Decompression Sickness Research Articles

A New Phantom that Simulates Electrically a Human Blood Vessel Surrounded by Tissues: Development and Validation Against In-Vivo Measurements.

This study aims to develop a phantom that simulates the electrical properties of a human blood vessel surrounded by tissues, inside which bubbles can be infused to mimic Decompression Sickness (DCS) conditions. This phantom may be used to calibrate novel electrical methods for bubbles detection in humans and study bubble dynamics during DCS. It may contribute to the limitation of in-vivo trials and time/effort saving, while its use can be extended to other biomedical applications. To facilitate the design of the phantom, we perform first in-vitro measurements in a flow-loop and in-vivo measurements in a swine, in order to detect infused bubbles of a few tenths μm-representing Decompression Sickness conditions-in the test liquid flow and blood flow, respectively, by means of "I-VED" EU patented electrical impedance spectroscopy technique. Results show that the proposed phantom, consisting of a spongy specimen soaked in agar gel in the presence of electrolyte with a hole along it, simulates adequately the electrical properties of a human blood vessel surrounded by tissues. I-VED demonstrates pretty high sensitivity to sense micro-bubbles over the partially conductive vessel walls of the phantom or the isolated animal vein, as well as in the flow-loop: bubbles presence increases electrical impedance and causes intense signal fluctuations around its mean value.

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.

Proposed Thalmann Algorithm Air Diving Decompression Table for the Swedish Armed Forces Based on Logistic Probabilistic Modeling of No-Stop Air Diving Data

The Swedish Armed Forces (SwAF) air dive tables are under revision. Currently, the air dive table from US Navy (USN) Diving manual (DM) Rev.6 is used with a msw to fsw conversion. Since 2017, USN has been diving according to USN DM rev. 7, which incorporates updated air dive tables derived from the exponential linear decompression algorithm (EL-DCM) Thalmann 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 2953 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). 154 wet validation dives were performed with air between 18-57 msw. Both direct ascent and decompression stop dives were conducted, resulting in two joint pain DCS (18msw/59min), one leg numbness CNS-DCS (51msw/10min with deco-stop), and nine marginal DCS, such as rashes and itching. A total of three DCS, 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, PFO. 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.

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.

Decompression sickness followed by diabetic ketoacidosis and sepsis shock: an unusual case report

Decompression sickness (DCS) is a disease caused by abrupt change of extracorporeal pressure, with varying severity. Symptoms range from mild musculoskeletal pain to severe organ dysfunction and death, especially among patients with chronic underlying disease. Here, we report an unusual case of a 49-year-old man who experienced DCS after a dive to a depth of 38 meters. The patient’s symptoms progressed, starting with mild physical discomfort that progressed to disturbance of consciousness on the second morning. During hospitalization, we identified that in addition to DCS he had also developed diabetic ketoacidosis, septic shock, and rhabdomyolysis. After carefully balancing the benefits and risks, we decided to provide a series of supportive treatment to sustain vital signs, including ventilation support, sugar-reducing therapy, fluid replacement, and anti-infection medications. We then administered delayed hyperbaric oxygen (HBO2) when his condition was stable. Ultimately, the patient recovered without any sequelae. This is the first case report of a diver suffering from DCS followed by diabetic ketoacidosis and septic shock. We have learned that when DCS, along with other critical illness is highly suspected, it is essential to assess the condition comprehensively and focus on the principal contradiction.

Inner ear decompression sickness after a routine dive and recompression chamber drill: A case report

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 in 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.

Role of health locus of control in preventing occupational decompression sickness among deep-sea fisherman divers

ABSTRACT Background Indigenous fisherman divers frequently experience decompression sickness (DCS). This study aimed to evaluate the associations between the level of knowledge of safe diving, beliefs in the health locus of control (HLC), and regular diving practices with DCS among the indigenous fisherman divers on Lipe island. The correlations among the level of beliefs in HLC, knowledge of safe diving and regular diving practices were evaluated also. Method We enrolled the fisherman divers on Lipe island and collected their demographics, health indices, levels of knowledge of safe diving, beliefs in external and internal HLC (EHLC and IHLC), and regular diving practices to evaluate the associations with the occurrence of DCS by logistic regression analysis. Pearson’s correlation was used to test the correlations among the level of beliefs in IHLC and EHLC, knowledge of safe diving, and regular diving practices. Results Fifty-eight male fisherman divers whose mean age was 40.39 (±10.61) (range 21–57) years were enrolled. Twenty-six (44.8%) participants had experienced DCS. Body mass index (BMI), alcohol consumption, diving depth, duration of time in the sea/dive, level of beliefs in HLC and regular diving practices were significantly associated with DCS (p < 0.05). Level of belief in IHLC had a significantly strong reverse correlation with that in EHLC and a moderate correlation with level of knowledge of safe diving and regular diving practices. By contrast, level of belief in EHLC had a significantly moderate reverse correlation with level of knowledge of safe diving and regular diving practices (p < 0.001). Conclusions Encouraging the fisherman divers’ belief in IHLC could be beneficial for their occupational safety.

