Aviation Decompression Sickness in Aerospace and Hyperbaric Medicine.

INTRODUCTION: The U.S. Navy experienced a series of physiological events in aircrew involving primarily the F/A-18 airframe related to rapid decompression of cabin pressures, of which aviation decompression sickness (DCS) was felt to contribute. The underlying pathophysiology of aviation DCS is the same as that of diving-related. However, based on the innate multifactorial circumstances surrounding hypobaric DCS, in clinical practice it continues to be unpredictable and less familiar as it falls at the intersect of aerospace and hyperbaric medicine. This retrospective study aimed to review the case series diagnosed as aviation DCS in a collaborative effort between aerospace specialists and hyperbaricists to increase appropriate identification and treatment of hypobaric DCS.METHODS: We identified 18 cases involving high-performance aircraft emergently treated as aviation DCS at a civilian hyperbaric chamber. Four reviewers with dual training in aviation and hyperbaric medicine retrospectively reviewed cases and categorized presentations as "DCS" or "Alternative Diagnosis".RESULTS: Reviewers identified over half of presenting cases could be attributed to an alternative diagnosis. In events that occurred at flight altitudes below 17,000 ft (5182 m) or with rapid decompression pressure changes under 0.3 atm, DCS was less likely to be the etiology of the presenting symptoms.CONCLUSIONS: Aviation physiological events continue to be difficult to diagnose. This study aimed to better understand this phenomenon and provide additional insight and key characteristics for both flight physicians and hyperbaric physicians. As human exploration continues to challenge the limits of sustainable physiology, the incidence of aerospace DCS may increase and underscores our need to recognize and appropriately treat it.Kutz CJ, Kirby IJ, Grover IR, Tanaka HL. Aviation decompression sickness in aerospace and hyperbaric medicine. Aerosp Med Hum Perform. 2023; 94(1):11-17.

Dysbaric osteonecrosis (DON) among the artisanal diving fishermen of Yucatán, Mexico.

INTRODUCTION: Artisanal diving fishermen in Yucatán, Mexico have high rates of decompression sickness as a result of frequently unsafe diving practices with surface supplied compressed air. In this study, we investigated the prevalence of dysbaric osteonecrosis (DON), a type of avascular necrosis, in the most susceptible joints in a cohort of these fishermen. METHODS: We performed radiographs of bilateral shoulders, hips, and knees of 39 fishermen in Mexico and surveyed them about their medical and diving histories. We performed pairwise correlations to examine if the fishermen's diving behaviours affected the numbers of joints with DON. RESULTS: The radiographs revealed Grade II or higher DON in 30/39 (76.9%) of the fishermen. Twenty-two of 39 fishermen (56.4%) had at least two affected joints. The number of joints with DON positively correlates with the lifetime maximum diving depth and average bottom time. CONCLUSIONS: These findings represent among the highest prevalence rates of DON in divers and reflect the wide-spread scale of decompression sickness among these fishermen. Through this work, we hope to further educate the fishermen on the sequelae of their diving with the aim of improving their diving safety.

Diving after SARS-CoV-2 (COVID-19) infection: Fitness to dive assessment and medical guidance.

Scuba diving is a critical activity for commercial industry, military activities, research, and public safety, as well as a passion for many recreational divers. Physicians are expected to provide return-to-diving recommendations after SARS-CoV-2 (COVID-19) infection based upon the best available evidence, often drawn from experience with other, similar diseases. Scuba diving presents unique physiologic challenges to the body secondary to immersion, increased pressure and increased work of breathing. The long-term sequelae of COVID-19 are still unknown, but if they are proven to be similar to other coronaviruses (such as Middle East respiratory syndrome or SARS-CoV-1) they may result in long-term pulmonary and cardiac sequelae that impact divers' ability to safely return to scuba diving. This review considers available literature and the pathophysiology of COVID-19 as it relates to diving fitness, including current recommendations for similar illnesses, and proposes guidelines for evaluation of divers after COVID-19. The guidelines are based upon best available evidence about COVID-19, as well as past experience with determination of diving fitness. It is likely that all divers who have contracted COVID-19 will require a medical evaluation prior to return to diving with emphasis upon pulmonary and cardiac function as well as exercise capacity.

