Diving and hyperbaric medicine最新文献

Introduction: We aimed to study middle ear barotrauma caused by fast compression followed by buoyant ascent escape from 200 m underwater and its effect on the auditory system, and to validate the preventive effect of tympanocentesis on middle ear barotrauma.

Methods: Twenty Sprague Dawley rats were divided into two groups: rats in group A underwent a simulated fast buoyant ascent escape from a depth of 200 m, while those in group B underwent tympanocentesis before the procedure described for group A. Ear endoscopy, acoustic conductance, and auditory brainstem response (ABR) tests were conducted before and after the procedure to evaluate the severity of middle ear barotrauma and auditory function in both groups. Additionally, histopathological examination of the middle ear in both groups was conducted to evaluate the severity of middle ear barotrauma by observing submucosal haemorrhage.

Results: None of the ears in either group showed any abnormalities before the experiment. In group A, middle ear barotrauma was universally observed after the simulation procedure. The tympanograms of all ears were initially type A and became type B after the procedure. Further, after the simulation, the hearing thresholds at different frequencies (4, 8, 16, 24, and 32 kHz) assessed by ABR significantly increased compared to those before the procedure. In group B, no middle ear barotrauma was observed, and the hearing threshold at each frequency did not change significantly compared with post-puncturing. After dissecting the middle ear, gross pathological observations were consistent with the above results. Microscopically, blood accumulation and submucosal haemorrhage in the middle ear cavity were observed in group A but not in group B.

Conclusions: Fast buoyant ascent from 200 m underwater can cause middle ear barotrauma, resulting in hearing loss. Tympanic membrane puncture can effectively prevent middle ear barotrauma caused by the rapid buoyant ascent escape procedure.

Therapeutic hyperbaric chambers require continuous monitoring and maintenance, including periodic requalification. The primary aim is to verify the suitability for continued safe service. Maintenance is regulated in Europe, and in France requalification is mandatory where a hyperbaric chamber operates above pressures equal to or greater than 4 bar gauge. French requalification requires a hydraulic (hydrostatic) pressure test to determine the absence of deformation and leaks during the test. However, in such cases, it is often necessary to move the chamber if the combined mass of the chamber and water may exceed the allowable floor loading strength. In 2009, an innovative alternative to a hydraulic pressure testing was authorised in France. It consists of carrying out a pneumatic pressure test simultaneously with a non-destructive monitoring technique called 'acoustic emission'. This can be compared to a microseismology technique, where sensors are applied to the pressure retaining boundary of the hyperbaric chamber, and signals emitted by the vessel under load are captured. These signals are analysed, prioritised, and classified, to determine the physical position of any sources (artifacts) through triangulation calculations. This technique makes it possible to assess the behaviour of the vessel very accurately in real time and, a posteriori, to assess its fitness for continued service. This technique reduces the unavailability time of the chamber to two days, compared to potentially several weeks when a hydraulic test is performed. Over and above financial considerations and availability of facilities, this technique provides a baseline of the integrity of pressure vessels and allows monitoring over time of any potential deterioration.

Introduction: The effects of methylphenidate, a stimulant often prescribed for the treatment of attention-deficit/hyperactivity disorder (ADHD), on the development of central nervous system oxygen toxicity (COT) have not been experimentally evaluated.

Methods: The records of all pure-oxygen-rebreather divers evaluated at our institution from 1975-2022 were assessed. Cases of COT were defined as a new onset of tinnitus, tunnel vision, myoclonus, headache, nausea, loss of consciousness, or seizures resolving within 15 minutes from breathing normobaric air, and matched 4:1 with similar controls. Any medications issued to the diver in the preceding three months, including methylphenidate, were recorded. In the animal arm of this study, male mice were exposed to increasing doses of methylphenidate orally, with subsequent exposure to hyperbaric O₂ until clinically evident seizures were recorded.

Results: Seventy-five cases of COT were identified in divers, occurring at a median of 80 (range 2-240) minutes after dive initiation at a median depth of 5 m (2-13). Hypercarbia was documented in 11 (14.7%) cases. Prescription of methylphenidate in the preceding three months was not associated with increased risk (OR 0.72, 95% CI 0.16-3.32) of COT. In mice, increasing methylphenidate exposure dose was associated with significantly longer mean COT latency time being 877 s (95% CI 711-1,043) with doses of 0 mg·kg⁻¹; 1,312 s (95% CI 850-1,773) when given 0.75 mg·kg⁻¹; and 1,500 s (95% CI 988-2,012) with 5 mg·kg⁻¹ (F = 4.635, P = 0.014).

