Effectiveness of hyperbaric chamber ventilation.

INTRODUCTION: Hyperbaric chamber ventilation (HCV) refers to the intentional introduction of fresh gas, whether air, oxygen, or heliox, into a pressurised hyperbaric chamber in order to remove stale or otherwise compromised gas. The minimum required continuous HCV rate is usually determined by mathematical models derived from the contaminant mass balance within a well-stirred compartment. Non-uniform contaminant distribution patterns inside a hyperbaric chamber could emerge and invalidate the predictions of well-stirred models. METHODS: Contaminant distribution was investigated inside a clinical hyperbaric chamber with the aim of comparing well-stirred model predictions with the actual contaminant concentration measurements. RESULTS: Local ventilation effectiveness inside a clinical hyperbaric chamber may be compromised, leading to higher contaminant concentration values compared to the predictions of a mathematical model with a well-stirred assumption. CONCLUSIONS: A well-stirred assumption in mathematical models is a useful simplification that allows reasonably accurate estimates of HCV requirements. However, local ventilation effectiveness values in a particular hyperbaric chamber might vary, with the potential for hazardous contaminant accumulation in under-ventilated zones.

Effectiveness of Hyperbaric Oxygen Therapy in SARS-CoV-2 Pneumonia: The Primary Results of a Randomised Clinical Trial.

Mortality in COVID-19 is mainly associated with respiratory failure, cytokine storm, and macrophage activation. Oxygenation and anti-inflammatory effects of Hyperbaric Oxygen Therapy (HBOT) suggest that it is a promising adjunct treatment for COVID-19. Repeated sessions of HBO with standard COVID-19 therapy were used to reduce the inflammation and increase oxygenation. We evaluated the safety and efficacy of HBOT in avoiding the replacement ventilation and/or ECMO and its effect on the inflammatory process. Twenty-eight moderate-to-severe COVID-19 patients were randomized into control or HBOT group. HBOT patients participated in 5 hyperbaric sessions (60 min). Before and after each session blood gas levels and vital parameters were monitored. Blood samples were collected for extended biochemical tests, blood morphology and immunological assays. There were 3 deaths in the control, no deaths in the HBOT group. No adverse events leading to discontinuation of HBOT were observed and patients receiving HBOT required lower oxygen delivery. We observed decrease in CRP, ferritin and LDH and increase in CD3 in HBOT group compared to control. This study confirmed the feasibility and safety of HBOT in patients with COVID-19 and indicated HBOT can lead to alleviation of inflammation and partial restoration of T cell responses.

Impact of Hyperbaric Oxygen Therapy on Cognitive Functions: a Systematic Review.

Hyperbaric oxygen therapy (HBOT) is a modality of treatment in which patients inhale 100% oxygen inside a hyperbaric chamber pressurised to greater than 1 atmosphere. The aim of this review is to discuss neuropsychological findings in various neurological disorders treated with HBOT and to open new perspectives for therapeutic improvement. A literature search was conducted in the MEDLINE (via PubMed) database from the inception up 10 May 2020. Eligibility criteria included original articles published in English. Case studies were excluded. Full-text articles were obtained from the selected studies and were reviewed on the following inclusion criteria (1) performed cognitive processes assessment (2) performed HBOT with described protocol. Two neuropsychologists independently reviewed titles, abstracts, full texts and extracted data. The initial search retrieved 1024 articles, and a total of 42 studies were finally included after applying inclusion and exclusion criteria. The search yielded controversial results with regard to the efficiency of HBOT in various neurological conditions with cognitive disturbance outcome. To the best of our knowledge this is the first state-of-the art, systematic review in the field. More objective and precise neuropsychological assessment methods are needed to exact evaluation of the efficacy of HBOT for neuropsychological deficits. Future studies should widen the assessment of HBOT effects on different cognitive domains because most of the existing studies have focussed on a single process. Finally, there is a need for further longitudinal studies.

Effect of Hyperbaric Oxygenation on Blood Cytokines and Arginine Derivatives; No Evidence for Induction of Inflammation or Endothelial Injury.

