0.480, p = 0.02), executive function (d = 0.739, p = 0.003), PPCS symptoms including emotional score (p = 0.04, d = – 0.676), behavioral symptoms including hyperactivity (d = 0.244, p = 0.03), global executive composite score (d = 0.528, p = 0.001), planning/organizing score (d = 1.09, p = 0.007). Clinical outcomes correlated with significant improvements in brain MRI microstructural changes in the insula, supramarginal, lingual, inferior frontal and fusiform gyri. The study suggests that HBOT improves both cognitive and behavioral function, PPCS symptoms, and quality of life in pediatric PPCS patients at the chronic stage, even years after injury. Additional data is needed to optimize the protocol and to characterize the children who can benefit the most.

Hyperbaric oxygen therapy for cognitive impairments in patients with traumatic brain injury: A systematic review

Cognitive deficits are the most common impairments after traumatic brain injury (TBI). It can be linked with poor physical function. Hyperbaric oxygen therapy (HBOT) increases blood flow and oxygen supply to the brain. This review aimed to summarize and evaluate the available literature on the influences of HBOT on cognitive deficits in patients with TBI. PubMed, SCOPUS, PEDro, REHABDATA, MIDLINE, CHINAL, EMBASE, and Web of Science were searched from inception until June 2021. The methodological quality was measured using the physiotherapy evidence database (PEDro) scale. Ten studies met the eligibility criteria. Six studies were randomized controlled trials, and four were pilot studies. The scores on the PEDro scale ranged from two to nine, with a median score of seven. The included studies showed heterogeneity results for the beneficial effects of HBOT on improving cognitive functions in patients with TBI. The evidence for the beneficial effects of HBOT on cognitive functions post-TBI was limited. Further randomized controlled trials with large sample sizes are strongly needed to understand the effects of HBOT on cognitive functions in patients with TBI.

Hyperbaric Oxygen Treatment: Effects on Mitochondrial Function and Oxidative Stress

Hyperbaric oxygen treatment (HBOT)—the administration of 100% oxygen at atmospheric pressure (ATA) greater than 1 ATA—increases the proportion of dissolved oxygen in the blood five- to twenty-fold. This increase in accessible oxygen places the mitochondrion—the organelle that consumes most of the oxygen that we breathe—at the epicenter of HBOT’s effects. As the mitochondrion is also a major site for the production of reactive oxygen species (ROS), it is possible that HBOT will increase also oxidative stress. Depending on the conditions of the HBO treatment (duration, pressure, umber of treatments), short-term treatments have been shown to have deleterious effects on both mitochondrial activity and production of ROS. Long-term treatment, on the other hand, improves mitochondrial activity and leads to a decrease in ROS levels, partially due to the effects of HBOT, which increases antioxidant defense mechanisms. Many diseases and conditions are characterized by mitochondrial dysfunction and imbalance between ROS and antioxidant scavengers, suggesting potential therapeutic intervention for HBOT. In the present review, we will present current views on the effects of HBOT on mitochondrial function and oxidative stress, the interplay between them and the implications for several diseases.

Hyperbaric Oxygen Treatment-From Mechanisms to Cognitive Improvement

Hyperbaric oxygen treatment (HBOT)—the medical use of oxygen at environmental pressure greater than one atmosphere absolute—is a very effective therapy for several approved clinical situations, such as carbon monoxide intoxication, incurable diabetes or radiation-injury wounds, and smoke inhalation. In recent years, it has also been used to improve cognition, neuro-wellness, and quality of life following brain trauma and stroke. This opens new avenues for the elderly, including the treatment of neurological and neurodegenerative diseases and improvement of cognition and brain metabolism in cases of mild cognitive impairment. Alongside its integration into clinics, basic research studies have elucidated HBOT’s mechanisms of action and its effects on cellular processes, transcription factors, mitochondrial function, oxidative stress, and inflammation. Therefore, HBOT is becoming a major player in 21st century research and clinical treatments. The following review will discuss the basic mechanisms of HBOT, and its effects on cellular processes, cognition, and brain disorders.

Immunohistochemical Analysis of 4-HNE, NGAL, and HO-1 Tissue Expression after Apocynin Treatment and HBO Preconditioning in Postischemic Acute Kidney Injury Induced in Spontaneously Hypertensive Rats

Oxidative stress has been considered as a central aggravating factor in the development of postischemic acute kidney injury (AKI). The aim of this study was to perform the immunohistochemical analysis of 4-hydroxynonenal (4-HNE), neutrophil gelatinase-associated lipocalin (NGAL), and heme oxygenase-1 (HO-1) tissue expression after apocynin (APO) treatment and hyperbaric oxygenation (HBO) preconditioning, applied as single or combined protocol, in postischemic acute kidney injury induced in spontaneously hypertensive rats (SHR). Twenty-four hours before AKI induction, HBO preconditioning was carried out by exposing to pure oxygen (2.026 bar) twice a day, for 60 min in two consecutive days. Acute kidney injury was induced by removal of the right kidney while the left renal artery was occluded for 45 min by atraumatic clamp. Apocynin was applied in a dose of 40 mg/kg body weight, intravenously, 5 min before reperfusion. We showed increased 4-HNE renal expression in postischemic AKI compared to Sham-operated (SHAM) group. Apocynin treatment, with or without HBO preconditioning, improved creatinine and phosphate clearances, in postischemic AKI. This improvement in renal function was accompanied with decreased 4-HNE, while HO-1 kidney expression restored close to the control group level. NGAL renal expression was also decreased after apocynin treatment, and HBO preconditioning, with or without APO treatment. Considering our results, we can say that 4-HNE tissue expression can be used as a marker of oxidative stress in postischemic AKI. On the other hand, apocynin treatment and HBO preconditioning reduced oxidative damage, and this protective effect might be expected even in experimental hypertensive condition.

Hyperbaric oxygen therapy improves neurocognitive functions of post-stroke patients - a retrospective analysis

Background:

Previous studies have shown that hyperbaric oxygen therapy (HBOT) can improve the motor functions and memory of post-stroke patients in the chronic stage.

Objective:

The aim of this study is to evaluate the effects of HBOT on overall cognitive functions of post-stroke patients in the chronic stage. The nature, type and location of the stroke were investigated as possible modifiers.

Methods:

A retrospective analysis was conducted on patients who were treated with HBOT for chronic stroke (>3 months) between 2008-2018. Participants were treated in a multi-place hyperbaric chamber with the following protocols: 40 to 60 daily sessions, 5 days per week, each session included 90 min of 100% oxygen at 2 ATA with 5 min air brakes every 20 minutes. Clinically significant improvements (CSI) were defined as > 0.5 standard deviation (SD).

Results:

The study included 162 patients (75.3% males) with a mean age of 60.75±12.91. Of them, 77(47.53%) had cortical strokes, 87(53.7%) strokes were located in the left hemisphere and 121 suffered ischemic strokes (74.6%).

