Reduction of skeletal muscle necrosis using intermittent hyperbaric oxygen in a model compartment syndrome

Is There a Place for Hyperbaric Oxygen Therapy?

Hyperbaric oxygen therapy (HBOT) involves treating patients by providing 100% oxygen through inhalation while inside a treatment pressurized chamber. The oxygen acts as a drug and the hyperbaric chamber as the dosing device. The effect of hyperbaric hyperoxia is dose dependent and, therefore, treatment depth and duration are important when considering its use. HBOT can either be the primary method of treatment or used adjunctively to medications or surgical techniques. The underpinning physiology is to bring oxygen-rich plasma to hypoxic tissue, preventing reperfusion injury, strengthening immune responsiveness, and encouraging new collagen deposition as well as endothelial cell formation.

Animal models in compartment syndrome: a review of existing literature

Objective:

Extremity compartment syndrome (ECS) is a morbid condition resulting in permanent myoneural damage. Currently, the diagnosis of compartment syndrome relies on clinical symptoms and/or intracompartment pressure measurements, both of which are poor predictors of ECS. Animal models have been used to better define cellular mechanisms, diagnosis, and treatment of ECS. However, no standardized model exists. The purpose of this study was to identify existing animal research on extremity compartment syndrome to summarize the current state of the literature and to identify weaknesses that could be improved with additional research.

Methods:

A MEDLINE database search and reverse inclusion protocol were utilized. We included all animal models of ECS.

Results:

Forty-one studies were included. Dogs were the most commonly used model species, followed by pigs and rats. Most studies sought to better define the pathophysiology of compartment syndrome. Other studies evaluated experimental diagnostic modalities or potential treatments. The most common compartment syndrome model was intracompartment infusion, followed by tourniquet and intracompartment balloon models. Few models incorporated additional soft tissue or osseous injury. Only 65.9% of the reviewed studies confirmed that their model created myoneural injury similar to extremity compartment syndrome.

Conclusions:

Study purpose, methodology, and outcome measures varied widely across included studies. A standardized definition for animal compartment syndrome would direct more consistent research in this field. Few animal models have investigated the pathophysiologic relationship between traumatic injury and the development of compartment syndrome. A validated, clinically relevant animal model of extremity compartment syndrome would spur improvement in diagnosis and therapeutic interventions.

Hyperbaric therapy provides no benefit for skeletal muscle and respiratory function and accelerates cardiac injury in mdx mice

Duchenne muscular dystrophy (DMD) is a uniformly fatal condition of striated muscle wasting resulting in premature death from respiratory and/or cardiac failure. Symptomatic therapy has prolonged survival by limiting deaths resulting from respiratory insufficiency, but there is currently no effective therapy for most patients with DMD. This grim prognosis has led patients and their families to seek unproven therapeutic approaches. One such approach is the use of hyperbaric therapies, which 14% of DMD patients self-report using. The primary goal of this study was to determine if intermittent hyperbaric exposure altered the muscle function of the mdx mouse, a genetic model of DMD. To do this, mdx mice were exposed to three daily 90-minute 1.3 atmosphere hyperbaric exposures for 4 weeks. Skeletal muscle, respiratory, and cardiac function were assessed in treated and untreated wild type and dystrophic mice. The results of these studies find that hyperbaric and hyperoxic approaches resulted in increased cardiac fibrosis in dystrophic mice and no beneficial effects on the functional parameters measured. These data suggest that these oxygen-based therapies are unlikely to provide therapeutic benefit to DMD patients.

Hyperbaric Oxygen Increases Stem Cell Proliferation, Angiogenesis and Wound-Healing Ability of WJ-MSCs in Diabetic Mice

Hyperbaric oxygen therapy (HBOT) is effective for the medical treatment of diverse diseases, infections, and tissue injury. In fact, in recent years there is growing evidence on the beneficial effect of HBOT on non-healing ischemic wounds. However, there is still yet discussion on how this treatment could benefit from combination with regenerative medicine strategies. Here we analyzed the effects of HBOT on three specific aspects of tissue growth, maintenance, and regeneration: (i) modulation of adult rodent (Mus musculus) intestinal stem cell turnover rates; (ii) angiogenesis dynamics during the development of the chorio-allantoic membrane (CAM) in Gallus gallus embryos; (iii) and wound-healing in a spontaneous type II diabetic mouse model with a low capacity to regenerate skin. To analyze these aspects of tissue growth, maintenance, and regeneration, we used HBOT alone or in combination with cellular therapy. Specifically, Wharton Jelly Mesenchymal Stem cells (WJ-MSC) were embedded in a commercial collagen-scaffold. HBOT did not affect the metabolic rate of adult mice nor of chicken embryos. Notwithstanding, HBOT modified the proliferation rate of stem cells in the mice small intestinal crypts, increased angiogenesis in the CAM, and improved wound-healing and tissue repair in diabetic mice. Moreover, our study demonstrates that combining stem cell therapy and HBOT has a collaborative effect on wound-healing. In summary, our data underscore the importance of oxygen tension as a regulator of stem cell biology and support the potential use of oxygenation in clinical treatments.

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.

Hyperbaric Oxygen Inhibits Reperfusion-Induced Neutrophil Polarization and Adhesion Via Plasmin-Mediated VEGF Release

Background:

Ischemia-reperfusion (IR) injury is seen in many settings such as free flap salvage and limb replantation/revascularization. The consequences—partial/total flap loss, functional muscle loss, or amputation—can be devastating. Of the treatment options available for IR injury, hyperbaric oxygen (HBO) is the most beneficial. HBO inhibits neutrophil-endothelial adhesion through interference of CD18 neutrophil polarization in IR, a process mediated by nitric oxide. The purposes of this study were to examine the involvement of vascular endothelial growth factor (VEGF) in the beneficial HBO effect on CD18 polarization and neutrophil adhesion and investigate the effect of plasmin on VEGF expression in skeletal muscle following IR injury.

Methods:

A rat gracilis muscle model of IR injury was used to evaluate the effect of VEGF in IR, with and without HBO, on neutrophil CD18 polarization and adhesion in vivo and ex vivo. Furthermore, we investigated the effects that plasmin has on VEGF expression in gracilis muscle and pulmonary tissue by blocking its activation with alpha-2-antiplasmin.

Results:

HBO treatment following IR injury significantly decreased neutrophil polarization and adhesion ex vivo compared with the IR group. Anti-VEGF reversed the beneficial HBO effect after IR with polarization and adhesion. In vivo adhesion was also increased by anti-VEGF. HBO treatment of IR significantly increased the VEGF protein in both gracilis and pulmonary vasculature. Alpha-2-antiplasmin significantly reversed the HBO-induced increase of VEGF in gracilis muscle.

