Hyperbaric Chamber Research Articles

The Gradient Perfusion Model Part 3: An extraordinary case of decompression sickness

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.

Comparison of Exogenous Ketone Supplements on Latency to CNS Oxygen Toxicity Seizures in Middle‐Aged Rats

Central nervous system oxygen toxicity (CNSOT) seizures manifest as tonic‐clonic seizures and are a limitation of hyperbaric oxygen therapy (HBOT) and Navy SEAL divers breathing 100% oxygen using closed circuit rebreathers. Previous studies showed that ketone ester (1,3‐butanediol acetoacetate diester, KE) delayed latency to seizures in 3 months old Sprague‐Dawley rats. Our present study explores the effect of exogenous ketone supplements on CNSOT seizures across different ketone formulations and dosages in 18‐month‐old Sprague‐Dawley rats that resemble middle age in humans. Rats received one dose of the ketogenic agent by oral gavage 60 minutes before a dive. Treatment groups included control (water), 1,3‐butanediol acetoacetate diester (KE 10g/kg, KE/2 5g/kg), KE+MCT (KE 5g/kg + medium chain triglyceride 5g/kg) and KS+MCT (CaNaBHB 5g/kg + MCT 5g/kg). To simulate a dive, rats were placed on 100% oxygen followed by gas compression to 5 atmospheres absolute (ATA) in a hyperbaric chamber and remained at 5 ATA until exhibiting CNSOT seizures, defined by tonic‐clonic movements. Upon seizure presentation, experiments were immediately terminated and the chamber was decompressed at a rate of 1 ATA/min. A small sample of blood was drawn and tested immediately for glucose and R‐beta‐hydroxybutyrate (βHB) levels. While βHB levels were significantly elevated in all aged‐rat treatment groups, compared to control, the latency to seizures was significantly delayed only in KE (p=0.0003), KE/2 (p=0.023) and KE+MCT (p=0.028) groups. In these groups, the severity of seizures was less than control. The latency to seizures in 18 months old rats were delayed by 179% in KE, 219% in KE+MCT and 55% in KE/2 groups, while only by 29% in KS+MCT group. Previous studies indicate that 3‐month‐old Sprague‐Dawley rats presented 574 ± 116% latency to seizure compared to control indicating age related influence on latency to seizure. Glucose levels were not significantly different from the control group. We can conclude that middle‐aged rats demonstrated increased latency to CNSOT seizures, although at a different rate than younger rats, in response to ketogenic supplements and their combinations, while elevating βHB levels.Support or Funding InformationThis work was supported by ONR Grant N000141310062 (DPD), ONR, Undersea Medicine Program (N000140710890, JBD), ONR, Undersea Medicine Program (N000141612537, JBD).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

TREATMENT WITH HYPERBARIC OXYGENATION AFTER 6 HOURS OF AN ACUTE MYOCARDIAL INFARCTION IN RATS

Acute myocardial infarction has been placed in the leading cause of death in the world. Coronary interventionism is the gold standard in the treatment of AMI, however its therapeutic window is very limited. The decrease in the area of myocardial infarction and hemodynamic improvement have been reported with the use of HBO therapy in the ongoing AMI, as well as angiogenesis, decreased inflammation and useful as ischemic preconditioning.MethodologyAn experimental study was designed to determine the effect of HBO on the rat cardiomyocyte after 6 hours of an AMI induced by ligation of the anterior descending coronary. The HBO was administered through a 100% hyperbaric chamber, at 2 ATA, for one hour daily. The size of the infarcted area was macroscopically measured, and antioxidant enzymes were evaluated. Six groups were compared.ResultsA statistically significant decrease of the infarcted area was obtained from the 3rd session of HBO. Regarding oxidative stress, significant results were obtained for TBARS, TAS and 3‐NT from the 5th session with HBO.ConclusionHyperbaric oxygen therapy shows a beneficial effect after 3 days of the induction of AMI, this is reflected by a decrease in the infarcted area; and after the 5th day reflected by a decrease in TBARS and 3‐NT.Support or Funding InformationSIp, COFAA, IPNThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