(1) Background: Hyperbaric oxygen therapy (HBOT) uses 100% oxygen delivered at 1.5-3 times the atmospheric pressure in a specialised chamber to achieve supraphysiological oxygen tension in blood and tissues. Besides its target, HBOT may affect inflammation, endothelial function or angiogenesis. This study analysed the effect of HBOT on blood concentrations of factors that may affect these processes in patients with necrotizing soft-tissue infections (NSTI), aseptic bone necrosis (ABN) and idiopathic sudden sensory neural hearing loss (ISSNHL). (2) Methods: Concentrations asymmetric dimethylarginine (ADMA) and other arginine derivatives were measured with liquid chromatography/mass spectrometry, whereas ELISA was used to quantitate vascular endothelial growth factor (VEGF) and cytokines (IL-1, IL-4, IL-6, IL-10, TGF-ß) before and after HBOT in 80 patients (NSTI n = 21, ISSNHL n = 53, ABN n = 6). (3) Results: While some differences were noted between patient groups in ADMA and other arginine derivatives as well as in cytokine concentrations, HBOT did not affect any of these parameters. (4) Conclusions: While cytokines and arginine derivatives concentrations were modified by underlying pathology, hyperbaric oxygenation did not immediately modify it suggesting that it is neutral for inflammation and is not inducing endothelial injury.

Oxygen: A Stimulus, Not "Only" a Drug.

Depending on the oxygen partial pressure in a tissue, the therapeutic effect of oxygenation can vary from simple substance substitution up to hyperbaric oxygenation when breathing hyperbaric oxygen at 2.5-3.0 ATA. Surprisingly, new data showed that it is not only the oxygen supply that matters as even a minimal increase in the partial pressure of oxygen is efficient in triggering cellular reactions by eliciting the production of hypoxia-inducible factors and heat-shock proteins. Moreover, it was shown that extreme environments could also interact with the genome; in fact, epigenetics appears to play a major role in extreme environments and exercise, especially when changes in oxygen partial pressure are involved. Hyperbaric oxygen therapy is, essentially, "intermittent oxygen" exposure. We must investigate hyperbaric oxygen with a new paradigm of treating oxygen as a potent stimulus of the molecular network of reactions.

Spinal cord decompression sickness in an inside attendant after a standard hyperbaric oxygen treatment session.

Medical personnel in hyperbaric treatment centres are at occupational risk for decompression sickness (DCS) while attending patients inside the multiplace hyperbaric chamber (MHC). A 51-year-old male hyperbaric physician, also an experienced diver, was working as an inside attendant during a standard hyperbaric oxygen therapy (HBOT) session (70 minutes at 253.3 kPa [2.5 atmospheres absolute, 15 metres' seawater equivalent]) in a large walk-in MHC. Within 10 minutes after the end of the session, symptoms of spinal DCS occurred. Recompression started within 90 minutes with an infusion of lignocaine and hydration. All neurological symptoms resolved within 10 minutes breathing 100% oxygen at 283.6 kPa (2.8 atmospheres absolute) and a standard US Navy Treatment Table 6 was completed. He returned to regular hyperbaric work after four weeks of avoiding hyperbaric exposures. Transoesophageal echocardiography with a bubble study was performed 18 months after the event without any sign of a persistent (patent) foramen ovale. Any hyperbaric exposure, even within no-decompression limits, is an essential occupational risk for decompression sickness in internal hyperbaric attendants, especially considering the additional risk factors typical for medical personnel (age, dehydration, tiredness, non-optimal physical capabilities and frequent problems with the lower back).

High-Altitude Decompression Sickness Treated with Hyperbaric Therapy and Extracorporeal Oxygenation.