Conclusions:

These results suggest that HBO inhibits CD18 polarization and neutrophil adhesion in IR injury through a VEGF-mediated pathway involving the extracellular matrix plasminogen system.

Analytic Reviews : Hyperbaric Oxygen Therapy

The physiological effects of hyperbaric oxygen extend beyond the elevation of oxygen concentration in body tissues, and clinical data is available to support its use in more than gas bubble diseases. Hyperbaric medicine is discussed within the context of its recognized mecha nisms of action. The experimental data and clinical ex perience for hyperbaric oxygen therapy are reviewed for the following conditions: clostridial myonecrosis, necrotizing soft-tissue infections, chronic refractory os teomyelitis, radiation necrosis, refractory cutaneous ul cerations, compromised skin grafts and flaps, crush in jury and acute peripheral ischemia, carbon monoxide poisoning, arterial gas embolism, decompression sick ness, and thermal burns. Risks associated with hyper baric oxygen therapy are discussed, and cost analysis data are noted for specific conditions.

The role of hyperbaric oxygen therapy in crush injuries

Hyperbaric oxygen therapy has been approved for primary or adjunctive care in 14 indications. A hyperbaric environment exists when a patient's whole body is physically exposed to 100% oxygen and pressure that is greater than one atmosphere absolute. Hyperbaric oxygen therapy works through the ideal gas laws and is effective as an adjunctive therapy in the treatment of crush injuries. Oxygen is considered a drug and can have contraindications and adverse effects. Hyperbaric therapy works through several different mechanisms in the crush injury. Effects of hyperoxygenation, reduction of edema, infection control enhancement, blood vessel and collagen formation, and reduction of free radicals and reperfusion injury help in healing in patient with crush injuries.

Use of Hyperbaric Oxygen as Adjunct in Salvage of Near-complete Ear Amputation

Summary:

There have been several cases of microvascular repair of traumatically avulsed or amputated ears in the literature. It seems that, if possible at the time of operation, microsurgical techniques yield the best results. However, because of the nature, complexity, and acuity of traumatic injuries, this option is not always feasible. Although the possibility of microsurgical repair exists, the small size of these vessels is often prohibitive, even for a skilled microsurgeon. Here, we present the case of a 4-year-old boy with almost complete amputation of the left ear attached by an inferior narrow skin pedicle after a dog bite. He was treated with primary repair and postoperative hyperbaric oxygen therapy (HBOT) with good results. This case is another example that even a narrow skin pedicle can contain artery and vein that can supply a large segment of the auricle, making primary repair feasible because of the vascular anatomy and communicating helical arcade. Also, this case demonstrates the successful use of HBOT with a pediatric patient as an adjuvant postoperative therapy.

The effect of hyperbaric oxygen on nitric oxide synthase activity and expression in ischemia-reperfusion injury

BACKGROUND

Hyperbaric oxygen (HBO) mitigates ischemia-reperfusion (IR) injury via a nitric oxide mechanism that is nitric oxide synthase (NOS) dependent. The purpose of this study was to investigate this NOS-dependent mechanism by examining isoform-specific, tissue-specific, and time-specific upregulation of NOS mRNA, protein, and enzymatic activity.

METHODS

We raised a gracilis flap in Wistar rats that were separated into early and late phases. Treatment groups included nonischemic control, IR, HBO-treated ischemia-reperfusion (IR-HBO), and nonischemic HBO control. We harvested tissue-specific samples from gracilis, rectus femoris, aorta, and pulmonary tissues and processed them by reverse transcription polymerase chain reaction and Western blot to determine upregulation of isoform-specific NOS mRNA and protein. We also harvested tissue for NOS activity to investigate upregulation of enzymatic activity. Data are presented as mean ± standard error of the mean with statistics performed by analysis of variance. P ≤ 0.05 was considered significant.

RESULTS

There was no increase in NOS mRNA in the early phase. In the late phase, there was a significant increase in endothelial-derived NOS (eNOS) mRNA in IR-HBO compared with IR in gracilis muscle (79.4 ± 22.3 versus 36.1 ± 4.5; P < 0.05) and pulmonary tissues (91.0 ± 31.2 versus 30.2 ± 3.1; P < 0.01). There was a significant increase in the late-phase eNOS pulmonary protein IR-HBO group compared with IR (235.5 ± 46.8 versus 125.2 ± 14.7; P < 0.05). Early-phase NOS activity was significantly increased in IR-HBO compared with IR in pulmonary tissue only (0.049 ± 0.009 versus 0.023 ± 0.003; P < 0.05).

CONCLUSIONS

The NOS-dependent effects of HBO on IR injury may result from a systemic effect involving an early increase in eNOS enzymatic activity followed by a late-phase increase in eNOS protein expression within the pulmonary tissues.

Compartment syndrome: pathophysiology, clinical presentations, treatment, and prevention in human and veterinary medicine

OBJECTIVE

To review the human and veterinary literature pertaining to all forms of compartment syndrome (CS).

DATA SOURCES

Data sources included scientific reviews and original research publications from the human and veterinary literature.

HUMAN DATA SYNTHESIS

While CS affecting the extremities has been recognized in people for decades, other forms of CS in the abdominal and thoracic cavities are recently gaining more attention. The role of CS in critically ill people is a rapidly growing area of interest. More research on prevention and treatment of CS is being conducted in people because some studies have found mortality rates as high as 80% for those suffering from these conditions.

VETERINARY DATA SYNTHESIS

While a significant amount of experimental studies of CS have been performed on small animals, there is a marked lack of primary veterinary studies. The majority of the veterinary literature includes case reports and series, and many of these studies were published over a decade ago. However, the increased recognition of CS in people has sparked an interest in veterinary critical care medicine and this has been demonstrated by the recent increased evaluation of compartment pressures in veterinary patients.

CONCLUSIONS

CS is a complex clinical condition where increased pressure within a compartment can cause significant adverse effects within the compartment as well as throughout the body. Systemic inflammatory responses and local ischemia-reperfusion elements can contribute to the detrimental effects seen in CS. This cascade of events results in increased mortality rates and contributes to the development of CS elsewhere. A better understanding of CS will help veterinarians improve patient care and outcome. Future studies on incidence, prevention, and treatment of CSs in the critical care patient are needed in veterinary medicine.