HBOT induced a significant increase in all the cognitive function domains (p < 0.05), with 86% of the stroke victims achieving CSI. There were no significant differences post-HBOT of cortical strokes compared to sub-cortical strokes (p > 0.05). Hemorrhagic strokes had a significantly higher improvement in information processing speed post-HBOT (p < 0.05). Left hemisphere strokes had a higher increase in the motor domain (p < 0.05). In all cognitive domains, the baseline cognitive function was a significant predictor of CSI (p < 0.05), while stroke type, location and side were not significant predictors.

Conclusions:

HBOT induces significant improvements in all cognitive domains even in the late chronic stage. The selection of post-stroke patients for HBOT should be based on functional analysis and baseline cognitive scores rather than the stroke type, location or side of lesion.

Human Adaptations to Multiday Saturation on NASA NEEMO

Human adaptation to extreme environments has been explored for over a century to understand human psychology, integrated physiology, comparative pathologies, and exploratory potential. It has been demonstrated that these environments can provide multiple external stimuli and stressors, which are sufficient to disrupt internal homeostasis and induce adaptation processes. Multiday hyperbaric and/or saturated (HBS) environments represent the most understudied of environmental extremes due to inherent experimental, analytical, technical, temporal, and safety limitations. National Aeronautic Space Agency (NASA) Extreme Environment Mission Operation (NEEMO) is a space-flight analog mission conducted within Florida International University’s Aquarius Undersea Research Laboratory (AURL), the only existing operational and habitable undersea saturated environment. To investigate human objective and subjective adaptations to multiday HBS, we evaluated aquanauts living at saturation for 9–10 days via NASA NEEMO 22 and 23, across psychologic, cardiac, respiratory, autonomic, thermic, hemodynamic, sleep, and body composition parameters. We found that aquanauts exposed to saturation over 9–10 days experienced intrapersonal physical and mental burden, sustained good mood and work satisfaction, decreased heart and respiratory rates, increased parasympathetic and reduced sympathetic modulation, lower cerebral blood flow velocity, intact cerebral autoregulation and maintenance of baroreflex functionality, as well as losses in systemic bodyweight and adipose tissue. Together, these findings illustrate novel insights into human adaptation across multiple body systems in response to multiday hyperbaric saturation.

A review on the neuroprotective effects of hyperbaric oxygen therapy

Hyperbaric oxygen therapy, intermittent breathing of 100% oxygen at a pressure upper than sea level, has been shown to be some of the neuroprotective effects and used therapeutically in a wide range of neurological disorders. This review summarizes current knowledge about the neuroprotective effects of hyperbaric oxygen therapy with their molecular mechanisms in different models of neurological disorders.

Effects of repetitive hyperbaric oxygen therapy on neuroprotection in middle cerebral artery occlusion rats

Hyperbaric oxygen (HBO) has been suggested as a possible therapy for brain injury. However, the effects of HBO after transient brain ischemia are inconsistent and the underlying mechanisms are not fully known. The present study aimed to investigate the effects of repetitive HBO intervention in a transient middle cerebral artery occlusion (MCAO) animal model. Seventy-two Sprague-Dawley rats received MCAO and were randomly assigned to normal air control or HBO intervention groups. Each group was divided into 3 subgroups according to the intervention time period (7, 14, and 21 days). HBO was started 24 h post-MCAO for 1 h/day at 3.0 ATA with no-air breaks. After the final intervention, half of the rats in each subgroup were sacrificed and the right motor cortex was removed to examine levels of Akt phosphorylation and glutathione (GSH), as well as glutathione peroxidase (GPx) and reductase (GR) activity. The other half of the rats were used to examine infarct volume. At 24 h post-MCAO and the end of the final intervention, rats underwent tests to examine motor performance. We noted that 14- and 21-day HBO interventions significantly reduced infarct volume and increased Akt phosphorylation and GSH levels and GPx and GR activity. Motor performance was also significantly improved after 14- and 21-day interventions. No significant differences were observed between the controls and 7-day intervention groups. Repetitive HBO intervention starting 24 h post-MCAO and applied for at least 14 days, provided neuroprotective effects through modulating the cell survival pathway and antioxidative defense system.

Hyperbaric oxygen preconditioning and the role of NADPH oxidase inhibition in postischemic acute kidney injury induced in spontaneously hypertensive rats

Renal ischemia/reperfusion injury is a common cause of acute kidney injury (AKI) and hypertension might contribute to the increased incidence of AKI. The purpose of this study was to investigate the effects of single and combined hyperbaric oxygen (HBO) preconditioning and NADPH oxidase inhibition on oxidative stress, kidney function and structure in spontaneously hypertensive rats (SHR) after renal ischemia reperfusion injury. HBO preconditioning was performed by exposing to pure oxygen (2.026 bar) twice a day for two consecutive days for 60 minutes, and 24h before AKI induction. For AKI induction, the right kidney was removed and ischemia was performed by clamping the left renal artery for 45 minutes. NADPH oxidase inhibition was induced by apocynin (40 mg/kg b.m., intravenously) 5 minutes before reperfusion. AKI significantly increased renal vascular resistance and reduced renal blood flow, which were significantly improved after apocynin treatment. Also, HBO preconditioning, with or without apocynin treatment showed improvement on renal hemodynamics. AKI significantly increased plasma creatinine, urea, phosphate levels and lipid peroxidation in plasma. Remarkable improvement, with decrease in creatinine, urea and phosphate levels was observed in all treated groups. HBO preconditioning, solitary or with apocynin treatment decreased lipid peroxidation in plasma caused by AKI induction. Also, combined with apocynin, it increased catalase activity and solitary, glutathione reductase enzyme activity in erythrocytes. While AKI induction significantly increased plasma KIM– 1 levels, HBO preconditioning, solitary or with apocynin decreased its levels. Considering renal morphology, significant morphological alterations present after AKI induction were significantly improved in all treated groups with reduced tubular dilatation, tubular necrosis in the cortico-medullary zone and PAS positive cast formation. Our results reveal that NADPH oxidase inhibition and hyperbaric oxygen preconditioning, with or without NADPH oxidase inhibition may have beneficial effects, but their protective role should be evaluated in further studies.

