Inner ear decompression sickness after a routine dive and recompression chamber drill.

Inner ear decompression sickness (IEDCS) is an uncommon diving-related injury affecting the vestibulocochlear system, with symptoms typically including vertigo, tinnitus, and hearing loss, either in isolation or combination. Classically associated with deep, mixed-gas diving, more recent case series have shown that IEDCS is indeed possible after seemingly innocuous recreational dives, and there has been one previous report of IEDCS following routine hyperbaric chamber operations. The presence of right-to-left shunt (RLS), dehydration, and increases in intrathoracic pressure have been identified as risk factors for IEDCS, and previous studies have shown a predominance of vestibular rather than cochlear symptoms, with a preference for lateralization to the right side. Most importantly, rapid identification and initiation of recompression treatment are critical to preventing long-term or permanent inner ear deficits. This case of a U.S. Navy (USN) diver with previously unidentified RLS reemphasizes the potential for IEDCS following uncomplicated diving and recompression chamber operations - only the second reported instance of the latter.

Complications After Covid-19 Infection In Singapore Military Divers: A Retrospective Cohort Study.

Studies suggest that COVID-19 infections may have longer-term and more significant complications, even with mild or absent symptoms. This may predispose divers to pulmonary barotrauma, arterial gas embolisms, and reduced exercise tolerance, and impact physical and cognitive performance during diving. Military diving is physically, physiologically, and psychologically taxing on the individual. This study aims to assess the incidence of complications after COVID-19 infections in a cohort of active military divers and the incidence of diving-related injuries such as decompression sickness and barotrauma following recovery from acute COVID-19 infections. A single-center, retrospective cohort study of complications after COVID-19 infections was done in a cohort of the Republic of Singapore Navy (RSN) Naval Diving Unit (NDU) Divers and involved the collection of retrospective data for 329 military divers who were diagnosed with COVID-19 infection from 25 Mar 2020 and 13 Feb 2023. We found no clinical or subclinical complications after COVID-19 infection in our fully vaccinated, low-risk population of NDU divers after asymptomatic or mild COVID-19 infection. There were also no incidences of diving-related injuries related to COVID-19 after recovery from the acute illness. Based on the study results, it is recommended that all military divers with asymptomatic or mild COVID-19 infections return to military diving activities immediately after recovery from acute COVID-19 infection with resolution of symptoms. As existing guidelines recommend, divers with moderate to critical COVID-19 infection should be reviewed by a diving physician and undergo necessary investigations before returning to military diving.

Acute aortic dissection during scuba diving.

A 60-year-old man with hypertension and dyslipidemia complained of chest pain upon ascending from a maximum depth of 27 meters while diving. After reaching the shore, his chest pain persisted, and he called an ambulance. When a physician checked him on the doctor's helicopter, his electrocardiogram (ECG) was normal, and there were no bubbles in his inferior vena cava or heart on a portable ultrasound examination. The physician still suspected that he had acute coronary syndrome instead of decompression illness; therefore, he was transported to our hospital. After arrival at the hospital, standard cardiac echography showed a flap in the ascending aorta. Immediate enhanced computed tomography revealed Stanford type A aortic dissection. The patient obtained a survival outcome after emergency surgery. To our knowledge, this is the first reported case of aortic dissection potentially associated with scuba diving. It highlights the importance of considering aortic dissection in patients with sudden-onset chest pain during physical activity. In addition, this serves as a reminder that symptoms during scuba diving are not always related to decompression. This report also suggests the usefulness of on-site ultrasound for the differential diagnosis of decompression sickness from endogenous diseases that induce chest pain. Further clinical studies of this management approach are warranted.

[The otolaryngologist's role in evaluating diving fitness]. / Beurteilung einer Tauchtauglichkeit als HNO-Arzt.

Scuba diving and other modes of device-supported diving are popular activities that can be especially demanding and hazardous for people with preexisting physical conditions. Due to the high ambient pressure, the temperature differences, and potential unpredictable events, which have manifold effects on the organism, diving carries a high risk of life-threatening disease. A special risk is present if the body does not readily equalize air pressure changes. Therefore, prior to diving, all divers should undergo detailed education regarding the physical principles of the sport as well as specific physical examination. Consultation of an otolaryngologist is of exceptional relevance because many otorhinolaryngologic diseases can lead to (usually temporary) unfitness to dive. The role of the modern otorhinolaryngologist trained in diving medicine is to correctly advise the patient and restore fitness for diving via conservative or invasive methods.

