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Thom S.R.,University of Pennsylvania | Milovanova T.N.,University of Pennsylvania | Bogush M.,University of Pennsylvania | Bhopale V.M.,University of Pennsylvania | And 6 more authors.
Journal of Applied Physiology | Year: 2012

The goal of this study was to evaluate annexin V-positive microparticles (MPs) and neutrophil activation in humans following decompression from open-water SCUBA diving with the hypothesis that changes are related to intravascular bubble formation. Sixteen male volunteer divers followed a uniform profile of four daily SCUBA dives to 18 m of sea water for 47 min. Blood was obtained prior to and at 80 min following the first and fourth dives to evaluate the impact of repetitive diving, and intravascular bubbles were quantified by trans-thoracic echocardiography carried out at 20-min intervals for 2 h after each dive. MPs increased by 3.4-fold after each dive, neutrophil activation occurred as assessed by surface expression of myeloperoxidase and the CD18 component of β 2-integrins, and there was an increased presence of the platelet-derived CD41 protein on the neutrophil surface indicating interactions with platelet membranes. Intravascular bubbles were detected in all divers. Surprisingly, significant inverse correlations were found among postdiving bubble scores and MPs, most consistently at 80 min or more after the dive on the fourth day. There were significant positive correlations between MPs and plateletneutrophil interactions after the first dive and between platelet-neutrophil interactions and neutrophil activation documented as an elevation in β 2-integrin expression after the fourth dive. We conclude that MPs- and neutrophil-related events in humans are consistent with findings in an animal decompression model. Whether there are causal relationships among bubbles, MPs, platelet-neutrophil interactions, and neutrophil activation remains obscure and requires additional study. Copyright © 2012 the American Physiological Society.


PubMed | University of Auckland, Lust for Rust Diving, Divers Alert Network and Auckland City Hospital
Type: Comparative Study | Journal: Diving and hyperbaric medicine | Year: 2016

Diving rebreathers use canisters containing sodalime preparations to remove carbon dioxide (CO) from the expired gas. These preparations have a limited absorptive capacity and therefore may limit dive duration. The Inspiration rebreather is designed for use with Sofnolime 797 but some divers use Spherasorb as an alternative. There are no published data comparing the CO2-absorbing efficacy of these sodalime preparations in an Inspiration rebreather.An Inspiration rebreather was operated in a benchtop circuit under conditions simulating work at 6 metabolic equivalents (MET). Ventilation was maintained at 45 Lmin (tidal volume 15 L; respiratory rate 30 min) with CO introduced to the expiratory limb at 2Lmin. The PiCO was continuously monitored in the inspiratory limb. The rebreather canister was packed to full volume with either Sofnolime or Spherasorb and 10 trials were conducted (five using each absorbent), in which the circuit was continuously run until the PiCO reached 1 kPa (breakthrough). Peak inspiratory and expiratory pressures during tidal ventilation of the circuit were also recorded.The mean operating duration to CO breakthrough was 138 4 (SD) minutes for 2.38kg Spherasorb and 202 minutes for 2.64kg Sofnolime (P < 0.0001). The difference between peak inspiratory and expiratory pressures was 10% less during use of Spherasorb, suggesting lower work of breathing.Under conditions simulating work at 6 MET during use of an Inspiration rebreather a canister packed with Spherasorb reached CO breakthrough 32% earlier with 10% less mass than Sofnolime packed to similar volume. Divers cannot alternate between these two preparations and expect the same endurance.


PubMed | University of Florida, Divers Alert Network and University of Western States
Type: Journal Article | Journal: Diving and hyperbaric medicine | Year: 2016

Cave divers enter an inherently dangerous environment that often includes little visibility, maze-like passageways and a ceiling of rock that prevents a direct ascent to the surface in the event of a problem.Reports of cave diving fatality cases occurring between 01 July 1985 and 30 June 2015 collected by Divers Alert Network were reviewed. Training status, safety rules violated, relevancy of the violations, and root causes leading to death were determined.A total of 161 divers who died were identified, 67 trained cave divers and 87 untrained. While the annual number of cave diving fatalities has steadily fallen over the last three decades, from eight to less than three, the proportion of trained divers among those fatalities has doubled. Data regarding trained cave divers were divided into two equal 15-year time periods. Trained cave divers who died in the most recent time period were older but little else differed. The most common cause of death was asphyxia due to drowning, preceded by running out of breathing gas, usually after getting lost owing to a loss of visibility caused by suspended silt. An overwhelming majority of the fatalities occurred in the state of Florida where many flooded caves are located.Even with improvements in technology, the greatest hazards faced by cave divers remain unchanged. Efforts to develop preventative interventions to address these hazards should continue.


