Medical and surgical management of pneumothorax in diving and hyperbaric chambers.

The presence of a pneumothorax within a pressurized chamber represents unique diagnostic and management challenges. This is particularly the case in the medical and geographic remoteness of many chamber locations. Upon commencing chamber decompression, unvented intrapleural air expands. If its initial volume and/or degree of chamber pressure reduction is significant enough, a tension pneumothorax will result. Numerous reports chronicle failure to diagnose and manage in-chamber pneumothorax with resultant morbidity and one fatal outcome. Such cases have occurred in both medically remote and clinically based settings. This paper reviews pneumothorax and tension pneumothorax risk factors and clinical characteristics. It suggests primary medical management using the principle of oxygen-induced inherent unsaturation in concert with titrated chamber decompression designed to prevent intrapleural air expanding faster than it contracts. Should this conservative approach prove unsuccessful, and surgical venting becomes necessary or otherwise immediately indicated, interventional options are reviewed.

Pneumothorax during manned chamber operations: A summary of reported cases.

In-chamber pneumothorax has complicated medically remote professional diving operations, submarine escape training, management of decompression illness, and hospital-based provision of hyperbaric oxygen therapy. Attempts to avoid thoracotomy by combination of high oxygen partial pressure breathing (the concept of inherent unsaturation) and greatly slowed rates of chamber decompression proved successful on several occasions. When this delicate balance designed to prevent the intrapleural gas volume from expanding faster than it contracts proved futile, chest drains were inserted. The presence of pneumothorax was misdiagnosed or missed altogether with disturbing frequency, resulting in wide-ranging clinical consequences. One patient succumbed before the chamber had been fully decompressed. Another was able to ambulate unaided from the chamber before being diagnosed and managed conventionally. In between these two extremes, patients experienced varying degrees of clinical compromise, from respiratory distress to cardiopulmonary arrest, with successful resuscitation. Pneumothorax associated with manned chamber operations is commonly considered to develop while the patient is under pressure and manifests during ascent. However, published reports suggest that many were pre-existing prior to chamber entry. Risk factors included pulmonary barotrauma-induced cerebral arterial gas embolism, cardiopulmonary resuscitation, and medical or surgical procedures usually involving the lung. This latter category is of heightened importance to hyperbaric operations as an iatrogenically induced pneumothorax may take as long as 24 hours to be detected, perhaps long after a patient has been cleared for chamber exposure.

The utility of hyperbaric oxygen therapy in post-transplant cyclophosphamide-induced hemorrhagic cystitis: a case report and review of the literature.

BACKGROUND: To date, there are only a few case reports of cyclophosphamide (Cy)-induced hemorrhagic cystitis (HC) in adult or pediatric allogeneic stem cell transplant (SCT) patients treated successfully with hyperbaric oxygen (HBO). In all the reported cases, Cy was used as a part of the conditioning regimen, rather than post-transplant for graft-versus-host-disease (GVHD) prophylaxis. More recently, the risk of HC in allogeneic SCT is further increased by the widespread use of post-transplantation cyclophosphamide (PTCy) as a highly effective strategy for GVHD prophylaxis. This is the first case reported of PTCy-induced HC successfully treated with HBO to the best of our knowledge. CASE PRESENTATION: In this article, we present a 58-year-old Caucasian male case of allogeneic SCT complicated by severe HC following PTCy, which was successfully treated with HBO, eliminating the need for cystectomy. CONCLUSION: HBO can be a safe, noninvasive, alternative treatment modality for PTCy-induced HC developing in allogeneic SCT patients.

Plasma flow distal to tourniquet placement provides a physiological mechanism for tissue salvage.

Military literature has demonstrated the utility and safety of tourniquets in preventing mortality for some time, paving the way for increased use of tourniquets in civilian settings, including perioperatively to provide a bloodless surgical field. However, tourniquet use is not without risk and the subsequent effects of tissue ischemia can impede downstream rehabilitative efforts to regenerate and salvage nerve, muscle, tissue and bone in the limb. Limb ischemia studies in both the mouse and pig models have indicated not only that there is residual flow past the tourniquet by means of microcirculation, but also that recovery from tissue ischemia is dependent upon this microcirculation. Here we expand upon these previous studies using portable Near-Infrared Imaging to quantify residual plasma flow distal to the tourniquet in mice, pigs, and humans and leverage this flow to show that plasma can be supersaturated with oxygen to reduce intracellular hypoxia and promote tissue salvage following tourniquet placement. Our findings provide a mechanism of delivery for the application of oxygen, tissue preservation solutions, and anti-microbial agents prior to tourniquet release to improve postoperative recovery. In the current environment of increased tourniquet use, techniques which promote distal tissue preservation and limb salvage rates are crucial.

