Recommendations on scuba diving in Birt-Hogg-Dubé syndrome.

INTRODUCTION: Although very uncommon, severe injury and death can occur during scuba diving. One of the main causes of scuba diving fatalities is pulmonary barotrauma due to significant changes in ambient pressure. Pathology of the lung parenchyma, such as cystic lesions, might increase the risk of pulmonary barotrauma. AREAS COVERED: Birt-Hogg-Dubé syndrome (BHD), caused by pathogenic variants in the FLCN gene, is characterized by skin fibrofolliculomas, an increased risk of renal cell carcinoma, multiple lung cysts and spontaneous pneumothorax. Given the pulmonary involvement, in some countries patients with BHD are generally recommended to avoid scuba diving, although evidence-based guidelines are lacking. We aim to provide recommendations on scuba diving for patients with BHD, based on a survey of literature on pulmonary cysts and pulmonary barotrauma in scuba diving. EXPERT OPINION: In our opinion, although the absolute risks are likely to be low, caution is warranted. Given the relative paucity of literature and the potential fatal outcome, patients with BHD with a strong desire for scuba diving should be informed of the potential risks in a personal assessment. If available a diving physician should be consulted, and a low radiation dose chest computed tomography (CT)-scan to assess pulmonary lesions could be considered.

Frostbite: a treatment guideline for prehospital treatment in a military environment.

Frostbite remains a severe medical condition that causes long-lasting sequelae and can threaten military operations. Information on prehospital treatment of frostbite is scarce and existing guidelines are aimed at the general population.This paper provides a guideline on prehospital emergency care of frostbite in the (Netherlands) Armed Forces. The insights gained from studies reporting on frostbite treatment in the prehospital setting were combined with the expert opinions of the authors and applied to the military context. The resulting guideline consists of two stages: (prolonged) field care and care at a Medical Treatment Facility. The cornerstones are rewarming in warm water and evacuation to a medical facility. Additional aspects of prehospital treatment are rehydration, proper analgesia, non-steroidal anti-inflammatory drugs and wound care.We suggest further collaboration among North Atlantic Treaty Organization partners and other affiliated nations, focusing on the full spectrum of military injury management including state-of-the-art aftercare, long-lasting sequelae and return to duty after frostbite.

Frostbite: a systematic review on freezing cold injuries in a military environment.

BACKGROUND: Military practice or deployment in extreme conditions includes risks, dangers and rare disorders. One of the challenges is frostbite; however, current literature does not provide an overview of this condition in a military context. This review aims to map the incidence, risk factors and outcome of frostbite in military casualties in the armed forces. METHODS: A systematic literature search on frostbite (freezing cold injuries) in military settings from 1995 to the present was performed. A critical appraisal of the included articles was conducted. Data on incidence, risk factors, treatment and outcome were extracted. RESULTS: Fourteen studies were included in our systematic review. Most studies of frostbite in a military setting were published nearly half a century ago. Frostbite incidence has declined from 7% to around 1% in armed forces in arctic regions but could be as high as 20% in small-scale arctic manoeuvres. Overall and military-specific risk factors for contracting frostbite were identified. CONCLUSION: During inevitable arctic manoeuvres, frostbite is a frequently diagnosed injury in service members. Postfreezing symptoms often persist after severe frostbite injury, which decreases employability within the service. Over time, military practice has changed considerably, and modern protective materials have been introduced; therefore, re-evaluation and future study in the military field are appropriate, preferably with other North Atlantic Treaty Organization partners.

It's all about timing, early treatment with hyperbaric oxygen therapy and corticosteroids is essential in acute acoustic trauma.