Breath-Hold Diving Injuries - A Primer for Medical Providers.

ABSTRACT: Breath-hold divers, also known as freedivers, are at risk of specific injuries that are unique from those of surface swimmers and compressed air divers. Using peer-reviewed scientific research and expert opinion, we created a guide for medical providers managing breath-hold diving injuries in the field. Hypoxia induced by prolonged apnea and increased oxygen uptake can result in an impaired mental state that can manifest as involuntary movements or full loss of consciousness. Negative pressure barotrauma secondary to airspace collapse can lead to edema and/or hemorrhage. Positive pressure barotrauma secondary to overexpansion of airspaces can result in gas embolism or air entry into tissues and organs. Inert gas loading into tissues from prolonged deep dives or repetitive shallow dives with short surface intervals can lead to decompression sickness. Inert gas narcosis at depth is commonly described as an altered state similar to that experienced by compressed air divers. Asymptomatic cardiac arrhythmias are common during apnea, normally reversing shortly after normal ventilation resumes. The methods of glossopharyngeal breathing (insufflation and exsufflation) can add to the risk of pulmonary overinflation barotrauma or loss of consciousness from decreased cardiac preload. This guide also includes information for medical providers who are tasked with providing medical support at an organized breath-hold diving event with a list of suggested equipment to facilitate diagnosis and treatment outside of the hospital setting.

Decompression strain in parachute jumpmasters during simulated high-altitude missions: a special reference to preoxygenation strategies.

PURPOSE: Military parachute operations are often executed at high altitude, from an unpressurized aircraft compartment. Parachute jumpmasters (JM) are thus regularly exposed to 29,500 ft for 60 min. The aim was to investigate the decompression strain during a simulated JM mission at high altitude and to compare two strategies of preoxygenation, conducted either at sea-level or below 10,000 ft, during ascent to mission altitude. METHODS: Ten JM completed, on separate occasions, a 45-min preoxygenation either at sea-level (normobaric: N) or 8200ft (hypobaric: H), followed by exposure to 28,000 ft for 60 min, whilst laying supine and breathing 100% oxygen. At min 45 of the exposure to 28,000 ft, the JM performed 10 weighted squats. Decompression strain was determined from ultrasound assessment of venous gas emboli (VGE) during supine rest (5-min intervals), after three unloaded knee-bends (15-min intervals) and immediately following the weighted squats. The VGE were scored using a six-graded scale (0-5). RESULTS: In condition H, two JM experienced decompression sickness (DCS), whereas no DCS incidents were reported in condition N. The prevalence of VGE was higher in the H than the N condition, at rest [median(range), 3(0-4) vs 0(0-3); p = 0.017], after unloaded knee-bends [3(0-4) vs 0(0-3); p = 0.014] and after the 10 weighted squats [3(0-4) vs 0(0-3); p = 0.014]. VGE were detected earlier in the H (28 ± 20 min, p = 0.018) than the N condition (50 ± 19 min). CONCLUSIONS: A preoxygenation/altitude procedure commonly used by JM, with a 60-min exposure to 28,000 ft after pre-oxygenation for 45 min at 8200 ft is associated with high risk of DCS. The decompression strain can be reduced by preoxygenating at sea level.

Proposed Thalmann algorithm air diving decompression table for the Swedish Armed Forces.

