Diving & hyperbaric medicine: Journals & articles

Objectives: We aimed to determine the value of thiol/disulfide homeostasis (TDH) as an oxidative stress marker in hyperbaric oxygen therapy (HBOT) and normobaric oxygen therapy (NBOT) patients presenting with carbon monoxide poisoning. In addition, we compared the effect of HBOT and NBOT on thiol/disulfide parameters.

Methods: This prospective study included 66 patients and 67 healthy individuals who presented to the emergency department. We evaluated serum native thiol, disulfide, and total thiol levels in 8 patients who received HBOT and 58 who received NBOT. We also compared pre- and post-treatment levels of disulfide/native thiol, disulfide/total thiol, and native thiol/total thiol.

Results: There was a statistically significant difference between the case and control groups in native thiol and total thiol before NBOT (p < 0.006, p < 0.006). We also found a statistically significant difference between the groups in pre- and post-NBOT levels of native thiol and total thiol (p < 0.002, p < 0.003). However, our comparison of HBOT and NBOT showed no significant difference in the levels of native thiol, total thiol, disulfide, disulfide/native thiol, disulfide/total thiol, or native thiol/total thiol (p < 0.544, p < 0.860, p < 0.644, p < 0.409, p < 0.409, p < 0.409, respectively).

Conclusions: Although thiol/disulfide parameters increased in patients receiving HBOT or NBOT, changes in antioxidant levels did not differ significantly between NBOT and HBOT patients. This suggests that NBOT and HBOT have similar effects on thiol/disulfide parameters. NBOT alone may be effective in centers that do not have HBOT facilities.

BACKGROUND Hyperbaric oxygen (HBO₂) therapy in a multiplace chamber is the standard treatment for severe altitude decompression illness (DCI). However, some hospitals may only have a monoplace chamber. Herein, we present the case of a patient with severe altitude DCI caused by rapid decompression during an actual flight operation that was successfully treated through emergency HBO₂ therapy with the Hart-Kindwall protocol, a no-air-break tables with the minimal-pressure oxygen approach in a monoplace chamber due to unavailability of rapid access to a multiplace chamber. CASE REPORT A 34-year-old male aviator presented with chest pain, paresthesia, and mild cognitive impairment following rapid decompression 20 minutes after take-off, which comprised 10 minutes of reaching a height of 10 058 m (33 000 feet) and 10 minutes of cruising at that altitude. He then initiated flight descent and landing. He visited a primary clinic, and severe DCI was suggested clinically. However, since the closest hospital with a multiplace chamber was a 3-hour drive away, we provided emergency HBO₂ therapy with the Hart-Kindwall protocol in a monoplace chamber at a nearby hospital 4 hours after the initial decompression. He recovered fully and returned to flight duty 2 weeks later. CONCLUSIONS Emergency HBO₂ therapy with the Hart-Kindwall protocol in a monoplace chamber may be a suitable option for severe DCI, especially in remote locations with no access to facilities with a multiplace chamber. However, prior logistical coordination must be established to transfer patients to hospitals with multiplace chambers if their symptoms do not resolve.

Background: The study was designed to evaluate the influence of hyperbaric oxygenation therapy (HBOT) on the parotid gland in patients following radiotherapy for head and neck tumours.

Patients and methods: HBOT response was monitored by 3T magnetic resonance imaging (MRI) using T 2 mapping and subsequent measurement of mean T 2 and T 2 variability as well as by salivary tests (salivary flow, buffer capacity, and pH). Eighteen patients previously treated with irradiation doses between 50 and 80 Gy as well as 18 healthy gender and age matched controls were enrolled. MRI was performed prior to HBOT (40.2 ± 20 months after radiotherapy) and after 20 daily HBOT at 2.5 ATA (absolute atmosphere). Each HBOT consisted of breathing 100% oxygen for 90 minutes.

Results: Significant differences in mean T 2 prior to HBOT were observed between the ipsilateral irradiated (121 ± 20 ms), contralateral parotids (107 ± 21) and control group (96 ± 12 ms). A positive correlation in patients between T 2 variability and irradiation dose was detected in contralateral parotids before HBOT (R = 0.489, p = 0.0287). In addition, negative correlations were observed between mean T 2 in the ipsilateral as well as the contralateral gland and salivary flow before and after HBOT. Negative correlations between mean T 2, T 2 variability and pH of unstimulated saliva were also observed in the sides of parotid before and after HBOT.