Caisson Disease among Recreational Divers: Review Literature

Introduction: Caisson disease is one of the most common emergencies in divers with very common signs and symptoms that clinicians must be careful to identify based on a complete history and physical examination. The disease also requires immediate and definitive management, usually hyperbaric therapy for a better prognosis.&#x0D; Content: This article discussed the types, pathophysiology, and management of caisson disease caused by the release of nitrogen gas bubbles into the blood or tissues during or after a pressure drop in the environment. This is a disease that can be prevented by paying attention to existing risk factors.&#x0D; Summary: Caisson disease or decompression sickness is a collection of symptoms that are often encountered in archipelagic countries and can affect anyone diving for seafood or recreational activities. The symptoms are common, but by knowing the pathophysiology, clinicians can identify the disease and immediately perform therapy, thereby preventing complications such as arterial a gas embolism (AGE) so the mortality and morbidity due to caisson disease can be reduced.

Pulsatile gas-liquid flow resembling Decompression Sickness: Computational Fluid Dynamics simulation and experimental validation.

This work performs two-dimensional Computational Fluid Dynamics (CFD) simulations of pulsatile bubbly flow in a column resembling the flow inside human vena cava during Decompression Sickness (DCS), aiming to illustrate the effect of certain parameters in bubbly blood flow and so facilitate the design of the: a) corresponding in-vitro bubbly flow experiments under pulsatile flow conditions inside a flow loop and b) in-vivo trials on swines for assessing a novel electrical impedance spectroscopy technique on the detection of bubbles (as those found during DCS) in their bloodstream. The commercially available ANSYS 2019-R3 CFD code was employed to simulate the pulsatile bubbly flow that resembled DCS. Simulations were validated against experiments conducted in a vertical co-current upward pulsatile bubbly flow provided by a flow loop equipped with electrical, optical and pressure diagnostics. CFD simulations under pulsatile conditions were initially validated by oscillatory in-vitro bubbly flow experiments. Then, the influence of pulsation parameters on void fraction, α, and flow velocity, U, profiles was computationally investigated. Intense periodic fluctuations of void fraction were observed along the column and their intensity increases with pulsation amplitude. Moreover, U and α radial profiles were uniform for bubbles 30 μm but showed a core-peaking profile for bubbles 300 μm. CFD simulations of pulsatile bubbly flow resembling DCS provided unconventional information about the influence of different-sized sub-millimetre bubbles on the flow velocity and void fraction profiles, which are expected to improve the design of in-vitro and in-vivo trials for the detection of bubbles such as those found in DCS.

Descriptive study of decompression illness in a hyperbaric medicine centre in Bangkok, Thailand from 2015 to 2021.

This study aimed to determine the characteristics of decompression illness patients and their treatment outcomes, at the Center of Hyperbaric Medicine, Somdech Phra Pinklao Hospital, one of the largest centres in Thailand. Past medical records of patients with decompression illness from 2015 to 2021 were retrieved and analysed. Ninety-eight records of diving-related illness from 97 divers were reviewed. Most of the divers were male (n = 50), Thai (n = 86), and were certified at least open water or equivalent (n = 88). On-site first aid oxygen inhalation was provided to 17 divers. Decompression sickness (DCS) cases were characterised according to organ systems involved. The most prominent organ system involved was neurological (57%), followed by mixed organs (28%), musculoskeletal (13%), and pulmonary (2%). There were three cases of arterial gas embolism (AGE). Median presentation delay was three days. Ninety patients were treated with US Navy Treatment Table 6. At the end of their hyperbaric oxygen treatment, most divers (65%) recovered completely. Despite oxygen first aid being given infrequently and long delays before definitive treatment, treatment outcome was satisfactory. Basic knowledge and awareness of diving-related illnesses should be promoted among divers and related personnel in Thailand along with further studies.

The potential of hyperbaric oxygen as a therapy for neurodegenerative diseases.

The World Health Organization estimates that by the year 2040, neurodegenerative diseases will be the second leading cause of death in developed countries, overtaking cancer-related deaths and exceeded only by cardiovascular disease-related death. The search for interventions has therefore become paramount to alleviate some of this burden. Based on pathways affected in neurodegenerative diseases, hyperbaric oxygen treatment (HBOT) could be a good candidate. This therapy has been used for the past 50years for conditions such as decompression sickness and wound healing and has been shown to have promising effects in conditions associated with neurodegeneration and functional impairments. The goal of this review was to explore the history of hyperbaric oxygen therapy, its uses, and benefits, and to evaluate its effectiveness as an intervention in treating neurodegenerative diseases. Additionally, we examined common mechanisms underlying the effects of HBOT in different neurodegenerative diseases, with a special emphasis on epigenetics.