The Swedish Armed Forces (SwAF) air dive tables are under revision. Currently, the air dive table from the U.S. Navy (USN) Diving Manual (DM) Rev. 6 is used with an msw-to-fsw conversion. Since 2017, the USN has been diving according to USN DM rev. 7, which incorporates updated air dive tables derived from the Thalmann Exponential Linear Decompression Algorithm (EL-DCM) with VVAL79 parameters. The SwAF decided to replicate and analyze the USN table development methodology before revising their current tables. The ambition was to potentially find a table that correlates with the desired risk of decompression sickness.  New compartmental parameters for the EL-DCM algorithm, called SWEN21B, were developed by applying maximum likelihood methods on 2,953 scientifically controlled direct ascent air dives with known outcomes of decompression sickness (DCS). The targeted probability of DCS for direct ascent air dives was ≤1% overall and ≤1‰ for neurological DCS (CNS-DCS). One hundred fifty-four wet validation dives were performed with air between 18 to 57 msw. Both direct ascent and decompression stop dives were conducted, resulting in incidences of two joint pain DCS (18 msw/59 minutes), one leg numbness CNS-DCS (51 msw/10 minutes with deco-stop), and nine marginal DCS cases, such as rashes and itching. A total of three DCS incidences, including one CNS-DCS, yield a predicted risk level (95% confidence interval) of 0.4-5.6% for DCS and 0.0-3.6% for CNS-DCS. Two out of three divers with DCS had patent foramen ovale. The SWEN21 table is recommended for the SwAF for air diving as it, after results from validation dives, suggests being within the desired risk levels for DCS and CNS-DCS.

Hyperbaric treatment deviations for U.S. Navy divers: Spinal DCS.

Introduction: The United States Navy (USN) developed and refined standardized oxygen treatment tables for diving injuries, but USN tables may not address all situations of spinal decompression sickness (DCS). We describe a detailed recompression treatment regimen that deviated from standard USN protocol for an active-duty USN diver with a severe, delayed presentation of spinal cord DCS. Case Report: A USN diver surfaced from his second of three dives on a standard Navy 'no-Decompression' Air SCUBA dive (Max depth 101 fsw utilizing a Navy Dive Computer) and developed mid-thoracic back pain, intense nausea, paresthesias of bilateral feet, and penile erection. Either not recognizing the con- stellation of symptoms as DCS and after resolution of the aforementioned symptoms, he completed the third planned dive (essentially an in-water recompression). Several hours later, he developed paresthesias and numbness of bilateral feet and legs and bowel incontinence. He presented for hyperbaric treatment twenty hours after surfacing from the final dive and was diagnosed with severe spinal DCS. Based on the severity of clinical presentation and delay to treatment, the initial and follow-on treatments were modified from standard USN protocol. MRI of the spine four days after initial presentation demonstrated a 2.2 cm lesion at the T4 vertebral level extending caudally. Follow-up examinations over two years demonstrated almost complete return of motor and sensory function; however, the patient continued to suffer fecal incontinence and demonstrated an abnormal post-void residual urinary volume. An atypical presenting symptom, a discussion of MRI findings, and clinical correlations to the syndrome of spinal DCS are discussed throughout treatment and long-term recovery of the patient.

Exceptional survival of an airplane stowaway, treated successfully with hyperbaric oxygen.

Survival of airplane stowaways is rare. Here we report an exceptional case of successful treatment and full recovery. After a transcontinental flight an unconscious stowaway was discovered in a wheel well of a Boeing 747-400F. Airport paramedics confirmed regular respiration and achieved 100% oxygen saturation (pulse oximetry) by high-flow oxygen. Rectal body temperature was 35.5 °C. On arrival at the emergency department, the patient's vital signs were stable. He did not respond to verbal stimuli. He localized to painful stimuli with both arms, however, there was no reaction to stimuli to both legs. We suspected his neurological deficits were caused by posthypoxic encephalopathy or altitude decompression sickness (DCS), the latter amenable to hyperbaric oxygen therapy (HBOT). HBOT was performed for 5 h (US Navy Treatment Table 6) and afterwards, full neurological recovery was documented. About 24 h after admission a new proximal paresis of the left leg was noted. Assuming recurrence of DCS, daily HBOT was scheduled for three days, after which motor function had again returned to normal. Stowaways travelling in airplane wheel wells experience extreme environmental circumstances. The presented patient survived an eight-hour exposure to calculated barometric pressures as low as 190 mmHg and ambient PO2 of 40 mmHg. Apart from creating awareness of this rare patient category, we want to stress the risk of altitude DCS in unpressurized flights. When DCS is suspected, immediate high-flow oxygen therapy should be initiated, followed by HBOT at the earliest opportunity.

Post-decompression bubble and inflammation interactions: a non-extensive dynamical system model.

