Dangerous Recreational Activity

Drowning isn’t the only danger in water - some aquatic animals can be deadly. The scuba diver who dies underwater poses a difficult diagnostic dilemma for investigating authorities and pathologists. Barotrauma caused by the failure of a gasfilled body cavity to equalize its internal pressure with changes in the ambient pressure is another cause of death. Investigation should be thorough and follow a standardized outline. This investigation should include the victim’s past medical and social history, dive profile, a detailed history of the terminal event and resuscitation efforts, environmental conditions, examination of the diving equipment and finally the autopsy.

An Underwater Pathfinding Algorithm for Optimised Planning of Survey Dives

In scientific and technical diving, the survey of unknown or partially unexplored areas is a common task that requires an accurate planning for ensuring the optimal use of resources and the divers’ safety. In particular, in any kind of diving activity, it is essential to foresee the “dive profile” that represents the diver’s exposure to pressure over time, ensuring that the dive plan complies with the specific safety rules that have to be applied in accordance with the diver’s qualification and the environmental conditions. This paper presents a novel approach to dive planning based on an original underwater pathfinding algorithm that computes the best 3D path to follow during the dive in order to be able to maximise the number of points of interest (POIs) visited, while taking into account the safety limitations. The proposed approach, for the first time, considers the morphology of the 3D space in which the dive takes place to compute the best path, taking into account the decompression limits and avoiding the obstacles through the analysis of a 3D map of the site. Moreover, three different cost functions are proposed and evaluated to identify the one that could suit the divers’ needs better.

Carbon monoxide poisoning while scuba diving: a rare event?

Contamination of breathing gas is a risk for all divers. Some hydrocarbon contaminants will be sensed by the diver and the dive profile aborted. On the contrary, carbon monoxide may not be recognized by the diver and catastrophic consequences can result. Reported here is the fatal case of carbon monoxide poisoning while scuba diving, an event that has rarely been reported in the medical literature. A detailed review of other published cases of CO poisoning while scuba diving is included, attempting to identify causes in common and propose methods of prevention.

A study of decompression sickness using recorded depth-time profiles

Introduction: 122,129 dives by 10,358 recreational divers were recorded by dive computers from 11 manufacturers in an exploratory study of how dive profile, breathing gas (air or nitrox [N2/O2] mixes), repetitive diving, gender, age, and dive site conditions influenced observed decompression sickness (DCSobs). Thirty-eight reports were judged as DCS. Overall DCSobs was 3.1 cases/104 dives. Methods: Three dive groups were studied: Basic (live-aboard and shore/dayboat), Cozumel Dive Guides, and Scapa Flow wreck divers. A probabilistic decompression model, BVM(3), controlled dive profile variability. Chi-squared test, t-test, logistic regression, and log-rank tests evaluated statistical associations. Results: (a) DCSobs was 0.7/104 (Basic), 7.6/104 (Guides), and 17.3/104 (Scapa) and differed after control for dive variability (p<0.001). (b) DCSobs was greater for 22%-29% nitrox (12.6/104) than for 30%-50% nitrox (2.04/104) (p ≤ 0.0064) which did not differ from air (2.97/104). (c) For daily repetitive dives (<12-hour surface intervals (SI)), DCS occurred only following one or two dives (4.3/104 DCSobs; p<0.001) where SIs were shorter than after three or more dives. (d) For multiday repetitive dives (SIs < 48 hours), DCS was associated with high multiday repetitive dive counts only for Guides (p = 0.0018). (e) DCSobs decreased with age at 3%/year (p ≤ 0.0144). (f) Males dived deeper (p<0.001) but for less time than females (p<0.001). Conclusions: Collecting dive profiles with dive computers and controlling for profile variability by probabilistic modeling was feasible, but analytical results require independent confirmation due to limited observed DCS. Future studies appear promising if more DCS cases are gathered, stakeholders cooperate, and identified data collection problems are corrected.

Immersion pulmonary edema: an analysis of 31 cases from Oceania

Aim: To review incidents of immersion pulmonary edema (IPE) from Oceania, to determine the demographics, diving parameters, and comorbidities that may be related to this disorder. Method: Incidents of IPE, most of which were documented by Divers Alert Network Asia-Pacific (DAN AP) or reported in our medical literature, were analyzed. They included interviews with the survivors and a review of available medical records. Only incidents diagnosed as IPE by specialist diving physicians or pathologists with experience in the investigation of diving accidents were included. Results: Thirty-one IPE incidents in divers from Oceania were documented. There were two surface snorkelers, 22 scuba air divers and seven nitrox divers, which included three closed-circuit rebreathers (CCR). The mean (SD) age was 53 (12) years, 58% of victims were females, and the average dive profile was to a maximum depth of 19 msw for 25 minutes. Six victims (19%) had previous episodes of IPE. There were nine recorded fatalities in this cohort. Medical comorbidities were recorded in 68%, with 42% being cardiac. The latter included valvular disease in 29%, transient cardiomyopathies in 26% and dysrhythmias in 16%. Conclusion: IPE was more likely in middle-aged females, in experienced divers, and during ascent or after surfacing. Commonly reported associations such as exertion, stress, cold exposure, negative inspiratory pressure, hypertension, overhydration, tight wetsuit, aspiration and certain medications were identified. This series supports the hypothesis that the elderly IPE subjects are likely to have comorbidities and be susceptible to IPE recurrences and fatalities unless the contributing factors can be identified and addressed.