Conclusions: The study confirmed that T 2 mapping had a potential for monitoring the differences between irradiated and normal parotid glands. It could also be useful in the assessment of the glandular tissue response to HBOT.

Background: Previously published short-term results (week 16) of this trial showed a significant improvement in clinical, radiologic and biochemical outcomes in Crohn's disease patients with therapy-refractory perianal fistulas after treatment with hyperbaric oxygen therapy.

Objective: To assess the long-term (week 60) efficacy, safety and feasibility of hyperbaric oxygen therapy in perianal fistula in Crohn's disease.

Methods: Crohn's disease patients with high perianal fistula(s) failing conventional treatment >6 months were included. Exclusion criteria were presence of a stoma, rectovaginal fistula(s) and recent changes in treatment regimens. Patients received 40 hyperbaric oxygen sessions and outcomes were assessed at week 16 and week 60.

Results: Twenty patients were included (median age 34 years). At week 16, median scores of the perianal disease activity index and modified Van Assche index (co-primary outcomes) decreased from 7.5 (95% CI 6-9) to 4 (95% CI 3-6, p < 0.001) and 9.2 (95% CI 7.3-11.2) to 7.3 (95% CI 6.9-9.7, p = 0.004), respectively. At week 60, the respective scores remained significantly lower than baseline: 4 (95% CI 3-7, p < 0.001) and 7.7 (95% CI 5.2-10.2, p = 0.003). Perianal disease activity index score of 4 or less (representing inactive perianal disease) was observed in 13 patients at week 16 and 12 patients at week 60. Using fistula drainage assessment, 12 and 13 patients showed a clinical response at week 16 and 60, respectively, and clinical remission was achieved in four patients for both time points. At week 16, a statistically significant biochemical improvement (C-reactive protein and faecal calprotectin levels) was found, but this effect was no longer significant at week 60.

Conclusions: The clinical and radiologic improvement of perianal fistula in Crohn's disease, that was found at week 16 after treatment with hyperbaric oxygen therapy, is maintained at 1-year follow-up.

Purpose: It is speculated that diving might be harmful to the nervous system. The aim of this study was to determine if established markers of neuronal injury were increased in the blood after diving.

Methods: Thirty-two divers performed two identical dives, 48 h apart, in a water-filled hyperbaric chamber pressurized to an equivalent of 42 m of sea water for 10 min. After one of the two dives, normobaric oxygen was breathed for 30 min, with air breathed after the other. Blood samples were obtained before and at 30-45 and 120 min after diving. Concentrations of glial fibrillary acidic, neurofilament light, and tau proteins were measured using single molecule array technology. Doppler ultrasound was used to detect venous gas emboli.

Results: Tau was significantly increased at 30-45 min after the second dive (p < 0.0098) and at 120 min after both dives (p < 0.0008/p < 0.0041). Comparison of matching samples showed that oxygen breathing after diving did not influence tau results. There was no correlation between tau concentrations and the presence of venous gas emboli. Glial fibrillary acidic protein was decreased 30-45 min after the first dive but at no other point. Neurofilament light concentrations did not change.

Conclusions: Tau seems to be a promising marker of dive-related neuronal stress, which is independent of the presence of venous gas emboli. Future studies could validate these results and determine if there is a quantitative relationship between dive exposure and change in tau blood concentration.

Introduction: Hyperbaric chambers and underwater environments are challenging and at risk of serious accidents. Personnel aiming to assist patients and subjects should be appropriately trained, and several courses have been established all over the world. In healthcare, simulation is an effective learning technique. However, there have been few peer-reviewed articles published in the medical literature describing its use in diving and hyperbaric medicine.

Methods: We implemented the curriculum of the Master's degree in hyperbaric and diving medicine held at the University of Padova with emergency medicine seminars created by the faculty and validated by external experts. These seminars integrated traditional lectures and eight in situ simulation scenarios.

Results: For the hyperbaric medicine seminar, simulations were carried out inside a real hyperbaric chamber at the ATIP Hyperbaric Treatment Centre, only using air and reproducing compression noise without pressurization to avoid damages to the manikins. The four scenarios consisted of hyperoxic seizures, pneumothorax, hypoglycemia, and sudden cardiac arrest. Furthermore, we added a hands-on session to instruct participants to prepare an intubated patient undergoing hyperbaric oxygen treatment with a checklist and simulating the patient transfer inside and outside the hyperbaric chamber. The diving medicine seminar was held at the Y-40 The Deep Joy pool in Montegrotto Terme (Italy), also involving SCUBA/breath-hold diving (BHD) instructors to rescue subjects from the water. These diving medicine scenarios consisted of neurologic syndrome ("taravana/samba") in BHD, drowning of a breath-hold diver, pulmonary barotrauma in BHD, and decompression illness in a SCUBA diver.