EFFECT OF HYPERBARIC OXYGEN ON THE RAT CARDIOMYOCYTE AFTER 6 HOURS OF AN ACUTE MYOCARDIAL INFARCTION

The current treatment of myocardial infarct (MI) is thrombolysis, or ideally percutaneous coronary angioplasty. Alternatively, benefits of hyperbaric oxygen (HBO) have been reported during an MI in progress, where it seems to reduce the number of infarcted cardiomyocytes favoring their neovascularization.Material and methodsMI was induced by ligation of the anterior descending coronary artery. HBO was administered by a hyperbaric chamber 100%, at 2 atmospheres of pressure, for one hour daily for 15 days. After this time the rats were sacrificed, the size of the infarcted area was measured histologically, and the number of vascular buttons and neoformation vessels was determined by detecting the Vascular Endothelial Growth Factor (VGEFR2) and CD34 by immunohistochemistry, respectively. Three groups of 10 rats each were compared: group A (HBO without MI), group B (MI with HBO), and group C (MI without HBO).ResultsImmunohistochemically, a greater number of VEGFR2 positive vascular buttons were found in the rats of group C than those of group B (7.15 vs 2.55 per field, p = 0.01), but in the group B there are more CD34 positive neoformation vessels (7.8 vs 4.2 per field, p = 0.01).ConclusionsHBO promotes early neovascularization of the rat cardiomyocyte after 6 hours of an MI.Support or Funding InformationSIP, COFAA, IPNThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Health effects of hyperbaric exposure on chamber attendants: a literature review.

Inside attendants working in hyperbaric chambers are exposed to risks related to the hyperbaric environment, handling and care. The aim of this study is to review the literature focusing on the impact of this activity on health. This is a literature review using the Medline database. Eight articles studied decompression illness (DCI). The incidence of DCI ranged from 0 to 37 per 100,000 sessions in hyperbaric chambers (SHC). The incidence of injuries ranged from 0 to 412 per 100,000 SHC. The most prevalent cause of accidental death was fire: 77 deaths (patients and attendants) between 1923 and 1996. Dysbaric osteonecrosis has been reported in one study only. Inside attendants face risks in the chamber, even if serious health effects seems rare compared to the total number of SHC.

IN VITRO STUDIES ON HEME OXYGENASE-1 AND P24 ANTIGEN HIV-1 LEVEL AFTERHYPERBARIC OXYGEN TREATMENTOFHIV-1 INFECTED ON PERIPHERAL BLOOD MONONUCLEAR CELLS (PBMCS).

Background:Heme oxygenase-1 (HO-1) is a protein secreted by immune cells as a part of immune response mechanism.HO-1 can be induced by variety agents that causingoxidative stress, such as exposure to 100% oxygenat2,4 ATA pressure.It plays a vital role in maintaining cellular homeostasis.This study was conducted to identify the effect of hyperbaric oxygen exposure in cultured ofPBMCthat infected by HIV-1.Material and Methods:Primary culture of PBMCs were isolated from 16 healthy volunteers and HIV-1 infected MT4 cell line by co-culture. The PBMCs were aliquoted into two wells as control group and treatment group. The 16 samples of HIV-1 infected PBMCwere exposed to oxygen at 2,4 ATA in animal hyperbaric chamber forthree times in 30 minutes periods with 5 minutes spacing period, that called 1 session.The Treatment done on 5 sessions within 5 days. 16 samples of HIV-1 infected PMBCs that have no hyperbaric treatment became control group.The supernatant were measured the HO-1 production by ELISA andmRNA expression of HO-1 by real time PCR and the number ofantigen p24 HIV-1by ELISA.Results:The result showed that there was no increasing of HO-1 at both mRNA level and protein level, there was a decreasing number of antigen p24 HIV-1 at the treatment group. In addition, hyperbaric exposure could not increase the expression of HO-1, more over the viral replication might be reduced by other mechanism.Conclusions:Hyperbaric oxygen could increases cellular adaptive response of PBMCs infected HIV-1 through increased expression of proteins that can inhibit HIV viralreplication.