BACKGROUND: Acute acoustic trauma (AAT) is an acute hearing impairment caused by intense noise-impact. The current management strategy for AAT with substantial hearing loss in the Dutch military is the combination therapy with corticosteroids and hyperbaric oxygen therapy (HBOT). In a previous study, early initiation of the combination therapy was associated with better outcomes. Therefore, we performed a new analysis to assess the difference in hearing outcome between patients in whom combination therapy was started within two days, versus after more than two days. METHODS: A retrospective analysis was performed on military patients diagnosed with AAT with substantial hearing loss who presented between February 2018 and March 2020. Absolute and relative hearing improvement between first and last audiograms were calculated for all affected frequencies (defined as loss of ≥20 dB on initial audiogram). We also determined the amount of patients who recovered to the level of Dutch military requirement, and performed speech discrimination tests. RESULTS: In this analysis, 30 male patients (49 ears) with AAT were included. The median age was 24.5 years (IQR 23-29). The median time to initiation of therapy with corticosteroids and HBOT were one and two days, respectively. HBOT was started within two days in 31 ears, and after more than two days in 18 ears. The mean absolute and relative hearing gains were 18.8 dB (SD 14.6) and 46.8% (SD 31.3) on all affected frequencies. The 100% discrimination/speech perception level improved from 64.0 dB to 51.7 dB (gain 12.3 dB ± 14.1). There was significantly more improvement in absolute and relative hearing improvement when HBOT was started in ≤2 days, compared to >2 days. CONCLUSION: Our analysis shows results in favor of early initiation (≤2 days) of the combination treatment of HBOT and corticosteroids in patients with AAT.

Hyperbaric oxygen therapy for the treatment of rectovaginal fistulas in patients with Crohn's disease: results of the HOT-REVA pilot study.

BACKGROUND: Positive effects of hyperbaric oxygen (HBO) on perianal fistulas in Crohn's disease (CD) have been described, but the effect on rectovaginal fistulas (RVFs) has not yet been studied. The aim was to investigate the efficacy, safety and feasibility of HBO in patients with RVF in CD. METHODS: In this prospective study, consecutive CD patients between November 2018 and February 2020 presenting with RVF at the outpatient fistula clinic of the Amsterdam University Medical Centre were included and selected to receive treatment with 30 daily HBO sessions, if fistulas were actively draining and any concomitant treatment regimen was stable at least 6 weeks prior to start of HBO. Patients with a stoma were excluded. The primary endpoint was clinical closure at 3-month follow-up, defined as cessation of complaints and/or closure of the external orifice if visible at baseline. Secondary outcomes were improvement of concomitant perianal fistulas as measured by the perianal disease activity index (PDAI) and fistula drainage assessment (FDA), as well as improvement in patient-reported outcomes (visual analogue scale (VAS), inflammatory bowel disease questionnaire (IBDQ), faecal incontinence quality of life scale (FIQL) and female sexual functioning index (FSFI)) at 3-month follow-up. RESULTS: Out of 14 eligible patients, nine patients (median age 50 years) were treated, all of whom had previously had one or more unsuccessful medical and/or surgical treatments for their RVF. Clinical closure occurred in none of the patients at 3-month follow-up. There was no improvement in PDAI and patient-reported outcomes (VAS, IBDQ, FIQL and FSFI). Two patients had concomitant perianal fistulas; using FDA, one patient had a clinical response and one patient was in clinical remission 3 months after HBO. There were two treatment-related adverse events during HBO concerning claustrophobia and fatigue. Furthermore, two patients had a surgical intervention due to RVF and two patients were treated with antibiotics for a urinary tract infection during follow-up. One patient had a dose reduction of ustekinumab because of decreased luminal complaints. CONCLUSION: Treatment with HBO was feasible, but in this therapy-refractory cohort without deviating ostomy no clinical closure of RVF or improvement in quality of life was seen 3 months after HBO. Treatment with HBO alone in this specific group of patients therefore appears to be ineffective.

The AirSeal® insufflation device can entrain room air during routine operation.

BACKGROUND: Surgical procedures that use insufflation carry a risk of gas embolism, which is considered relatively harmless because of the high solubility of carbon dioxide. However, an in vitro study suggested that valveless insufflation devices may entrain non-medical room air into the surgical cavity. Our aim was to verify if this occurs in actual surgical procedures. METHODS: The oxygen percentage in the pneumoperitoneum or pneumorectum/pneumopelvis of eight patients operated with use of the AirSeal® was continuously measured, to determine the percentage of air in the total volume of the surgical cavity. RESULTS: Basal air percentage in the surgical cavity was 0-5%. During suctioning from the operative field air percentage increased to 45-65%. CONCLUSIONS: The AirSeal® valveless insufflation device maintains optimal distension of the surgical cavity not only by insufflating carbon dioxide, but also by entraining room air, especially during suctioning from the operative field. This may theoretically lead to air embolism in patients operated on with this device.