Conclusion: With this experience, we report the integration of simulation in the curriculum of a teaching course in diving and hyperbaric medicine. Future studies should be performed to investigate learning advantages, concept retention, and satisfaction of participants.

Purpose: The aim of this study was to compare intrathecal 1% chloroprocaine with 2% hyperbaric prilocaine in the setting of ambulatory knee arthroscopy. We hypothesized that complete resolution of the sensory block was faster with chloroprocaine.

Methods: Eighty patients scheduled for knee arthroscopy were included in this prospective randomized double-blind study. Spinal anesthesia was performed with either chloroprocaine (50 mg) or hyperbaric prilocaine (50 mg). Characteristics of sensory and motor blocks and side effects were recorded.

Results: Mean time to full sensory block recovery was shorter with chloroprocaine (169 (56.1) min vs 248 (59.4)). The characteristics of the sensory blocks were similar at the T12 dermatome level between the two groups. Differences appeared at T10: the percentage of patients with a sensory block was higher, onset quicker and duration longer with hyperbaric prilocaine. The number of patients with a sensory block at T4 dermatome level in both groups was minimal. Times to full motor recovery were identical in both groups (85 (70-99) vs 86 (76-111) min). Time to spontaneous voiding was shorter with chloroprocaine (203 (57.6) min vs 287.3 (47.2) min). Incidence of side effects was low in both groups.

Conclusions: When considering the characteristics of the sensory block, the use of chloroprocaine may allow an earlier discharge of patients. Cephalic extension was to a higher dermatomal level and the sensory block at T10 level was of prolonged duration with hyperbaric prilocaine, suggesting that the choice between the two drugs should also be performed based on the level of the sensory block requested by the surgery. This study is registered in the US National Clinical Trials Registry, registration number: NCT030389 , the first of February 2017, Retrospectively registered.

Abstract
Background: Medical support for space exploration missions must prepare for severe medical events in conditions of microgravity. A key component to managing these events is techniques of airway management. The aim of the present trial is to compare airway management devices in simulated microgravity.

Methods: In this randomized cross-over trial (RCT), four different devices were compared under simulated microgravity conditions utilizing a neutrally buoyant free-floating underwater manikin and poolside in normal gravity (control group). The primary endpoint was the successful placement of the airway device. The secondary endpoints were the number of attempts and the duration of each attempt.

Results: A total of 20 participants performed placement of each device in both gravity conditions in an Airway mannequin. The fastest time to initial ventilation in simulated microgravity was possible with the laryngeal tube (18.9 ± 8 seconds) followed by laryngeal mask (20.1 ± 9 seconds). The I-gel® supraglottic airway device required substantially more time for successful insertion in simulated microgravity (35.4 ± 25 seconds) as did endotracheal tube intubation by direct laryngoscopy (70.4 ± 35 seconds). Simulated microgravity conditions prolonged time to initial ventilation by 3.3 seconds (LM), 3.9 seconds (LT), 19.9 seconds (I-gel) and 43.1 seconds (endotracheal intubation, ETI) when compared to poolside attempts in normogravity.

Conclusion: In simulated microgravity conditions, use of the laryngeal tube or laryngeal mask provided the quickest time to initial ventilation, without deliberate tethering of the mannequin and rescuer to a fixed surface. Endotracheal intubation required significantly longer procedure times and, thus, was considered insufficient for clinical use in microgravity.