Preventive effects of hyperbaric oxygen treatment on glycerol-induced myoglobinuric acute renal failure in rats

Myoglobinuric acute renal failure (ARF) is a uremic syndrome caused by traumatic or non-traumatic skeletal muscle breakdown and intracellular elements that are released into the bloodstream. We hypothesized that hyperbaric oxygen (HBO) therapy could be beneficial in the treatment of myoglobinuric ARF caused by rhabdomyolysis. A total of 32 rats were used in the study. The rats were divided into four groups: control, control+hyperbaric oxygen (control+HBO), ARF, and ARF+hyperbaric oxygen (ARF+HBO). Glycerol (8 ml/kg) was injected into the hind legs of each of the rats in ARF and ARF+HBO groups. 2.5 atmospheric absolute HBO was applied to the rats in the control+HBO and ARF+HBO groups for 90 min on two consecutive days. Plasma urea, creatinine, sodium, potassium, calcium, aspartate aminotransferase, alanine aminotransferase, lactic dehydrogenase, creatinine kinase and urine creatinine and sodium were examined. Creatinine clearance and fractional sodium excretion could then be calculated. Superoxide dismutase, catalase, glutathione and malondialdehyde (MDA) levels were assessed in renal tissue. Tissue samples were evaluated by Hematoxylin-eosin, PCNA and TUNEL staining histopathologically. MDA levels were found to be significantly decreased whereas SOD and CAT were twofold higher in the ARF+HBO group compared to the ARF group. Renal function tests were ameliorated by HBO therapy. Semiquantitative evaluation of histopathological findings indicated that necrosis and cast formation was decreased by HBO therapy and TUNEL staining showed that apoptosis was inhibited. PCNA staining showed that HBO therapy did not increase regeneration. Ultimately, we conclude that, in accordance with our hypothesis, HBO could be beneficial in the treatment of myoglobinuric ARF.

Hyperbaric oxygen inhibits ischemia-reperfusion-induced neutrophil CD18 polarization by a nitric oxide mechanism

BACKGROUND

Hyperbaric oxygen decreases ischemia-reperfusion-induced neutrophil/intercellular adhesion molecule-1 adhesion by blocking CD18 polarization. The purpose of this study was to evaluate whether this hyperbaric oxygen effect is nitric oxide dependent and to determine whether nitric oxide synthase is required.

METHODS

A gracilis muscle flap was raised in nine groups of male Wistar rats. Global ischemic injury was induced by clamping the gracilis muscle pedicle artery and vein for 4 hours. The hyperbaric oxygen treatment consisted of 100% oxygen at 2.5 atm absolute during the last 90 minutes of ischemia. Groups were repeated with and without various nitric oxide synthase inhibitors and carboxy-2-phenyl-4,4,5,5,-tetramethylimidazoline-1-oxyl-3-oxide (C-PTIO), a nitric oxide scavenger. Normal neutrophils were exposed to activated plasma on intercellular adhesion molecule-1-coated coverslips (percentage adherent) and labeled with fluorescein isothiocyanate/antirat-CD11b for confocal microscopy (percentage polarized). The percentage of adherent and polarized cells was reported as mean + or - SEM. Statistical analysis was by analysis of variance. A value of p < or = 0.05 was considered significant.

RESULTS

C-PTIO-treated ischemia-reperfusion/hyperbaric oxygen plasma showed a significant increase in the percentage polarization of CD18 compared with ischemia-reperfusion/hyperbaric oxygen-untreated plasma from 4.1 + or - 2.5 percent to 33.7 + or - 7.7 percent (p < or = 0.05). The nitric oxide scavenger C-PTIO also increased the percentage of adherent cells from 1.6 + or - 0.4 percent to 20.3 + or - 5.9 percent (p < or = 0.05). Administration of N-nitro-L-arginine methyl ester and other nitric oxide synthase inhibitors before hyperbaric oxygen treatment restored neutrophil adhesion and CD18 polarization to ischemia-reperfusion control values, significantly greater than ischemia-reperfusion/hyperbaric oxygen alone.

CONCLUSION

These results suggest that the hyperbaric oxygen reduction of ischemia-reperfusion-induced neutrophil polarization of CD18 and adherence to intercellular adhesion molecule-1 is mediated through a nitric oxide mechanism that requires nitric oxide synthase.

Infiltration and extravasation: update on prevention and management

Infiltration and extravasation are risks of intravenous administration therapy involving unintended leakage of solution into the surrounding tissue. Consequences range from local irritation to amputation. While immediate action using appropriate measures (ie, dilution, extraction, antidotes, and supportive treatments) can decrease the need for surgical intervention, many injuries may be prevented by following established policy and procedures. However, timely surgical intervention, when necessary, can prevent more serious adverse outcomes. Clinicians should be prepared to act promptly when an event occurs. Thorough incident documentation helps determine whether infusion care meets the standard of practice and is a keystone to medicolegal defense.

Effects of hyperbaric oxygen on the replanted extremity subjected to prolonged warm ischaemia

In this investigation, the influence of hyperbaric oxygen (HBO) therapy on the survival of a replanted extremity subjected to prolonged warm ischaemia is evaluated. Among the relative contraindications to replantation are prolonged warm ischaemia time, since an obstruction to blood reflow ('no-reflow phenomenon') may occur in amputated parts that are subjected to more than 6h of warm ischaemia. Twenty-three rat hindlimbs were amputated and subjected to 4h of normothermic ischaemia. The average weight of the animals was 500 gm, and re-plantation of the hindlimb was performed by bone fixation followed by microvascular anastomosis of the femoral vessels. Limb re-vascularisation was confirmed at the end of all procedures by the milk test, clinical assessment and pulse oximetry recordings (>90%). Eleven animals served as a control group and no further therapy was instituted, whereas 12 animals served as the study (replantation) group and were subjected to HBO therapy for 3 days postoperatively. The therapy was conducted in a large animal chamber for 90 min at 2.5 ata. Limb survival was assessed by capillary refill upon compression, skin turgor assessment and colour. Confirmation of clinical findings was conducted with daily pulse oximetry readings of >90%. Animals were followed up for 7 days at which point all animals were euthanized or were euthanized earlier if a non-viable limb was present. Two of the 11 limbs in the control group survived following re-plantation, whereas eight of the 12 limbs in the experimental HBO group survived at least 7 days following replantation. This difference was statistically significant (p=0.0361) using chi-square analysis and Fisher's exact test. Although re-plantation of an amputated extremity after prolonged warm ischaemia is considered a relative contraindication due to the possibility of poor outcomes, our results indicate that the window for replantation may be increased if adjunctive HBO therapy is employed in the postoperative period.