Arrhythmogenicity of scuba diving: Holter monitoring in a hyperbaric environment.

INTRODUCTION: About 26% of diving-related fatalities are caused by cardiac disease, part of which might be associated with fatal arrhythmias. This raises the question as to whether fatal arrhythmias are being provoked by hyperbaric conditions themselves or if exercise or stress provokes the fatal arrhythmias in cases of underlying (ischemic) cardiac disease. OBJECTIVE: To measure the influence of hyperbaric conditions (50 msw) on cardiac conduction and arrhythmias in professional divers by means of ECG. METHODS: This is a prospective study on military divers in a hyperbaric chamber with continuous ECG monitoring using Holter registrations. Supraventricular and ventricular ectopy was registered during hyperbaric conditions. RR, PR, QRS, QT and QTc intervals were calculated at 50 msw and compared with ECGs at rest. RESULTS: Included were 17 male military divers who made 20 dives. A total of 10 PVCs, 45 PACs, four atrial runs and four atrial pairs were seen. Significant prolongation of the PR interval was seen and a decrease of in QRS duration at 50 msw. There was no significant change in the RR, QT and QTc intervals. CONCLUSION: In these divers, no clinically relevant arrhythmias were observed during wet dives in a recompression chamber at 50 msw. We observed a small prolongation of PR interval that is probably not clinically relevant in divers without any known conduction disorders.

Hyperbaric oxygen therapy for the treatment of perianal fistulas in Crohn's disease (HOT-TOPIC): study protocol of a prospective interventional cohort study with one-year follow-up.

Background: Perianal fistulizing Crohn's disease (pCD) has a significant impact on patients' health and quality of life. Current treatment options have a relatively low success rate and a high recurrence risk. Positive effects of hyperbaric oxygen (HBO2) therapy have been indicated in animal studies as well as in small case series. Methods/Design: This is a non-randomized, controlled pilot study. A total of 20 patients with pCD who have been refractory to standard therapy for at least six months will be included. Patients with a seton and stable treatment regimen will be included. Patients with anal strictures, rectovaginal fistulas, stoma or deep ulceration of the rectum will be excluded. Patients who are eligible but refuse HBO2 will be asked to serve as controls. Patients in the HBO2 group will be treated with 40 sessions of HBO2 therapy at 243-253 kPa, with the seton being removed after 30 sessions. Co-primary endpoints are changes in the perianal disease activity index and MRI-scores. Secondary outcomes are fistula drainage assessment, laboratory findings and patient-reported outcomes. Assessment will be done at baseline, 16 weeks, 34 weeks and 60 weeks after finishing HBO2. Discussion: The aim of this study is to investigate the feasibility and therapeutic effect of HBO2 on pCD. The one-year follow-up should provide information on the effect durability. A comparison between patients treated with HBO2 and patients who continue to receive standard care will be made. The risk of bias will be limited by using clearly defined inclusion and exclusion criteria, baseline characteristics and consecutive recruitment of patients through an outpatient fistula clinic. Trial registration: The HOT-TOPIC trial has been approved by the local Medical Ethical Committee of the Academic Medical Centre in Amsterdam, the Netherlands. The trial has been registered at the Netherlands Trial Register (www.trialregister.nl), registration number: NTR 6676. Protocol version: August 2017, version 3.0.

Markers of Pulmonary Oxygen Toxicity in Hyperbaric Oxygen Therapy Using Exhaled Breath Analysis.