Microbial Contamination of a Diving Suit

Abstract Pathogenic micro-organisms can easily transfer from the surface of a diver’s skin onto the surfaces of a protective suit. A long-term stay in a hyperbaric chamber during a saturation dive increases the risk of infection if in the chamber there is even a single carrier of disease-causing pathogens. The conducted research has confirmed that the diving equipment located in Diving Centres is a place of many different bacteria and fungi, including pathogenic ones. The vast majority of microbes found on the surfaces of wetsuits, etc. are commensals (with some being opportunistic organisms). This fact allows us to realise that the surfaces of diving equipment are an excellent “transmission route” for various dermatoses and other diseases. In order to reduce the risk of infection the diving equipment used by various people should be subject to the process of decontamination. The authors recommend decontamination with the use of gaseous hydrogen peroxide which does not cause damage to equipment.

Assessment of the Importance of Tympanic Membrane Mechanoreceptors on Eustachian Tube Function Based on Pressure Chamber Measurements.

Previously, it was demonstrated how the Eustachian tube (ET) opening function can be influenced by middle ear pressure and movement of the tympanic membrane via neural control. Mechanoreceptors on the tympanic membrane may be part of the afferent arc and could influence the middle ear pressure by activating the musculus veli palatini as part of a reflex. In a hypo and hyperbaric pressure chamber, 17 participants (34 ears) were twice exposed to a standardized pressure profile of pressure decrease and increase. The ET function reflecting parameters-ET opening pressure (ETOP), ET opening duration (ETOD), and ET opening frequency (ETOF)-were determined before and after local anesthesia of the right tympanic membrane. After pressure exposure by pressure increase (active induced equalization) and pressure decrease (passive equalization) there was no significant difference between the mean value of ETOP, ETOD, and ETOF before and after local anesthesia of the right tympanic membrane on the right (anesthetized) or left side (not anesthetized). These results may lead to the hypothesis that tympanic membrane mechanoreceptors may play a minor role in regulating the ET function in humans.

The potential long-term neurological improvement of early hyperbaric oxygen therapy on hemorrhagic stroke in the diabetics

AimsAlthough Hyperbaric oxygen therapy (HyperBOT) attract our attention successfully these days, it is still full of controversy on the treatment of acute stroke. The aim of this study is to assess the potential long-term neurological consequences and safety of using HyperBOT on intracerebral hemorrhage (ICH) in the diabetics. MethodsIn this prospective, randomized controlled trial, 79 diabetes patients suffering from acute ICH were randomized to treat for 60 min in a monoplace hyperbaric chamber pressurized with pure oxygen to 2.5-atm absolute (ATA) in the HyperBOT group or 1.5 ATA in the normobaric oxygen therapy (NormBOT) group, which was performed as control. Both short-term and long-term neurological consequences were studied and compared in each group on National Institutes of Health Stroke Scale [NIHSS], Barthel Index, modified Rankin Scale [mRS] and Glasgow Outcome Scale [GOS]. The related complications or side-events of all patients were recorded as well at the final follow-up of six months after onset. ResultsNo distinct difference was observed between each group at one month follow-up. However, in the long-term follow-up of six months, a higher frequency of patients in the HyperBOT group resulted into good outcome with a relative high neurological consequence compared with the NormBOT group (Barthel Index: 85.1% versus 65.6%, P = 0.080; mRS: 89.4% versus 68.8%, P = 0.045; GOS: 83.0% versus 62.5%, P = 0.073; NIHSS: 80.9% versus 56.2%, P = 0.035). ConclusionsEarly HyperBOT was found to be safe and effective with regards to the long-term neurological outcome of diabetic patients suffering from ICH.