Buzzacott P.,University of Western Australia | Buzzacott P.,University of Western Brittany | Pollock N.W.,Divers Alert Network | Pollock N.W.,Duke University | Rosenberg M.,University of Western Australia
Diving and Hyperbaric Medicine | Year: 2014

Introduction: Episodic exercise is a risk factor for acute cardiac events and cardiac complications are increasingly recognized in fatalities during recreational scuba diving. What is not known is the exercise intensity involved in typical recreational diving. Methods: This study used pre- to post-dive gas cylinder pressure drop to estimate air consumption and, from that, exercise intensity during recreational dives. Dive profiles were captured electronically and divers self-reported cylinder pressure changes, perceived workload, thermal status and any problems during dives. Mean surface air consumption (SAC) rate per kg body weight and mean exercise intensity (reported in metabolic equivalents, MET, multiples of assumed resting metabolic rate of 3.5 mL·kg-1·min-1) were then estimated. Data are reported as mean ± standard deviation. Results: A total of 959 recreational air dives (20 ± 9 metres' sea water maximum depth; 50 ± 12 min underwater time) by 139 divers (42 ± 10 y age; 11 ± 10 y of diving; 12% smokers; 73% male) were monitored. Problems were reported with 129/959 dives: buoyancy (45%), equalization (38%), rapid ascent (10%), vertigo (5%) and other (2%). Assuming a 10% overestimate due to cylinder cooling and uncontrolled gas loss, the estimated exercise intensity associated with monitored dives was 5 ± 1 MET. Mean ± 2SD, or 7 MET, captures the effort associated with the vast majority of dives monitored. Conclusion: Our estimates suggest that uncomplicated recreational dives require moderate-intensity energy expenditure to complete, with a 7-MET capacity generally adequate. Higher levels of aerobic fitness are still strongly recommended to ensure ample reserves. Further research is needed to quantify energetic demands of recreational diving during both typical and emergent events in both experienced and less experienced divers.


Gutvik C.R.,Norwegian University of Science and Technology | Dunford R.G.,Divers Alert Network | Dujic Z.,University of Split | Brubakk A.O.,Norwegian University of Science and Technology
Medical and Biological Engineering and Computing | Year: 2010

Decompression Sickness (DCS) may occur when divers decompress from a hyperbaric environment. To prevent this, decompression procedures are used to get safely back to the surface. The models whose procedures are calculated from, are traditionally validated using clinical symptoms as an endpoint. However, DCS is an uncommon phenomenon and the wide variation in individual response to decompression stress is poorly understood. And generally, using clinical examination alone for validation is disadvantageous from a modeling perspective. Currently, the only objective and quantitative measure of decompression stress is Venous Gas Emboli (VGE), measured by either ultrasonic imaging or Doppler. VGE has been shown to be statistically correlated with DCS, and is now widely used in science to evaluate decompression stress from a dive. Until recently no mathematical model has existed to predict VGE from a dive, which motivated the development of the Copernicus model. The present article compiles a selection experimental dives and field data containing computer recorded depth profiles associated with ultrasound measurements of VGE. It describes a parameter estimation problem to fit the model with these data. A total of 185 square bounce dives from DCIEM, Canada, 188 recreational dives with a mix of single, repetitive and multi-day exposures from DAN USA and 84 experimentally designed decompression dives from Split Croatia were used, giving a total of 457 dives. Five selected parameters in the Copernicus bubble model were assigned for estimation and a non-linear optimization problem was formalized with a weighted least square cost function. A bias factor to the DCIEM chamber dives was also included. A Quasi-Newton algorithm (BFGS) from the TOMLAB numerical package solved the problem which was proved to be convex. With the parameter set presented in this article, Copernicus can be implemented in any programming language to estimate VGE from an air dive. © 2010 International Federation for Medical and Biological Engineering.


Dardeau M.R.,Dauphin Island Sea Laboratory | Pollock N.W.,Divers Alert Network | McDonald C.M.,University of California at San Diego | Lang M.A.,Smithsonian Institution
Diving and Hyperbaric Medicine | Year: 2012

Background: The American Academy of Underwater Science (AAUS) constitutes the single largest pool of organizations with scientific diving programmes in North America. Members submit annual summaries of diving activity and any related incidents. Methods: All diving records for a 10-year period between January 1998 and December 2007 were reviewed. Incidents were independently classified or reclassified by a four-person panel with expertise in scientific diving and diving safety using a previously published protocol. Subsequent panel discussion produced a single consensus classification of each case. Results: A total of 95 confirmed incidents were reported in conjunction with 1,019,159 scientific dives, yielding an overall incidence of 0.93/10,000 person-dives. A total of 33 cases were determined to involve decompression illness (DCI), encompassing both decompression sickness and air embolism. The incidence of DCI was 0.324/10,000 person-dives, substantially lower than the rates of 0.9-35.3/10,000 published for recreational, instructional/guided, commercial and/or military diving. Conclusions: Scientific diving safety may be facilitated by a combination of relatively high levels of training and oversight, the predominance of shallow, no-decompression diving and, possibly, low pressure to complete dives under less than optimal circumstances.