Inert gas bubbles in tissues and in blood have been historically considered as the only triggering factors for DCS, but now many other factors are considered to affect the final outcome of a decompression profile for a certain individual. In this sense, inflammation seems to play a relevant role, not only due to the physical damage of tissues by the bubbles, but as a potentiator of the process as a whole. The present study aims to put forward a mathematical model of bubble formation associated with an inflammatory process related to decompression. The model comprises four state-variables (inert gas pressure, inert gas bubbles, proinflammatory and inflammatory factors) in a set of non-linear differential equations. The model is non-extensive: inert gas transitions between liquid and gaseous phases do not change the concentration of the dissolved gas. The relationship between bubbles and inflammation is given through parameters that form a positive feedback loop. The results of the model were compared with the experimental results of echocardiography from volunteers in two dive/decompression profiles; the model shows a very good agreement with the empirical data and previews different inflammatory outcomes for different experimental profiles. We suggest that slight changes in the parameters' values might turn the simulations from a non-inflammatory to an inflammatory profile for a given individual. Therefore, the present model might help address the problem of DCS on a particular basis.

[Biological effects due to exposure to different concentrations of oxygen from hypo to hyperoxemia]. / Efectos biológicos de la exposición a distintas concentraciones de oxígeno: desde la hipoxia hipobárica al oxígeno hiperbárico.

The systemic effects of oxygen deficiency or excess are not thoroughly described. Knowledge is evolving towards the description of beneficial and detrimental effects of both extremes of partial pressure of oxygen (PaO2). The cellular and tissue mediators derived from the modulation of the oxidative tone and the production of reactive oxygen species (ROS) are widely characterized biochemically, but the pathophysiological characterization is lacking. Preclinical models support the use of hypobaric hypoxia preconditioning, based on its beneficial effects on ventricular function or its reduction in infarct size. A very important use of oxygen today is in commercial diving. However, novel clinical indications for oxygen such as the healing of diabetic foot ulcers and bone injury caused by radiotherapy are increasingly used. On the other hand, the modulation of the hypoxic response associated with exposure to high altitude environments (hypobaric), favors Chile and its highlands as a natural laboratory to determine certain cardiovascular, cerebral and metabolic responses in the resident population. Also, the consequences of the intermittent exposure to high altitudes in workers also deserves attention. This review discusses the physiopathological response to hypo and hyperoxemia, associated with environments with different oxygen concentrations, and brings back the concept of oxygen as a pharmacological mediator in extreme environments such as high altitudes and hyperbaric medicine in divers, decompression sickness, osteonecrosis associated with radiotherapy and sudden sensorineural hearing loss.

SCUBA Diver's Knee: A Case Report.

ABSTRACT: With more than 9 million recreational certified self-contained underwater breathing apparatus divers in the United States, clinicians should be aware of the unique diving-related injuries. One of the most common diving-related injuries is type 1 decompression sickness, or "the bends." The bends commonly manifest as localized joint pain, most often occurring within 24 h of surfacing and resolving over the following 1 to 2 d. We report a unique case of a patient who experienced an exacerbation of musculoskeletal joint pain following initial recovery. This 35-year-old man had nearly complete resolution of his joint pain following the bends, then developed severe right knee pain with swelling after a high-volume lower body workout. Following unremarkable imaging and unsuccessful conservative treatment, ultrasound-guided aspiration of his right knee was performed, which resolved the patient's symptoms. This case highlights a unique presentation of the bends and demonstrates a potentially beneficial treatment if recurrence of the bends is suspected.

Vascular Function Recovery Following Saturation Diving.

