[The Japanese Law Regulating Underwater and Caisson Work: Current Issues and Future Developments].

The Japan "Ordinance on Safety and Health of Work under High Pressure", which is the law regulating health conditions for workers under high pressure environments, was amended in 2014. The revised regulations have highlighted other difficulties and new problems, but they have not yet written an appropriate amendment based on the aspect of occupational and environmental health. Health management for occupational divers and caisson workers in accordance with the new regulations has not determined the best approach to reducing related disorders and will cause other legal problems. This paper presents some issues in the new regulations for hyperbaric workers, which directly or indirectly involve occupational health physicians. Health checkups and work limitations should be done in consideration of the occupational characteristics of the undersea and hyperbaric environment. Regular examinations using specific studies are useful to diagnose the early stages of chronic conditions for workers, and are also useful for determining the hiring suitability for hyperbaric workers. Work limitations should be decided by the conditions that induce serious accidents or disorders that result from exposure to hyperbaric environments, and depend on the obstacles for work due to sequelae of decompression sickness. The new regulations need to be properly revised, based on scientific evidence, to include health management for workers in undersea and hyperbaric environments.

Decompression Illness in Repetitive Breath-Hold Diving: Why Ischemic Lesions Involve the Brain?

Nitrogen (N2) accumulation in the blood and tissues can occur due to breath-hold (BH) diving. Post-dive venous gas emboli have been documented in commercial BH divers (Ama) after repetitive dives with short surface intervals. Hence, BH diving can theoretically cause decompression illness (DCI). "Taravana," the diving syndrome described in Polynesian pearl divers by Cross in the 1960s, is likely DCI. It manifests mainly with cerebral involvements, especially stroke-like brain attacks with the spinal cord spared. Neuroradiological studies on Ama divers showed symptomatic and asymptomatic ischemic lesions in the cerebral cortex, subcortex, basal ganglia, brainstem, and cerebellum. These lesions localized in the external watershed areas and deep perforating arteries are compatible with cerebral arterial gas embolism. The underlying mechanisms remain to be elucidated. We consider that the most plausible mechanisms are arterialized venous gas bubbles passing through the lungs, bubbles mixed with thrombi occlude cerebral arteries and then expand from N2 influx from the occluded arteries and the brain. The first aid normobaric oxygen appears beneficial. DCI prevention strategy includes avoiding long-lasting repetitive dives for more than several hours, prolonging the surface intervals. This article provides an overview of clinical manifestations of DCI following repetitive BH dives and discusses possible mechanisms based on clinical and neuroimaging studies.

Diving-related disorders in commercial breath-hold divers (Ama) of Japan.

Decompression illness (DCI) is well known in compressed-air diving but has been considered anecdotal in breath-hold divers. Nonetheless, reported cases and field studies of the Japanese Ama, commercial or professional breath-hold divers, support DCI as a clinical entity. Clinical characteristics of DCI in Ama divers mainly suggest neurological involvement, especially stroke-like cerebral events with sparing of the spinal cord. Female Ama divers achieving deep depths have rarely experienced a panic-like neurosis from anxiety disorders. Neuroradiological studies of Ama divers have shown symptomatic and/or asymptomatic ischaemic lesions situated in the basal ganglia, brainstem, and deep and superficial cerebral white matter, suggesting arterial insufficiency. The underlying mechanism(s) of brain damage in breath-hold diving remain to be elucidated; one of the plausible mechanisms is arterialization of venous nitrogen bubbles passing through right to left shunts in the heart or lungs. Although the treatment for DCI in Ama divers has not been specifically established, oxygen breathing should be given as soon as possible for injured divers. The strategy for prevention of diving-related disorders includes reducing extreme diving schedules, prolonging surface intervals and avoiding long periods of repetitive diving. This review discusses the clinical manifestations of diving-related disorders in Ama divers and the controversial mechanisms.

[What is the Best Therapeutic Strategy for Decompression Illness? First Aid Oxygen Inhalation and Hyperbaric Oxygen Therapy].