Abstract
Pneumatosis cystoides intestinalis (PCI) is characterized by gas-filled cysts within gastrointestinal tract wall from esophagus to rectum, with preferential involvement of large and small intestine. PCI is rare with an estimated incidence of 0.03 to 0-2% in general population. PCI can be distinguished into idiopathic (15%) or secondary (85%) and the clinical picture ranges from completely asymptomatic to life-threatening intraabdominal complications. Although etiology of PCI appears to be multifactorial, the exact pathophysiology is poorly understood and two main theories have been proposed (mechanical and bacterial). Over the last decades, an enormous therapeutic armamentarium was considered in PCI's management, including hyperbaric oxygen therapy (HBOT). Treatment comprises conservative treatment in mild cases to surgery in highly symptomatic and complicated PCI. In the late 70s, HBOT started to be used in selected cases of PCI not responding to conservative measures. Since then, several case reports, case series, and reviews have been published in the literature with variable outcomes. The overall response rate and complete response were 92.1% (n = 82/89) and 65.2% (n = 58/89), respectively, with a median follow-up of 7 months. Furthermore, HBOT is extremely safe, with few reported complications in the literature when used for PCI. Nevertheless, a randomized, controlled, and double-blind clinical trial is unlikely to occur given the rarity of PCI, logistical issues of HBOT, and methodological considerations related to adequate blinding with a sham-controlled group. HBOT in combination with personalized diet and antibiotics may be beneficial for moderate to severe PCI in patients with no indication for emergency exploratory laparotomy. The purpose of this article is to synthesize the existing data, analyse results of previous studies, identify gaps in knowledge, and discuss PCI' management, including the proposal of an algorithm, with a special focus on HBOT.

Abstract
Introduction: Hyperbaric oxygen therapy (HBOT) is a commonly used treatment for a variety of medical issues, including more than a dozen currently approved uses. However, there are alternative proposed uses that have significant implications among an active duty military or veteran population as treatments for PTSD, mild traumatic brain injury (mTBI), and traumatic brain injury (TBI). These applications have seen a recent groundswell of support from the operator and veteran communities, raising the visibility of using HBOT for alternative applications. The current review will cover the existing evidence regarding alternative uses of HBOT in military medicine and provide several possibilities to explain the potential conflicting evidence from empirical results.

Materials and methods: There were no inclusion or exclusion criteria for articles addressing currently approved HBOT uses as covered under the military health system. These references were provided for comparison and illustration as needed. For alternative HBOT uses, the review focuses explicitly upon three alternative uses in PTSD, mTBI, and TBI. The review addresses any piece of case study evidence, observational data, quasi-experimental design, or randomized-controlled trial that explored any or a combination of these issues within an active duty population, a veteran population, or a civilian population.

Results: The existing medical evidence does not support a consensus viewpoint for these alternative uses of HBOT. Based on the literature review, there are four competing positions to explain the lack of consistency among the empirical results. These possibilities are described in no particular order. First, an explanation suggests that the results are because of placebo effects. The combination of participant expectations and subjective symptom reporting creates the potential that reported improvements are because of placebo rather than casual mechanisms. Second, another position suggests that experiments have utilized sham conditions which induced therapeutic benefits. If sham conditions have actually been weakened active treatment conditions, rather than placebo controls, it could explain the lack of observed significant differences in randomized clinical trials. Third, there has been a substantial amount of heterogeneity both in the symptoms treated and the treatments applied. This heterogeneity could explain the inconsistency of the data and the difficulty in reaching a consensus viewpoint. Fourth, the HBOT treatments may actively treat some tangential medical issue the patient is having. The treatment would thus promote an environment of healing without directly treating either PTSD, mTBI, or TBI, and the reduction in orthogonal medical issues facilitates a pathway to recovery by reducing tangential medical problems.

Conclusions: The mixed empirical evidence does not support recommending HBOT as a primary treatment for PTSD, mTBI, or TBI. If applied under the supervision of a licensed military medical professional, the consistently safe track record of HBOT should allow it to be considered as an alternative treatment for PTSD, mTBI, or TBI once primary treatment methods have failed to produce a benefit. However, the evidence does warrant further clinical investigation with particular emphasis on randomized clinical trials, better placebo controls, and a need to develop a consistent treatment protocol.

Abstract
Background: Central airway stenosis (CAS) is a severe airway complication after lung transplantation associated with bronchial ischemia and necrosis. We sought to determine whether hyperbaric oxygen therapy (HBOT), an established treatment for tissue ischemia, attenuates post-transplant bronchial injury.

Methods: We performed a randomized, controlled trial comparing usual care with HBOT (2 atm absolute for 2 hours × 20 sessions) in subjects with extensive airway necrosis 4 weeks after transplantation. Endobronchial biopsies were collected at 4, 7, and 10 weeks after transplantation for a quantitative polymerase chain reaction. Coprimary outcomes were incidence of airway stenting and acute cellular rejection (ACR) at 1 year.