Inner Ear Decompression Sickness (Iedcs) in Divers

Background: Inner ear decompression sickness (IEDCS) is a common disease in divers. In Indonesia, IEDCS is often experienced by diver fishermen in fulfilling their daily needs. In general, decompression sickness (DCS) is caused by the formation of gas bubbles in blood vessels and organ tissues. This is due to the deposition of gas bubbles in the endolymphatic and perilymphatic spaces during the process of their rapid rise to the surface.&#x0D; &#x0D; Objective: This study aims to identify IEDCS disease in divers.&#x0D; &#x0D; Method: This study used a qualitative approach with a case study model that analyzes and identifies the symptoms that appear in divers suffering from IEDCS.&#x0D; &#x0D; Result: Symptoms of classic IEDCS develop in about 30 minutes and are vestibular, these include vertigo, ataxia, nausea, and vomiting. The preferred therapy that can be given to people with DCS and IEDCS is hyperbaric oxygen therapy (recompression therapy) immediately. Complications are rare after hyperbaric oxygen therapy. After therapy and DCS sufferers recover, there will usually still be residual deficits in balance and hearing. Diving according to protocol and providing information about DCS through education, counseling, or other media needs to be done for at-risk groups to create knowledge that is relevant and can take precautions.&#x0D; &#x0D; Conclusion: The disease of decompression of the part ear is common in compressed gas divers. This is due to the deposition of gas bubbles in the endolymphatic and perilymphatic chambers during the process of rising to the surface quickly.

The Japanese Law Regulating Underwater and Caisson Work: Current Issues and Future Developments

The Japan "Ordinance on Safety and Health of Work under High Pressure", which is the law regulating health conditions for workers under high pressure environments, was amended in 2014. The revised regulations have highlighted other difficulties and new problems, but they have not yet written an appropriate amendment based on the aspect of occupational and environmental health. Health management for occupational divers and caisson workers in accordance with the new regulations has not determined the best approach to reducing related disorders and will cause other legal problems. This paper presents some issues in the new regulations for hyperbaric workers, which directly or indirectly involve occupational health physicians. Health checkups and work limitations should be done in consideration of the occupational characteristics of the undersea and hyperbaric environment. Regular examinations using specific studies are useful to diagnose the early stages of chronic conditions for workers, and are also useful for determining the hiring suitability for hyperbaric workers. Work limitations should be decided by the conditions that induce serious accidents or disorders that result from exposure to hyperbaric environments, and depend on the obstacles for work due to sequelae of decompression sickness. The new regulations need to be properly revised, based on scientific evidence, to include health management for workers in undersea and hyperbaric environments.

Theoretical and Experimental Studies of Acoustic Reflection of Bubbly Liquid in Multilayer Media

Bubbly liquids are widely present in the natural environment and industrial fields, such as seawater near the ocean bottom, the multiphase flow in petroleum reservoirs, and the blood with bubbles resulting in decompression sickness. Therefore, accurate measurement of the gas content is of great significance for hydroacoustic physics, oil and gas resources exploration, and disease prevention and diagnosis. Trace bubbles in liquids can lead to considerable changes in the acoustic properties of gas–liquid two-phase media. Acoustic measurements can therefore be applied for trace bubble detection. This study derived the reflection coefficient of acoustic waves propagating in a sandwich layering model with liquid, bubbly liquid, and liquid. The influences of gas contents on the reflection coefficient at the layer interface were analyzed based on theoretical calculations. It was revealed that the magnitude of the reflection coefficient and the frequency interval between its valleys have a quantitative correlation with the gas contents. Thus, a novel means to detect the contents of trace bubbles was proposed by evaluating the reflection coefficients. The reflection features of a thin layer with bubbly liquid were then studied through experiments. It was validated by acoustical measurements and theories that the reflection coefficient is considerably sensitive to the change of gas contents as long as the gas content is tiny. With the increasing gas content, the maximum value of the reflection coefficient increases; meanwhile, the frequency intervals between the valleys become smaller. However, when the gas content is extensive enough, e.g., greater than 1%, the effect of the change of gas content on the reflection coefficient becomes inapparent. In that case, it is not easy to measure the gas content by the acoustic reflection signals with satisfying precision. This proposed method has potential applications for the detection of trace gas bubble content in several scenarios, e.g., decompression illness prevention and diagnosis.