Decompression illness (DCI), a syndrome following inadequate reduction in environmental pressure, has two forms: decompression sickness and arterial gas embolism after pulmonary barotrauma. Recompression therapy using oxygen, a kind of hyperbaric oxygen therapy, has been considered the gold standard treatment for DCI, although there is no randomized controlled trial evidence for its use. We evaluated the effectiveness of recompression therapy in treating DCI by reviewing the reported therapeutic results of serious DCI, especially neurological disorders. Early or ultra-early recompression therapy did not dramatically improve clinical recovery from DCI symptoms, including spinal cord disorders. In contrast, early first aid normobaric oxygen inhalation highly improved or stabilized clinical conditions of DCI. Based on these clinical results, the international committee for hyperbaric and diving medicine has stated that cases of mild DCI may be managed without recompression therapy. Further work is needed to clarify the clinical utility of recompression therapy for spinal injury as a common symptom of DCI. We also point out that the Japanese decree "Ordinance on Safety and Health of Work under High Pressure", which describes work under hyperbaric environments, has some serious issues and should be amended on the basis of scientific evidence.

[New Therapeutic Strategies and Future Issues in Hyperbaric Medicine].

Hyperbaric medicine includes two different medical fields: hyperbaric oxygenation (HBO) as emergency and intensive care, and diving medicine. Recent topics in hyperbaric therapy include radiation oncology and regenerative medicine. Of special interest are clinical studies of radiotherapy after HBO that were conducted at some institutes to evaluate its therapeutic effects for cancer patients. A few studies have shown that HBO improves memory disturbance following traumatic brain injury and hypoxic and ischemic events. There is a great possibility that HBO enhances the therapeutic effects of radiotherapy and potentiates regenerative medicine. Randomized controlled trials, however, have indicated the re-examination of its viable treatment effects in some conditions, including decompression illness, carbon monoxide poisoning, and serious soft tissue infection. As recent trends in the treatment of decompression illness have changed on the basis of clinical series, the laws related to diving and caisson work should be amended in the future.

Hyperacute brain magnetic resonance imaging of decompression illness in a commercial breath-hold diver.

Decompression illness in breath-hold diving is a rare dysbaric disease mainly characterized by stroke-like neurological disorders. The early use of DWI-MRI combined with ADC map in suspected cases can help in the early diagnosis and treatment.

[Central Nervous System Involvement in Breath-Hold Diving].

Diving accident in breath-hold (BH) divers (Ama) is a stroke-like neurological condition involving the brain. Ama divers are at a risk of ischemic brain injuries which are situated in watershed or terminal zones of cerebral arteries, and/or corticomedullary junctional area of cerebral arteries. The underlying mechanisms of brain damage in BH diving remains to be elucidated. After repetitive BH dives, nitrogen (N2) bubbles may be formed in the venous side of tissues and flow into the right atrium. N2 bubbles passing through the heart or the lungs is the most likely contributing factor. The pathophysiology of diving accident in BH diving is unclear, and more studies for stroke are needed to further elucidate its nature. (Received 29 July, 2019; Accepted 10 January, 2020; Published 1 May, 2020).

Cerebrospinal vascular diseases misdiagnosed as decompression illness: the importance of considering other neurological diagnoses.

The diagnosis of decompression illness (DCI), which is based on a history of decompression and clinical findings, can sometimes be confounded with other vascular events of the central nervous system. The authors report three cases of divers who were urgently transported to a hyperbaric facility for hyperbaric oxygen treatment of DCI which at admission turned out to be something else. The first case, a 45-year-old experienced diver with unconsciousness, was clinically diagnosed as having experienced subarachnoid hemorrhage, which was confirmed by CT scan. The second case, a 49-year-old fisherman with a hemiparesis which occurred during diving, was diagnosed as cerebral stroke, resulting in putaminal hemorrhage. The third case, a 54-year-old fisherman with sensory numbness, ataxic gait and urinary retention following sudden post-dive onset of upper back pain, was diagnosed as spinal epidural hematoma; he also showed blood collection in the spinal canal. Neurological insults following scuba diving can present clinically with confusing features of cerebral and/or spinal DCI. We emphasize the importance of considering cerebral and/or spinal vascular diseases as unusual causes of neurological deficits after or during diving.

Brain damage in commercial breath-hold divers.