Case control study: hyperbaric oxygen treatment of mild traumatic brain injury persistent post-concussion syndrome and post-traumatic stress disorder.

Mild traumatic brain injury (TBI) persistent post-concussion syndrome (PPCS) and post-traumatic stress disorder (PTSD) are epidemic in United States Iraq and Afghanistan War veterans. Treatment of the combined diagnoses is limited. The aim of this study is to assess safety, feasibility, and effectiveness of hyperbaric oxygen treatments (HBOT) for mild TBI PPCS and PTSD. Thirty military subjects aged 18-65 with PPCS with or without PTSD and from one or more blast-induced mild-moderate traumatic brain injuries that were a minimum of 1 year old and occurred after 9/11/2001 were studied. The measures included symptom lists, physical exam, neuropsychological and psychological testing on 29 subjects (1 dropout) and SPECT brain imaging pre and post HBOT. Comparison was made using SPECT imaging on 29 matched Controls. Side effects (30 subjects) experienced due to the HBOT: reversible middle ear barotrauma (n = 6), transient deterioration in symptoms (n = 7), reversible bronchospasm (n = 1), and increased anxiety (n = 2; not related to confinement); unrelated to HBOT: ureterolithiasis (n = 1), chest pain (n = 2). Significant improvement (29 subjects) was seen in neurological exam, symptoms, intelligence quotient, memory, measures of attention, dominant hand motor speed and dexterity, quality of life, general anxiety, PTSD, depression (including reduction in suicidal ideation), and reduced psychoactive medication usage. At 6-month follow-up subjects reported further symptomatic improvement. Compared to Controls the subjects' SPECT was significantly abnormal, significantly improved after 1 and 40 treatments, and became statistically indistinguishable from Controls in 75% of abnormal areas. HBOT was found to be safe and significantly effective for veterans with mild to moderate TBI PPCS with PTSD in all four outcome domains: clinical medicine, neuropsychology, psychology, and SPECT imaging. Veterans also experienced a significant reduction in suicidal ideation and reduction in psychoactive medication use.

Hyperbaric Oxygen Promotes Proximal Bone Regeneration and Organized Collagen Composition during Digit Regeneration.

Oxygen is critical for optimal bone regeneration. While axolotls and salamanders have retained the ability to regenerate whole limbs, mammalian regeneration is restricted to the distal tip of the digit (P3) in mice, primates, and humans. Our previous study revealed the oxygen microenvironment during regeneration is dynamic and temporally influential in building and degrading bone. Given that regeneration is dependent on a dynamic and changing oxygen environment, a better understanding of the effects of oxygen during wounding, scarring, and regeneration, and better ways to artificially generate both hypoxic and oxygen replete microenvironments are essential to promote regeneration beyond wounding or scarring. To explore the influence of increased oxygen on digit regeneration in vivo daily treatments of hyperbaric oxygen were administered to mice during all phases of the entire regenerative process. Micro-Computed Tomography (µCT) and histological analysis showed that the daily application of hyperbaric oxygen elicited the same enhanced bone degradation response as two individual pulses of oxygen applied during the blastema phase. We expand past these findings to show histologically that the continuous application of hyperbaric oxygen during digit regeneration results in delayed blastema formation at a much more proximal location after amputation, and the deposition of better organized collagen fibers during bone formation. The application of sustained hyperbaric oxygen also delays wound closure and enhances bone degradation after digit amputation. Thus, hyperbaric oxygen shows the potential for positive influential control on the various phases of an epimorphic regenerative response.

Epidermal closure regulates histolysis during mammalian (Mus) digit regeneration.

