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Durham, NC, United States

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

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. Source

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

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. Source

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

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. Source

Ranapurwala S.I.,University of North Carolina at Chapel Hill | Ranapurwala S.I.,University of Iowa | Denoble P.J.,Divers Alert Network | Poole C.,University of North Carolina at Chapel Hill | And 3 more authors.
International Journal of Epidemiology

Background: Scuba diving mishaps, caused by equipment problems or human errors, increase the occurrence of injuries and fatalities while diving. Pre-dive checklists may mitigate mishaps. This study evaluated the effect of using a pre-dive checklist on the incidence of diving mishaps in recreational divers. Methods: A multi-location cluster-randomized trial with parallel groups and allocation concealment was conducted between 1 June and 17 August 2012. The participants had to be at least 18 years of age, permitted to dive by the dive operator and planning to dive on the day of participation. They were recruited at the pier and dive boats at four locations. The intervention group received a pre-dive checklist and post-dive log. The control group received a post-dive log only. The outcomes, self-reported major and minor mishaps, were prompted by a post-dive questionnaire. Mishap rates per 100 dives were compared using Poisson regression with generalized estimating equations. Intent-totreat, per-protocol and marginal structural model analyses were conducted. Results: A total of 1043 divers (intervention 1/4 617; control 1/4 426) made 2041 dives, on 70 location-days (intervention1/440; control1/430) at four locations. Compared with the control group, the incidence of major mishaps decreased in the intervention group by 36%, minor mishaps by 26% and all mishaps by 32%. On average, there was one fewer mishap in every 25 intervention dives. Conclusions: In this trial, pre-dive checklist use prevented mishaps which could lead to injuries and fatalities. Pre-dive checklists can increase diving safety and their use should be promoted. © The Author 2015. Source

Harvey D.,Auckland City Hospital | Pollock N.W.,Divers Alert Network | Pollock N.W.,Duke University | Gant N.,University of Auckland | And 4 more authors.
Diving and Hyperbaric Medicine

Introduction: Diving rebreathers use canisters containing sodalime preparations to remove carbon dioxide (CO2) 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. Methods: An Inspiration rebreather was operated in a benchtop circuit under conditions simulating work at 6 metabolic equivalents (MET). Ventilation was maintained at 45 L•min-1 (tidal volume 1.5 L; respiratory rate 30 min-1) with CO2 introduced to the expiratory limb at 2 L•min-1. The PICO2 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 PICO2 reached 1 kPa ('breakthrough'). Peak inspiratory and expiratory pressures during tidal ventilation of the circuit were also recorded. Results: The mean operating duration to CO2 breakthrough was 138 ± 4 (SD) minutes for 2.38 kg Spherasorb and 202 ± minutes for 2.64 kg Sofnolime (P < 0.0001). The difference between peak inspiratory and expiratory pressures was 10% less during use of Spherasorb, suggesting lower work of breathing. Conclusions: Under conditions simulating work at 6 MET during use of an Inspiration rebreather a canister packed with Spherasorb reached CO2 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. © 2016, South Pacific Underwater Medicine Society. All rights reserved. Source

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