Number 3

[Position Statement] DOI: 10.22462/05.06.2018.15

[Letter] DOI: 10.22462/05.06.2018.14

[Letter] DOI: 10.22462/05.06.2018.13

Objectives: There are limited data regarding the safety of cochlear implants during exposure to pressure changes associated with scuba and hyperbaric oxygen therapy. There are no data regarding the effects of barometric pressure changes on preserved low-frequency hearing after cochlear implantation. This case report evaluates the effect of barometric pressure changes on preserved low-frequency hearing after cochlear implantation. Patient: This is a case report of a patient who underwent successful cochlear implantation with postoperative preservation of residual low-frequency hearing. Interventions: 20 scuba dives up to depths of 92 feet (3.8 atmospheres absolute).Main outcome measures: Preservation of hearing and maintained integrity of the implant. Results: Audiometric testing both before and after scuba shows no change in hearing thresholds. The internal receiver-stimulator of the cochlear implant was unaffected by prolonged and repeated pressures up to approximately 3.8 atmospheres absolute. The patient had no adverse middle ear effects during or after the dives, and no evidence of inner ear barotrauma or decompression sickness as a result of the elevated pressures. Conclusions: This is the first report of preserved hearing after cochlear implantation being maintained following scuba diving, and corroborates previous literature showing that exposure to increased pressures with a cochlear implant in situ is safe without ..

We evaluated the efficacy of hyperbaric oxygen (HBO2) therapy used as a supplement to the first-line medical treatment of sudden sensorineural hearing loss (SSNHL). We tested 68 patients suffering from SSNHL within seven days of hearing loss: 21 patients received the standard treatment protocol of our department (control group) and 47 individuals were treated with an additional application of HBO2 therapy. Treatment success was assessed using pre- and post-treatment audiograms. Outcomes of our study showed a statistically significant improvement in auditory threshold in all frequency groups for the HBO2 group (P < 0.001), whereas in the control group the statistically significant mean auditory gain was observed only for the frequency zone 1,000 to 2,000 Hertz (P = 0.01). Furthermore, the rate of hearing gain in the HBO2 group was more than doubled (61.7%) compared to the control group (28.6%). Complete recovery of the hearing gain in the control group was observed only in the first two frequency groups (14.29%; 4.76%; 0.00%), whereas in the HBO2 group complete recovery was seen in all the frequency groups (19.15%; 21.13%; 6.38%) as well as in the whole frequency range (6.38%). The efficiency of both treatment protocols was statistically significant (P < 0.001) in both groups ..

Nuclear factor kappa B (NF-κB) is the critical transcriptional factor in the pathogenesis of acute lung injury (ALI). NF-κB regulates the expression changes of inflammatory factors such as tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and interleukin 6 (IL-6). In a previous study we showed that decompression sickness (DCS) caused by simulated unsafe fast buoyancy ascent escape (FBAE) could result in ALI, which was characterized by expression changes of inflammatory factors in rat lung tissue. The purpose of the present work was to study the roles of NF-κB and TNF-α in the process of DCS-induced rat lung injury caused by simulated unsafe FBAE. The research methods aimed to detect the rat lung tissue messenger ribonucleic acid (mRNA) and protein level variations of NF-κB, inhibitory κB (IκB), TNF-α, IL-1β, IL-6, IL-10 and IL-13 by using pretreatment of the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) and TNF-α antibody (Ab). Our experimental results demonstrated that PDTC could improve the survival rate of the rats with DCS caused by unsafe FBAE more effectively than TNF-α Ab. However, the inhibition of TNF-α Ab on the nuclear translocated protein expression of NF-κB was more effective than PDTC. Both PDTC and TNF-α Ab can abrogate the increment of the ..

Purpose: Experiments have shown that hyperbaric oxygen (HBO2) therapy reduces cyanide-induced cerebral distress. The exact mechanism behind HBO2’s neuroprotective effect is unknown, but has been proposed to be mediated by an increased neuronal nitric oxide (NO) bioavailability, which may compete with cyanide for the active site of cytochrome oxidase in the mitochondrial respiratory chain. We hypothesized that the ameliorating effect of HBO2 is caused by an increased bioavailability of NO, which can be attenuated by injection of the selective neuronal NO synthase inhibitor, 7-nitroindazole, preceding the HBO2 procedure. Methods: A total of 41 anesthetized female Sprague-Dawley rats were allocated to four groups: 1) vehicle [1.2 ml isotonic NaCl via intra-arterial administration]; cyanide [5.4 mg/kg potassium CN (KCN) intra-arterial] + 7-nitroindazole [25 mg/kg 7-nitroindazole via intraperitoneal injection];  cyanide+7-nitroindazole + HBO2 [284 kPa for 90 minutes]; cyanide + 7-nitroindazole + normobaric oxygen [101.3 kPa for 90 minutes].  Cerebral interstitial lactate, glucose, glycerol and pyruvate were evaluated by means of microdialysis. Results: HBO2 during inhibition of nNOS worsened cerebral metabolism compared to both solely CN-intoxicated animals and normobaric oxygen-treated animals. This was indicated by elevated lactate (in mM; 0.85 vs. 0.63 and 0.42, P=0.006 and P<0.001, respectively), glycerol (in mM; 46 vs. 17 and 14, both P<0.001), glucose (in ..

