Microcirculation and tissue oxygenation in the head and limbs during hyperbaric oxygen treatment.

INTRODUCTION: Hyperbaric oxygen (HBO) exposure for 10-15 min has been shown to reduce peripheral blood flow due to vasoconstriction. However, the relationship between decreased peripheral blood flow and the therapeutic effects of HBO treatment on peripheral circulatory disorders remain unknown. Longer exposures have been reported to have vasodilatory effects and increase peripheral blood flow. This study investigated the effect of HBO treatment on blood flow and transcutaneous oxygen pressure (TcPO2). METHODS: Twenty healthy volunteers aged 20-65 years (nine males) participated in this study. All participants breathed oxygen for 60 min at 253.3 kPa. Peripheral blood flow using laser Doppler flowmetry and TcPO2 on the ear, hand, and foot were continuously measured from pre-HBO exposure to 10 min post-exposure. RESULTS: Peripheral blood flow in each body part decreased by 7-23% at the beginning of the HBO exposure, followed by a slow increase. Post-exposure, peripheral blood flow increased 4-76% in each body part. TcPO2 increased by 840-1,513% during the exposure period, and remained elevated for at least 10 min after the exposure. CONCLUSIONS: The findings of the current study suggest vasoconstriction during HBO treatment is transient, and even when present does not inhibit the development of increased tissue oxygen partial pressure. These findings are relevant to studies investigating changes in peripheral blood flow during HBO treatment in patients with circulatory disorders.

Multiple and early hyperbaric oxygen treatments enhance muscle healing after muscle contusion injury: a pilot study.

BACKGROUND: The optimal timing of hyperbaric oxygen (HBO2) treatments for the best recovery following muscle injury has yet to be determined. Thus, the optimal number and timing of HBO2 treatments for maximal muscle regeneration were explored. METHODS: The HBO2 treatment protocol consisted of 2.5 ATA 100% oxygen for 120 minutes. Muscle-injured rats were randomized to one of 10 groups: single HBO2 treatment immediately after injury (HBO 1T day 0), one day (HBO 1T day 1), three days (HBO 1T day 3) and five days (HBO 1T day 5) after injury; three HBO2 treatments from immediately after injury to two days after injury (HBO 3T day 0-2), from one to three days after injury (HBO 3T day 1-3), from three to five days after injury (HBO 3T day 3-5), from five to seven days after injury (HBO 3T day 5-7); five daily HBO2 treatments (HBO 5T); and no treatment (NT). RESULTS: HBO 5T and HBO 3T day 0-2, days 1-3 and days 3-5 significantly promoted CD206-positive cell infiltration, satellite cell differentiation and muscle regeneration compared to the NT group. CONCLUSION: Five HBO2 treatments and three HBO2 treatments within three days of injury promote muscle regeneration.

Use of hyperbaric oxygen therapy for preventing delayed neurological sequelae in patients with carbon monoxide poisoning: A multicenter, prospective, observational study in Japan.

BACKGROUND: The purpose of this study was to clarify the practical clinical treatment for acute carbon monoxide (CO) poisoning in Japan and to investigate the efficacy of hyperbaric oxygen (HBO2) therapy in preventing delayed neurological sequelae (DNS) in the acute phase of CO poisoning. METHODS: We conducted a multicenter, prospective, observational study of acute CO poisoning in Japan. Patients with acute CO poisoning were enrolled and their treatment details were recorded. The primary endpoint was the onset of DNS within 2 months of CO exposure. Factors associated with DNS were assessed with logistic regression analysis. RESULTS: A total of 311 patients from 57 institutions were registered and 255 were analyzed: 171 received HBO2 therapy (HBO2 group) and 84 did not (normobaric oxygen [NBO2] group). HBO2 therapy was performed zero, once, twice, or three times within the first 24 h in 1.8%, 55.9%, 30.9%, and 11.3% of the HBO2 group, respectively. The treatment pressure in the first HBO2 session was 2.8 ATA (47.9% of the HBO2 group), 2.0 ATA (41.8%), 2.5 ATA (7.9%), or another pressure (2.4%). The incidence of DNS was 13/171 (7.6%) in the HBO2 group and 3/84 (3.6%) in the NBO2 group (P = 0.212). The number of HBO2 sessions in the first 24 h was one of the factors associated with the incidence of DNS (odds ratio, 2.082; 95% confidence interval, 1.101-3.937; P = 0.024). CONCLUSIONS: The practical clinical treatment for acute CO poisoning, including HBO2 therapy, varied among the institutions participating in Japan. HBO2 therapy with inconsistent protocols showed no advantage over NBO2 therapy in preventing DNS. Multiple HBO2 sessions was associated with the incidence of DNS.