Background and Objectives: Saturation diving is a technique used in commercial diving. Decompression sickness (DCS) was the main concern of saturation safety, but procedures have evolved over the last 50 years and DCS has become a rare event. New needs have evolved to evaluate the diving and decompression stress to improve the flexibility of the operations (minimum interval between dives, optimal oxygen levels, etc.). We monitored this stress in saturation divers during actual operations. Materials and Methods: The monitoring included the detection of vascular gas emboli (VGE) and the changes in the vascular function measured by flow mediated dilatation (FMD) after final decompression to surface. Monitoring was performed onboard a diving support vessel operating in the North Sea at typical storage depths of 120 and 136 msw. A total of 49 divers signed an informed consent form and participated to the study. Data were collected on divers at surface, before the saturation and during the 9 h following the end of the final decompression. Results: VGE were detected in three divers at very low levels (insignificant), confirming the improvements achieved on saturation decompression procedures. As expected, the FMD showed an impairment of vascular function immediately at the end of the saturation in all divers but the divers fully recovered from these vascular changes in the next 9 following hours, regardless of the initial decompression starting depth. Conclusion: These changes suggest an oxidative/inflammatory dimension to the diving/decompression stress during saturation that will require further monitoring investigations even if the vascular impairement is found to recover fast.

Risk stratification of neurological decompression sickness in divers.

INTRODUCTION: Patent foramen ovale (PFO) is a risk factor of decompression sickness (DCS). However, data on risk stratification of divers with a PFO are sparse. This study sought to evaluate the risk of neurological DCS (DCSneuro), based on the presence and grade of a right-to-left shunt (RLS). METHODS: A total of 640 divers were screened for a RLS using TCD between 1/2006 and 4/2017. RLS was graded as low, medium, or high grade with two subgroups - after a Valsalva maneuver or at rest. Divers were questioned about their DCS history. Survival analysis techniques were used to assess risk factors for unprovoked DCS. RESULTS: A RLS was found in 258 divers (40.3 %). 44 (17.1 %) divers with a RLS experienced DCSneuro compared to 5 (1.3 %) divers without a RLS (p <0.001). The proportion of DCSneuro increased from 4.6 % in the low-grade RLS subgroup to 57.1 % in the subgroup with high-grade RLS at rest. The hazard ratio for DCSneuro and RLS was11.806 (p <0.001). CONCLUSIONS: Divers with a RLS had a higher risk of DCSneuro and the risk increased with RLS grade. We suggest that TCD is an appropriate method for RLS screening and risk stratification in divers (Tab. 4, Fig. 2, Ref. 29).

Decompression sickness in SCUBA divers.

ABSTRACT: There are approximately 2.8 million active self-contained underwater breathing apparatus (SCUBA) divers in the US who are at risk for decompression sickness. This article discusses the pathophysiology, common signs and symptoms, and treatments of this multisystem complication of SCUBA diving.

Inner ear decompression sickness in a hyperbaric chamber inside tender: a case report.

Inner ear decompression sickness (IEDCS) is a rare diving complication that presents with vestibular dysfunction, cochlear dysfunction, or a combination of both. While scuba diving is a known cause, no cases have been reported in the occupational hyperbaric setting. We present the case of a 55-year-old man who developed IEDCS after working as a hyperbaric multiplace chamber inside tender. The patient was treated with seven sessions of hyperbaric oxygen therapy, resulting in resolution of the majority of his symptoms. This case illustrates a potential occupational hazard of working in a hyperbaric chamber and demonstrates successful treatment with hyperbaric oxygen therapy.

Hyperbaric oxygen for decompression sickness.

Decompression sickness (DCS, "bends") is caused by formation of bubbles in tissues and/or blood when the sum of dissolved gas pressures exceeds ambient pressure (supersaturation). This may occur when ambient pressure is reduced during any of the following: ascent from a dive; depressurization of a hyperbaric chamber; rapid ascent to altitude in an unpressurized aircraft or hypobaric chamber; loss of cabin pressure in an aircraft; and during space walks.

Inner ear decompression sickness in Finland: a retrospective 20-year multicenter study.