Introduction: Acute lung injury (ALI) is generally caused by oxidative damages and pulmonary overinflammations. Hyperbaric oxygen preconditioning (HBO2-PC) has been proven protective against oxidative-stress-related injuries. In this study, we investigated the effect of HBO2-PC on lipopolysaccharide (LPS)-induced ALI in rats. Methods: Thirty-two Sprague-Dawley rats randomly assigned into Sham, HBO2-PC, ALI and HBO2-PC+ALI groups (eight in each group) were sacrificed at 12 hours after the injection of LPS. The severity of ALI in rats was assessed in terms of histopathological changes in addition to wet/dry weight ratios. The levels of tumor necrosis factor-? (TNF-?), interleukin (IL)-6 and IL-1β in serum and lung homogenates were measured by enzyme-linked immunosorbent and qRT-PCR assays. Activities by hydrogen peroxide (H2O2), malondialdehyde (MDA), myeloperoxidase (MPO) as well as superoxide dismutase (SOD) in rat lungs were tested for neutrophil infiltration. Meanwhile the oxidative stress molecular markers nuclear factor-kappa B(NF-κB) p65 and nuclear factor erythroid 2-related factor 2 (Nrf2), together with its downstream heme-oxygenase 1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1) were also quantified. Results: HBO2-PC significantly alleviated LPS-induced ALI, lowered the lung injury scores, reduced lung water content, and reduced H2O2, MDA levels as well as MPO activity, while simultaneously improving the arterial partial oxygen pressure (PaO2) ..

Hookah diving is a fishing method used in many small-scale fisheries in the Gulf of Mexico and the Caribbean Sea, as well as in many coastal fisheries around the world. Many high-value species like sea cucumber and spiny lobster, among others, are harvested via hookah diving. However, the fishing method presents a risk for both decompression illness and carbon monoxide poisoning, both causes of disabilities and death among small-scale fishers, and with significant negative impacts on the social and economic status of households and coastal communities. Currently, there is a misunderstanding among fishers concerning diving risks. Using a mixed-method analysis, this study reports the risk perceptions of small-scale fishers and hyperbaric personnel about hookah diving, and the actual diving accidents which occur in the spiny lobster and sea cucumber fisheries in the Yucatán northeastern ports. The study highlights the need for appropriate fishing technologies and increased awareness among fishers about the consequences of hookah diving. Fishery managers and health services can make priority decisions based on the information generated. DOI: 10.22462/05.06.2018.7

Introduction: Decompression sickness (DCS) has been associated with unusual circumstances such as breath-hold diving, shallow depths, and short bottom times. We report a case of DCS with an extraordinary cause and course. Materials and Methods: A 72-year-old healthy Hispanic female was referred to our 24/7 Hyperbaric Medicine Unit for emergency hyperbaric oxygen recompression treatment (HBO2 RCT) after developing lower-extremity paralysis following a hyperbaric air exposure in a homemade hyperbaric chamber. Findings/Case report: After an uneventful exposure to hyperbaric air at a maximum 72-foot depth (3.2 ATA, 32.3 psig), the patient had the delayed onset of abdominal pain and paraplegia after eating a meal. After HBO2 RCT in accordance with our management algorithm, the patient had a full recovery. Conclusions: This patient’s presentation and course corresponded to what we label as “disordered decompression” and conformed to our Gradient Perfusion Model. With a finite blood volume and the need to perfuse two “intermediate” tissues simultaneously, we postulate that a “steal” syndrome arose to cause the abdominal and paralysis symptoms. DOI: 10.22462/05.06.2018.6

Introduction: In Part 1 of this three-part series, we provided an explanation as to why and at what sites decompression sickness (DCS) occurs, using the Gradient-Perfusion Model (GPM). In this part, we provide information to substantiate the concept and present clinical cases that were initially labeled as “unexplained DCS,” but later disordering events were identified to explain the clinical presentations. Materials and Methods: Among 500 cases of DCS we have managed for over 50 years, a cohort of these patients was initially diagnosed as unexplained DCS. However, some have shown that disordering events are the likely cause of their DCS. Results: By pairing the tissue involved with the patient’s dive history, a gradient-perfusion imbalance connection was identified. In all serious (Type 2) presentations of DCS, alterations in perfusion of the fast tissues were able to account for the clinical findings. The consequences demonstrated that the gradients overwhelmed the ability of altered perfusion to offgas/offload the inert gas. Pain-only and peripheral neuropathy presentations involved both intermediate and slowly perfused tissues. Rather than perfusion, gradient limitations were the reasons for the clinical presentations of these patients. Conclusions: The GPM accounts for signs and symptom presentations in DCS. This provides the basis for appropriate treatments ..