BACKGROUND: High-altitude decompression sickness (HADCS) is a rare condition that has been associated with aircraft accidents. To the best of our knowledge, the present paper is the first case report of a patient treated for severe HADCS using recompression therapy and veno-venous extracorporeal oxygenation (VV-ECMO) with a complete recovery.CASE REPORT: After depressurization of a cabin, the 51-yr-old jet pilot was admitted to the Military Institute of Medicine with a life-threatening HADCS approximately 6 h after landing from a high-altitude flight, in a dynamically deteriorating condition, with progressing dyspnea and edema, reporting increasing limb paresthesia, fluctuating consciousness, and right-sided paresis. Hyperbaric oxygen therapy in the intensive care mode was initiated. A therapeutic recompression with U.S. Navy Treatment Table 6 was performed with neurological improvement. Due to cardiovascular collapse, sedation, mechanical ventilation, and significant doses of catecholamines were started, followed by continuous veno-venous hemodialysis. In the face of disturbances in oxygenation, during the second day of treatment the patient was commenced on veno-venous extracorporeal oxygenation. Over the next 6 d, the patient's condition slowly improved. On day 7, VV-ECMO was discontinued. On day 19, the patient was discharged with no neurological deficits.DISCUSSION: We observed two distinct stages during the acute phase of the disease. During the first stage, signs of hypoperfusion, neurological symptoms, and marbled skin were observed. During the second stage, multiple organ dysfunction dominated, including heart failure, pulmonary edema, acute kidney injury, and fluid overload, all of which can be attributed to extensive endothelial damage.Siewiera J, Szalanski P, Tomaszewski D, Kot J. High-altitude decompression sickness treated with hyperbaric therapy and extracorporeal oxygenation. Aerosp Med Hum Perform. 2020; 91(2):106-109.

The Hyperbaric Protective Tube: A housing for a left ventricular assist device (LVAD) in a multiplace hyperbaric chamber.

INTRODUCTION: During a hyperbaric oxygen therapy (HBOT) session, every medical device that is used within the hyperbaric chamber is exposed to several hazards, including an increased ambient pressure and partial pressure of oxygen. In Europe, all medical devices marketed and/or sold for use in hyperbaric conditions must be tested by the manufacturer and marked 'CE' if approved. At the moment, no left ventricular assist device (LVAD) has been formally approved and CE-marked for HBOT. CASE: A 65-year-old male was referred to our Hyperbaric Centre for HBOT due to a persistent life-threating soft tissue infection of the non-removable wire connecting the external controller with the pump implanted into the left ventricle of the heart (Heartware LVAD). The aim of the intervention reported here was to safely conduct HBOT sessions with this non-CE marked medical device. After risk analysis, the decision was made to isolate the external part of the LVAD (controller and batteries) from the ambient conditions in the hyperbaric chamber by placing it in a pressure-resistant housing that was vented to the external atmosphere. The housing, a 'Hyperbaric Protective Tube' was built and tested, and the resulting operating procedures were practiced by personnel involved in the patient's care. Thirty uneventful HBOT standard sessions were conducted with subsequent clinical improvement of the soft tissue infection, resulting in an extended timeframe for awaiting heart transplantation. CONCLUSION: An isolation housing that vents into the dumping system of the hyperbaric chamber allows for the safe use of critical medical devices without prior testing for their compatibility with the hyperbaric environment.

Correction to Mathieu D, Marroni A, Kot J: Tenth European Consensus Conference on Hyperbaric Medicine: recommendations for accepted and non-accepted clinical indications and practice of hyperbaric oxygen treatment. Diving Hyperb Med. 2017 Mar;47(1):24-32.

Consistent with the Committee on Publication Ethics guidelines, we the above authors are initiating a partial retraction and correction of our paper: Mathieu D, Marroni A, Kot J: Tenth European Consensus Conference on Hyperbaric Medicine: recommendations for accepted and non-accepted clinical indications and practice of hyperbaric oxygen treatment. Diving Hyperb Med. 2017 Mar;47(1):24-32. We wish to make the following statement: "Regardless of the strict process of editing and proof-reading of tables included in the above-mentioned publication, we received some comments from readers which showed us that imperfect layout of Table 1 and incorrect layout of Table 2 changed significantly the conclusions which could be drawn from them. Table 1 described the relation between strength of recommendations given by the Jury of the Consensus Conference and the level of evidence based on the GRADE system. There should be a clear and straight relation showing that Level 1 "strong recommendation" should be based on GRADE A "high level of evidence (LOE)", Level 2 "weak recommendation" should be based on GRADE B "moderate LOE", Level 3 "neutral recommendation" should be based on GRADE C "low LOE" and finally no recommendation should be given when only GRADE D "very low LOE" are present. Note that there is no change to the content of the table, but only visual representation of this relationship. Table 2 has been incorrectly printed. In fact, there is no GRADE A LOE. All X marks placed in the column A should be moved to the right, to GRADE B LOE. In the same way, all X marks placed in the column B should be moved to the right, to GRADE C LOE. We voluntarily retract these tables from the above-mentioned publication, expressing our regret for the situation."