Imaging-based predictors for hyperbaric oxygen therapy outcome in post-stroke patients. Report 1

We tested the hypothesis that if SPECT/CT-detected volumes of active and inactive parts of brain tissue present correlation with the results of hyperbaric oxygen therapy (HBOT) of ischemic stroke, SPECT imaging may serve as a selective tool for post-stroke patients to indicate cases that may significantly benefit from HBOT. A retrospective analysis was conducted on 62 consecutive patients administered for HBOT after the ischemic stroke episode. All patients received 60 daily hyperbaric sessions consisting of 90 min of exposure to 100% oxygen at a pressure of 0.2 MPa. The results of the treatment were assessed in correlation with SPECT/CT-detected changes of volumes of the penumbra area around the stroke zone. Patients who significantly benefitted from HBOT (n = 24) by an improvement of their clinical neurologic status and quality of life had the large penumbra zone (363 ± 20.5 ml) that was significantly diminished during HBOT. Patients who did not benefit from HBOT (n = 20) had a relatively small volume of the penumbra zone (148 ± 29.3 ml) and its further diminishing during HBOT was insignificant. The HBOT results were unclear in 18 patients with penumbra volumes between these values. These findings support our hypothesis that the large volume of the penumbra area around the stroke zone can serve as a significant predictor for positive clinical outcome following HBOT in post-stroke patients. The SPECT/CT-based assessment procedure of the volume of the penumbra may serve as an effective selecting tool when HBOT is administered for patients with ischemic stroke.

Hyperbaric oxygenation and glucose/amino acids substitution in human severe placental insufficiency

In the first case, the AA and glucose were infused through a perinatal port system into the umbilical vein at 30 weeks' gestation due to severe IUGR. The patient received daily hyperbaric oxygenation (HBO, 100% O₂) with 1.4 atmospheres absolute for 50 min for 7 days. At 31⁺⁴ weeks' gestation, the patient gave birth spontaneously to a newborn weighing 1378 g, pH 7.33, APGAR score 4/6/intubation. In follow‐up examinations at 5 years of age, the boy was doing well without any neurological disturbance or developmental delay. In the second case, the patient presented at 25/⁵ weeks' gestation suffering from severe IUGR received HBO and maternal AA infusions. The cardiotocography was monitored continuously during HBO treatment. The short‐time variations improved during HBO from 2.9 to 9 msec. The patient developed pathologic CTG and uterine contractions 1 day later and gave birth to a hypotrophic newborn weighing 420 g. After initial adequate stabilization, the extremely preterm newborn unfortunately died 6 days later. Fetal nutrition combined with HBO is technically possible and may allow the prolongation of the pregnancy. Fetal‐specific amino‐acid composition would facilitate the treatment options of IUGR fetuses and extremely preterm newborn.

Safety and Tolerability of Hyperbaric Oxygen Therapy in Cats and Dogs

This prospective clinical trial was designed to evaluate the safety of hyperbaric oxygen therapy (HBOT) in a population of cats and dogs with a variety of naturally occurring diseases. Seventy-eight dogs and twelve cats with various naturally occurring disease conditions, who had the potential to benefit from HBOT, were enrolled in the study. These patients were treated with HBOT in a monoplace hyperbaric oxygen chamber at 2 air pressure absolute for a treatment length of either 45 min or 60 min. There were 230 hyperbaric oxygen treatments performed during the study period. No major adverse effects were observed. There were 76 minor adverse effects recorded, which were not considered to be of clinical significance. Hyperbaric oxygen therapy was well tolerated and there were no major adverse effects recorded during treatment.

Neuroprotective effects of hyperbaric oxygen (HBO) therapy on neuronal death induced by sciatic nerve transection in rat

Background

Recent studies shows that hyperbaric oxygen (HBO) therapy exerts some protective effects against neural injuries. The purpose of this study was to determine the neuroprotective effects of HBO following sciatic nerve transection (SNT).

Methods

Rats were randomly divided into five groups (n = 14 per group): Sham-operated (SH) group, SH + HBO group, SNT group, and SNT + pre- and SNT + post-HBO groups (100% oxygen at 2.0 atm absolute, 60 min/day for five consecutive days beginning on 1 day before and immediately after nerve transaction, respectively). Spinal cord segments of the sciatic nerve and related dorsal root ganglions (DRGs) were removed 4 weeks after nerve transection for biochemical assessment of malodialdehyde (MDA) levels in spinal cord, biochemical assessment of superoxide dismutase (SOD) and catalse (CAT) activities in spinal cord, immunohistochemistry of caspase-3, cyclooxigenase-2 (COX-2), S100beta (S100ß), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) in spinal cord and DRG.

Results

The results revealed that MDA levels were significantly decreased in the SNT + pre-HBO group, while SOD and CAT activities were significantly increased in SNT + pre- and SNT + post-HBO treated rats. Attenuated caspase-3 and COX-2 expression, and TUNEL reaction could be significantly detected in the HBO-treated rats after nerve transection. Also, HBO significantly increased S100ß expression.

Conclusions

Based on these results, we can conclude that pre- and post-HBO therapy had neuroprotective effects against sciatic nerve transection-induced degeneration.

Hyperbaric Oxygen Effects on Depression-Like Behavior and Neuroinflammation in Traumatic Brain Injury Rats

OBJECTIVE

The aim of this study was to determine whether hyperbaric oxygen (HBO) therapy causes attenuation of traumatic brain injury (TBI)-induced depression-like behavior and its associated anti-neuroinflammatory effects after fluid percussion injury.

METHODS

Anesthetized male Sprague-Dawley rats were divided into 3 groups: sham operation plus normobaric air (NBA) (21% oxygen at 1 absolute atmosphere [ATA]), TBI plus NBA, and TBI plus HBO (100% oxygen at 2.0 ATA). HBO was applied immediately for 60 min/d after TBI for 3 days. Depression-like behavior was tested by a forced swimming test, motor function was tested by an inclined plane test, and infarction volume was tested by triphenyltetrazolium chloride (TTC) staining on days 4, 8, and 15. Neuronal apoptosis (terminal deoxynucleotidyl transferase dUTP nick-end labeling assay), microglial (marker OX42) activation, and tumor necrosis factor (TNF)-α expression in microglia in the hippocampus CA3 were measured by immunofluorescence methods.

RESULTS

Compared with the TBI controls, without significant changes in TTC staining or in the motor function test, TBI-induced depression-like behavior was significantly attenuated by HBO therapy by day 15 after TBI. Simultaneously, TBI-induced neuronal apoptosis, microglial (marker OX42) activation, and TNF-α expression in the microglia in the hippocampus CA3 were significantly reduced by HBO.

CONCLUSIONS

Our results suggest that HBO treatment may ameliorate TBI-induced depression-like behavior in rats by attenuating neuroinflammation, representing one possible mechanism by which depression-like behavior recovery might occur. We also recommend HBO as a potential treatment for TBI-induced depression-like behavior if early intervention is possible.

Hyperbaric oxygen therapy for people with autism spectrum disorder (ASD)

BACKGROUND

The rising prevalence of autism spectrum disorder (ASD) has increased the need for evidence-based treatments to lessen the impact of symptoms. Presently, no therapies are available to effectively treat individuals with all of the symptoms of this disorder. It has been suggested that hyperbaric oxygen therapy may alleviate the biochemical dysfunction and clinical symptoms of ASD.

OBJECTIVES

To determine whether treatment with hyperbaric oxygen:1. improves core symptoms of ASD, including social communication problems and stereotypical and repetitive behaviors;2. improves noncore symptoms of ASD, such as challenging behaviors;3. improves comorbid states, such as depression and anxiety; and4. causes adverse effects.