VEGF and bFGF induction by nitric oxide is associated with hyperbaric oxygen-induced angiogenesis and muscle regeneration.

Hyperbaric oxygen (HBO) treatment promotes early recovery from muscle injury. Reactive oxygen species (ROS) upregulation is a key mechanism of HBO, which produces high O2 content in tissues through increased dissolution of oxygen at high pressure. Nitric oxide (NO), a type of ROS, generally stabilizes hypoxia-inducible factor (HIF) 1α and stimulates secretion of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) from endothelial cells and macrophages, which then induces angiogenesis. The purpose of the present study was to investigate whether HBO could promote angiogenesis via induction of NO and induce muscle regeneration in contused rat skeletal muscles. The HBO protocol consisted of 2.5 atmospheres absolute (ATA) 100% oxygen for 120 minutes, once a day for 5 consecutive days. We also evaluated the effects of a ROS inhibitor (NAC) or NOS-specific inhibitor (L-NAME) on HBO. HBO significantly increased NO3-, VEGF, and bFGF levels and stabilized HIF1α within 1 day. HBO promoted blood vessel formation at 3-7 days and muscle healing at 5-7 days after contusion. Administration of both NAC and L-NAME before HBO suppressed angiogenesis and muscle regeneration even after HBO. HBO thus promoted angiogenesis and muscle regeneration mainly through generation of NO in the early phase after muscle contusion injury.

Effects of hyperbaric oxygen therapy on recovery acceleration in Japanese professional or semi-professional rugby players with grade 2 medial collateral ligament injury of the knee: A comparative non-randomized study.

INTRODUCTION: The effects of hyperbaric oxygen (HBO2) therapy on sprains, ligament injuries, and muscle strains have been reported in several animal studies. In a dog model of compartment syndrome and in a rat contused skeletal muscle injury model, the significant effects of HBO2 therapy on the reduction of edema and muscle necrosis have been reported. In basic research HBO2 therapy stimulated fibroblast activity to improve the healing process. Because of this it expected that HBO2 therapy might improve focal edema and pain in the acute phase and accelerate the healing of injured tissues in athletes with a medial collateral ligament (MCL) injury of the knee. This study aimed to examine the short-term effects of HBO2 application subjectively, and the long-term effects of HBO2 therapy in Japanese professional or semi-professional rugby players with grade 2 MCL injury of the knee. METHODS: Thirty-two professional or semi-professional rugby players with grade 2 MCL injury of the knee were investigated. First, in the HBO2 group (n=16), HBO2 therapy was performed during the acute phase. Visual analog scales (VASs) immediately before and after HBO2 therapy on the same day were compared. Next, we retrospectively evaluated the time to return to play in the HBO2 (n=16) and non-HBO2 (n=16) groups. RESULTS: VAS scores for pain while walking immediately before and after HBO2 therapy on the same day were 37.4 ± 20.1 (mean ± standard deviation) and 32.4 ± 21.8, respectively (p⟨0.001). The VAS scores for pain while jogging were 50.7 ± 25.6 and 43.9 ± 25.0, respectively (p⟨0.001). The time to return to play was 31.4 ± 12.2 days in the HBO2 group and 42.1 ± 15.8 days in the non-HBO2 group, indicating a significant difference between the groups (p⟨0.05). CONCLUSION: HBO2 therapy may reduce pain and accelerate the return to play in athletes with grade 2 MCL injury of the knee in this non-randomized study.

Hyperbaric oxygen reduces inflammation, oxygenates injured muscle, and regenerates skeletal muscle via macrophage and satellite cell activation.

Hyperbaric oxygen treatment (HBO) promotes rapid recovery from soft tissue injuries. However, the healing mechanism is unclear. Here we assessed the effects of HBO on contused calf muscles in a rat skeletal muscle injury model. An experimental HBO chamber was developed and rats were treated with 100% oxygen, 2.5 atmospheres absolute for 2 h/day after injury. HBO reduced early lower limb volume and muscle wet weight in contused muscles, and promoted muscle isometric strength 7 days after injury. HBO suppressed the elevation of circulating macrophages in the acute phase and then accelerated macrophage invasion into the contused muscle. This environment also increased the number of proliferating and differentiating satellite cells and the amount of regenerated muscle fibers. In the early phase after injury, HBO stimulated the IL-6/STAT3 pathway in contused muscles. Our results demonstrate that HBO has a dual role in decreasing inflammation and accelerating myogenesis in muscle contusion injuries.