Effect of different periods of hyperbaric oxygen on ischemia-reperfusion injury of rat skeletal muscle

The effect of hyperbaric oxygen (HBO) on ischemia-reperfusion injury of skeletal muscle, applied during different periods, was studied in 56 male rats. Animals were subjected to 6-h ischemia by a tourniquet over the major femoral trocanter and 4 (A) or 24 (B) h of reperfusion. HBO was carried out during 1 h in an acrylic chamber at a pressure of 2.0 ATA (100% oxygen): in the last 60 min of ischemia (II), after ischemia, during 1-h reperfusion time (III), and during the last hour of ischemia plus 1-h reperfusion (IV). Group I was the control group. After 4- or 24-h reperfusion, samples of the soleus muscle were stained by H&E and analyzed immunohistochemically. No interstitial hemorrhage, neutrophil infiltrate, or cellular necrosis were induced by HBO. The apoptosis index did not differ among the groups. HBO reduced morphologic alterations and promoted better results when administered in the ischemia plus reperfusion period (GIV).

Hyperbaric oxygenation attenuates renal ischemia-reperfusion injury in rats

BACKGROUND

Oxygen-derived free radicals play an important role in ischemia-reperfusion injury (IR). Hyperbaric oxygenation (HO) decreases free radical production. The aim of this study was to determine the effect of HO treatment on renal ischemia-reperfusion injury in rats.

METHODS

Rats were divided into four groups. All groups underwent right nephrectomy. Group I served as the control group; group II had left renal ischemia-reperfusion; group III was pretreated with HO; and group IV, ischemia-reperfusion and HO pretreatment. Tissue malondialdehyde (MDA) and glutathione (GSH) levels were measured, and histopathologic damage scored.

RESULTS

HO pretreatment significantly decreased tissue MDA levels and histopathologic scores among rats with IR. There was an increased GSH in HO-pretreated rats with IR; however, the difference was not significant.

CONCLUSION

HO prior to ischemia displayed a beneficial effect on renal IR by reducing oxygen radical peroxidation of lipid membranes.

Fasciotomy closure using simultaneous vacuum-assisted closure and hyperbaric oxygen

Fasciotomies performed for compartment syndrome and ischemic vascular disease often requires closure in 2 to 4 weeks by skin graft. This leaves the patient with an unsightly scar and a limb with reduced strength. The use of vacuum-assisted closure (VAC) and hyperbaric oxygen therapy (HBOT) quickly reduce the edema and permit earlier closure with adjacent skin. A study of three trauma patients with compartment syndrome, fasciotomies, and the use of the VAC and HBOT to close the fasciotomy wounds with adjacent skin is presented. The pathophysiology of compartment syndrome and ischemia-reperfusion syndrome is discussed. These patients had closure of the fasciotomy wounds in 3 to 18 days. The simultaneous use of HBOT and VAC accelerates the reduction of edema in a synergistic fashion, permitting early closure of fasciotomy wounds.

Effects of hyperbaric oxygen on gene expressions of procollagen, matrix metalloproteinase and tissue inhibitor of metalloproteinase in injured medial collateral ligament and anterior cruciate ligament

Animal experiments were performed to investigate whether and how the administration of hyperbaric oxygen (HBO) affects gene expressions of procollagens, matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in injured medial collateral ligament (MCL) and anterior cruciate ligament (ACL). In 64 Sprague-Dawley rats, the MCL of the left knee was lacerated at the midsubstance, and the ACL of the left knee was lacerated adjacent to the tibial insertion in another 64 rats. Of these, 32 rats with lacerated MCL and 32 rats with lacerated ACL were housed in individual cages at normal atmospheric pressure (Groups MC and AC, respectively), while the remaining 64 rats were exposed to 100% oxygen at 2.5 atmospheres absolute for 2 h for 5 days a week (Groups MH and AH, respectively). Rats were sacrificed at 3, 7, 14 and 28 days postoperatively. After macroscopic examination, bilateral MCLs were harvested from Groups MC and MH, and bilateral ACLs from Groups AC and AH. Total RNA was extracted from each specimen and gene expressions of type I and type III procollagens, MMP-2, -9 and -3, and TIMP-1 and -2 were estimated using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Macroscopically, lacerated MCL healed by scar tissue formation, the amount of which appeared to be greater in Group MH than in Group MC. In contrast, no lacerated ACLs united, and little, if any, differences were apparent in macroscopic findings between Groups AH and AC. Gene expression of type I procollagen was significantly greater in Group MH than in Group MC at 7 days postoperatively and was also significantly greater in Group AH than in Group AC at 28 days (P<0.05). No significant differences in type III procollagen gene expression were noted between Groups MH and MC or between Groups AH and AC. In addition, no significant differences in gene expressions of MMPs were seen in either ligament, except that gene expression of MMP-13 was significantly lower at 7 days in Group MH than in Group MC (P<0.05). Gene expressions of TIMPs did not differ significantly between Groups MH and MC in each time interval, whereas gene expressions of TIMPs were significantly greater in Group AH than in Group AC at 7, 14 and 28 days for TIMP-1 and at 3, 7 and 14 days for TIMP-2 (P<0.05). RT-PCR results suggested that HBO enhances structural protein synthesis and inhibits degradative processes by enhancing TIMP activities in the lacerated ACL. However, none of the lacerated ACLs united macroscopically despite administration of HBO, indicating that the effect of HBO is insufficient for healing of the injured ACL. If HBO therapy is used as an adjunctive therapy after primary repair of the injured ACL, the success rate of surgery seems likely to be increased.

Hyperbaric oxygen: a novel technology for modulating myocardial schemia-reperfusion via a single drug

Over the years, the anecdotal medical use of oxygen has demonstrated, in a non-evidence-based manner, that it may have wide-ranging clinical consequences. Although oxygen is a critical substrate in the alleviation of hypoxia, anoxia, and ischemia, paradoxically, it also functions as a deleterious metabolite during the reperfusion of previously ischemic tissues. In adding to this controversy, a spate of new pioneering work has identified hyperoxygenation (hyperoxia) and its metabolites as solely and purposefully demonstrating cellular and clinical benefit,particularly in the field of ischemic reperfusion injury (IRI). Furthermore, the beneficial effects of oxygen have been technologically augmented by administration at doses above atmospheric pressure and at higher concentrations. The novel technology that involves oxygen treatment at supra-atmospheric pressures in high concentrations is known as hyperbaric oxygen (HBO). Although the concept of hyperbaric oxygen has been around since the mid 20th century, it is only during the past decade or so that its therapeutic potential as a new technology-based drug has been exploited for the purposes of cellular tolerance and protection. HBO has recently been shown to be a useful adjunct in several models of IRI, including myocardial infarction. How it does this remains to be elucidated. This article attempts to bring into the spotlight some pertinent developments regarding HBO and myocardial IRI, while simultaneously stimulating intellect, thought, and discussion as to whether this novel technology--HBO--which consists of only a singular drug--oxygen--is a therapy that warrants further laboratory and clinical investigation as a therapeutic modality that may be safe and cost-effective, without producing significant adverse effects.