Sorption of pentachlorophenol (PCP) in the marine bottom sediments\u2014batch sorption experiment at varying pressure

Study was undertaken to determine the effect of hydrostatic pressure on the sorption of pentachlorophenol (PCP). The experiment was conducted at atmospheric pressure (1000 hPa) and at increased pressure (6000 hPa) simulating conditions at the water depth of 50 m. The sorption of PCP was examined in an artificial environment (microcosm) consisting of the marine water and the bottom sediments from a Polish harbor and the southern Baltic Sea. The first part of the experiment comprised the determination of PCP sorption parameters in the microcosms and parameters of the sediments (organic matter content, conductivity) and of the overlying water (pH, ion concentration) at 1000 hPa. The second part of the experiment was conducted at 6000 hPa inside the hyperbaric chamber. The hyperbaric exposure affected parameters of the harbor sediments and the overlying water but had little influence on the concentration of PCP in the microcosms containing the southern Baltic Sea sediments. Considering the specific characteristics of the harbor sediments, it can be assumed that the impact of hydrostatic pressure on the sorption process of PCP at 50-m depth appears to be negligible.

Autonomic Nervous System Measurement in Hyperbaric Environments Using ECG and PPG Signals.

The main aim of this paper was to characterize the Autonomic Nervous System response in hyperbaric environments using electrocardiogram (ECG) and pulse-photoplethysmogram (PPG) signals. To that end, 26 subjects were introduced into a hyperbaric chamber and five stages with differentatmospheric pressures (1atm; descent to 3 and 5atm; ascent to 3 and 1atm) were recorded. Respiratory information was extracted from the ECG and PPG signals and a combined respiratory rate was studied. This information was also used to analyze Heart Rate Variability (HRV) and Pulse Rate Variability (PRV). The database was cleaned by eliminating those cases where the respiratory rate dropped into the low frequency band (LF: 0.04-0.15Hz) and those in which there was a discrepancy between the respiratory rates estimated using the ECG and PPG signals. Classical temporal and frequency indices were calculated in such cases. The ECG results showed a time-related dependency, with the heart rate and sympathetic markers (normalized power in LF and LF/HF ratio) decreasing as more time was spent inside the hyperbaric environment. A dependence between the atmospheric pressure and the parasympathetic response, as reflected in the high-frequency band power (HF: 0.15-0.40Hz), was also found, with power increasing with atmospheric pressure. The combined respiratory rate also reached a maximum in the deepest stage; thus, highlighting a significant difference between this stage and the first one. The PPG data gave similar findings and also allowed the oxygen saturation to be computed; therefore, we propose the use of this signal for future studies in hyperbaric environments.

Numerical study and parametric analysis of the propagation buckling behaviour of subsea pipe-in-pipe systems

Propagation buckling mechanisms in pipe-in-pipe (PIP) systems with thin and moderately thin carrier pipes with a diameter-to-thickness (Do/to) ratio in the range 26–40 are investigated using 2D analytical and 3D nonlinear (material and geometry) finite element (FE) models. The FE models are validated against hyperbaric chamber tests of a PIP system with Do/to of 30. Using the validated FE model a parametric study is conducted and two distinct buckle propagation modes in PIPs are observed. Empirical expressions for each mode are proposed and are found to be different from previous expressions suggested for PIPs with (Do/to) ratio in the range 15–25.

Influence of exposure in hyperbaric chambers on selected parameters of oxidative stress in professional divers