Elimination of CT-detected gas bubbles derived from decompression illness with abdominal symptoms after a short hyperbaric oxygen treatment in a monoplace chamber: a case report.

We report the case of a 54-year-old male compressed-air worker with gas bubbles detected by computed tomography (CT). He had complained of strong abdominal pain 30 minutes after decompression after working at a pressure equivalent to 17 meters of sea water for three hours. The initial CT images revealed gas bubbles in the intrahepatic portal vein, pulmonary artery and bilateral femoral vein. After the first hyperbaric oxygen treatment (HBO2 at 2.5 atmospheres absolute/ATA for 150 minutes), no bubbles were detected on repeat CT examination. The patient still exhibited abdominal distension, mild hypesthesia and slight muscle weakness in the upper extremities. Two sessions of U.S. Navy Treatment Table 6 (TT6) were performed on Days 6 and 7 after onset. The patient recovered completely on Day 7. This report describes the important role of CT imaging in evaluating intravascular gas bubbles as well as eliminating the diagnosis of other conditions when divers or compressed-air workers experience uncommon symptoms of decompression illness. In addition, a short treatment table of HBO2 using non-TT6 HBO2 treatment may be useful to reduce gas bubbles and the severity of decompression illness in emergent cases.

Hyperbaric oxygen therapy for a refractory skin ulcer after radical mastectomy and radiation therapy: a case report.

BACKGROUND: Radiation therapy is performed as an adjuvant therapy when indicated following surgical resection of malignant tumors. However, radiation exposure induces acute or chronic dermatitis, depending on the radiation dose, interval, tissue volume, or irradiated area of the body. Radiation-induced skin ulcers and osteomyelitis of the underlying bone are intractable late-stage complications of radiation therapy, and often require reconstructive surgery to cover exposed tissue. Hyperbaric oxygen therapy has been suggested as a treatment for delayed radiation injury with soft tissue and bony necrosis. CASE PRESENTATION: A 74-year-old Japanese female underwent left radical mastectomy for breast cancer (T3N3M0, stage IIIB) in 1987. Radiation therapy was initiated 6 weeks after the surgery. She received telecobalt-60 in a total dose of 50 Gy with 25 fractions to the left supraclavicular, parasternal and left axillary regions, and electron treatment (9 MeV) in a total dose of 50 Gy in 25 fractions to the left chest wall. After irradiation, her skin became thinner and more fragile on the left chest wall, but no severe infections were observed. She noticed a small ulcer that repeatedly healed and recurred in 2000. She visited the hospital where she received radiation therapy and was treated for a skin ulcer on the left chest wall in December 2012. A fistula developed and then pus was discharged in January 2013. She was referred to the hyperbaric medical center in February 2013, and the fistula (1.5 × 3 cm) with pus discharge was observed. She was diagnosed with a late-onset radiation-induced skin ulcer that developed 25 years after radical mastectomy. HBO2 (2.5 atmospheres absolute with 100% oxygen for 60 minutes) was indicated for the refractory ulcer and osteomyelitis of the ribs. The patient was treated with HBO2 a total of 101 times over the course of 1 year and completely recovered. CONCLUSIONS: Hyperbaric oxygen therapy can be performed safely for even more than 100 sessions in patients with radiation-induced skin ulcers and osteomyelitis. Hyperbaric oxygen therapy can be considered as an alternative, conservative treatment when surgical resection for late-onset, radiation-induced skin ulcers is not indicated because of fragile skin in the irradiated areas.

The facilitatory effects of hyperbaric oxygen treatment on membrane bone wound healing in a rat calvarial defect model.