Hyperbaric oxygen as an adjunctive therapy for bilateral compartment syndrome, rhabdomyolysis and acute renal failure after heroin intake

Heroin abuse causes various medical and surgical complications. We report a case of heroin-induced severe bilateral compartment syndrome complicated by rhabdomyolysis, acute renal failure and extremely elevated creatinine kinase. A 30-year-old male heroin addict presented to the emergency department of Mount Vernon Hospital, Mount Vernon, New York complaining of severe pain and burning sensation in both legs and feet 1 day after abusing intravenous heroin. He had severe swelling and tenderness of both legs and feet. Laboratory data revealed tremendous elevation of creatine kinase (236,000 IU/L) consistent with rhabdomyolysis. Acute renal failure developed over subsequent days. Treatment consisted of fasciotomy, hyperbaric oxygen therapy (HBO2) and supportive therapy. The condition gradually improved over 4 weeks and the patient did not require dialysis or amputation.

Clinical Approach to Wounds: D??bridement and Wound Bed Preparation Including the Use of Dressings and Wound-Healing Adjuvants

This is a clinical review of current techniques in wound bed preparation found to be effective in assisting the wound-healing process. The process begins with the identification of a correct diagnosis of the wound's etiology and continues with optimizing the patient's medical condition, including blood flow to the wound site. Débridement as the basis of most wound-healing strategies is then emphasized. Various débridement techniques, including surgery, topical agents, and biosurgery, are thoroughly discussed and illustrated. Wound dressings, including the use of negative pressure wound therapy, are then reviewed. To properly determine the timing of advance therapeutic intervention, the wound-healing progress needs to be monitored carefully with weekly measurements. A reduction in wound area of 10 to 15 percent per week represents normal healing and does not mandate a change in the current wound-healing strategy. However, if this level of wound area reduction is not met consistently on a weekly basis, then alternative healing interventions should be considered. There is a growing body of evidence that can provide guidance on the appropriate use of such adjuvants in the problem wound. Several adjuvants are discussed, including growth factor, bioengineered tissues, and hyperbaric medicine.

Hyperbaric oxygen therapy for hepatic artery thrombosis following liver transplantation: current concepts

This article presents the case of an infant who underwent an orthotopic liver transplant and then developed hepatic artery thrombosis that was detected on routine post-operative right upper quadrant ultrasound. Alteplase (TPA) failed to open the artery, so the child received systemic heparin and hyperbaric oxygen (HBO) therapy. After six HBO treatments, the hepatic artery had recanalized and his liver function tests had returned to normal or near normal. There were no complications to the HBO therapy, and 1 yr after the transplant, the child's liver is functioning well. The present study discusses the beneficial effects of HBO therapy and the proposed mechanisms for its favorable results. In our patient, systemic heparin and HBO therapy prevented liver failure and need for retransplantation.

Popliteal artery injury: Royal Perth experience and literature review

BACKGROUND

Popliteal artery injury is uncommon but poses a significant challenge in Australian trauma care. Blunt trauma and knee dislocations appear to be associated with higher amputation rates. The aim of the present study was to review the authors' experience with this condition and discuss the best approach to investigation and management.

METHODS

The medical records of all patients with popliteal artery injury (n = 19) who were entered prospectively onto the Royal Perth Hospital Trauma Registry from 1995 to 2003 were reviewed. Their demographic data, investigations, primary operative procedures, fasciotomy, primary and secondary amputation rates and mortality were determined.

RESULTS

There were 17 male and two female patients with a median age of 34 years (range 17-62 years). Most patients (84%) were under 40 years in age. Blunt trauma was the commonest cause of popliteal artery injury (68.4%), and 84.6% of the patients had associated skeletal injury. The amputation rate in the present study was 26.3% (5/19). There were no intraoperative or in-hospital deaths. Three of 13 patients (23%) with blunt trauma underwent amputation, compared to two of six (33.3%) with penetrating injury. Two of three amputee patients in the blunt trauma group had dislocated knees.

CONCLUSION

Despite technical improvements in management of popliteal artery injury, a high amputation rate is still seen, especially in patients with one or more of the following factors: extensive soft-issue injury, associated skeletal trauma, knee dislocation, and prolonged ischaemia time. Measures to reduce the amputation rate, ranging from more prompt diagnosis to modified surgical treatment techniques, are discussed.

[Pain management in non-juvenile, aseptic osteonecrosis]

BACKGROUND

Adult aseptic osteonecrosis (ON) represents a clinical picture with unexplained etiology. Since curative treatment of this disease often succeeds only in the early stage, pain therapy plays an important role in the treatment process.

METHOD

We compared established and novel treatment options for ON as well as our own results after i.v. administration of the prostacyclin analogue iloprost with corresponding studies in the literature.

RESULTS

In addition to treatment with nonsteroidal antirheumatic agents and opioids, surgical "core decompression," vasoactive medications, and hyperbaric oxygenation are effective. Treatment with iloprost for 5 days resulted in highly significant pain reduction.

CONCLUSION

Symptomatic treatment is indicated in all stages of ON and curative treatment in stage I and early stage II. In cases of disease progression in the large joints, early endoprosthetic replacement is indicated to avoid secondary damage. In addition to employing vasoactive substances, a further curative treatment approach could be the use of mesenchymal stem cells.

Effect of hyperbaric oxygen on the ligament healing process in rats

Animal experiments were done to investigate whether administration of hyperbaric oxygen promotes scar tissue formation, increases expression of the Type I procollagen gene, and improves the tensile properties of healing ligament. In 76 Sprague-Dawley rats, a 2-mm segment of the medial collateral ligament was removed. Thirty-eight rats were exposed to hyperbaric oxygen at 2.5 atmospheres absolute for 2 hours 5 days per week (Group H), whereas the remaining rats were exposed to room air (Group C). The animals were sacrificed at 3, 7, 14, and 28 days postoperatively. In situ hybridization histochemistry was done to examine the Type I procollagen gene expression in healing ligaments in 40 rats, whereas a tensile failure test was done in the remaining rats. The amount of scar tissue was greater in Group H than in Group C. Type I procollagen gene expression at 7 or 14 days was significantly greater in Group H than in Group C. The ultimate load and stiffness in Group H were significantly greater than in Group C at 14 days. Administration of hyperbaric oxygen promotes scar tissue formation and increases Type I procollagen gene expression in healing ligaments. These effects are associated with the improvement of their tensile properties.