SEARCH METHODS

On 10 December 2015, we searched CENTRAL, Ovid MEDLINE, Embase, and 15 other databases, four of which were Chinese language databases. We also searched multiple trial and research registers.

SELECTION CRITERIA

We selected randomized controlled trials (RCTs) and quasi-RCTs of any dose, duration, and frequency for hyperbaric oxygen therapy compared with no treatment or sham treatment for children and adults with ASD.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration, in that three review authors independently selected studies, assessed them for risk of bias, and extracted relevant data. We also assessed the quality of the evidence by using the GRADE approach.

MAIN RESULTS

We included one trial with a total of 60 children with a diagnosis of ASD who randomly received hyperbaric oxygen therapy or a sham treatment. Using GRADE criteria, we rated the quality of the evidence as low because of the small sample size and wide confidence intervals (CIs). Other problems included selection bias and short duration or follow-up.Overall, study authors reported no improvement in social interaction and communication, behavioral problems, communication and linguistic abilities, or cognitive function. With regard to the safety of hyperbaric oxygen therapy (adverse events), they reported minor-grade ear barotrauma events. Investigators found significant differences between groups in total number of side effect events (Peto odds ratio (OR) 3.87, 95% CI 1.53 to 9.82) and in the number of children who experienced side effects (Peto OR 4.40, 95% CI 1.33 to 14.48).

AUTHORS' CONCLUSIONS

To date, there is no evidence that hyperbaric oxygen therapy improves core symptoms and associated symptoms of ASD. It is important to note that adverse effects (minor-grade ear barotrauma events) can occur. Given the absence of evidence of effectiveness and the limited biological plausibility and possible adverse effects, the need for future RCTs of hyperbaric oxygen therapy must be carefully considered.

Hyperbaric oxygen therapy in experimental and clinical stroke

Stroke, which is defined as a neurologic deficit caused by sudden impaired blood supply, has been considered as a common cause of death and disability for decades. The World Health Organization has declared that almost every 5 seconds a new stroke occurs, placing immense socioeconomic burdens. However, the effective and available treatment strategies are still limited. Additionally, the most effective therapy, such as thrombolysis and stenting for ischemic stroke, generally requires a narrow therapeutic time window after the event. A large majority of patients cannot be admitted to hospital and receive these effective treatments for reperfusion timely. Hyperbaric oxygen therapy (HBOT) has been frequently applied and investigated in stroke since 1960s. Numerous basic and clinical studies have shown the beneficial efficacy for neurological outcome after stroke, and meanwhile many underlying mechanisms associated with neuroprotection have been illustrated, such as cerebral oxygenation promotion and metabolic improvement, blood-brain barrier protection, anti-inflammation and cerebral edema, intracranial pressure modulation, decreased oxidative-stress and apoptosis, increased vascular and neural regeneration. However, HBOT in human stroke is still not sufficiently evidence-based, due to the insufficient randomized double-blind controlled clinical studies. To date, there are no uniform criteria for the dose and session duration of HBOT in different strokes. Furthermore, the additional effect of HBOT combined with drugs and other treatment strategies are being investigated recently. Therefore, more experimental and clinical research is imperative to identify the mechanisms more clearly and to explore the best protocol of HBOT in stroke treatment.

Treatment of persistent post-concussion syndrome due to mild traumatic brain injury: current status and future directions

Persistent post-concussion syndrome caused by mild traumatic brain injury has become a major cause of morbidity and poor quality of life. Unlike the acute care of concussion, there is no consensus for treatment of chronic symptoms. Moreover, most of the pharmacologic and non-pharmacologic treatments have failed to demonstrate significant efficacy on both the clinical symptoms as well as the pathophysiologic cascade responsible for the permanent brain injury. This article reviews the pathophysiology of PCS, the diagnostic tools and criteria, the current available treatments including pharmacotherapy and different cognitive rehabilitation programs, and promising new treatment directions. A most promising new direction is the use of hyperbaric oxygen therapy, which targets the basic pathological processes responsible for post-concussion symptoms; it is discussed here in depth.

MRI of cerebral blood flow under hyperbaric conditions in rats

Hyperbaric oxygen (HBO) therapy has a number of clinical applications. However, the effects of acute HBO on basal cerebral blood flow (CBF) and neurovascular coupling are not well understood. This study explored the use of arterial spin labeling MRI to evaluate changes in baseline and forepaw stimulus-evoked CBF responses in rats (n = 8) during normobaric air (NB), normobaric oxygen (NBO) (100% O2 ), 3 atm absolute (ATA) hyperbaric air (HB) and 3 ATA HBO conditions. T1 was also measured, and the effects of changes in T1 caused by increasing oxygen on the CBF calculation were investigated. The major findings were as follows: (i) increased inhaled oxygen concentrations led to a reduced respiration rate; (ii) increased dissolved paramagnetic oxygen had significant effects on blood and tissue T1 , which affected the CBF calculation using the arterial spin labeling method; (iii) the differences in blood T1 had a larger effect than the differences in tissue T1 on CBF calculation; (iv) if oxygen-induced changes in blood and tissue T1 were not taken into account, CBF was underestimated by 33% at 3 ATA HBO, 10% at NBO and <5% at HB; (v) with correction, CBF values under HBO, HB and NBO were similar (p > 0.05) and all were higher than CBF under NB by ~40% (p < 0.05), indicating that hypercapnia from the reduced respiration rate masks oxygen-induced vasoconstriction, although blood gas was not measured; and (vi) substantial stimulus-evoked CBF increases were detected under HBO, similar to NB, supporting the notion that activation-induced CBF regulation in the brain does not operate through an oxygen-sensing mechanism. CBF MRI provides valuable insights into the effects of oxygen on basal CBF and neurovascular coupling under hyperbaric conditions. Copyright © 2016 John Wiley & Sons, Ltd.

Therapeutic effect of tPA in ischemic stroke is enhanced by its combination with normobaric oxygen and hypothermia or ethanol

BACKGROUND AND PURPOSE

Our lab has previously elucidated the neuroprotective effects of normobaric oxygen (NBO) and ethanol (EtOH) in ischemic stroke. The present study further evaluated the effect of EtOH or hypothermia (Hypo) in the presence of low concentration of NBO and determined whether EtOH can substitute hypothermia in a more clinically relevant autologous embolus rat stroke model in which reperfusion was established by tissue-type plasminogen activator (t-PA).

METHODS

At 1h of middle cerebral artery occlusion (MCAO) by an autologous embolus, rats received t-PA. In addition, at the same time, ischemic animals were treated with either EtOH (1.0 g/kg) or hypothermia (33°C for 3h) in combination with NBO (60% for 3h). Extent of neuroprotection was assessed by apoptotic cell death measured by ELISA and Western immunoblotting analysis for pro- (AIF, activated Caspase-3, Bax) and anti-apoptotic (Bcl-2) protein expression at 3 and 24h of reperfusion induced by t-PA administration.