We examined the effect of hyperbaric oxygen (HBO2) treatment on bone wound healing in a rat calvarial defect. Critical-sized defects were created in the calvaria of adult Wistar rats. The animals were divided into four groups--HBO2, normobaric oxygen, hyperbaric air, and no treatment. Treatments were performed five days a week, for two weeks. Micro-computerized tomography and histological analysis were used to evaluate the bone defects. Regenerated bone areas were calculated as the percentage of new bone in the cross-sectional area of defect. The new bone cross-sectional area was significantly greater in the HBO2 group than in the other groups. There were no significant differences in the numbers of nucleated cells in the new bone areas. Although new bone volume per defect volume was significantly greater in the HBO2 group than in the other groups, no significant differences in bone mineral density in the new bone area were observed. These findings indicate the facilitatory role of HBO2 treatment on bone wound healing in the rat calvarial bone defect, and it does not appear to have any negative effects on bone maturity. We propose that HBO2 treatment would be useful in promoting bone regeneration following injury in the orofacial region.

Altered Sleep Spindles in Delayed Encephalopathy after Acute Carbon Monoxide Poisoning.

ABSTRACT: Delayed encephalopathy (DE) affects not only the cerebral white matter and globus pallidus but also the cortex and thalamus. However, it remains unknown whether these brain lesions alter sleep along with clinical manifestations of DE. A 46-year-old man with DE underwent repetitive hyperbaric oxygen therapy. The patient was evaluated by not only neuropsychological and neuroimaging testing but polysomnography over the clinical course. Neurological symptoms improved markedly; however, profound frontal cognitive deficits continued. The polysomnography revealed prolonged absence and delayed recovery of sleep spindles across recordings. Alterations in spindle oscillations in DE could provide further insight into sleep regulatory networks.

Transient osteoporosis of the hip treated with hyperbaric oxygen therapy: a case series.

INTRODUCTION: Transient osteoporosis of the hip (TOH) is a self-limiting disorder characterized by bone marrow edema at the femoral head and neck. Patients report pain as moderate or severe at onset; pain gradually subsides at about six months (range four to 12 months). Differential diagnosis of the early stages of osteonecrosis of the femoral head (ONFH) is sometimes difficult. Because hyperbaric oxygen (HBO2) therapy is effective for reduction of edema in soft tissue injury and early stages of ONFH, we hypothesized that HBO2 could be effective in TOH for accelerated recovery. METHODS: Five cases of TOH treated with HBO2 were clinically evaluated. HBO2 was started from three to eight weeks after onset and performed four or five times a week, averaging a total of 27.8 ± 4.7 treatments (range 20-32). Clinical features were evaluated repeatedly with clinical examination, subjective evaluation of pain, and imaging methods that included magnetic resonance imaging (MRI) and bone scans. RESULTS: The average time to return-to-normal hip range of motion was 15.4 ± 7.8 weeks after onset, and relief of subjective pain was 16.6 ± 4.0 weeks. The average time to return-to-normal signal level in MRI was 22.0 ± 2.5 weeks, which was one to two months after relief of subjective pain. COMCLUSIONS: Multiple HBO2 treatments have the possibility of contributing to recovery acceleration in patients with TOH. However, in this study, we found that HBO2 treatment did not significantly accelerate the recovery of these five patients with TOH. The use of HBO2 should therefore be limited to patients in whom the differential diagnosis between TOH and early stage ONFH cannot be established.

Otological complications associated with hyperbaric oxygen therapy.

The objective of the present study was to clarify the features of otological complications for hyperbaric oxygen therapy (HBOT) and the risk factors for these complications. We enrolled 1115 patients (776 males and 339 females; age 5-89 years) who underwent HBOT. All otological symptoms experienced during HBOT sessions were evaluated, and risk factors were analysed using multivariate logistic regression analysis. Otoscopic findings and interventions for otological complications were assessed in 58 symptomatic patients who visited the Otolaryngology Department. Otological symptoms were experienced by 165 (14.8 %) of the 1115 patients. The multivariate logistic regression analysis identified ages of >60 years and female sex as independent risk factors, whereas patients with sports injuries were at lower risk than those with other primary diseases, except for severe infectious disease. Eighty-two patients (49.7 %) suffered from symptoms at the first HBOT session. The most prevalent symptoms were otalgia (157/165), followed by ear fullness (13/165), hearing loss (12/165) and tinnitus (3/165). One patient experienced vertigo and deterioration of the bone-conduction pure-tone thresholds, suggesting inner ear barotrauma. In 116 ears of the 58 symptomatic patients, abnormal otoscopic findings were recognized in 58 ears (50.0 %). Twenty-seven of the 58 ears required myringotomy or tube insertion, and HBOT was stopped in eight ears in four patients. Of the remaining 58 ears with normal otoscopic findings, 51 received no treatment. Physicians should be aware of both middle and inner ear barotrauma as potential complications of HBOT.