Movements and dive behaviour of a toothfish-depredating killer and sperm whale

Depredation of demersal longlines by killer and sperm whales is a widespread behaviour that impacts fisheries and whale populations. To better understand how depredating whales behave in response to fishing activity, we deployed satellite-linked location and dive-profile tags on a sperm and killer whale that were depredating Patagonian toothfish from commercial longlines off South Georgia. The sperm and killer whale followed one fishing vessel for &gt;180 km and &gt;300 km and repeatedly depredated when longlines were being retrieved over periods of 6 and 7 d, respectively. Their behaviours were also sometimes correlated with the depths and locations of deployed gear. They both dove significantly deeper and faster when depredating compared with when foraging naturally. The killer whale dove &gt;750 m on five occasions while depredating (maximum: 1087 m), but these deep dives were always followed by long periods (3.9–4.6 h) of shallow (&lt;100 m) diving. We hypothesize that energetically and physiologically costly dive behaviour while depredating is driven by intra- and inter-specific competition due to the limited availability of this abundant resource.

Context-dependent variability in blue whale acoustic behaviour

Acoustic communication is an important aspect of reproductive, foraging and social behaviours for many marine species. Northeast Pacific blue whales ( Balaenoptera musculus ) produce three different call types—A, B and D calls. All may be produced as singular calls, but A and B calls also occur in phrases to form songs. To evaluate the behavioural context of singular call and phrase production in blue whales, the acoustic and dive profile data from tags deployed on individuals off southern California were assessed using generalized estimating equations. Only 22% of all deployments contained sounds attributed to the tagged animal. A larger proportion of tagged animals were female (47%) than male (13%), with 40% of unknown sex. Fifty per cent of tags deployed on males contained sounds attributed to the tagged whale, while only a few (5%) deployed on females did. Most calls were produced at shallow depths (less than 30 m). Repetitive phrasing (singing) and production of singular calls were most common during shallow, non-lunging dives, with the latter also common during surface behaviour. Higher sound production rates occurred during autumn than summer and they varied with time-of-day: singular call rates were higher at dawn and dusk, while phrase production rates were highest at dusk and night.

Bubbles, microparticles, and neutrophil activation: changes with exercise level and breathing gas during open-water SCUBA diving

The study goal was to evaluate responses in humans following decompression from open-water SCUBA diving with the hypothesis that exertion underwater and use of a breathing mixture containing more oxygen and less nitrogen (enriched air nitrox) would alter annexin V-positive microparticle (MP) production and size changes and neutrophil activation, as well as their relationships to intravascular bubble formation. Twenty-four divers followed a uniform dive profile to 18 m of sea water breathing air or 22.5 m breathing 32% oxygen/68% nitrogen for 47 min, either swimming with moderately heavy exertion underwater or remaining stationary at depth. Blood was obtained pre- and at 15 and 120 min postdive. Intravascular bubbles were quantified by transthoracic echocardiography postdive at 20-min intervals for 2 h. There were no significant differences in maximum bubble scores among the dives. MP number increased 2.7-fold, on average, within 15 min after each dive; only the air-exertion dive resulted in a significant further increase to 5-fold over baseline at 2 h postdive. Neutrophil activation occurred after all dives. For the enriched air nitrox stationary at depth dive, but not for other conditions, the numbers of postdive annexin V-positive particles above 1 μm in diameter were correlated with intravascular bubble scores (correlation coefficients ∼0.9, P < 0.05). We conclude that postdecompression relationships among bubbles, MPs, platelet-neutrophil interactions, and neutrophil activation appear to exist, but more study is required to improve confidence in the associations.

Field Comparison of Open-Circuit Scuba to Closed-Circuit Rebreathers for Deep Mixed-Gas Diving Operations

A comparison of open-circuit scuba diving to closed-circuit (“rebreather”) diving was conducted while collecting fishery data on black coral beds in Hawaii. Both methodologies used mixed gas from the same ship-based support system. The comparison was based on a series of eight dives, four open-circuit and four closed-circuit. These were used to make a direct-comparison of the gear in a square dive profile, a multilevel profile and two dives of varying profiles. Four general criteria were considered: time requirements for topside equipment preparation and maintenance, consumption of expendables, decompression efficiency, and potential dive durations and bailout capabilities for each of the two technologies. The open-circuit divers required 4 times as much topside equipment preparation as the rebreather divers, consumed 17 times as much gas, and cost 7 times more in expendables. The open-circuit divers incurred 42% more decompression time for the square profile dives and 70% more decompression time for the multilevel profile dives than the closed-circuit dive team. Most of the decompression advantage for the closed-circuit team is from the benefit of real-time decompression calculations, but some benefit comes from the breathing gas optimization inherent to rebreathers. For a given mass of equipment, the rebreathers allow for as much as 7.7 times more bottom time, or emergency bailout capability (depending on the chosen depth of the dive), compared with the open-circuit system.