RESULTS

Compared to ischemic rats treated only with t-PA, animals with NBO, hypothermia or EtOH had significantly reduced apoptotic cell death by 32.5%, 43.1% and 36.0% respectively. Furthermore, combination therapy that included NBO+EtOH or NBO+Hypo with t-PA exhibited a much larger decline (p<0.01) in the cell death by 71.1% and 73.6%, respectively. Similarly, NBO+EtOH or NBO+Hypo treatment in addition to t-PA enhanced beneficial effects on both pro- and anti-apoptotic protein expressions as compared to other options.

CONCLUSIONS

Neuroprotection after stroke can be enhanced by combination treatment with either EtOH or hypothermia in the presence of t-PA and 60% NBO. Because the effects produced by EtOH and hypothermia are comparable, their mechanism of action may be not only similar but also could be interchangeable in future clinical trials.

Does normobaric hyperoxia increase oxidative stress in acute ischemic stroke? A critical review of the literature

Stroke, one of the most debilitating cerebrovascular and nuerological diseases, is a serious life-threatening condition and a leading cause of long-term adult disability and brain damage, either directly or by secondary complications. Most effective treatments for stroke are time dependent such as the only FDA-approved therapy, reperfusion with tissue-type plasminogen activator; thus, improving tissue oxygenation with normobaric hyperoxia (NBO) has been considered a logical and potential important therapy. NBO is considered a good approach because of its potential clinical advantages, and many studies suggest that NBO is neuroprotective, reducing ischemic brain injury and infarct volume in addition to improving pathologic and neurobehavorial outcomes. However, increased reactive oxygen species (ROS) generation may occur when tissue oxygen level is too high or too low. Therefore, a major concern with NBO therapy in acute ischemic stroke is the potential increase of ROS, which could exacerbate brain injury. The purpose of this review is to critically review the current literature reports on the effect of NBO treatment on ROS and oxidative stress with respect to acute ischemic stroke. Considering the available data from relevant animal models, NBO does not increase ROS or oxidative stress if applied for a short duration; therefore, the potential that NBO is a viable neuroprotective strategy for acute ischemic stroke is compelling. The benefits of NBO may significantly outweigh the risks of potential increase in ROS generation for the treatment of acute ischemic stroke.

Repetitive hyperbaric oxygenation attenuates reactive astrogliosis and suppresses expression of inflammatory mediators in the rat model of brain injury

The exact mechanisms by which treatment with hyperbaric oxygen (HBOT) exerts its beneficial effects on recovery after brain injury are still unrevealed. Therefore, in this study we investigated the influence of repetitive HBOT on the reactive astrogliosis and expression of mediators of inflammation after cortical stab injury (CSI). CSI was performed on male Wistar rats, divided into control, sham, and lesioned groups with appropriate HBO. The HBOT protocol was as follows: 10 minutes of slow compression, 2.5 atmospheres absolute (ATA) for 60 minutes, and 10 minutes of slow decompression, once a day for 10 consecutive days. Data obtained using real-time polymerase chain reaction, Western blot, and immunohistochemical and immunofluorescence analyses revealed that repetitive HBOT applied after the CSI attenuates reactive astrogliosis and glial scarring, and reduces expression of GFAP (glial fibrillary acidic protein), vimentin, and ICAM-1 (intercellular adhesion molecule-1) both at gene and tissue levels. In addition, HBOT prevents expression of CD40 and its ligand CD40L on microglia, neutrophils, cortical neurons, and reactive astrocytes. Accordingly, repetitive HBOT, by prevention of glial scarring and limiting of expression of inflammatory mediators, supports formation of more permissive environment for repair and regeneration.

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.

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.

Use of hyperbaric oxygenation in neonatal patients: a pilot study of 8 patients

This article presents a pilot study to determine the value of hyperbaric oxygenation (HBO₂) in the acute management of neonatal hypoxia (hypoxic ischemic encephalopathy) and necrotizing enterocolitis. Neonates with hypoxic-ischemic encephalopathy and NE were treated in a Sechrist monoplace chamber. Electroencephalogram, evoked potential, ophthalmic evaluation, ultrasonograph, laboratory exams, and radiographs were obtained before and after HBO₂. Treatment protocol was 2.0 atm abs/45 minutes. Preventive myringotomies were conducted in all patients. A follow-up was done at 3 and 6 months. All patients (n = 8) were ventilator-dependent and required bag-valve-mask ventilation by a neonatologist during the treatment. All showed a resolution after HBO₂. There was also a dramatic improvement (P < .05) in hemoglobin, hematocrit, total proteins, serum sodium, triglycerides, and pH. There were favorable changes in all other studies although they did not meet statistical significance. There was a marked reduction of the morbidity and mortality. There were no adverse effects on the ophthalmologic or Central Nervous System. When used promptly, HBO₂ can modify the local and systemic inflammatory response caused by intestinal inflammation or cerebral or systemic hypoxia. It helps to preserve the marginal tissue and recover the ischemic and metabolic penumbra. This pilot study suggests that HBO₂ could be a safe and effective treatment in the acute management of neonatal necrotizing enterocolitis or hypoxic ischemic encephalopathy. There is a need for a prospective, randomized, controlled, and double-blinded study to determine the real use of HBO₂ in these cases.

The medical use of oxygen: a time for critical reappraisal

Oxygen treatment has been a cornerstone of acute medical care for numerous pathological states. Initially, this was supported by the assumed need to avoid hypoxaemia and tissue hypoxia. Most acute treatment algorithms, therefore, recommended the liberal use of a high fraction of inspired oxygen, often without first confirming the presence of a hypoxic insult. However, recent physiological research has underlined the vasoconstrictor effects of hyperoxia on normal vasculature and, consequently, the risk of significant blood flow reduction to the at-risk tissue. Positive effects may be claimed simply by relief of an assumed local tissue hypoxia, such as in acute cardiovascular disease, brain ischaemia due to, for example, stroke or shock or carbon monoxide intoxication. However, in most situations, a generalized hypoxia is not the problem and a risk of negative hyperoxaemia-induced local vasoconstriction effects may instead be the reality. In preclinical studies, many important positive anti-inflammatory effects of both normobaric and hyperbaric oxygen have been repeatedly shown, often as surrogate end-points such as increases in gluthatione levels, reduced lipid peroxidation and neutrophil activation thus modifying ischaemia-reperfusion injury and also causing anti-apoptotic effects. However, in parallel, toxic effects of oxygen are also well known, including induced mucosal inflammation, pneumonitis and retrolental fibroplasia. Examining the available 'strong' clinical evidence, such as usually claimed for randomized controlled trials, few positive studies stand up to scrutiny and a number of trials have shown no effect or even been terminated early due to worse outcomes in the oxygen treatment arm. Recently, this has led to less aggressive approaches, even to not providing any supplemental oxygen, in several acute care settings, such as resuscitation of asphyxiated newborns, during acute myocardial infarction or after stroke or cardiac arrest. The safety of more advanced attempts to deliver increased oxygen levels to hypoxic or ischaemic tissues, such as with hyperbaric oxygen therapy, is therefore also being questioned. Here, we provide an overview of the present knowledge of the physiological effects of oxygen in relation to its therapeutic potential for different medical conditions, as well as considering the potential for harm. We conclude that the medical use of oxygen needs to be further examined in search of solid evidence of benefit in many of the current clinical settings in which it is routinely used.