Effect of allopurinol, superoxide-dismutase, and hyperbaric oxygen on flap survival

The effect of allopurinol, superoxide-dismutase, and hyperbaric oxygen was compared on axial pattern skin flap survival. An abdominal flap based on the inferior epigastric pedicle was raised in rats for this purpose. Three experimental groups were studied. In the first group, adult male Wistar rats received 50 mg/kg I.P. of allopurinol. The second received 20,000 I.U./kg of superoxide-dismutase. The third group was submitted to hyperbaric oxygen therapy. The flaps were exposed to 8-h warm ischemia. Flap survival was evaluated on postoperative day 7. All flaps survived, and the mean survival areas were 63.53%, 83.03%, and 55.98%, respectively, in the allopurinol, superoxide-dismutase, and hyperbaric groups. The percentage of flap necrosis was significantly smaller in all experimental groups when compared to controls (P < 0.05). It was clear that the superoxide-dismutase group had better results on axial pattern ischemic skin flap survival, under the tested conditions. The tested methods improved flap survival to ischemic injury, and the flap designed is a reliable model for further investigations.

Acute compartment syndromes

BACKGROUND

Acute compartment syndrome is both a limb- and life-threatening emergency that requires prompt treatment. To avoid a delay in diagnosis requires vigilance and, if necessary, intracompartmental pressure measurement. This review encompasses both limb and abdominal compartment syndrome, including aetiology, diagnosis, treatment and outcome.

METHODS

A Pubmed and Cochrane database search was performed. Other articles were cross-referenced.

RESULTS AND CONCLUSION

Diagnosis of limb compartment syndrome is based on clinical vigilance and repeated examination. Many techniques exist for tissue pressure measurement but they are indicated only in doubtful cases, the unconscious or obtunded patient, and children. However, monitoring of pressure has no harmful effect and may allow early fasciotomy, although the intracompartmental pressure threshold for such an undertaking is still unclear. Abdominal compartment syndrome requires measurement of intra-abdominal pressure because clinical diagnosis is difficult. Treatment is by abdominal decompression and secondary closure. Both types of compartment syndrome require prompt treatment to avoid significant sequelae.

Hyperbaric oxygen

This cutting edge article discusses the most frequent uses of hyperbaric oxygen for the orthopedic surgeon. Hyperbaric oxygen therapy is an adjunct to orthopedic interventions when healing problems are anticipated due to wound hypoxia or uncontrolled infection.

Effects of different exposures of hyperbaric oxygen on ligament healing in rats

Hyperbaric oxygen (HBO) is a method of augmenting, intermittently, oxygen availability to tissues. We examined the effect of three different HBO exposures on the healing of experimentally induced ligament lacerations in the right hind limb of 44 male Wistar rats. Animals were divided into four groups after ligament injury: (a) control group, animals breathed room air at 1 ATA (atmosphere absolute) in a hyperbaric chamber for 60 min; (b) HBO treatment at 1.5 ATA for 30 min once a day, (c) HBO treatment at 2 ATA for 30 min once a day, (d) 2 ATA for 60 min once a day. At 14 days post-ligament injury, we compared the ligaments of the four treatment groups for gross appearance, histology and expression of pro-alpha(I) mRNA by northern hybridization. Our results indicate that HBO was effective in promoting ligament healing compared to control (p < 0.01). Of these three exposures, HBO at 2 ATA for 60 min was the most effective, resulting in enhanced extra-cellular matrix deposition as measured by collagen synthesis.

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

The basic mechanisms behind the pharmacologic effects of hyperbaric oxygen therapy are not clear. Reactive oxygen metabolites are generally associated with the adverse reactions to hyperbaric oxygen exposure but they are also believed to be involved in the antibacterial effects of this therapy. The possibility that reactive oxygen metabolites are responsible for some of the other reported beneficial effects of hyperbaric oxygen therapy has not been investigated. This hypothesis paper briefly reviews the literature suggesting that the pharmacologic actions underlying some of the beneficial effects of hyperbaric oxygen therapy may be caused by superoxide and/or hydrogen peroxide. Elucidation of the pharmacologic mechanisms is fundamental in order to fully exploit the therapeutic potential of hyperbaric oxygen and we incite experimental research to be done within this area.

Applications of hyperbaric oxygen in otolaryngology head and neck surgery: facial cutaneous flaps

Hyperbaric oxygen therapy is of significant benefit in the setting of an ischemic flap of the head and neck. Mechanistically, hyperbaric oxygen decreases local tissue edema and improves oxygen delivery to compromised tissues. Both capillary and fibroblast in-growth occur at a greater rate with hyperbaric oxygen therapy, and there is an increase in the tensile strength of the wound. Additional indications in the head and neck include traumatic composite amputations, necrotizing soft-tissue infections, and osteoradionecrosis of the facial skeleton.

Hyperbaric medicine in soft tissue trauma

Severe crush injuries of the soft tissues can result in tears of the large vessels and destruction of the microcirculation. This produces ischaemia and tissue necrosis and contributes to the development of oedema and compartment syndromes. All these factors compromise tissue survival. Immediately following a crush injury some areas of tissue are obviously irreversibly damaged, and others undamaged. It is common to have a ‘grey area’ between these, where there is uncertainty as to what will survive. Management of crush injury must involve surgical repair of vessels and soft tissues, debridement of obviously dead tissue, and bone stabilization. At the same time tissue perfusion must be maintained by manoeuvres such as fluid replacement and diminution of oedema, and when necessary fasciotomy. It has been proposed that hyperbaric oxygen therapy has a role, as an adjunct, in the maintenance of tissue oxygenation under these conditions, and will improve survival of tissues in the grey area, and thus minimize tissue loss. Hyperbaric oxygen therapy involves breathing 100% oxygen at pressures greater than one atmosphere. Presently, the pressures most often used are in the range 2-3 atmospheres absolute.