Introduction: Decompression sickness (DCS) is manifested by the quantity and location of bubbles in body tissues after reduction in ambient pressures. Models have been formulated to explain why bubbles form, but none provide satisfactory explanations as to why the findings of DCS occur as they do. This first of a three-part series explains why and at what sites DCS occurs. Materials and Methods: Over a 50-year span and 500 cases of DCS we have managed, it has become apparent that almost all “unexplained DC"S" (i.e., cases with no obvious explanation as to how/why they occurred) have physiological explanations. The vagaries of the physiology of tissue perfusion and the physics of gradients as a cause of autochthonous bubble formation were analyzed. Findings: Perfusion is highly variable, with so-called “fast” tissues (i.e., tissues with a rapid rate of saturation) requiring a constant blood supply, “intermediate” tissues requiring a blood supply proportional to needs, and “slow” tissues having minimal perfusion requirements. The 5-liter blood volume in a vascular system with greater than a 20-liter capacity requires careful regulation. Disruptions in the regulation and/or overwhelming gradients explain why DCS occurs. Conclusions: Our Gradient-Perfusion Model provides an explanation as to why disordering events account for almost all ..

 Guidelines for the pre-hospital management of decompression illness (DCI) had not been formally revised since the 2004 Divers Alert Network/Undersea and Hyperbaric Medical Society workshop held in Sydney, entitled “Management of mild or marginal decompression illness in remote locations.” A contemporary review was initiated by the Divers Alert Network and undertaken by a multinational committee with members from Australasia, the USA and Europe. The process began with literature reviews by designated committee members on: the diagnosis of DCI; first aid strategies for DCI; remote triage of possible DCI victims by diving medicine experts; evacuation of DCI victims; effect of delay to recompression in DCI; pitfalls in management when DCI victims present at hospitals without diving medicine expertise and in-water recompression. This was followed by presentation of those reviews at a dedicated workshop at the 2017 UHMS Annual Scientific Meeting, discussion by registrants at that workshop and, finally, several committee meetings to formulate statements addressing points considered of prime importance to the management of DCI in the field. The committee placed particular emphasis on resolving controversies around the definition of “mild DCI” arising over 12 years of practical application of the 2004 workshop’s findings, and on the controversial issue of ..

 Successful submarine operations rely on the performance of tactical teams who must work under conditions of physiological and cognitive fatigue. Sleep loss and circadian disruption contribute to fatigue in this setting and, although the effects of this fatigue have been studied extensively in individuals, little is understood about how fatigue impacts team performance – especially in a submarine environment. The present review provides an overview of the fatigue on submarine teams and is divided into four main sections: A discussion of factors that should be considered in team fatigue research. An outline of how sleep and circadian rhythms of submariners are impacted by submarine-specific factors. A discussion of the known effects of fatigue from sleep loss and circadian disruption on individual performance.  A consideration of how this fatigue impacts team performance. As the submarine force has recognized the need to protect submariner sleep and improve team dynamics, it is vital that future research accounts for the interplay between these two factors. DOI: 10.22462/05.06.2018.2

Introduction: While otic barotrauma (OBT) is a common condition experienced by divers, data related to military divers is limited. This study aimed to determine the incidence of OBT in Canadian armed forces (CAF) shallow-water diver (SWD) students trained through the Fleet Dive Unit (Atlantic) (FDU[A]) between 2011-2015. Methods: A retrospective cohort evaluation was performed. The study group consisted of all SWD candidates who embarked on an SWD course through FDU(A) between 2011-2015. A total of 241 subjects comprised the final data analysis. Results: A total of 56 individuals (23.2%) suffered 60 instances of OBT, yielding an incidence density rate of 8.68 per 1,000 person-days on course. A total of 73 diving days (10.44 per 1,000 planned person-course days, or 4.87 diving days per course) were lost due to OBT. Of the reported OBT cases, 18% resulted in cessation of training, 72% in temporary removal from diving. There was no statistically significant association between sex, history of environmental allergies, previous dive qualification, age or rank and the development of OBT. Conclusion: This study reveals that OBT is prevalent among CAF SWD candidates, with operational impact due to missed diving days. This study is limited, and further prospective study is recommended. DOI: 10.22462/05.06.2018.1