Hyperbaric oxygen therapy can improve post concussion syndrome years after mild traumatic brain injury - randomized prospective trial

Background

Traumatic brain injury (TBI) is the leading cause of death and disability in the US. Approximately 70-90% of the TBI cases are classified as mild, and up to 25% of them will not recover and suffer chronic neurocognitive impairments. The main pathology in these cases involves diffuse brain injuries, which are hard to detect by anatomical imaging yet noticeable in metabolic imaging. The current study tested the effectiveness of Hyperbaric Oxygen Therapy (HBOT) in improving brain function and quality of life in mTBI patients suffering chronic neurocognitive impairments.

Methods and Findings

The trial population included 56 mTBI patients 1–5 years after injury with prolonged post-concussion syndrome (PCS). The HBOT effect was evaluated by means of prospective, randomized, crossover controlled trial: the patients were randomly assigned to treated or crossover groups. Patients in the treated group were evaluated at baseline and following 40 HBOT sessions; patients in the crossover group were evaluated three times: at baseline, following a 2-month control period of no treatment, and following subsequent 2-months of 40 HBOT sessions. The HBOT protocol included 40 treatment sessions (5 days/week), 60 minutes each, with 100% oxygen at 1.5 ATA. “Mindstreams” was used for cognitive evaluations, quality of life (QOL) was evaluated by the EQ-5D, and changes in brain activity were assessed by SPECT imaging. Significant improvements were demonstrated in cognitive function and QOL in both groups following HBOT but no significant improvement was observed following the control period. SPECT imaging revealed elevated brain activity in good agreement with the cognitive improvements.

Conclusions

HBOT can induce neuroplasticity leading to repair of chronically impaired brain functions and improved quality of life in mTBI patients with prolonged PCS at late chronic stage.

Trial Registration

ClinicalTrials.gov

NCT00715052

Effects of normobaric oxygen on the progression of focal cerebral ischemia in rats

Normobaric oxygen (NBO) reduces infarction at 24-48 h in experimental models of focal cerebral ischemia. However, to be clinically relevant, longer term safety and efficacy must be explored. Here, we assessed the effects of NBO on glial activation, neurovascular recovery, and behavioral outcomes at 2 weeks after transient focal ischemia in rats. 100 min transient focal ischemia was induced by intraluminal occlusion of the middle cerebral artery in adult male Sprague-Dawley rats. Animals were randomized into sham, controls or 85'NBO started 15 min after ischemic onset. Infarct volumes and behavioral outcomes were blindly quantified. Immunohistochemistry was used to examine the effects of NBO on glial activation and neurovascular responses. After 2 weeks of reperfusion the infarct volume was marked reduced in animals subjected to NBO. They also had better outcomes in forelimb placement test and in body-swing test and weight loss reduction. After 14 days, NBO decreased expression of Iba1, a marker of activated microglia, and GFAP, a marker of activated astrocytes. NBO treatment had no detectable effect on angiogenesis. These results suggest that protective effects of NBO may persist for up to 2 weeks post-stroke.

Hyperbaric oxygenation alters temporal expression pattern of superoxide dismutase 2 after cortical stab injury in rats

Aim

To evaluate the effect of hyperbaric oxygen therapy (HBOT) on superoxide dismutase 2 (SOD2) expression pattern after the cortical stab injury (CSI).

Methods

CSI was performed on 88 male Wistar rats, divided into control, sham, lesioned, and HBO groups. HBOT protocol was the following: pressure applied was 2.5 absolute atmospheres, for 60 minutes, once a day for consecutive 3 or 10 days.‎ The pattern of SOD2 expression and cellular localization was analyzed using real-time polymerase chain reaction, Western blot, and double-label fluorescence immunohistochemistry. Neurons undergoing degeneration were visualized with Fluoro-Jade^®B.

Results

CSI induced significant transient increase in SOD2 protein levels at day 3 post injury, which was followed by a reduction toward control levels at post-injury day 10. At the same time points, mRNA levels for SOD2 in the injured cortex were down-regulated. Exposure to HBO for 3 days considerably down-regulated SOD2 protein levels in the injured cortex, while after 10 days of HBOT an up-regulation of SOD2 was observed. HBOT significantly increased mRNA levels for SOD2 at both time points compared to the corresponding L group, but they were still lower than in controls. Double immunofluorescence staining revealed that 3 days after CSI, up-regulation of SOD2 was mostly due to an increased expression in reactive astrocytes surrounding the lesion site. HBOT attenuated SOD2 expression both in neuronal and astroglial cells. Fluoro-Jade^®B labeling showed that HBOT significantly decreased the number of degenerating neurons in the injured cortex.

Conclusion

HBOT alters SOD2 protein and mRNA levels after brain injury in a time-dependent manner.

Hyperbaric oxygen induces late neuroplasticity in post stroke patients--randomized, prospective trial

Background

Recovery after stroke correlates with non-active (stunned) brain regions, which may persist for years. The current study aimed to evaluate whether increasing the level of dissolved oxygen by Hyperbaric Oxygen Therapy (HBOT) could activate neuroplasticity in patients with chronic neurologic deficiencies due to stroke.

Methods and Findings

A prospective, randomized, controlled trial including 74 patients (15 were excluded). All participants suffered a stroke 6–36 months prior to inclusion and had at least one motor dysfunction. After inclusion, patients were randomly assigned to "treated" or "cross" groups. Brain activity was assessed by SPECT imaging; neurologic functions were evaluated by NIHSS, ADL, and life quality. Patients in the treated group were evaluated twice: at baseline and after 40 HBOT sessions. Patients in the cross group were evaluated three times: at baseline, after a 2-month control period of no treatment, and after subsequent 2-months of 40 HBOT sessions. HBOT protocol: Two months of 40 sessions (5 days/week), 90 minutes each, 100% oxygen at 2 ATA. We found that the neurological functions and life quality of all patients in both groups were significantly improved following the HBOT sessions while no improvement was found during the control period of the patients in the cross group. Results of SPECT imaging were well correlated with clinical improvement. Elevated brain activity was detected mostly in regions of live cells (as confirmed by CT) with low activity (based on SPECT) – regions of noticeable discrepancy between anatomy and physiology.

Conclusions

The results indicate that HBOT can lead to significant neurological improvements in post stroke patients even at chronic late stages. The observed clinical improvements imply that neuroplasticity can still be activated long after damage onset in regions where there is a brain SPECT/CT (anatomy/physiology) mismatch.