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

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

Effects of hyperbaric oxygen on muscle fatigue after maximal intermittent plantar flexion exercise.

The purpose of this study was to investigate the effects of hyperbaric oxygen (HBO) treatment on muscle fatigue after maximal intermittent plantar flexion exercise. Twenty healthy male volunteers (aged from 21 to 24 years) were randomly assigned to either HBO or normoxic group and were blinded to their treatment and group assignment. The HBO group breathed 100% oxygen under 2.5 atmosphere absolute (ATA) for 60 minutes, whereas the normoxic group breathed room air under 1.2 ATA for 70 minutes. The subjects performed a fatigue test, which consisted of 50 maximal unilateral isometric plantar flexions, before and after intervention. Surface electromyography was recorded from triceps surae muscle. Subjects performed maximal voluntary contractions of isometric plantar flexions, and voluntary activation and twitch contractile properties were evaluated with cutaneous tibial nerve stimuli before and after intervention. Compared with initial values during repetitions 4-10, the plantar flexion torque during repetitions 41-50 decreased to 88.5 and 83.2% after HBO and normoxic treatment, respectively. A smaller decrease in muscle force was observed in the HBO group compared with the normoxic group. No differences in function between treatment groups were observed after nerve stimulation. These results suggest that HBO contributes to sustained force production due to suppressing the muscle fatigue progression. In practice, HBO can contribute to the prevention of excess fatigue of agonist muscles for specific exercises involving repeated jumping.

Enhancement of satellite cell differentiation and functional recovery in injured skeletal muscle by hyperbaric oxygen treatment.

Recently, the use of hyperbaric oxygen (HBO) treatments by elite athletes to accelerate recovery from muscle injuries has become increasingly popular. However, the mechanism of promoting muscle regeneration under HBO conditions has not yet been defined. In this study, we investigated whether HBO treatments promoted muscle regeneration and modulated muscle regulatory factor expression in a rat skeletal muscle injury model. Muscle injury was induced by injecting cardiotoxin (CTX) into the tibialis anterior (TA) muscles. As the HBO treatment, rats were placed in an animal chamber with 100% oxygen under 2.5 atmospheres absolute for 2 h/day, 5 days/wk for 2 wk. We then performed histological analyses, measured the maximum force-producing capacity of the regenerating muscle fibers, and performed quantitative RT-PCR analysis of muscle regulatory factor mRNAs. The cross-sectional areas and maximum force-producing capacity of the regenerating muscle fibers were increased by HBO treatment after injury. The mRNA expression of MyoD, myogenin, and IGF-1 increased significantly in the HBO group at 3 and 5 days after injury. The number of Pax7(+)/MyoD(+), Pax7(-)/MyoD(+), and Pax7(+)/BrdU(+)-positive nuclei was increased by HBO treatment. In this study, we demonstrated that HBO treatment accelerated satellite cell proliferation and myofiber maturation in rat muscle that was injured by a CTX injection. These results suggest that HBO treatment accelerates healing and functional recovery after muscle injury.

Secondary hyperbaric oxygen therapy for idiopathic sudden sensorineural hearing loss in the subacute and chronic phases.

This study investigated the efficacy of hyperbaric oxygen therapy (HBOT) as a secondary treatment for patients with idiopathic sudden sensorineural hearing loss (ISSNHL) in the subacute and chronic phases. Forty-eight ISSNHL patients (HBOT group) who had received primary conventional treatment within 4 weeks after onset and underwent HBOT between 4 and 20 weeks post-onset were retrospectively compared with 44 ISSNHL patients (control group) with primary conventional treatment alone. Mean hearing gain was slight, with gains of 5.2 +/- 8.9 dB in the HBOT group and 2.0 +/- 7.6 dB in the control group. However, no significant difference was recognized between the two groups. In the HBOT group, no significant difference was observed in hearing gain among patients with HBOT initial time at 4-7, 8-11, 12-15 or 16-20 weeks after onset. Meanwhile, hearing gain was significantly higher in patients with profound hearing loss than in the other patients. We conclude that the effectiveness of secondary HBOT for ISSNHL patients in either subacute or chronic phase remains unproven, and thus, the decision administer HBOT should be made with caution.