Iatrogenic Arterial Gas Embolism From Esophagogastroduodenoscopy.

BACKGROUND: Arterial gas embolus (AGE) is a rare complication of esophagoduodenoscopy (EGD) that has been described in only a few case reports in the literature. The exact etiology remains unknown, but many of the cases share some common characteristics. CASE REPORT: We report the case of a 52-year-old otherwise healthy man who underwent outpatient EGD for a sensation of retained food in his esophagus. During the procedure, he suffered a tonic-clonic seizure, bradycardia, and hypoxia. Subsequent emergency department workup showed pneumocephalus on computed tomography brain imaging, and he was diagnosed with a cerebral AGE (CAGE). He was transferred to our facility for treatment of CAGE with hyperbaric oxygen therapy (HBOT). After multiple hyperbaric treatments, he was discharged with a residual left hemiparesis, which represented a significant improvement in his overall neurologic status. We also present a review of similar EGD CAGE cases from the literature and discuss their outcomes and the need for HBOT. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Although CAGE from EGD is rare, these patients will often be transferred to the ED from gastrointestinal procedural suites and an emergency physician should understand that an iatrogenic CAGE can result from this procedure and that CAGE is a clinical diagnosis. Definitive care at a critical care-capable hyperbaric chamber will provide the patient with the best chance of meaningful recovery, and transport should be arranged as expeditiously as possible.

Use of hyperbaric oxygen therapy in pediatric neuro-oncology: a single institutional experience.

INTRODUCTION: Hyperbaric oxygen therapy (HBOT) has been utilized as adjunctive treatment of CNS tumors and for radiation necrosis (RN) with reported success. The safety and efficacy in pediatric patients is less understood. METHODS: Seven patients (ages 10-23 years, six females) were treated with HBOT (3-60 sessions) for either RN (n = 5) or tumor-associated edema (n = 2). Tumor diagnosis included low-grade glioma (n = 4, two with neurofibromatosis type 1), meningioma (n = 1), medulloblastoma (n = 1) and secondary high grade glioma (n = 1). Prior therapies included: surgery (n = 4), chemotherapy (n = 4) and radiation (N = 5: four focal, one craniospinal). Three underwent biopsy: one confirming RN, one high-grade glioma, and one low-grade glioma. Patients were assessed for clinical and radiographic changes post HBOT. RESULTS: Median time to clinical and radiographic presentation was 8.5 months (range 6 months-11 years) in those who had prior radiation. Clinical improvement after HBOT (median: 40 sessions) was observed in four of seven patients. Symptoms were stable in two and worsened in one patient. Radiographic improvement was seen in four patients; three had radiographic disease progression. In the subgroup treated for presumed and biopsy-confirmed RN (n = 5), four of five (80%) had clinical and radiographic improvement. There were no long-term adverse events due to HBOT. CONCLUSIONS: HBOT is safe and well-tolerated in pediatric and young adult patients with CNS tumors. Clinical and radiographic improvements were observed in over half of patients. Clinical trials are needed to establish safety and efficacy of HBOT as adjunct therapy in pediatric CNS tumors.

Injection of SVF combined with HBO2 improves viability of unfavorably designed flaps.

PURPOSE: Soft-tissue reconstruction is complicated by ischemia and reperfusion injury. Animal trials have documented the independent healing benefits of hyperbaric oxygen preconditioning (HBOP) and stem cell delivery in cutaneous flaps. We explored the role of HBOP and stem cell delivery in flap preconditioning and survival. METHODS: We designed a randomized controlled trial to assess the effects of hyperbaric oxygen preconditioning and stromal vascular fraction (SVF) delivery on flap survival. Of the first 24 guinea pigs, six received neither HBOP nor injections, and six underwent HBOP without injections. Of the remaining 12 animals, six received SVF or saline injections in the absence of HBOP. The final six animals received autologous SVF injections or saline injections followed by four HBOP treatments. To enhance clinical relevance, a group of 6 animals underwent HBOP prior to SVF or saline injections. Thereafter, an unfavorably designed cutaneous flap was elevated and assessed via study-blinded observer, as well as by quantification of TUNEL-positive cells. RESULTS: Distal necrosis of the tissue flap was more extensive in the no-intervention group (45% of flap). Flaps treated with HBOP only and those treated with SVF injections demonstrated only 38.2% and 27.1% distal necrosis. The most significant difference occurred in the combination HBOP and SVF group, where distal necrosis was only 21.1% of the flap (p ≤ 0.05). SVF delivery immediately prior to flap elevation further minimized distal necrosis of the flap to 15.6%. These findings were mirrored by the TUNEL assay. CONCLUSIONS: Combining HBOP and SVF improves flap viability.