This study evaluated the influence of hyperbaric exposure chambers on selected parameters of oxidative stress in divers' blood. 25 healthy men (non-smoking experienced divers) ages 18-40 took part in the experiment. Subjects were exposed to hyperbaric conditions similar to those at 30 meters of depth while diving. A control group consisted of 20 healthy men who have never dived or been exposed to hyperbaric conditions. Blood was drawn from the cubital vein after overnight fasting. Superoxide dismutase (SOD-1) activity and malondialdehyde (MDA) concentration were marked in red blood cells (RBCs), carbonyl group concentration marked in serum proteins, and nitrate/nitrite concentrations were estimated in plasma. Statistically significant differences were found between the divers and the control group in MDA concentration in erythrocytes and carbonyl group concentration in serum proteins. Nitrite/nitrate concentrations in plasma plus SOD-1 activity in RBCs decreased significantly in the diver group compared with the control group. After hyperbaric exposure MDA concentration in erythrocytes increased considerably in the test group and a significant increase in SOD-1 activity was observed. A significant increase of nitrite/nitrate concentration was noted in plasma as well as an increase in the carbonyl group in serum proteins. Considerably weak enzymatic antioxidative defense was observed in the RBCs of individuals exposed to hyperbaric pressures versus those in normobary. This issue indicates that a diver's system has a larger susceptibility for negative effects from oxidative stress. The results also indicate that hyperbaric conditions can intensify reactions via free radicals.

An approach to treating a patient with a HeartMate IITM left ventricular assist device in a multiplace hyperbaric chamber: a case report

Left-ventricular assist devices (LVAD) are becoming a common therapy for end-stage heart failure. These devicesare not tested for pressurization in a hyperbaricchamber by the manufacturer. In this article, we present an approach to modify the power supply in order to safely treat a patient with an LVAD. Our patient had a HeartMateII™ LVAD and presented for hyperbaric oxygen treatments for severe radiation cystitis. In order to modify this patient's equipment to be compliant with NFPA6 safety standards we made several modifications. In brief, this included eliminating the usage of lithium-ion batteries, modifying the cord to be compatible with Fink chamber outlets, and enclosing the power module in a nitrogen purge. We then used a mock circulatory system to test our modifications and make sure the LVAD continued to have appropriate flow rates. We then conducted training for staff and developed a disaster plan should the LVAD fail at any point. Once we felt comfortable with the modifications and had a plan developed should any problems arise, we then proceeded to treat our patient in the hyperbaric chamber. He successfully underwent 44 hyperbaric treatments for radiation cystitis without complications. This case is the second reported patient in the literature with an LVAD that was successfully treated in a multiplace hyperbaric chamber. As LVADs become increasingly popular to manage heart failure, more patients with these devices will present for hyperbaric treatments. With a few modifications, an LVAD patient can be safely and successfully treated in a hyperbaric chamber.

Perfluorocarbon in Delayed Recompression with a Mixed Gender Swine Model of Decompression Sickness.

Perfluorocarbons (PFC) are fluorinated hydrocarbons that dissolve gases to a much greater degree than plasma and hold promise in treating decompression sickness (DCS). The efficacy of PFC in a mixed gender model of DCS and safety in recompression therapy has not been previously explored. Swine (25 kg; N = 104; 51 male and 53 female) were randomized into normal saline solution (NSS) or PFC emulsion treatment groups and subjected to compression on air in a hyperbaric chamber at 200 fsw for 31 min. Then the animals were decompressed and observed for signs of DCS. Afterwards, they were treated with oxygen and either PFC (4 cc · kg-1) or NSS (4 cc · kg-1). Surviving animals were observed for 4 h, at which time they underwent recompression therapy using a standard Navy Treatment Table 6. After 24 h the animals were assessed and then euthanized. Survival rates were not significantly different between NSS (74.04%) and PFC (66.67%) treatment groups. All swine that received recompression treatment survived to the end of the study and no seizures were observed in either PFC or NSS animals. Within the saline treated swine group there were no significant differences in DCS survival between male (75.00%, N = 24) and female (73.08%, N = 26) swine. Within the PFC treated swine, survival of females (51.85%, N = 27) was significantly lower than males (81.48%, N = 27). In this large animal mixed gender efficacy study in DCS, PFC did not improve mortality or spinal cord injury, but appears safe during recompressive therapy. Gender differences in DCS treatment with PFC will need further study.Cronin WA, Hall AA, Auker CR, Mahon RT. Perfluorocarbon in delayed recompression with a mixed gender swine model of decompression sickness. Aerosp Med Hum Perform. 2018; 89(1):14-18.