Effect of hyperbaric oxygen exposure on oxygen tension within the medullary canal in the rabbit tibial osteomyelitis model

The effect on intramedullary oxygen tension of 100% oxygen exposure at 1, 2, 2.4, and 3 atm pressure was studied in 12 New Zealand white rabbits with chronic right tibial osteomyelitis. The model, modified from that described by others, incorporates a multipuncture silastic closure plug placed transcortically in the proximal tibial metaphysis through which platinum needle, polarographic electrode oxygen tension determinations can be made without repeat surgical exposure. In 40% of the control, left, noninfected tibial metaphyses the baseline oxygen tension with the animals breathing room air at sea level was suboptimal for leukocyte bacterial killing. This oxygen tension was depressed further in the infected right tibia. Medullary canal oxygen tension increased in response to hyperbaric oxygen exposure in both the infected and noninfected tibiae. Whereas the amount of the oxygen tension increase varied with the presence of infection and depth of dive, neither the time for oxygen tension to plateau nor the time required for return to baseline tension after completion of hyperbaric oxygen exposure varied with the presence of infection or depth of dive. After completion of hyperbaric oxygen exposure, the oxygen tension within the medullary canal returned to baseline within 15 min.

Effects of hyperbaric oxygen treatment on axonal outgrowth in sciatic nerve grafts in rats

We studied the effect of hyperbaric oxygen treatment on axonal outgrowth in grafts of sciatic nerves in 40 rats. The sciatic nerve was transsected and a 10 mm long segment from the opposite side was immediately sutured in as a nerve graft. Postoperatively 17 animals were treated with 100% oxygen at 3.2 atmospheres absolute pressure for 45 minutes and the treatment was repeated at four and eight hours postoperatively and then every eight hours until evaluation. At seven days the axonal outgrowth was evaluated by immunohistochemical staining of neurofilaments in the nerve grafts. The axonal outgrowth was significantly longer in animals treated with hyperbaric oxygen. We conclude that hyperbaric oxygen can improve nerve regeneration in sciatic nerve grafts in rats.

Timing of microcirculatory injury from ischemia reperfusion

The low flow state that results from ischemia and reperfusion injury is a potentially reversible process that is important in numerous clinical situations. However, the point in time during the course of reperfusion where tissue injury becomes irreversible is unknown. This experiment evaluated the continuum of tissue damage in skeletal muscle after ischemic insult by quantifying the number of flowing capillaries and percentage muscle necrosis in a male Wistar rat skeletal muscle model. A gracilis muscle flap was raised on the vascular pedicle of 39 male Wistar rats and examined at 832x using intravital videomicroscopy. The numbers of flowing capillaries in five consecutive high-power fields were counted for baseline values. The flap was then subjected to 4 hours of global ischemia (except in sham animals, n = 7) by placing a microvascular clamp on the pedicle artery and vein. Upon reperfusion, flowing capillaries were counted in the same five high-power fields at intervals of 5, 15, 30, and 60 minutes, then at 2 to 8 (1-hour intervals), 24, and 48 hours. The gracilis muscle was then harvested at these intervals during reperfusion and assessed for viability. Compared with baseline, flowing capillaries from the ischemia and reperfusion group (mean +/- SEM) decreased significantly in the first 8 hours of reperfusion (7.7 +/- 0.2 to 3.2 +/- 0.3, p < 0.001) with minimal change noted from 8 to 48 hours. Percentage muscle necrosis increased progressively in ischemia and reperfusion preparations from 1 to 7 hours of reperfusion (16.5 +/- 2.6 percent to 38.9 +/- 1.2 percent, p < 0.001). No significant change in muscle necrosis in the ischemia and reperfusion group was noted between 7 and 48 hours. Sham preparations showed no change in the number of flowing capillaries through 3 hours of reperfusion, with a slight decrease at 24 hours. This rat gracilis microcirculation skeletal muscle model demonstrates a heterogeneous reperfusion injury. The decrease in flowing capillaries correlated with the increase in percentage necrosis and appeared to stabilize at the 7- to 8-hour interval. This finding may have important implications for the timing of interventions aimed at minimizing tissue damage from ischemia-reperfusion.

Hyperbaric oxygen improves contractile function of regenerating rat skeletal muscle after myotoxic injury

There is growing interest in hyperbaric oxygen (HBO) as an adjunctive treatment for muscle injuries. This experiment tested the hypothesis that periodic inhalation of HBO hastens the functional recovery and myofiber regeneration of skeletal muscle after myotoxic injury. Injection of the rat extensor digitorum longus (EDL) muscle with bupivacaine hydrochloride causes muscle degeneration. After injection, rats breathed air with or without periodic HBO [100% O(2) at either 2 or 3 atmospheres absolute (ATA)]. In vitro maximum isometric tetanic force of injured EDL muscles and regenerating myofiber size were unchanged between 2 ATA HBO-treated and untreated rats at 14 days postinjury but were approximately 11 and approximately 19% greater, respectively, in HBO-treated rats at 25 days postinjury. Maximum isometric tetanic force of injured muscles was approximately 27% greater, and regenerating myofibers were approximately 41% larger, in 3 ATA HBO-treated rats compared with untreated rats at 14 days postinjury. These findings demonstrate that periodic HBO inhalation increases maximum force-producing capacity and enhances myofiber growth in regenerating skeletal muscle after myotoxic injury with greater effect at 3 than at 2 ATA.

Hyperbaric oxygen downregulates ICAM-1 expression induced by hypoxia and hypoglycemia: the role of NOS

Hyperbaric oxygen (HBO) is being studied as a therapeutic intervention for ischemia/reperfusion (I/R) injury. We have developed an in vitro endothelial cell model of I/R injury to study the impact of HBO on the expression of intercellular adhesion molecule-1 (ICAM-1) and polymorphonuclear leukocyte (PMN) adhesion. Human umbilical vein endothelial cell (HUVEC) and bovine aortic endothelial cell (BAEC) induction of ICAM-1 required simultaneous exposure to both hypoxia and hypoglycemia as determined by confocal laser scanning microscopy, ELISA, and Western blot. HBO treatment reduced the expression of ICAM-1 to control levels. Adhesion of PMNs to BAECs was increased following hypoxia/hypoglycemia exposure (3. 4-fold, P < 0.01) and was reduced to control levels with exposure to HBO (P = 0.67). Exposure of HUVECs and BAECs to HBO induced the synthesis of endothelial cell nitric oxide synthase (eNOS). The NOS inhibitor nitro-L-arginine methyl ester attenuated HBO-mediated inhibition of ICAM-1 expression. Our findings suggest that the beneficial effects of HBO in treating I/R injury may be mediated in part by inhibition of ICAM-1 expression through the induction of eNOS.