BACKGROUND: Acute decompression illness (DCI) involving the brain (Cerebral DCI) is one of the most serious forms of diving-related injuries which may leave residual brain damage. Cerebral DCI occurs in compressed air and in breath-hold divers, likewise. We conducted this study to investigate whether long-term breath-hold divers who may be exposed to repeated symptomatic and asymptomatic brain injuries, show brain damage on magnetic resonance imaging (MRI). SUBJECTS AND METHODS: Our study subjects were 12 commercial breath-hold divers (Ama) with long histories of diving work in a district of Japan. We obtained information on their diving practices and the presence or absence of medical problems, especially DCI events. All participants were examined with MRI to determine the prevalence of brain lesions. RESULTS: Out of 12 Ama divers (mean age: 54.9±5.1 years), four had histories of cerebral DCI events, and 11 divers demonstrated ischemic lesions of the brain on MRI studies. The lesions were situated in the cortical and/or subcortical area (9 cases), white matters (4 cases), the basal ganglia (4 cases), and the thalamus (1 case). Subdural fluid collections were seen in 2 cases. CONCLUSION: These results suggest that commercial breath-hold divers are at a risk of clinical or subclinical brain injury which may affect the long-term neuropsychological health of divers.

Doppler detection in Ama divers of Japan.

OBJECTIVE: Symptoms consistent with neurological decompression sickness (DCS) in commercial breath-hold (Ama) divers has been reported from a few districts of Japan. The aim of this study was to detect circulating intravascular bubbles after repetitive breath-hold diving in a local area where DCS has been reported in Ama divers. METHODS: The participants were 12 partially assisted (descent using weights) male Ama divers. The equipment (AQUALAB system) consisted of continuous-wave Doppler with a 5-MHz frequency, and the Doppler probe was placed in the precordial site with the ultrasonic wave directed into the pulmonary infundibulum. We carried out continuous monitoring for 10 minutes at the end of the series of repetitive dives, and the recordings were made on numerical tracks and graded in a blind manner by 2 experienced investigators, according to the Spencer Doppler code. RESULTS: Depths and number of dives were 8 to 20 m and 75 to 131 times. Mean diving duration and surface interval were 64 ± 12 seconds and 48 ± 8 seconds, respectively (mean ± SD). We detected the lowest grade of intravascular bubbles (Spencer's grade I) in an Ama diver whose mean surface interval was only 35.2 ± 6.2 seconds. His mean descending, bottom, and ascending times were 10.4 ± 1.6 seconds, 39.2 ± 8 seconds, and 18.2 ± 3.0 seconds, respectively, over the course of 99 dives. CONCLUSIONS: Intravascular bubbles may be formed after repetitive breath-hold dives with short surface intervals or after a long breath-holding session in Ama divers. Symptoms consistent with neurological accidents in repetitive breath-hold diving may be caused in part by the intravascular presence of bubbles, indicating the need for safety procedures.

Potential roles of hyperbaric oxygenation in the treatments of brain tumors.

Over the past 50 years hyperbaric oxygen (HBO2) therapy has been used in a wide variety of medical conditions, and one of them is cancer. Many clinical studies have been conducted to evaluate potential therapeutic effects of HBO2 as a part of cancer treatment. This review briefly summaries the potential role of HBO2 therapy in the treatment of malignant tumors and radiation injury of the brain. HBO2 therapy is used for the enhancement of radiosensitivity in the treatment of some cancers, including malignant brain tumors. Radiotherapy within 15 minutes following HBO2 exposure, a relatively new treatment regimen, has been studied at several institutes and has demonstrated promising clinical results for malignant gliomas of the brain. HBO2 therapy also increases sensitivity to some antineoplastic agents; non-randomized clinical trials using carboplatin-based chemotherapy combined with HBO2 show a significant advantage in survival for recurrent malignant gliomas. The possibilities of combining HBO2 therapy with radiotherapy and/or chemotherapy to overcome newly diagnosed and recurrent malignant gliomas deserve extensive clinical trials. HBO2 therapy also shows promising potential for the treatment and/or prevention of radiation injury of the brain after stereotactic radiosurgery for brain lesions. The possibilities with HBO2 to enhance the therapeutic effect of irradiation per se, and to even increase the radiation dose if there are ways to combat the side effects, should boost new scientific interest into the whole field of oncology looking for new armamentaria to fight cancer.

Old but new methods in radiation oncology: hyperbaric oxygen therapy.