Mammalian digit regeneration progresses through consistent stages: histolysis, inflammation, epidermal closure, blastema formation, and finally redifferentiation. What we do not yet know is how each stage can affect others. Questions of stage timing, tissue interactions, and microenvironmental states are becoming increasingly important as we look toward solutions for whole limb regeneration. This study focuses on the timing of epidermal closure which, in mammals, is delayed compared to more regenerative animals like the axolotl. We use a standard wound closure device, Dermabond (2-octyl cyanoacrylate), to induce earlier epidermal closure, and we evaluate the effect of fast epidermal closure on histolysis, blastema formation, and redifferentiation. We find that fast epidermal closure is reliant upon a hypoxic microenvironment. Additionally, early epidermal closure eliminates the histolysis stage and results in a regenerate that more closely replicates the amputated structure. We show that tools like Dermabond and oxygen are able to independently influence the various stages of regeneration enabling us to uncouple histolysis, wound closure, and other regenerative events. With this study, we start to understand how each stage of mammalian digit regeneration is controlled.

Endogenous bone regeneration is dependent upon a dynamic oxygen event.

Amputation of the digit tip within the terminal phalangeal bone of rodents, monkeys, and humans results in near-perfect regeneration of bone and surrounding tissues; however, amputations at a more proximal level fail to produce the same regenerative result. Digit regeneration is a coordinated, multifaceted process that incorporates signaling from bioactive growth factors both in the tissue matrix and from several different cell populations. To elucidate the mechanisms involved in bone regeneration we developed a novel multi-tissue slice-culture model that regenerates bone ex vivo via direct ossification. Our study provides an integrated multi-tissue system for bone and digit regeneration and allows us to circumvent experimental limitations that exist in vivo. We used this slice-culture model to evaluate the influence of oxygen on regenerating bone. Micro-computed tomography (µCT) and histological analysis revealed that the regenerative response of the digit is facilitated in part by a dynamic oxygen event, in which mutually exclusive high and low oxygen microenvironments exist and vacillate in a coordinated fashion during regeneration. Areas of increased oxygen are initially seen in the marrow and then surrounding areas of vasculature in the regenerating digit. Major hypoxic events are seen at 7 days postamputation (DPA 7) in the marrow and again at DPA 12 in the blastema, and manipulation of oxygen tensions during these hypoxic phases can shift the dynamics of digit regeneration. Oxygen increased to 21% oxygen tension can either accelerate or attenuate bone mineralization in a stage-specific manner in the regenerative timeline. These studies not only reveal a circumscribed frame of oxygen influence during bone regeneration, but also suggest that oxygen may be one of the primary signaling influences during regeneration.

The effect of hyperbaric oxygen on severe anemia.

As a respiratory pigment, hemoglobin allows blood to carry unnaturally high levels of nascent, molecular oxygen at one atmosphere of pressure in chemical solution to capillary beds and post-capillary venules supplying parenchymal cells of all organ systems in the body. When hemoglobin drops to critical levels to disallow proper oxygen delivery, hyperbaric oxygen therapy may be used as bridge therapy to emergently supply oxygen. Hyperbaric-administered oxygen allows oxygen to be dissolved in increased concentration in red blood cell-poor plasma or crystalloid/ colloid-diluted intravascular fluids in a volume-resuscitated patient. Additionally in both subacutely and chronically anemic patients, pulsed, intermittently provided normobaric or hyperbaric oxygen induces an increase in red blood cell/hemoglobic mass. Transfusions of separate donor red blood cells are transplantations of tissue not uncomplicated by immunomodulatory reactions. In the long term, autologous blood products may be less problematic than transfused, homologous packed red blood cells to reduce patient oxygen debt in illness or injury. Hyperbaric oxygen can reduce oxygen debt decisively in the polar clinical extremes of exsanguination with cardiopulmonary arrest all the way to resuscitation of the severely anemic patient who cannot be transfused with red blood cells for religious reasons, immunologic reasons, or blood availability problems. A hyperbaric oxygen treatment is equivalent in wholesale cost to a unit of packed red blood cells in the western world. By controversy, but true, hyperbaric oxygen provides a low-technology, cost-competitive means of pharmacologically reducing accumulated oxygen debt in the anemic, injured or critically ill patient with little side effect. To address severe anemia in trauma or illness, the future may well afford the use of hyperbaric oxygen therapy in the military far-forward, in pre-hospital EMS settings, in trauma center emergency departments, in operative and recovery units, and in intensive care units of hospitals.

A phase I study of low-pressure hyperbaric oxygen therapy for blast-induced post-concussion syndrome and post-traumatic stress disorder.