Results: The trial was stopped after enrolling 20 subjects (n = 10 per group) after a pre-planned interim analysis showed no difference between usual care and HBOT groups in stenting (both 40%), ACR (70% and 40%, respectively), or CAS (40% and 60%, respectively). Time to first stent placement (median [interquartile range]) was significantly shorter in the HBOT group (150 [73-150] vs 186 [167-206] days, p < 0.05). HIF gene expression was significantly increased in donor tissues at 4, 7, and 10 weeks after transplantation but was not altered by HBOT. Subjects who developed CAS or required stenting had significantly higher HMOX1 and VEGFA expression at 4 weeks (both p < 0.05). Subjects who developed ACR had significant FLT1, TIE2, and KDR expression at 4 weeks (all p < 0.05).

Conclusions: Incidence of CAS is high after severe, established airway necrosis after transplantation. HBOT does not reduce CAS severity or stenting. Elevated HMOX1 and VEGFA expressions appear to associate with airway complications.

Abstract
Studies have suggested that hyperbaric oxygen therapy (HBOT) is effective in the healing of diabetic foot ulcer (DFU); however, there is a lack of consensus. Therefore, to assess the efficacy of HBOT on diabetic foot ulcer among diabetic patients, controlled clinical trials were searched through PubMed, EMBASE, Clinical key, Ovid Discovery, ERMED, Clinical Trials.gov databases for randomized controlled trials (RCTs) and other sources until 15 September 2020. Studies that evaluated the effect of HBOT on diabetic foot ulcer, complete healing, amputation, adverse events, ulcer reduction area, and mortality rate were included. Of 1984 study records screened, 14 studies (768 participants) including twelve RCTs, and two CCTs were included as per inclusion criteria. The results with pooled analysis have shown that HBOT was significantly effective in complete healing of diabetic foot ulcer (OR = 0.29; 95% CI 0.14-0.61; I2 = 62%) and reduction of major amputation (RR = 0.60; 95% CI 0.39-0.92; I2 = 24%). Although, it was not effective for minor amputations (RR = 0.82; 95% CI 0.34-1.97; I2 = 79%); however, less adverse events were reported in standard treatment group (RR = 1.68; 95% CI 1.07-2.65; I2 = 0%). Nevertheless, reduction in mean percentage of ulcer area and mortality rate did not differ in HBOT and control groups. This review provides an evidence that hyperbaric oxygen therapy is effective as an adjunct treatment measure for the diabetes foot ulcers. These findings could be generalized cautiously by considering methodological flaws within all studies.

Abstract
It has been shown that one recreational SCUBA (rSCUBA) diving session is sufficient to cause changes in plasma level of cardiovascular (CV) and muscular biomarkers. To explore whether repetitive rSCUBA diving triggers an adaptive response of the CV, muscular, and immune system, we measured the cardiac damage (NT-proBNP, hs-TnI, and CK-MB), muscle damage (myoglobin (Mb), galectin-3, CK, and LDH), vascular endothelial activation (ET-1 and VEGF), and inflammatory (leukocyte count (Lkc), CRP, and IL-6) biomarkers. A longitudinal intervention study included divers (N = 14) who conducted one dive per week over 5 weeks at the depth of 20-30 m for 30 min after a non-dive period of 5 months. The blood samples were collected before and after the first, third, and fifth dives and specific biomarkers were measured in plasma or serum by the standard laboratory methods. The concentrations of the majority of measured biomarkers increased after every single dive; the exception was ET-1 concentration that decreased. The cumulative effect of five dives has been reflected in diminishing changes in hs-TnI, Mb, galectin-3, ET-1, VEGF, and IL-6 levels, and more pronounced increases in NT-proBNP and hs-CRP levels. The median values of all measured biomarkers in all time points, except Mb, remained within the corresponding reference range. Repeatedly performed rSCUBA diving activates an adaptive response of the CV, muscular, and immune system that is reflected in changes in the specific biomarker concentration.

This journal (formerly Aviation, Space, and Environmental Medicine), representing the members of the Aerospace Medical Association, is published monthly for those interested in aerospace medicine and human performance. It is devoted to serving and supporting all who explore, travel, work, or live in hazardous environments ranging from beneath the sea to the outermost reaches of space.

Diving and Hyperbaric Medicine (DHM) is published quarterly by the South Pacific Medicine Underwater Medicine Society and the European Underwater and Baromedical Society.

The Undersea and Hyperbaric Medicine is the UHMS' quarterly, peer-reviewed journal.