Conclusions: Observational human data did not demonstrate an association between methylphenidate and an increased risk of COT. Methylphenidate exposure in mice prolongs COT latency and may have protective effects against COT.

Diving accidents result from a variety of causes including human error, inadequate health and fitness, environmental hazards and equipment problems. They usually involve a cascade of events resulting in the diver being injured or deceased. The accuracy and usefulness of a diving accident investigation relies on well-targeted interviews, good field investigation, evidence collection and preservation, and appropriate equipment assessment. In the event of a fatality, a thorough and targeted autopsy is indicated. Investigators should have the appropriate knowledge, training, skills and support systems to perform the required tasks. Relevant investigations include the victim's medical and diving history, the dive circumstances and likely accident scenario, management of the accident including rescue and first aid, equipment inspection and testing and a thorough postmortem examination conducted by a forensic pathologist with an awareness of the special requirements of a diving autopsy and the knowledge to correctly interpret the findings. A chain of events analysis can determine the likely accident scenario, identify shortcomings and inform countermeasures.

Systemic air embolism is a rare but potentially life-threatening complication of computed tomography (CT)-guided lung biopsy. The largest lung biopsy audits report an incidence rate of approximately 0.061% for systemic air embolism, with a mortality rate of 0.07-0.15%. A prompt diagnosis with high index of suspicion is essential, and hyperbaric oxygen treatment (HBOT) is the definitive management. We report the case of a 44-year-old lady who developed a lateral ST elevation myocardial infarction from coronary artery air embolism following CT-guided lung biopsy for evaluation of a left lung lesion. The biopsy was performed in the right lateral decubitus position, and the patient reported chest pain after coughing during the procedure. The clinician decided to proceed, taking four biopsy samples as no pneumothorax was identified in the intraprocedural CT image. The patient was noted to have hypotension with ongoing chest pain post-procedure. Resuscitative measures were taken to stabilise her haemodynamics, and she was successfully treated with HBOT with total resolution of air embolism. She developed a left sided pneumothorax post-treatment and needed intercostal chest drain insertion. The left lung fully re-expanded, and the patient was discharged home after day two of admission.

Introduction: This study analysed treatment outcomes in a patient cohort diagnosed with spondylodiscitis, who received adjunct hyperbaric oxygen treatment (HBOT) in addition to antibiotic therapy at our clinic. Important considerations included the timing of HBOT initiation on treatment success, and recurrence rates.

Methods: We retrospectively reviewed the records of all patients diagnosed with spondylodiscitis who received HBOT at the Underwater and Hyperbaric Medicine Clinic in Gulhane Training and Research Hospital, between 1 November 2016 and 25 October 2022. The patients received HBOT at 243.2 kPa for a total of 120 minutes per session, once daily for five days a week for a total of 30 sessions.

Results: Twenty-five patients with spondylodiscitis were evaluated before and after combination HBOT and targeted antibiotic treatment. After treatment, patients had lower median (range) visual analogue pain scores (8 [4-10] vs 3 [0-7], P < 0.001) and C-reactive protein (22.3 [4.3-79.9] mg·L⁻¹ vs 6.8 [0.1-96.0] mg·L⁻¹, P = 0.002) and lower mean (standard deviation) white blood cell counts (8.8 [3.5] x 109·L⁻¹ vs 6.1 [1.6] x 109·L⁻¹, P = 0.002). When patients were examined (median) 48 months (2-156 months) after the completion of treatment, there were no persistent cases of spondylodiscitis.

Conclusions: Combination HBOT with targeted antibiotic therapy effectively managed our cohort of patients diagnosed with spondylodiscitis. Hyperbaric oxygen treatment was safe, with no complications experienced. Moreover, HBOT may have helped to eliminate persistence and recurrence of symptoms with long term follow-up. A randomised controlled study with a larger number of patients is needed for more definitive conclusions.

Introduction: Aortic dissections and dissections of cervical, cerebral, and coronary arteries have been previously reported in scuba divers. These incidents may be the consequence of a variety of physiological effects. We review the reported cases of arterial dissection in scuba divers and discuss potential contributing factors related to immersion and diving.

Methods: Medline, CINAHL Plus, and SPORTDiscus were searched for published reports of arterial dissection and the Australasian Diving Safety Foundation fatality database was searched for additional cases from Australia. Identified cases were recorded and scrutinised for possible contributing factors.