Remarkable consistency of spinal cord microvasculature in highly adapted diving odontocetes.

Odontocetes are breath-hold divers with a suite of physiological, anatomical, and behavioral adaptations that are highly derived and vastly different from those of their terrestrial counterparts. Because of these adaptations for diving, odontocetes were originally thought to be exempt from the harms of nitrogen gas embolism while diving. However, recent studies have shown that these mammals may alter their dive behavior in response to anthropogenic sound, leading to the potential for nitrogen supersaturation and bubble formation which may cause decompression sickness in the central nervous system (CNS). We examined the degree of interface between blood, gases, and neural tissues in the spinal cord by quantifying its microvascular characteristics in five species of odontocetes (Tursiops truncatus, Delphinus delphis, Grampus griseus, Kogia breviceps, and Mesoplodon europaeus) and a model terrestrial species (the pig-Sus scrofa domesticus) for comparison. This approach allowed us to compare microvascular characteristics (microvascular density, branching, and diameter) at several positions (cervical, thoracic, and lumbar) along the spinal cord from odontocetes that are known to be either deep or shallow divers. We found no significant differences (p < 0.05 for all comparisons) in microvessel density (9.30-11.18%), microvessel branching (1.60-2.12 branches/vessel), or microvessel diameter (11.83-16.079µm) between odontocetes and the pig, or between deep and shallow diving odontocete species. This similarity of spinal cord microvasculature anatomy in several species of odontocetes as compared to the terrestrial mammal is in contrast to the wide array of remarkable physio-anatomical adaptations marine mammals have evolved within their circulatory system to cope with the physiological demands of diving. These results, and other studies on CNS lipids, indicate that the spinal cords of odontocetes do not have specialized features that might serve to protect them from Type II DCS.

Increasing the gas dissolution rate of bubbles via a non-invasive resonant acoustic technique

An acoustic technique designed to increase the gas-dissolution rate of a bubble in a liquid medium is here presented. The increased gas-dissolution rate is achieved by increasing the bubble’s surface-to-volume ratio via bubble fragmentation. This was accomplished by attaching an electroacoustic transducer to the system or load in which bubbles travel and exciting the transducer at the frequency of resonance. We have demonstrated that the electric resonance of the transducer attached to the system corresponds in frequency to the mechanical resonance which allows for achieving such a state without the use of an internally placed hydrophone to certify the resonance state. The acoustic bubble fragmentation technique proved to be able to increase the dissolution rate 4 to 5 times of bubbles with initial diameters between 150 and 550 µm in distilled water and in medical grade saline solution. Possible mechanisms responsible for the results obtained are discussed as well as additional advantages of the technique. The technique has potential medical applications such as an on-site emergency treatment for scuba divers suspected to be at risk of developing decompression sickness and in any other clinical scenario where the risk of an air embolism might be present.

Comment to "Severe acute kidney injury caused by decompression sickness syndrome" 2022; 97: 298-304. doi: 10.5414/CN110662.

Comment to "Severe acute kidney injury caused by decompression sickness syndrome" 2022; 97: 298-304. doi: 10.5414/CN110662.

Authors' response to comment to "Severe acute kidney injury caused by decompression sickness syndrome" 2022; 97: 298-304. doi: 10.5414/CN110662.

Authors' response to comment to "Severe acute kidney injury caused by decompression sickness syndrome" 2022; 97: 298-304. doi: 10.5414/CN110662.

Does swimming activity influence gas bubble trauma in fish?

AbstractTotal dissolved gas (TDG) supersaturation from sources such as hydroelectric dams can cause harmful bubble growth in the tissues of aquatic animals, known as gas bubble trauma (GBT). Locomotion is known to exacerbate bubble growth in tissues during decompression under certain conditions (such as in diving animals), possibly because of increased bubble nucleation. As with decompression sickness, GBT is caused by the supersaturation of tissues with gas, and thus we hypothesize that locomotion promotes bubble nucleation in the tissues of fish exposed to TDG supersaturation. Many previous laboratory studies have tested the effects of TDG on fish exposed to low‐velocity, non‐directional flow, whereas fish in field conditions are exposed to higher‐velocity flows and are likely more active. Therefore, it is important to understand the effects of locomotion on GBT to apply laboratory results to active fish in field conditions. We exposed rainbow trout (Oncorhynchus mykiss) to either control (100% TDG) or TDG supersaturation (123% TDG) in either static or flowing water conditions (1.8 Bl/s) and recorded time to 50% loss of equilibrium (LOE). We observed no statistically significant difference in time to 50% LOE between flow conditions. Given the lack of statistically significant difference between static and flowing water, our findings indicate that results from GBT experiments on rainbow trout in non‐directional flow are applicable to more active individuals.

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.