ECHM Consensus Conference and levels of evidence - Reply.

Dr Sherlock asks for clarification on the approach adopted by the European Committee on Hyperbaric Medicine (ECHM) to assessing evidence for establishing indications for hyperbaric oxygen treatment (HBOT). Firstly, regardless of the strict process of editing and proof-reading of tables included in the above-mentioned publication, we received comments from some readers that identified imperfect layout of Table 1 and incorrect layout of Table 2 which significantly changed the conclusions to be drawn from them. This concerned both the details of the methodology used and description of the ECHM recommendations and associated levels of evidence. Therefore, those tables are republished in their correct forms in this issue, hoping that this will explain at least some of the doubts and misunderstandings. Both the Editor and ourselves apologise for these errors of publication. Secondly, in the ECHM Consensus Conference methodology, we scored the evidence for clinical studies requiring double-blind randomised controlled trials (RCT) as Level A and B when, at the same time, some scoring scales require simply 'RCT', as correctly pointed out by Dr Sherlock. Long experience in organising evidence based medicine (EBM) meetings and discussions has taught us that RCTs that are not double blinded are often criticised as having serious potential bias and so are denied as level A evidence. Although we acknowledge that double blinding a clinical study in HBOT is a source of difficulty, we chose a priori to consider only double-blinded RCTs in our grading scale to avoid endless discussions about this potential bias. We are well aware that doing so means that Level A evidence is a difficult target for the hyperbaric community. We agree that many evidence scoring systems have a low level of inter-observer agreement. This is why we treat the Consensus Conference as a valuable tool that provides a better opportunity for discussing the evidence than analysis by a small group of 'experts'. This is because the whole process is transparent and available to all participants' comments and input. The final process of voting by the audience after the general discussion thus truly reflects the position of the professional hyperbaric community in Europe on the issued recommendations. By these two mechanisms, the blind application of disputable evidence scoring systems may be avoided or, at least, decreased. Thirdly, the problem of 'sham' treatments in hyperbaric research has been raised. While this has been discussed many times in the past, hyperbaric research is not the sole field where such sham treatment raises some difficulty. Surgery is probably the best example where RCTs with control arms utilising sham surgical procedures (possibly including the administration of anaesthesia) are rare and can raise major ethical problems. Nevertheless, from an EBM viewpoint, the difficulty of designing a double-blind study is never taken into account during evaluation of clinical studies. Finally, Dr Sherlock pointed out her doubts on the recommendations issued by the ECHM on idiopathic sudden sensorineural hearing loss (ISSHL). While there is no possibility to cite here the full experts' report on that issue presented during the conference, we understand that a detailed report from the Conference is being prepared for publication. In brief, the strength of evidence has been scored as Level B, in general agreement with the last Cochrane review and the UHMS Committee report. Based on this level of evidence, the Type 1 recommendation was issued with the agreement of the large majority of the Consensus Conference participants.

Tenth European Consensus Conference on Hyperbaric Medicine: recommendations for accepted and non-accepted clinical indications and practice of hyperbaric oxygen treatment.