This is a preliminary report on the safety and efficacy of 1.5 ATA hyperbaric oxygen therapy (HBOT) in military subjects with chronic blast-induced mild to moderate traumatic brain injury (TBI)/post-concussion syndrome (PCS) and post-traumatic stress disorder (PTSD). Sixteen military subjects received 40 1.5 ATA/60 min HBOT sessions in 30 days. Symptoms, physical and neurological exams, SPECT brain imaging, and neuropsychological and psychological testing were completed before and within 1 week after treatment. Subjects experienced reversible middle ear barotrauma (5), transient deterioration in symptoms (4), and reversible bronchospasm (1); one subject withdrew. Post-treatment testing demonstrated significant improvement in: symptoms, neurological exam, full-scale IQ (+14.8 points; p<0.001), WMS IV Delayed Memory (p=0.026), WMS-IV Working Memory (p=0.003), Stroop Test (p<0.001), TOVA Impulsivity (p=0.041), TOVA Variability (p=0.045), Grooved Pegboard (p=0.028), PCS symptoms (Rivermead PCSQ: p=0.0002), PTSD symptoms (PCL-M: p<0.001), depression (PHQ-9: p<0.001), anxiety (GAD-7: p=0.007), quality of life (MPQoL: p=0.003), and self-report of percent of normal (p<0.001), SPECT coefficient of variation in all white matter and some gray matter ROIs after the first HBOT, and in half of white matter ROIs after 40 HBOT sessions, and SPECT statistical parametric mapping analysis (diffuse improvements in regional cerebral blood flow after 1 and 40 HBOT sessions). Forty 1.5 ATA HBOT sessions in 1 month was safe in a military cohort with chronic blast-induced PCS and PTSD. Significant improvements occurred in symptoms, abnormal physical exam findings, cognitive testing, and quality-of-life measurements, with concomitant significant improvements in SPECT.

Hyperbaric Oxygen Therapy as an Adjunct to Pre-hospital Advanced Trauma Life Support.

Most commercial diving operations and naval operations have 24/7, on-site availability of hyperbaric oxygen therapy to perform routine surface decompression or immediate treatment of arterial gas embolism or decompression sickness. Availability and prompt use of hyperbaric oxygen therapy in the field for treatment of divers with dysbaric conditions has demonstrated its efficacy in acute, co-morbid conditions such as acute exsanguination, blast injury, crush injury, and cardiopulmonary arrest affecting those same divers. Hyperbaric oxygen therapy applied in these cases has demonstrated its utility to augment the efficacy of conventional, pre-hospital advanced cardiac life support and advanced trauma life support. Case studies gleaned from actual experience with the diving industry illustrate the use of hyperbaric oxygen therapy in these conditions. The unexpectedly favorable results have been replicated by controlled laboratory animal studies. The deck decompression or saturation multiplace chambers used by offshore diving operations can easily and quickly be converted for use as medical field resuscitative units. Lightweight and mobile hyperbaric chambers can be outfitted for use in ambulances or helicopters to address civilian street injury or military "far-forward" injury. These transport chambers are compact in design to be efficient transport stretchers designed to hold both the patient and the medical support clinician. It is hoped that hyperbaric oxygen therapy will gain an increasing role as an adjunct to pre-hospital advanced cardiac life support and advanced trauma life support resuscitative efforts as a low-cost, high-yield intervention. In this regard HBO as applied to ATLS/ACLS in civilian and military medical systems may be a productive, disruptive new application of technology.

Determination of oxygen dosage effects on cytochrome oxidase after anoxia in brain.

Recent evidence reports that high doses of O(2) administered via hyperbaric oxygen therapy (HBOT) improve the return of spontaneous circulation (ROSC), and the outcome of damage to the heart following a 25 min normothermic cardiac arrest. However, excessive O(2) during HBOT can be toxic. Near infrared absorbance spectroscopy (NIRS) measures and determines when cytochrome oxidase (aa(3)), the O(2) end user, changes from reduced to oxidized, signifying adequate dosage. Present NIRS monitoring methods do not account for change in scattering expected in severe anoxia. Given this limitation, we simultaneously measured changes in intensity and scattering that occurred over time after 830 nm light traveled 4.25 cm through brain tissue during both normoxia and anoxia. Results indicated increased intensity and scattering during anoxia with correlation between the two, demonstrating that scattering does not remain constant and is associated with intensity. With this additional insight in concurrent scattering and intensity change during anoxia, we believe improvements can be made to our aa(3) measuring technique resulting in a method to ascertain adequate O(2) dosage during HBOT.