Hyperbaric oxygen therapy as adjuvant for treating wound complications after extensive resection for vulvar malignancy

Necrosis, wound breakdown, and infection represent major complications associated with radical vulvectomy. We aimed to analyze the feasibility of hyperbaric oxygen (HBO₂) therapy as an adjunctive treatment for such complications. We performed a retrospective analysis of the medical records, clinical charts, and operative records of vulvar cancer patients who underwent hyperbaric oxygen therapy after extensive surgical resection in our institute between 2012 and 2016, with a comparison of the clinical outcomes of patients with similar surgical procedures andsevere wound complications who did not undergo HBO₂. A total of 16 patients were included in the study. In the subgroup treated with HBO₂, seven patients were identified. Two patients had primary surgery, while five had recurrent surgery (of these, two had previously undergone radiation therapy). Six patients received reconstructive flaps (five myocutaneous and onefasciocutaneous), while one patient had primary suture. Dehiscence, ischemia and necrosis were estimated to cover 30%-80% of the surgical surface area. Surgical debridement was performed in six patients. Daily 90-minute sessions in the hyperbaric chamber were performed at a pressure of 2.2 atmospheres absolute, with partial oxygen pressure of 1672 mbar. Infection control and satisfactory healing were achieved using 10-61 sessions. All patients in the subgroup who did not receive HBO₂ required surgical debridement due to partial or near-total flap necrosis, with two reconstructive interventions required. Hyperbaric oxygen therapy was an efficient adjuvant for wound healing and infection control in managing wound complications after extensive vulvar resections.

Improvement of satisfaction in burn patients receiving adjuvant hyperbaric oxygen therapy

Background: Hyperbaric oxygen (HBO) therapy is an adjuvant treatment in patients with burns. However, evidence regarding the effectiveness of the HBO therapy for the improvement of patient's satisfaction has seldom been discussed; thus, we share our experience in this topic. Aim and Objectives: This study aimed to evaluate the improvement of burn patients' satisfaction after adjuvant HBO therapy. Materials and Methods: This was a retrospective case–control study involving 35 burn patients admitted to our hospital without a history of chronic pain and burn treatments from 2012 to 2015. Group I consisted of 18 burn patients who received HBO therapy to manage burns. The HBO therapy was administered in the hyperbaric chamber and received 60 min of 100% oxygen at a therapeutic pressure at 50 feet for 20 sessions. Group II consisted of 17 burn patients without a history of HBO therapy. Age, gender, total body surface area (TBSA), scar progression, improvement of visual analogue scale score, satisfaction improvement, and infection rate were documented and analyzed. Results: The mean age of Group I (37.0 ± 9.2) was significantly lower than that of Group II (49.4 ± 17.4) (P = 0.015). The mean improvement pain score in Group I (4.7 ± 1.1) was significantly higher than that of Group II (3.6 ± 0.9) (P = 0.004). The mean satisfaction improvement of Group I (3.4 ± 0.5) was significantly higher than that of Group II (2.9 ± 0.6) (P = 0.009). No significant difference was observed between gender, TBSA, debridement times, skin graft times, skin graft surface, infection rate, length of hospital stay, and progression of scar score in both groups, but there was a positive correlation between HBO therapy and the progression of scar score, so does the infection rate. There is no significant interaction between the two factors (HBO and age) on the improvement of pain score and improvement of satisfaction. Conclusion: Evaluation of the results obtained in the study suggests that the HBO therapy has a significant improvement in the pain relieve and satisfaction improvement after control of age factor in patients with thermal burns.