PubMed | Divers Alert Network and University of Western Australia
Type: Journal Article | Journal: Journal of travel medicine | Year: 2016

Adult male recreational diver fatalities (n = 698) in North America from 2004 to 2013 were examined. Compared with non-harvesters, boat (86 vs 59%), solo (26 vs 13%) and night diving (10 vs 3%) were more common among harvesters. Of the divers who were low-on or out-of air, 20% were harvesters and 11% non-harvesters (OR=2.0, P = 0.03).


Vann R.,Divers Alert Network | Vann R.,Duke University | Lang M.,Smithsonian Institution
Undersea and Hyperbaric Medicine | Year: 2011

The risks of dying during recreational diving are small. The Divers Alert Network (DAN) held a workshop to consider whether the risks could be reduced further. Topics included investigation, surveillance, operational safety and cardiovascular disease. Investigation is essential to determine causes and involves on-scene inquiry, forensic examination of the deceased, and testing of life support equipment, but thorough investigations are unusual. Independent annual fatality rates were presented and reviewed for diving, jogging, and motor vehicle accidents and for divers in training. Common factors associated with diving fatalities included running out of gas, entrapment or entanglement, buoyancy control, equipment misuse, rough waters and emergency ascent. Asphyxia by drowning, air embolism and cardiac events were the principal injuries or causes of death. About one-quarter of the deaths were associated with cardiac events, mostly in older divers. Revised procedures were recommended for identifying occult cardiovascular disease in candidate divers who warrant further investigation, but older, previously certified divers may be at greatest risk. Copyright © 2011 Undersea & Hyperbaric Medical Society, Inc.


Bilopavlovic N.,University of Split | Marinovic J.,University of Split | Ljubkovic M.,University of Split | Obad A.,University of Split | And 4 more authors.
European Journal of Applied Physiology | Year: 2013

During SCUBA diving decompression, there is a significant gas bubble production in systemic veins, with rather frequent bubble crossover to arterial side even in asymptomatic divers. The aim of the current study was to investigate potential changes in humoral markers of endothelial and brain damage (endothelin-1, neuron-specific enolase and S-100β) after repetitive SCUBA diving with concomitant assessment of venous gas bubble production and subsequent arterialization. Sixteen male divers performed four open-water no-decompression dives to 18 msw (meters of sea water) lasting 49 min in consecutive days during which they performed moderate-level exercise. Before and after dives 1 and 4 blood was drawn, and bubble production and potential arterialization were echocardiographically evaluated. In addition, a control dive to 5 msw was performed with same duration, water temperature and exercise load. SCUBA diving to 18 msw caused significant bubble production with arterializations in six divers after dive 1 and in four divers after dive 4. Blood levels of endothelin-1 and neuron-specific enolase did not change after diving, but levels of S-100β were significantly elevated after both dives to 18 msw and a control dive. Creatine kinase activity following a control dive was also significantly increased. Although serum S-100β levels were increased after diving, concomitant increase of creatine kinase during control, almost bubble-free, dive suggests the extracranial release of S-100β, most likely from skeletal muscles. Therefore, despite the significant bubble production and sporadic arterialization after open-water dives to 18 msw, the current study found no signs of damage to neurons or the blood-brain barrier. © 2013 Springer-Verlag Berlin Heidelberg.


Ranapurwala S.I.,Divers Alert Network | Ranapurwala S.I.,University of North Carolina at Chapel Hill | Bird N.,Duke University | Vaithiyanathan P.,Divers Alert Network | Denoble P.J.,Divers Alert Network
Diving and Hyperbaric Medicine | Year: 2014

Background: Scuba diving injuries vary greatly in severity and prognosis. While decompression sickness (DCS) and arterial gas embolism can be tracked easily, other forms of diving injury remain unaccounted for. Purpose: The purpose of this paper is to assess rates of overall self-reported scuba-diving-related injuries, self-reported DCS-like symptoms, and treated DCS and their association with diver certification level, diving experience and demographic factors. Methods: We analyzed self-reported data from a Divers Alert Network membership health survey conducted during the summer of 2011. Poisson regression models with scaled deviance were used to model the relative rates of reported injuries. Models were adjusted for sex, age, body mass index (BMI) and average annual dives, based on the bias-variance tradeoff. Results: The overall rate of diving-related injury was 3.02 per 100 dives, self-reported DCS symptoms was 1.55 per 1,000 dives and treated DCS was 5.72 per 100,000 dives. Diving-related injury and self-reported DCS symptom rates decreased for higher diver certification levels, increasing age, increasing number of average annual dives and for men; they increased for increasing BMI. Conclusions: Diving injury rates may be higher than previously thought, indicating a greater burden on the diving community. Self-reported DCS-like symptoms are a small fraction of all dive-related injuries and those receiving treatment for DCS are an even smaller fraction. The small number of divers seeking treatment may suggest the mild nature and a tendency towards natural resolution for most injuries.

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