Trial Registration

ClinicalTrials.gov NCT00715897

Spatio-temporal course of macrophage-like cell accumulation after experimental embolic stroke depending on treatment with tissue plasminogen activator and its combination with hyperbaric oxygenation

Inflammation following ischaemic stroke attracts high priority in current research, particularly using human-like models and long-term observation periods considering translational aspects. The present study aimed on the spatio-temporal course of macrophage-like cell accumulation after experimental thromboembolic stroke and addressed microglial and astroglial reactions in the ischaemic border zone. Further, effects of tissue plasminogen activator (tPA) as currently best treatment for stroke and the potentially neuroprotective co-administration of hyperbaric oxygen (HBO) were investigated. Rats underwent middle cerebral artery occlusion and were assigned to control, tPA or tPA+HBO. Twenty-four hours, 7, 14 and 28 days were determined as observation time points. The accumulation of macrophage-like cells was semiquantitatively assessed by CD68 staining in the ischaemic area and ischaemic border zone, and linked to the clinical course. CD11b, ionized calcium binding adaptor molecule 1 (Iba), glial fibrillary acidic protein (GFAP) and Neuronal Nuclei (NeuN) were applied to reveal delayed glial and neuronal alterations. In all groups, the accumulation of macrophage-like cells increased distinctly from 24 hours to 7 days post ischaemia. tPA+HBO tended to decrease macrophage-like cell accumulation at day 14 and 28. Overall, a trend towards an association of increased accumulation and pronounced reduction of the neurological deficit was found. Concerning delayed inflammatory reactions, an activation of microglia and astrocytes with co-occurring neuronal loss was observed on day 28. Thereby, astrogliosis was found circularly in contrast to microglial activation directly in the ischaemic area. This study supports previous data on long-lasting inflammatory processes following experimental stroke, and additionally provides region-specific details on glial reactions. The tendency towards a decreasing macrophage-like cell accumulation after tPA+HBO needs to be discussed critically since neuroprotective properties were recently ascribed to long-term inflammatory processes.

Hyperbaric oxygenation improves locomotor ability by enhancing neuroplastic responses after cortical ablation in rats

OBJECTIVE

To investigate whether hyperbaric oxygenation (HBO) can improve the recovery of motor functions in rats after suction ablation of the right sensorimotor cortex.

METHODS

The experimental paradigm implies the following groups: Control animals (C), Control + HBO (CHBO), Sham controls (S), Sham control + HBO (SHBO), Lesion group (L), right sensorimotor cortex was removed by suction, Lesion + HBO (LHBO). Hyperbaric protocol: pressure applied 2.5 atmospheres absolute, for 60 minutes, once a day for 10 days. A beam walking test and grip strength meter were used to evaluate the recovery of motor functions. Expression profiles of growth-associated protein 43 (GAP43) and synaptophysin (SYP) were detected using immunohistochemistry.

RESULTS

The LHBO group achieved statistically superior scores in the beam walking test compared to the L group. Additionally, the recovery of muscle strength of the affected hindpaw was significantly enhanced after HBO treatment. Hyperbaric oxygenation induced over-expression of GAP43 and SYP in the neurons surrounding the lesion site.

CONCLUSIONS

Data presented suggest that hyperbaric oxygen therapy can intensify neuroplastic responses by promoting axonal sprouting and synapse remodelling, which contributes to the recovery of locomotor performances in rats. This provides the perspective for implementation of HBO in clinical strategies for treating traumatic brain injuries.

Hyperbaric oxygen therapy for traumatic brain injury

Traumatic brain injury (TBI) is a major public health issue. The complexity of TBI has precluded the use of effective therapies. Hyperbaric oxygen therapy (HBOT) has been shown to be neuroprotective in multiple neurological disorders, but its efficacy in the management of TBI remains controversial. This review focuses on HBOT applications within the context of experimental and clinical TBI. We also discuss its potential neuroprotective mechanisms. Early or delayed multiple sessions of low atmospheric pressure HBOT can reduce intracranial pressure, improve mortality, as well as promote neurobehavioral recovery. The complimentary, synergistic actions of HBOT include improved tissue oxygenation and cellular metabolism, anti-apoptotic, and anti-inflammatory mechanisms. Thus HBOT may serve as a promising neuroprotective strategy that when combined with other therapeutic targets for TBI patients which could improve long-term outcomes.

Neuroprotective effects of hyperbaric oxygen treatment on traumatic brain injury in the rat

This study was designed to evaluate the potential benefits of hyperbaric oxygen (HBO) in the treatment of traumatic brain injury (TBI). The right cerebral cortex of rats was injured by the impact of a 20-g object dropped from a predetermined height. The rats received HBO treatment at 3 ATA for 60 min after TBI. Neurological behavior score, brain water content, neuronal loss in the hippocampus, and cell apoptosis in brain tissue surrounding the primary injury site were examined to determine brain damage severity. Three and six hours after TBI, HBO-treated rats displayed a significant reduction in brain damage. However, by 12 h after TBI, the efficacy of HBO treatment was considerably attenuated. Furthermore, at 24, 48, and 72 h after TBI, the HBO treatment did not show any notable effects. In contrast, multiple HBO treatments (three or five times in all), even when started 48 h after TBI, remarkably reduced neurology deficit scores and the loss of neuronal numbers in the hippocampus. Although multiple treatments started at 48 h significantly improved neurological behaviors and reduced brain injury, the overall beneficial effects were substantially weaker than those seen after a single treatment at 6 h. These results suggest that: (1) HBO treatment could alleviate brain damage after TBI; (2) a single treatment with HBO has a time limitation of 12 h post-TBI; and (3) multiple HBO treatments have the possibility to extend the post-TBI delivery time window. Therefore, our results clearly suggest the validity of HBO therapy for the treatment of TBI.

Oxygen, a Key Factor Regulating Cell Behavior during Neurogenesis and Cerebral Diseases

Oxygen is vital to maintain the normal functions of almost all the organs, especially for brain which is one of the heaviest oxygen consumers in the body. The important roles of oxygen on the brain are not only reflected in the development, but also showed in the pathological processes of many cerebral diseases. In the current review, we summarized the oxygen levels in brain tissues tested by real-time measurements during the embryonic and adult neurogenesis, the cerebral diseases, or in the hyperbaric/hypobaric oxygen environment. Oxygen concentration is low in fetal brain (0.076-7.6 mmHg) and in adult brain (11.4-53.2 mmHg), decreased during stroke, and increased in hyperbaric oxygen environment. In addition, we reviewed the effects of oxygen tensions on the behaviors of neural stem cells (NSCs) in vitro cultures at different oxygen concentration (15.2-152 mmHg) and in vivo niche during different pathological states and in hyperbaric/hypobaric oxygen environment. Moderate hypoxia (22.8-76 mmHg) can promote the proliferation of NSCs and enhance the differentiation of NSCs into the TH-positive neurons. Next, we briefly presented the oxygen-sensitive molecular mechanisms regulating NSCs proliferation and differentiation recently found including the Notch, Bone morphogenetic protein and Wnt pathways. Finally, the future perspectives about the roles of oxygen on brain and NSCs were given.