The tenth European Consensus Conference on Hyperbaric Medicine took place in April 2016, attended by a large delegation of experts from Europe and elsewhere. The focus of the meeting was the revision of the European Committee on Hyperbaric Medicine (ECHM) list of accepted indications for hyperbaric oxygen treatment (HBOT), based on a thorough review of the best available research and evidence-based medicine (EBM). For this scope, the modified GRADE system for evidence analysis, together with the DELPHI system for consensus evaluation, were adopted. The indications for HBOT, including those promulgated by the ECHM previously, were analysed by selected experts, based on an extensive review of the literature and of the available EBM studies. The indications were divided as follows: Type 1, where HBOT is strongly indicated as a primary treatment method, as it is supported by sufficiently strong evidence; Type 2, where HBOT is suggested as it is supported by acceptable levels of evidence; Type 3, where HBOT can be considered as a possible/optional measure, but it is not yet supported by sufficiently strong evidence. For each type, three levels of evidence were considered: A, when the number of randomised controlled trials (RCTs) is considered sufficient; B, when there are some RCTs in favour of the indication and there is ample expert consensus; C, when the conditions do not allow for proper RCTs but there is ample and international expert consensus. For the first time, the conference also issued 'negative' recommendations for those conditions where there is Type 1 evidence that HBOT is not indicated. The conference also gave consensus-agreed recommendations for the standard of practice of HBOT.

Hyperbaric oxygen therapy for intensive care patients: position statement by the European Committee for Hyperbaric Medicine.

Many of the accepted indications for hyperbaric oxygen treatment (HBOT) may occur in critically ill patients. HBOT itself may cause a number of physiological changes which may further compromise the patient's state. Guidelines on the management of critically ill patients in a hyperbaric facility have been founded on the conclusions of the 2007 European Committee for Hyperbaric Medicine (ECHM) meeting. With regard to patient management, HBOT should be included in the overall care of ICU patients only after a risk/benefit assessment related to the specifics of both the hyperbaric centre and the patient's clinical condition and should not delay or interrupt their overall management. Neither patient monitoring nor treatment should be altered or stopped due to HBOT, and any HBOT effects must be strictly evaluated and appropriately mitigated. With regard to the hyperbaric facility itself, the hyperbaric chamber should be specifically designed for ICU patients and should be fully equipped to allow continuation of patient monitoring and treatment. The hyperbaric chamber ideally should be located in, or around the immediate vicinity of the ICU, and be run by a sufficiently large and well-trained team of physicians, nurses, chamber operators and technicians. All devices to be introduced into the chamber should be evaluated, tested and acknowledged as safe for use in a hyperbaric environment and all procedures (standard and emergency) should be tested and written before being implemented.

Staffing and training issues in critical care hyperbaric medicine.

The integrated chain of treatment of the most severe clinical cases that require hyperbaric oxygen therapy (HBOT) assumes that intensive care is continued while inside the hyperbaric chamber. Such an approach needs to take into account all the risks associated with transportation of the critically ill patient from the ICU to the chamber and back, changing of ventilator circuits and intravascular lines, using different medical devices in a hyperbaric environment, advanced invasive physiological monitoring as well as medical procedures (infusions, drainage, etc) during long or frequently repeated HBOT sessions. Any medical staff who take care of critically ill patients during HBOT should be certified and trained according to both emergency/intensive care and hyperbaric requirements. For any HBOT session, the number of staff needed for any HBOT session depends on both the type of chamber and the patient's status--stable, demanding or critically ill. For a critically ill patient, the standard procedure is a one-to-one patient-staff ratio inside the chamber; however, the final decision whether this is enough is taken after careful risk assessment based on the patient's condition, clinical indication for HBOT, experience of the personnel involved in that treatment and the available equipment.

High Pressure Injection Injury of the Thumb. Case Study.

High-pressure injection injury (HPII) is a rare severe hand trauma associated with high rates of complications and amputations of the peripheral parts of the fingers and permanent hand dysfunction. Early detection and treatment are crucial as any delay may result in a considerable functional deficit of the affected limb or amputation. The rate of amputation following HPII is 48%. This case report aims mainly to present the problem of HPII and general standards of management of such injuries. The routine use of supportive treatment in hyperbaric chambers, in the absence of contraindications, is also encouraged.