An anti-barotrauma system for preventing barotrauma during hyperbaric oxygen therapy

In the present study, a tympanometry-based anti-barotrauma (ABT) device was designed using eardrum admittance measurements to develop an objective method of preventing barotrauma that occurs during hyperbaric oxygen (HBO₂) therapy. The middle ear space requires active equalization, and barotrauma of these tissues during HBO₂therapy constitutes the most common treatment-associated injury. Decongestant nasal sprays and nasal steroids are used, but their efficacy is questionable to prevent middle ear barotrauma (MEB) during HBO₂ treatment. Accordingly, a tympanometry-based ABT device was designed using eardrum admittance measurements to develop an objective method for preventing MEB, which causes pain and injury, and represents one of the principal reasons for patients to stop treatment. This study was conducted to test a novel technology that can be used to measure transmembrane pressures, and provide chamber attendants with real-time feedback regarding the patient's equalization status prior to the onset of pain or injury. Eardrum admittance values were measured according to pressure changes inside a hyperbaric oxygen chamber while the system was fitted to the subject. When the pressure increased to above 200 daPa, eardrum admittance decreased to 16.255% of prepressurization levels. After pressure equalization was achieved, eardrum admittance recovered to 95.595% of prepressurization levels. A one-way repeated measures analysis of variance contrast test was performed on eardrum admittance before pressurization versus during pressurization, and before pressurization versus after pressure equalization. The analysis revealed significant differences at all points during pressurization (P⟨0.001), but no significant difference after pressure equalization was achieved. This ABT device can provide objective feedback reflecting eardrum condition to the patient and the chamber operator during HBO₂ therapy.

Determining barotrauma in the Pictus catfish, Pimelodus pictus, experimentally exposed to simulated hydropower turbine passage

Hydropower development poses severe threats to the aquatic diversity and ecosystem services. One such threat is the exposure of fish to extreme conditions within hydropower facilities. Fish may suffer rapid decompression when passing through turbines or when entering the draft tubes, which can lead to barotrauma and mortality. We aimed to evaluate the effects of rapid decompression on the Amazonian benthic species Pimelodus pictus (Pictus catfish), by simulating in hypo–hyperbaric chambers. The most frequent injuries in Pictus catfish exposed to simulated rapid decompression were swim-bladder rupture, intestine rupture, internal haemorrhage and embolism. The occurrence and magnitude of internal haemorrhaging and emboli were related to the ratio of pressure change and the decompression timespan, whereas swim-bladder rupture occurred even at relatively low ratios. Emboli was present almost entirely among fish with a ruptured swim bladder. Importantly, all fish were negatively buoyant before exposure to decompression, posing challenges to data analysis. Therefore, barotrauma studies with benthic fish species are deemed to be challenging and are likely to require the use of complementary approaches. Research is needed to understand the state of buoyancy of benthic fish in the wild and to develop methods to accurately replicate these in a controlled testing environment.

Hyperbaric Oxygen Therapy in Necrotizing Soft Tissue Infections: A Retrospective Study.

Necrotizing soft tissue infection is a severe life-threatening disease correlated with high mortality. Until now, therapeutic concepts include antimicrobial, intensive care and surgical interventions, as well as the application of hyperbaric oxygenation (HBO), which still has a controversial status. Evidence of the therapeutic concept of HBO is, so far, limited to positive experiences in case studies and physiological benefits in animal studies. That is why the HBO therapy method is not yet fully established. In this light, a retrospective data analysis was conducted. The analysis involved 91 intensive care patients in the Clinic for Anesthesiology and Surgical Intensive Care at the University Hospital Halle (Saale) who, because of a necrotizing soft tissue infection, were treated with HBO therapy (period of observation from 2008 to second quarter 2017). Treatment outcome was examined with regard to mortality, complications, time spent in the intensive care unit, and functional limitations. The criteria of therapy relevance, therapy management, and conclusions drawn from the treatment results were evaluated. By examining the result of combining all four categories of treatment, we aim to investigate established guidelines and their practicability. We expect treatment with HBO to have no disadvantages compared with acknowledged treatment concepts. This study considers the success of treatment as a result of complying with optimal therapy. In a contribution to establish coverage use and an inventory of hyperbaric chambers, we also aim to create a national case register, so that patients do not have to depend on long and risky transportations.