Results: Nineteen cases of arterial dissection, both fatal and non-fatal, were identified. These included cervical or intracranial artery dissection (n = 14), aortic dissection (n = 4), and coronary artery dissection (n = 1). There were 14 male and five female victims; mean age 44 years (SD 14, range 18-65). Contributing factors may include a combination of vasoconstriction and blood redistribution, untreated hypertension, increased pulse pressure, abnormal neck movement or positioning, constrictive and burdensome equipment, exercise, increased gas density and circuit resistance with concomitant elevated work of breathing, atheroma, and possibly the mammalian dive response.

Conclusions: Dissecting aneurysms of the aorta or cervical, cerebral, and coronary arteries should be considered as a potential complication of scuba diving. The development of aneurysms associated with scuba diving is likely multifactorial in pathogenesis. Detailed reporting is important in the evaluation of cases. The potential role of the mammalian dive response as a contributing factor requires further evaluation.

This retrospective study analysed a series of investigations on lung function in military divers and the importance of computed tomography (CT) scans concerning fitness to dive. We examined the incidence of blebs and bullae in a population of military divers with large lungs prompted by six cases of pulmonary barotrauma. All of these divers' medicals were normal apart from having large lungs (FVC > 120% predicted). A subsequent survey of the database of all divers and submariners of the Royal Netherlands Navy (RNLN) found another 72 divers/submariners with large lungs who were then evaluated by a CT scan. This resulted in the identification of three further individuals with blebs and/or bullae, who were then declared unfit to dive. In total, the incidence of these lung abnormalities in this cohort was 11.5%. We discuss the possible consequences for fitness to dive with regard to the current literature on the subject, and also consider the most recent standards of reference values for pulmonary function indices. Based on our results and additional insights from other studies, we advise using the Global Lung Initiative reference values for pulmonary function, while performing high resolution CT scans only in divers with clinical indications.

Cricoid chondronecrosis is a rare entity and is scarcely reported in the literature. Its prevalence is increasing in the form of chondroradionecrosis among the survivorship of head and neck carcinoma patients treated with radiotherapy. We have reported a case of cricoid chondronecroisis caused by trauma from repeated tracheostomy. The patient presented with hoarseness and dyspnoea. Radiological findings in multidetector computed tomography showed disintegration of the cricoid and confirmed the diagnosis. Conservative treatment was given in the form of antibiotics, steroids and nebulised anticholinergics and bronchodilators. However, the patient did not improve and his condition worsened throughout two months of hospitalisation. He was referred for hyperbaric oxygen treatment, which was given over 30 sessions. This was associated with improvement in his condition and he was able to be decannulated from tracheostomy. Six monthly follow up of the patient showed a well-healed tracheostomy scar.

Introduction: The stability of a new hyperbaric ventilator (Shangrila590, Beijing Aeonmed Company, Beijing, China) at different clinically relevant pressures in a hyperbaric chamber during pressure-controlled ventilation (PCV) was investigated.

Methods: The ventilator was connected to a test lung in the multiplace hyperbaric chamber. The inspiratory pressure (PI) of the ventilator was set to 1.0, 1.5, 2.0, 2.5 and 3.0 kPa (approximately 10, 15, 20, 25 and 30 cmH₂O). The compliance and resistance of the test lung were set to 200 mL·kPa⁻¹ and 2 kPa·L⁻¹·s⁻¹, respectively. Experiments were conducted at 101, 203 and 284 kPa ambient pressure (1.0, 2.0 and 2.8 atmospheres absolute respectively). At each of the 5 PI values, the tidal volume (VT), peak inspiratory pressure (Ppeak) and peak inspiratory flow (Fpeak) displayed by the ventilator and the test lung were recorded for 20 cycles. Test lung data were considered the actual ventilation values. The ventilation data were compared among the three groups to evaluate the stability of the ventilator.

Results: At every PI, the Ppeak detected by the ventilator decreased slightly with increasing ambient pressure. The Fpeak values measured by the test lung decreased substantially as the ambient pressure increased. Nevertheless, the reduction in VT at 284 kPa and PI 30 cmH₂O (compared to performance at 101 kPa) was comparatively small (approximately 60 ml).

Conclusions: In PCV mode this ventilator provided relatively stable VT across clinically relevant PI values to ambient pressures as high as 284 kPa. However, because Fpeak decreases at higher ambient pressure, some user adjustment might be necessary for precise VT maintenance during clinical use at higher PIs and ambient pressures.