Introduction: Inner ear decompression sickness (IEDCS) is a condition from which only a minority of patients recover completely, the majority ending up with mild to moderate residual symptoms. IEDCS has been reported after deep technical dives using mixed breathing gases, and moderate recreational dives with compressed air as the breathing gas. Considering this and the high proportion of technical diving in Finland, a comparison between IEDCS cases resulting from technical and recreational dives is warranted. Methods: This is a retrospective examination of IEDCS patients treated at Hyperbaric Center Medioxygen or National Hyperbaric Centre of Turku University Hospital from 1999 to 2018. Patients were included if presenting with hearing loss, tinnitus, or vertigo and excluded if presenting only with symptoms of middle ear or cerebellar involvement. Patients were divided into technical and recreational divers, based on incident dive. Results: A total of 89 (15.6%) of all DCS patients presented with IEDCS, two-thirds treated during the latter decade. The most common predisposing factors were consecutive days of diving (47.2%), multiple dives per day (53.9%), and factors related to an increase in intrathoracic pressure (27.0%). The symptoms were cochlear in 19.1% and vestibular in 93.3% of cases, symptoms being more common and severe in technical divers. Complete recovery was achieved in 64.5% of technical and 71.4% of recreational divers. Conclusion: The incidence of IEDCS in Finland is increasing, most likely due to changing diving practices. A comprehensive examination should be carried out after an incident of IEDCS in all cases, irrespective of clinical recovery.

Ten-year Spanish cohort of diving-related injuries in a non-hyperbaric tertiary hospital on the Spanish Mediterranean coast.

INTRODUCTION: Global evidence on the epidemiology of prevalent diving-related injuries (DRI) different from decompression sickness (DCS) and other fatalities is lacking. This study aimed to perform a comprehensive review of DRIs in the year-period between 2010-2020 in a non-hyperbaric tertiary hospital in the Spanish Mediterranean coast, in addition to identifying patient risk factors for severe middle ear barotrauma. METHODS: The study was conducted via a retrospective review of medical records during a 10-year period (2010-2020) at the University and Polytechnic Hospital La Fe (UPHLF) of Valencia. We performed a case-control study recruiting controls through an online survey to identify independent predictors for severe middle ear barotrauma. RESULTS: A total of 68 patients with DRI attended the emergency department of our tertiary referral hospital. Barotrauma accounted for more than 80% of DRI, followed by unrecognized DCS and animal-related injuries. Most patients required neither hospital admission nor surgery; appropriate treatment could be carried out largely on an outpatient basis. The presence of subsequent sequelae was minimal. Previous presence of significant ear, nose and throat (ENT) comorbidities (OR 3.05 - CI 95% 1.11 - 8.35), and older age (OR of younger age 0.94 - CI 95% 0.91 - 0.98) were identified as independent risk factors for severe middle ear barotrauma, with an acceptable discrimination capacity (AUC 0.793, 95% CI 0.71 - 0.87). CONCLUSION: The incidence of DRI may be higher than previously thought, and the need to know their epidemiology, their associated morbidity, and the deficiencies of the diving management system is becoming steadily important in order to develop prevention, diagnostic and therapeutic protocols in non-hyperbaric hospitals of these regions.

Variability in venous gas emboli following the same dive at 3,658 meters.

Exposure to a reduction in ambient pressure such as in high-altitude climbing, flying in aircrafts, and decompression from underwater diving results in circulating vascular gas bubbles (i.e., venous gas emboli [VGE]). Incidence and severity of VGE, in part, can objectively quantify decompression stress and risk of decompression sickness (DCS) which is typically mitigated by adherence to decompression schedules. However, dives conducted at altitude challenge recommendations for decompression schedules which are limited to exposures of 10,000 feet in the U.S. Navy Diving Manual (Rev. 7). Therefore, in an ancillary analysis within a larger study, we assessed the evolution of VGE for two hours post-dive using echocardiography following simulated altitude dives at 12,000 feet. Ten divers completed two dives to 66 fsw (equivalent to 110 fsw at sea level by the Cross correction method) for 30 minutes in a hyperbaric chamber. All dives were completed following a 60-minute exposure at 12,000 feet. Following the dive, the chamber was decompressed back to altitude for two hours. Echocardiograph measurements were performed every 20 minutes post-dive. Bubbles were counted and graded using the Germonpré and Eftedal and Brubakk method, respectively. No diver presented with symptoms of DCS following the dive or two hours post-dive at altitude. Despite inter- and intra-diver variability of VGE grade following the dives, the majority (11/20 dives) presented a peak VGE Grade 0, three VGE Grade 1, one VGE Grade 2, four VGE Grade 3, and one VGE Grade 4. Using the Cross correction method for a 66-fsw dive at 12,000 feet of altitude resulted in a relatively low decompression stress and no cases of DCS.