The presence of hypoxic tumor cells is widely regarded as one of the main reasons behind the failure to control malignant tumors with radiotherapy treatments. Since hyperbaric oxygenation (HBO) improves the oxygen supply to the hypoxic tumor cells, HBO therapy has previously been used in combination with simultaneous radiotherapy to treat malignant tumors. In some clinical trials, significant improvements in local control and survival have been seen in cancers of the head and neck and the uterine cervix. However, the delivery of simultaneous HBO therapy and radiotherapy is both complex and time-consuming, with some trials reporting increased side effects. As a result, the regimen of HBO therapy in combination with simultaneous radiotherapy has yet to be used as a standard treatment for malignant tumors. In recent years, however, radiotherapy immediately after HBO therapy has been emerging as an attractive approach for overcoming hypoxia in cancer treatment. Several studies have reported that radiotherapy immediately after HBO therapy was safe and seemed to be effective in patients with high-grade gliomas. Also, this approach may protect normal tissues from radiation injury. To accurately estimate whether the delivery of radiotherapy immediately after HBO therapy can be beneficial in patients with high-grade gliomas and other cancers, further prospective studies are warranted.

Revised trauma scoring system to predict in-hospital mortality in the emergency department: Glasgow Coma Scale, Age, and Systolic Blood Pressure score.

INTRODUCTION: Our aim in this study was to assess whether the new Glasgow Coma Scale, Age, and Systolic Blood Pressure (GAP) scoring system, which is a modification of the Mechanism, Glasgow Coma Scale, Age, and Arterial Pressure (MGAP) scoring system, better predicts in-hospital mortality and can be applied more easily than previous trauma scores among trauma patients in the emergency department (ED). METHODS: This multicenter, prospective, observational study was conducted to analyze readily available variables in the ED, which are associated with mortality rates among trauma patients. The data used in this study were derived from the Japan Trauma Data Bank (JTDB), which consists of 114 major emergency hospitals in Japan. A total of 35,732 trauma patients in the JTDB from 2004 to 2009 who were 15 years of age or older were eligible for inclusion in the study. Of these patients, 27,154 (76%) with complete sets of important data (patient age, Glasgow Coma Scale (GCS) score, systolic blood pressure (SBP), respiratory rate and Injury Severity Score (ISS)) were included in our analysis. We calculated weight for the predictors of the GAP scores on the basis of the records of 13,463 trauma patients in a derivation data set determined by using logistic regression. Scores derived from four existing scoring systems (Revised Trauma Score, Triage Revised Trauma Score, Trauma and Injury Severity Score and MGAP score) were calibrated using logistic regression models that fit in the derivation set. The GAP scoring system was compared to the calibrated scoring systems with data from a total of 13,691 patients in a validation data set using c-statistics and reclassification tables with three defined risk groups based on a previous publication: low risk (mortality < 5%), intermediate risk, and high risk (mortality > 50%). RESULTS: Calculated GAP scores involved GCS score (from three to fifteen points), patient age < 60 years (three points) and SBP (> 120 mmHg, six points; 60 to 120 mmHg, four points). The c-statistics for the GAP scores (0.933 for long-term mortality and 0.965 for short-term mortality) were better than or comparable to the trauma scores calculated using other scales. Compared with existing instruments, our reclassification tables show that the GAP scoring system reclassified all patients except one in the correct direction. In most cases, the observed incidence of death in patients who were reclassified matched what would have been predicted by the GAP scoring system. CONCLUSIONS: The GAP scoring system can predict in-hospital mortality more accurately than the previously developed trauma scoring systems.

A survey of neurological decompression illness in commercial breath-hold divers (Ama) of Japan.

A survey was conducted in the northern district of Yamaguchi, Japan to determine the relationship between neurological diving accidents and risk factors among commercial breath-hold divers (Ama). A questionnaire was distributed to 381 Ama divers who are members of the Ama diving union. We sought information on their dive practices (depth of single dive, single dive time, surface interval, length of dive shifts, lunch break) and the presence or absence of medical problems, such as hypertension, cardiac arrhythmia, diabetic mellitus and other issues. Of the 381 Ama divers, 173 responded (45%): 29 were Funado (assisted-descent using weights) and 144 Cachido (unassisted) divers. Twelve had experienced strokelike symptoms during or after repetitive breath-hold diving; 11 were assisted and one unassisted (Funado vs. Cachido). Only two of 12 divers with neurological diving accidents had musculoskeletal symptoms. Neurological events were significantly correlated with dive depth, dive time, and surface interval; however, they were not related to medical history. Neurological diving accidents are more likely to happen among assisted Ama divers than unassisted ones. Repetitive breath-hold diving with a deep dive depth, long dive time, and short surface interval predisposes divers to decompression illness, which characteristically manifests as cerebral stroke.