INTRODUCTION: Although hyperbaric oxygen therapy (HBOT) has beneficial effects, some patients experience fatigue and pulmonary complaints after several sessions. The current limits of hyperbaric oxygen exposure to prevent pulmonary oxygen toxicity (POT) are based on pulmonary function tests (PFT), but the limitations of PFT are recognized worldwide. However, no newer modalities to detect POT have been established. Exhaled breath analysis in divers have shown volatile organic compounds (VOCs) of inflammation and methyl alkanes. This study hypothesized that similar VOCs might be detected after HBOT. METHODS: Ten healthy volunteers of the Royal Netherlands Navy underwent six HBOT sessions (95 min at 253 kPa, including three 5-min "air breaks"), i.e., on five consecutive days followed by another session after 2 days of rest. At 30 min before the dive, and at 30 min, 2 and 4 h post-dive, exhaled breath was collected and followed by PFT. Exhaled breath samples were analyzed using gas chromatography-mass spectrometry (GC-MS). After univariate tests and correlation of retention times, ion fragments could be identified using a reference database. Using these fragments VOCs could be reconstructed, which were clustered using principal component analysis. These clusters were tested longitudinally with ANOVA. RESULTS: After GC-MS analysis, eleven relevant VOCs were identified which could be clustered into two principal components (PC). PC1 consisted of VOCs associated with inflammation and showed no significant change over time. The intensities of PC2, consisting of methyl alkanes, showed a significant decrease (p = 0.001) after the first HBOT session to 50.8%, remained decreased during the subsequent days (mean 82%), and decreased even further after 2 days of rest to 58% (compared to baseline). PFT remained virtually unchanged. DISCUSSION: Although similar VOCs were found when compared to diving, the decrease of methyl alkanes (PC2) is in contrast to the increase seen in divers. It is unknown why emission of methyl alkanes (which could originate from the phosphatidylcholine membrane in the alveoli) are reduced after HBOT. This suggests that HBOT might not be as damaging to the pulmonary tract as previously assumed. Future research on POT should focus on the identified VOCs (inflammation and methyl alkanes).

Evaluation of a Concept for a Military Expedition Performance Environment.

To evaluate four factors essential in the preparation of high-altitude expeditions and of the performance during these expeditions, the Manaslu 2016 Medical Team, as part of the medical team of the Royal Netherlands Marine Corps (RNLMC), developed the Military Expedition Performance Environment (MEPE) concept. The scope of this concept is intended to cover (1) selection of a team, (2) medical planning and support, (3) competencies in the field (team work and human factors), and (4) and chain of command.

Cutis marmorata in decompression illness may be cerebrally mediated: a novel hypothesis on the aetiology of cutis marmorata.

INTRODUCTION: Cutaneous decompression sickness (DCS) is often considered to be a mild entity that may be explained by either vascular occlusion of skin vessels by bubbles entering the arterial circulation through a right-to-left shunt or bubble formation due to saturated subcutaneous tissue during decompression. We propose an alternative hypothesis. METHODS: The case is presented of a 30-year-old female diver with skin DCS on three separate occasions following relatively low decompression stress dives. Also presented are the findings of cutaneous appearances in previously reported studies on cerebral arterial air embolism in pigs. RESULTS: There was a close similarity in appearance between the skin lesions in this woman (and in other divers) and those in the pigs, suggesting a common pathway. CONCLUSIONS: From this, we hypothesize that the cutaneous lesions are cerebrally mediated. Therefore, cutaneous DCS might be a more serious event that should be treated accordingly. This hypothesis may be supported by the fact that cutis marmorata is also found in other fields of medicine in a non-diving context, where the rash is referred to as livedo reticularis or livedo racemosa. These are associated with a wide number of conditions but of particular interest is Sneddon's syndrome, which describes the association of livedo racemosa with cerebrovascular events or vascular brain abnormalities. Finally, there is a need for further research on the immunocytochemical pathway of cutaneous DCS.

Hyperbaric oxygen diving affects exhaled molecular profiles in men.

Exhaled breath contains volatile organic compounds (VOCs) that are associated with respiratory pathophysiology. We hypothesized that hyperbaric oxygen exposure (hyperoxia) generates a distinguishable VOC pattern. This study aimed to test this hypothesis in oxygen-breathing divers. VOCs in exhaled breath were measured in 10 male divers before and 4h after diving to 9msw (190kPa) for 1h. During the dive they breathed 100% oxygen or air in randomized order. VOCs were determined using two-dimensional gas chromatography with time-of-flight mass spectrometry. Compared to air dives, after oxygen dives there was a significant increase in five VOCs (predominately methyl alkanes). Furthermore, a strong, positive correlation was found between increments in 2,4-dimethyl-hexane and those of 4-ethyl-5-methyl-nonane. Although non-submerged hyperoxia studies on VOCs have been performed, the present study is the first to demonstrate changes in exhaled molecular profiles after submerged oxygen diving. The pathophysiological background might be attributed to either a lipid peroxidation-induced pathway, an inflammatory pathway, or to both.