Low pressure hyperbaric oxygen therapy and SPECT brain imaging in the treatment of blast-induced chronic traumatic brain injury (post-concussion syndrome) and post traumatic stress disorder: a case report.

A 25-year-old male military veteran presented with diagnoses of post concussion syndrome and post traumatic stress disorder three years after loss of consciousness from an explosion in combat. The patient underwent single photon emission computed tomography brain blood flow imaging before and after a block of thirty-nine 1.5 atmospheres absolute hyperbaric oxygen treatments. The patient experienced a permanent marked improvement in his post-concussive symptoms, physical exam findings, and brain blood flow. In addition, he experienced a complete resolution of post-traumatic stress disorder symptoms. After treatment he became and has remained employed for eight consecutive months. This case suggests a novel treatment for the combined diagnoses of blast-induced post-concussion syndrome and post-traumatic stress disorder.

Hyperbaric oxygen improves rate of return of spontaneous circulation after prolonged normothermic porcine cardiopulmonary arrest.

AIM: This controlled, prospective, randomized porcine study tests the hypothesis that high-dose hyperbaric oxygen (HDHBO2) compared with normobaric oxygen (NBO2) or standard-dose hyperbaric oxygen (SDHBO2), improves return of sustained spontaneous circulation (ROSC) after a normothermic, normobaric, 25-min, non-intervened-upon cardiopulmonary arrest. The study incorporated a direct mechanical ventricular assist device (DMVAD) for open chest continuous cardiac compressions (OCCC) to assist advanced cardiac life support (ACLS). The experiment demonstrates a dose response to oxygen concentration in the breathing mix used in resuscitative ventilation. MATERIALS AND METHODS: Male pigs (average 30kg weight) underwent a 25-min, normothermic, non-intervened-upon cardiopulmonary arrest. Following arrest all animals were ventilated with 100% oxygen and were subjected to OCCC, incorporating DMVAD-aided ACLS. The animals so treated were randomized to be in one of three groups, with six animals in each group. The NBO2 group remained at 1.0 atmosphere absolute (ATA), while the SDHBO2 and HDHBO2 groups were initially placed at 1.9 and 4.0ATA, respectively. Uniform, but not American Heart Association (AHA) protocol, ACLS was maintained as needed over the ensuing 2h for all animals in all groups. At the end of 2h, the animals were euthanized. RESULTS: Continuously sustained ROSC (mean arterial pressure > or =50mmHg at all times), without the need of the pump assist over the 2-h resuscitation attempt that followed the 25-min arrest, occurred in four out of six animals in the HDHBO2 group, and in none of the animals in the NBO2 or SBHBO2 groups (p< or =0.001). CONCLUSIONS: Our results show significantly sustained ROSC using HDHBO2 to resuscitate swine after a 25-min, non-intervened-upon, normothermic cardiopulmonary arrest. These results could not be achieved using NBO2 or SDHBO2.

Hyperbaric oxygen therapy improves spatial learning and memory in a rat model of chronic traumatic brain injury.

In the present experiment we use a rat model of traumatic brain injury to evaluate the ability of low-pressure hyperbaric oxygen therapy (HBOT) to improve behavioral and neurobiological outcomes. The study employed an adaptation of the focal cortical contusion model. 64 Male Long-Evans rats received unilateral cortical contusion and were tested in the Morris Water Task (MWT) 31-33 days post injury. Rats were divided into three groups: an untreated control group (N=22), an HBOT treatment group (N=19) and a sham-treated normobaric air group (N=23). The HBOT group received 80 bid, 7 days/week 1.5 ATA/90-min HBOTs and the sham-treated normobaric air group the identical schedule of air treatments using a sham hyperbaric pressurization. All rats were subsequently retested in the MWT. After testing all rats were euthanized. Blood vessel density was measured bilaterally in hippocampus using a diaminobenzadine stain and was correlated with MWT performance. HBOT caused an increase in vascular density in the injured hippocampus (p<0.001) and an associated improvement in spatial learning (p<0.001) compared to the control groups. The increased vascular density and improved MWT in the HBOT group were highly correlated (p<0.001). In conclusion, a 40-day series of 80 low-pressure HBOTs caused an increase in contused hippocampus vascular density and an associated improvement in cognitive function. These findings reaffirm the clinical experience of HBOT-treated patients with chronic traumatic brain injury.

Adjuvant hyperbaric oxygen therapy in the management of crush injury and traumatic ischemia: an evidence-based approach.