Use of normobaric and hyperbaric oxygen in acute focal cerebral ischemia - a preclinical and clinical review

High socioeconomic burden is attributed to acute ischemic stroke, but treatment strategies are still limited. Normobaric (NBO) and hyperbaric oxygen therapy (HBO) were frequently investigated in preclinical studies following acute focal cerebral ischemia with predominantly beneficial effects in different outcome measurements. Best results were achieved in transient cerebral ischemia, starting HBO early after artery occlusion, and by using relatively high pressures. On molecular level, oxygen application leads to blood-brain barrier stabilization, reduction of excitotoxic metabolites, and inhibition of inflammatory processes. Therefore, NBO and HBO appear excessively hopeful in salvaging impaired brain cells during ischemic stroke. However, harmful effects have been noted contributing to damaging properties, for example, vasoconstriction and free oxygen radicals. In the clinical setting, NBO provided positive results in a single clinical trial, but HBO failed to show efficacy in three randomized trials. To date, the translation of numerous evidentiary experimental results into clinical implementation remains open. Recently, oxygen became interesting as an additional therapy to neuroprotective or recanalization drugs to combine positive effects. Further preclinical research is needed exploring interactions between NBO, HBO, and key factors with multiphasic roles in acute damaging and delayed inflammatory processes after cerebral ischemia, for example, matrix-metalloproteinases and hypoxia-inducible factor-1α.

Pretreatment with normobaric and hyperbaric oxygenation worsens cerebral edema and neurologic outcomes in a murine model of surgically induced brain injury

BACKGROUND

Hyperbaric oxygenation is a readily available treatment modality, and its ability to improve neurological outcomes in a variety of animal models has been demonstrated. This study was designed to investigate the use of a single pretreatment regimen of either hyperbaric oxygenation or normobaric oxygenation to determine its effects in a murine model of surgically induced brain injury (SBI).

MATERIALS AND METHODS

Hyperbaric oxygen (2.5ATM, 1 h), normobaric oxygen (100% FIO2, 1 h) or room air (21% FIO2, 1 h) was applied on CD-1 mice immediately, or at 1, 2 or 3 h followed by SBI or sham surgical operation. Neurological assessment of the animals was done by a blinded observer at 24 and 72 h using a 21-point modified Garcia scale, wire hanging test, and beam balance test. The brain edema was evaluated using brain water content at 24 and 72 h after SBI.

RESULTS

There was no statistically significant difference in the mortality rate after treatment compared with the SBI group. The brain water content after SBI was significantly increased in the right (ipsilateral) frontal lobe surrounding the site of surgical resection compared with the sham group. Both hyperbaric and normobaric oxygen treatment significantly increased the brain edema and worsened the neurological outcomes using a 21-point Garcia score compared with the SBI group. The brain edema at 24 h after injury was most pronounced in the group treated with normobaric oxygenation 2 h prior to surgery. These differences disappeared at 72 h after SBI.

CONCLUSION

Immediate pretreatment with either hyperbaric (2.5ATM, 1 h) or normobaric oxygen (100% FIO2, 1 h) increased brain edema and worsened neurological function at 24 h following SBI.

Oxygen therapy reduces secondary hemorrhage after thrombolysis in thromboembolic cerebral ischemia

Hyperbaric oxygen (HBO) and normobaric hyperoxia (NBO) protect the brain parenchyma and the cerebral microcirculation against ischemia. We studied their effect on secondary hemorrhage after thrombolysis in two thromboembolic middle cerebral artery occlusion (MCAO) (tMCAO) models. Beginning 60 minutes after tMCAO with either thrombin-induced thromboemboli (TT) or calcium-induced thromboemboli (CT), spontaneously hypertensive rats (n=96) breathed either air, 100% O(2) (NBO), or 100% O(2) at 3 bar (HBO) for 1 hour. Immediately thereafter, recombinant tissue plasminogen activator (rt-PA, 9 mg/kg) was injected. Although significant reperfusion was observed after thrombolysis in TT-tMCAO, vascular occlusion persisted in CT-tMCAO. In TT-tMCAO, NBO and HBO significantly reduced diffusion-weighted imaging-magnetic resonance imaging (MRI) lesion volume and postischemic blood-brain barrier (BBB) permeability on postcontrast T1-weighted images. NBO and, significantly more potently, HBO reduced macroscopic hemorrhage on T2* MRI and on corresponding postmortem cryosections. Oxygen therapy lowered hemoglobin content and attenuated activation of matrix metalloproteinases in the ischemic hemisphere. In contrast, NBO and HBO failed to reduce infarct size in CT but both decreased BBB damage and microscopic hemorrhagic transformation. Only HBO reduced hemoglobin extravasation in the ischemic hemisphere. In conclusion, NBO and HBO decrease infarct size after thromboembolic ischemia only if recanalization is successful. As NBO and HBO also reduce postthrombolytic intracerebral hemorrhage, combining the two with thrombolysis seems promising.

Oxygen-sensitive outcomes and gene expression in acute ischemic stroke

Acute ischemic stroke (AIS) results in focal deprivation of blood-borne factors, one of them being oxygen. The purpose of this study was two-fold: (1) to identify therapeutic conditions for supplemental oxygen in AIS and (2) to use transcriptome-wide screening toward uncovering oxygen-sensitive mechanisms. Transient MCAO in rodents was used to delineate the therapeutic potential of normobaric (NBO, 100% O(2), 1ATA) and hyperbaric oxygen (HBO, 100% O(2), 2ATA) during ischemia (iNBO, iHBO) and after reperfusion (rNBO, rHBO). Stroke lesion was quantified using 4.7 T MRI at 48 h. Supplemental oxygen during AIS significantly attenuated percent stroke hemisphere lesion volume as compared with that in room air (RA) controls, whereas identical treatment immediately after reperfusion exacerbated lesion volume (RA=22.4+/-1.8, iNBO=9.9+/-3.6, iHBO=6.6+/-4.8, rNBO=29.8+/-3.6, rHBO=35.4+/-7.6). iNBO and iHBO corrected penumbra tissue pO(2) during AIS as measured by EPR oxymetry. Unbiased query of oxygen-sensitive transcriptome in stroke-affected tissue identified 5,769 differentially expressed genes. Candidate genes were verified by real-time PCR using neurons laser-captured from the stroke-affected somatosensory cortex. Directed microarray analysis showed that supplemental oxygen limited leukocyte accumulation to the infarct site by attenuation of stroke-inducible proinflammatory chemokine response. The findings provide key information relevant to understanding oxygen-dependent molecular mechanisms in the AIS-affected brain.