Spinal decompression sickness in an artisanal diving fisherman in Yucatán, Mexico: a case report.

Artisanal fishermen around the world employ scuba and surface-supplied diving for their livelihoods and often undergo provocative dive profiles due to economic pressures. Consequently, rates of decompression sickness (DCS) are much greater than in recreational scuba divers. Here we present the case of a surface-supplied diving fisherman from the Yucatán Peninsula of Mexico, who suffered a significant episode of spinal DCS and underwent hyperbaric oxygen therapy treatments, with a favorable outcome. Additionally, we review the proposed mechanisms underlying spinal DCS.

Incidence of DCS and oxygen toxicity in chamber attendants: a 28-year experience.

Decompression sickness (DCS) and central nervous system oxygen toxicity are inherent risks for "inside" attendants (IAs) of hyperbaric chambers. At the Hyperbaric Medicine Center at the University of California San Diego (UCSD), protocols have been developed for decompressing IAs. Protocol 1: For a total bottom time (TBT) of less than 80 minutes at 2.4 atmospheres absolute (atm abs) or shallower, the U.S. Navy (1955) no-decompression tables were utilized. Protocol 2: For a TBT between 80 and 119 minutes IAs breathed oxygen for 15 minutes prior to initiation of ascent. Protocol 3: For a TBT between 120-139 minutes IAs breathed oxygen for 30 minutes prior to ascent. These protocols have been utilized for approximately 28 years and have produced zero cases of DCS and central nervous system oxygen toxicity. These results, based upon more than 24,000 exposures, have an upper limit of risk of DCS and oxygen toxicity of 0.02806 (95% CI) using UCSD IA decompression Protocol 1, 0.00021 for Protocol 2, and 0.00549 for Protocol 3. We conclude that the utilization of this methodology may be useful at other sea-level multiplace chambers.

Diplopia due to mask barotrauma.

BACKGROUND: Scuba diving is a very popular and safe sport. Occasionally divers will suffer an injury from barotrauma, decompression sickness or an arterial gas embolism. The history and physical examination are important when determining the etiology of the injury and its subsequent treatment. OBJECTIVES: This article will help readers identify key components of the history and physical examination in a patient to help differentiate between and injury caused by barotrauma or arterial gas embolism. CASE REPORT: This is a case of a diver that was initially felt to have an arterial gas embolism after scuba diving. After obtaining further history and performing a detailed physical exam it was determined that his diplopia was due to barotrauma from his mask. This was confirmed by an orbital computed tomography (CT) scan. SUMMARY: Scuba diving is a very safe sport. When injuries occur it is important to obtain a careful history and physical examination to determine the exact cause of the injury because treatments vary according to the type of injury. In this case, the history and physical examination showed that the only neurologic sign the patient had was diplopia, which is not consistent with a diagnosis of arterial gas embolism. The CT scan helped with the diagnosis because it proved the patient had an orbital hematoma causing his proptosis and double vision.

Hyperbaric oxygen therapy for hepatic artery thrombosis following liver transplantation: current concepts.

This article presents the case of an infant who underwent an orthotopic liver transplant and then developed hepatic artery thrombosis that was detected on routine post-operative right upper quadrant ultrasound. Alteplase (TPA) failed to open the artery, so the child received systemic heparin and hyperbaric oxygen (HBO) therapy. After six HBO treatments, the hepatic artery had recanalized and his liver function tests had returned to normal or near normal. There were no complications to the HBO therapy, and 1 yr after the transplant, the child's liver is functioning well. The present study discusses the beneficial effects of HBO therapy and the proposed mechanisms for its favorable results. In our patient, systemic heparin and HBO therapy prevented liver failure and need for retransplantation.