Hyperbaric oxygen therapy (HBO) has been recommended as an adjunct treatment in acute traumatic ischemia and crush injury. Several animal models have shown better outcomes when HBO is used in crush injury and compartment syndrome. Animal and in vitro models have suggested that these beneficial effects may be mediated by attenuation of ischemia-reperfusion injury. We did a systematic review of the literature using the Eastern Association for the Surgery of Trauma (EAST) recommendations for evidence-based reviews. An electronic search using Medline, OVID technologies, and the Cochrane database was performed. Only clinical papers published between 1966 and December 2003 with at least five patients that included enough information to evaluate were selected. A group of trauma experts reviewed the selected articles and scored them applying the instrument developed by the EAST practice management guidelines committee. Nine documents fulfilled the inclusion criteria for a total of approximately 150 patients. Most documents were retrospective, uncontrolled, and case series lacking a standardized methodology (class III). There was one prospective controlled randomized trial with some limitations on its design. We determined that eight of nine studies showed a beneficial effect from HBO with only one major complication. We concluded that adjunctive HBO is not likely to be harmful and could be beneficial if administered early. Well designed clinical studies are warranted.

[Treatment of mucormycosis with adjunctive hyperbaric oxygen: five cases treated at the same institution and review of the literature]. / Tratamiento adjunto con oxigenación hiperbárica en mucormicosis. Presentación de cinco casos tratados en la misma institución y revisión de la literatura.

INTRODUCTION: Mucormycosis is an invasive fungal infection that affects decompensated diabetics, immunosupressed patients and occasionally healthy individuals. Despite advances in anti-fungal therapy and surgical techniques, the morbidity and mortality remain high. Adjuvant hyperbaric oxygen therapy (HBO) has been proposed based on pathophysiology and several favorable clinical reports. MATERIAL AND METHODS: A chart review of mucormycosis patients referred to the HBO service was performed. Also an electronic search in Medline of relevant literature was undertaken. RESULTS: Five mucormycosis patients referred for HBO had complete charts available. Four had craniofacial involvement and one had left upper extremity involvement. The predisposing diseases were leukemia (n = 3), diabetes mellitus plus sarcoidosis (n = 1), and trauma (n = 1). All patients were managed with amphotericin B, surgical debridement and HBO. Survival was 60% (3/5) three months after the diagnosis was established. The literature was scarce but favors HBO. CONCLUSION: Considering the pathophysiology of mucormycosis adjuvant HBO therapy seems reasonable. However, the clinical experience is still too limited to make HBO part of the standard of care. Prospective, randomized, controlled trials will help to define the role of HBO in this devastating infection.

Decompression sickness in Miskito Indian lobster divers: review of 229 cases.

BACKGROUND: The Miskito Indian lobster divers of Central America employ very provocative diving profiles and experience severe neurological decompression sickness (DCS) and/or arterial gas embolism (AGE). Scientific data are scarce regarding the clinical patterns of injury, response to treatment, and functional outcomes for such cases. METHODS: A retrospective review of 229 cases of DCS and/or AGE was conducted at 2 hyperbaric units in Central America. RESULTS: The following deficits were recorded on presentation: any neurological deficit: 94%; motor: 79%; sensory: 60%; urinary: 48%; reflex: 45%; and loss of consciousness: 20%. The patterns of weakness (n = 182) were as follows: paraparesis: 27%; paraplegia: 26%; lower extremity monoparesis: 14%; lower extremity monoplegia: 6%; quadriparesis: 4%; hemiparesis: 4%; hemiplegia: 3%; and quadriplegia: 2%. Treatment was delayed by a mean and median of 5 and 2 d, respectively. The majority received hyperbaric oxygen and systemic steroids. Motor function on discharge (n = 182) was as follows: normal: 30%; paraparesis: 15%; lower extremity monoparesis: 15%; paraplegia: 3%; quadriparesis: 2%; hemiparesis: 2%; and missing data/other: 33%. Gait on discharge (n = 182) was as follows: normal: 19%; abnormal: 19%; required one crutch: 10%; required two crutches: 16%; not ambulatory: 5%; and missing data: 31%. DISCUSSION: The majority of severe injuries could be localized to the thoracolumbar spinal cord. One-fifth had bilateral cerebral dysfunction manifested by loss of consciousness. Despite long delays to treatment, divers responded to hyperbaric oxygen. At the time of discharge, almost a third had complete recovery of strength and the majority were ambulatory.