Detection of cerebral arterial gas embolism using regional cerebral oxygen saturation, quantitative electroencephalography, and brain oxygen tension in the swine.

BACKGROUND: Cerebral air emboli occur as a complication of invasive medical procedures. The sensitivity of cerebral monitoring methods for the detection of air emboli is not known. This study investigates the utility of electroencephalography and non-invasively measured cerebral oxygen saturation in the detection of intracerebrovascular air. NEW METHOD: In 12 pigs oxygen saturation was continuously measured using transcranial near-infrared spectroscopy and oxygen tension was continuously measured using intraparenchymal probes. Additionally, quantitative electroencephalography and microdialysis were performed. Doses of 0.2, 0.4, 0.8, and 1.6 ml of air were injected into the cerebral arterial vasculature through a catheter. RESULTS: Oxygen saturation and electroencephalography both reacted almost instantaneously on the air emboli, but were less sensitive than the intraparenchymal oxygen tension. There was reasonable correlation (ρ ranging from 0.417 to 0.898) between oxygen saturation, oxygen tension, electroencephalography and microdialysis values. COMPARISON WITH EXISTING METHODS: Our study is the first to demonstrate the effects of cerebral air emboli using multimodal monitoring, specifically on oxygen saturation as measured using near-infrared spectroscopy. CONCLUSIONS: Our results show that non-invasively measured oxygen saturation and quantitative electroencephalography can detect the local effects of air emboli on cerebral oxygenation, but with reduced sensitivity as compared to intraparenchymal oxygen tension. Prospective human studies using multimodal monitoring incorporating electroencephalography and oxygen saturation should be performed.

Nitric oxide and carbon monoxide diffusing capacity after a 1-h oxygen dive to 9 m of sea water.

INTRODUCTION: To prevent extensive pulmonary lesions in submerged oxygen divers lung function like the forced vital capacity (FVC) or the diffusing capacity for carbon monoxide (DL,co) are used to monitor pulmonary oxygen toxicity (POT). As the diffusing capacity for nitric oxide (DL,no) measures more accurately the membrane diffusing capacity compared to DL,co we hypothesized that DL,no is superior in monitoring the onset of physiological changes indicative of POT as compared to DL,co or FVC. METHOD: 26 healthy divers (mean age 30.7 ± 6.2 years) made two submerged dives to 190 kPa for 1 h on two randomized separate days, whilst breathing 100% oxygen or compressed air. FVC, DL,no, DL,co and alveolar volume (VA ) were measured 6 times during a 26-h period. RESULTS: Up to 8 h no significant differences in outcomes were found between the oxygen and air dives. However, at 8 h after the oxygen dives there was a significant reduction in DL,no, DL,co and VA as compared with air dives. In contrast, the reduction in FVC was significantly greater after the air dive. At 22 h there were no longer differences in outcomes between the dives. CONCLUSIONS: These data show that DL,no and DL,co are significantly reduced 8 h after submerged oxygen dives as compared to similar air dives. Together with the reduction in VA this may be indicative of interstitial edema as an early sign of POT. Our data warrant validation of the superiority of DL,no and DL,co over FVC in the practical monitoring of divers.

Assessment of pulmonary oxygen toxicity: relevance to professional diving; a review.

When breathing oxygen with partial oxygen pressures PO2 of between 50 and 300 kPa pathological pulmonary changes develop after 3-24h depending on the PO2. This kind of injury (known as pulmonary oxygen toxicity) is not only observed in ventilated patients but is also considered an occupational hazard in oxygen divers or mixed gas divers. To prevent these latter groups from sustaining irreversible lesions adequate prevention is required. This review summarizes the pathophysiological effects on the respiratory tract when breathing oxygen with PO2 of 50-300 kPa (hyperoxia). We discuss to what extent the most commonly used lung function parameters change after exposure to hyperoxia and its role in monitoring the onset and development of pulmonary oxygen toxicity in daily practice. Finally, new techniques in respiratory medicine are discussed with regard to their usefulness in monitoring pulmonary oxygen toxicity in divers.