Hyperbaric oxygen: a means of decreasing ischemic epiphyseal damage in a pediatric rabbit model

The effect of hyperbaric oxygen on epiphyseal ischemia was evaluated using a pediatric rabbit model. Forty-five animals were compared in this study: 23 from a control pilot study and 22 hyperbaric exposed animals. In each animal the right distal femoral and proximal tibial epiphyses were isolated on a popliteal vascular pedicle. The left leg acted as the control. The growth difference between the rabbit's hindlimbs was the means of comparison throughout the groups established. Warm ischemia was induced by applying a vascular clamp to the right popliteal artery for 12 hours (20 animals) and 7 hours (17 animals). The remaining 8 animals underwent a sham operation without interruption of epiphyseal perfusion. On completion of the ischemic period hyperbaric oxygen therapy (HBOT) was performed on 12 12-hour (12h-HBOT) and 10 7-hour (7h-HBOT) animals at 2 atmospheres for 90 minutes twice per day for 4 postoperative days. The animals were killed on either postoperative day 14 or 90. Measurement of longitudinal bone growth was performed on the 90-day animals from serial radiographs at the time of surgery and then at 1 month, 2 months, and 3 months after surgery. There was no significant difference in longitudinal bone growth between the sham-operated and the 7h-HBOT animals at 1, 2, and 3 months. There was a statistically significant difference, however, between the normal growth of the 7h-HBOT group compared with the abnormal growth of the 7-hour, 12-hour, and 12h-HBOT animals. Histology was consistent, with the bone growth data demonstrating relative normalcy of the 7h-HBOT group epiphyseal plates versus severe architectural aberrance and necrosis of the 12h-HBOT group epiphyses. Our experimental data indicate that a clinical trial should be instituted using HBO for pediatric replantation patients when warm ischemia exceeds 7 hours. (J Hand Surg 2000; 25A:159-165.

Raised intracompartmental pressure and compartment syndromes

Raised intracompartmental pressure (ICP) has become recognized as the final common pathway of a variety of pathologies which lead to failure of the microcirculation with resultant tissue hypoxia and cell death. While commonly seen after trauma, either accidental or operative, raised ICP may result from either an increase in the volume of tissue within a closed osseo-fascial or fascial compartment or by the application of an external force compressing a compartment, and it is associated with a wide variety of insults. The advent of reproducible techniques of measuring ICP has added science to a well-recognized clinical picture and allowed a rational approach to management. Controversies still remain, particularly in regard to the level of pressure at which intervention becomes mandatory, and the role of prophylactic interventions. This review attempts to present current thinking on the pathophysiology of the microcirculation and the background to these controversies.

Hyperbaric oxygen and thrombolysis in myocardial infarction: the "HOT MI" pilot study

Hyperbaric oxygen treatment (HBO) in combination with thrombolysis has been demonstrated to salvage myocardium in acute myocardial infarction in the animal model. Therefore a randomized pilot trial was undertaken to assess the safety and feasibility of this treatment in human beings. Patients with an acute myocardial infarction (AMI) who received recombinant tissue plasminogen activator (rTPA) were randomized to treatment with HBO combined with rTPA or rTPA alone. Sixty-six patients were included for analysis. Forty-three patients had inferior AMIs (difference not significant) and the remainder had anterior AMIs. The mean creatine phosphokinase level at 12 and 24 hours was reduced in the patients given HBO by approximately 35% (p = 0.03). Time to pain relief and ST segment resolution was shorter in the group given HBO. There were two deaths in the control group and none in those treated with HBO. The ejection fraction on discharge was 52.4% in the group given HBO compared with 47.3% in the control group (difference not significant). Adjunctive treatment with HBO appears to be a feasible and safe treatment for AMI and may result in an attenuated rise in creatine phosphokinase levels and more rapid resolution of pain and ST segment changes.

Hyperbaric oxygen therapy in the management of crush injuries: a randomized double-blind placebo-controlled clinical trial

Hyperbaric Oxygen (HBO) therapy is advocated for the treatment of severe trauma of the limbs in association with surgery because of its effects on peripheral oxygen transport, muscular ischemic necrosis, compartment syndrome, and infection prevention. However, no controlled human trial had been performed until now to specify the role of HBO in the management of crush injuries. Thirty-six patients with crush injuries were assigned in a blinded randomized fashion, within 24 hours after surgery, to treatment with HBO (session of 100% O2 at 2.5 atmosphere absolute (ata) for 90 minutes, twice daily, over 6 days) or placebo (session of 21% O2 at 1.1 ata for 90 minutes, twice daily, over 6 days). All the patients received the same standard therapies (anticoagulant, antibiotics, wound dressings). Transcutaneous oxygen pressure (PtCO2) measurements were done before (patient breathing normal air) and during treatment (HBO or placebo) at the first, fourth, eighth, and twelfth sessions. The two groups (HBO group, n = 18; placebo group, n = 18) were similar in terms of age; risk factors; number, type or location of vascular injuries, neurologic injuries, or fractures; and type, location, or timing of surgical procedures. Complete healing was obtained for 17 patients in the HBO group vs. 10 patients in the placebo group (p < 0.01). New surgical procedures (such as skin flaps and grafts, vascular surgery, or even amputation) were performed on one patient in the HBO group vs. six patients in the placebo group (p < 0.05). Analysis of groups of patients matched for age and severity of injury showed that in the subgroup of patients older than 40 with grade III soft-tissue injury, wound healing was obtained for seven patients (87.5%) in the HBO group vs. three patients (30%) in the placebo group (p < 0.05). No significant differences were found in the length of hospital stay and number of wound dressings between groups. For the patients with complete healing, the PtCO2 values of the traumatized limb, measured in normal air, rose significantly between the first and the twelfth sessions (p < 0.001). No significant change in PtCO2 value was found for the patients whose healing failed. The Bilateral Perfusion Index (BPI = PtCO2 of the injured limb/PtCO2 of the uninjured limb) at the first session increased significantly from 1 ata air to 2.5 ata O2 (p < 0.05). In patients with complete healing, the BPI was constantly greater than 0.9 to 2.5 ata O2 during the following sessions, whereas the BPI in air progressively rose between the first and the twelfth sessions (p < 0.05), reaching normal values at the end of the treatment. In conclusion, this study shows the effectiveness of HBO in improving wound healing and reducing repetitive surgery. We believe that HBO is a useful adjunct in the management of severe (grade III) crush injuries of the limbs in patients more than 40 years old.