Lung function before and after oxygen diving: a randomized crossover study.

RATIONALE: Breathing oxygen with a partial pressure of > 50 kPa can cause pulmonary oxygen toxicity (POT). Diffusing capacity for carbon monoxide (DL(CO)) is thought to be a more sensitive indicator of POT than vital capacity (VC). Because diffusing capacity can be measured more specifically using nitric oxide (DL(NO)), we hypothesized that DL(NO) is better able to monitor and exclude POT than DL(CO). OBJECTIVE: To compare changes in lung function after oxygen and air dives which include measurement of DL(NO) and DL(CO). METHOD: Eleven healthy male divers (mean age 27.5 +/- 3.1 years) made two immersed dives to 150 kPa for three hours on two separate days, during which they randomly breathed 100% oxygen or air. VC, DL(NO) and DL(CO) were measured six times during a 26-hour period on both days and on a third non-diving day. RESULTS: There were no significant changes in DL(CO), DL(NO) or other diffusing capacity or spirometric parameters after either type of dive. CONCLUSION: Lung function after a single three-hour oxygen dive at a pO2 of approximately 150 kPa is comparable to that after an air dive at the same depth and duration. This suggests that such an oxygen dive does not induce detectable signs of POT. Our hypothesis that DL(NO) is more sensitive than DL(CO) for detection of POT could not be tested because the oxygen exposure did not affect either parameter.

Differences in spirometry and diffusing capacity after a 3-h wet or dry oxygen dive with a PO(2) of 150 kPa.

RATIONALE: Breathing oxygen with a partial pressure of >50 kPa causes pulmonary oxygen toxicity (POT), resulting in a decrease in vital capacity (VC) and in diffusing capacity for carbon monoxide (DLco). As submersion is thought to potentiate POT, we hypothesized that submerged oxygen divers are at increased risk for POT. OBJECTIVE: To compare changes in lung function after submerged (wet) and non-submerged (dry) oxygen dives. METHOD: Thirteen healthy male divers (mean ± SD: 25 ± 2 years, 184 ± 7 cm, 85 ± 10 kg) made a dry and a wet dive to 150 kPa for 3 h, during which they breathed 100% oxygen. At baseline, within 1 and 4 h after their dives, spirometry and diffusing capacity were measured. Data were analysed with ANOVA using Bonferroni correction and paired t-tests. RESULTS: Compared with baseline, there was a significant reduction in DLco (-1·6 mmol kPa(-1) min(-1)) after a wet oxygen dive but not after a dry dive. In addition, relative to baseline, there was a significant difference in ΔDLco and ΔVC when comparing wet and dry oxygen dives. CONCLUSION: Diffusing capacity is more impaired after a wet oxygen dive than after a dry one. This suggests that wet oxygen divers are at increased risk for POT. Monitoring studies during daily practice of professional divers are mandatory to determine the exact operational relevance of the present findings.

Conservative treatment of acute appendicitis: an overview.

BACKGROUND: Although the standard treatment for appendicitis (since 1883) is an appendectomy, this is not always possible in a maritime or military setting. To avoid relying on improvisation in such situations this study examines the evidence for conservative management of appendicitis. MATERIAL AND METHODS: PubMed was searched for studies on conservative treatment of appendicitis. Both prospective and retrospective studies with a well-defined description of the protocol were included. RESULTS: Finally, 5 publications (a total of 342 patients) were included in this overview. For these reports, the success rate for conservative treatment of appendicitis is 90.8% (88-95%) with a risk of relapse within 12 months of 15.9% (5-37%). For complicated appendicitis these mean rates decrease to 89% (67-100%) and 9.8% (0-39.6%), respectively. DISCUSSION AND CONCLUSIONS: This overview indicates that appendicitis can be safely and effectively treated conservatively. The studies differed in their treatment protocols. Appendicitis can best be treated with a third-generation cephalosporin and an imidazole derivative (2 days intravenously and 10 days orally). This is based on evidence from a combination of the studies presented here, and on expert opinion. Currently, this combination is the best available "evidence" on this topic.