Chain of events analysis in diving accidents treated by the Royal Netherlands Navy 1966-2023

Introduction

Diving injuries are influenced by a multitude of factors. Literature analysing the full chain of events in diving accidents influencing the occurrence of diving injuries is limited. A previously published 'chain of events analysis' (CEA) framework consists of five steps that may sequentially lead to a diving fatality. This study applied four of these steps to predominately non-lethal diving injuries and aims to determine the causes of diving injuries sustained by divers treated by the Diving Medical Centre of the Royal Netherlands Navy.

Methods

This retrospective cohort study was performed on diving injuries treated by the Diving Medical Centre between 1966 and 2023. Baseline characteristics and information pertinent to all four steps of the reduced CEA model were extracted and recorded in a database.

Results

A total of 288 cases met the inclusion criteria. In 111 cases, all four steps of the CEA model could be applied. Predisposing factors were identified in 261 (90%) cases, triggers in 142 (49%), disabling agents in 195 (68%), and 228 (79%) contained a (possible-) disabling condition. The sustained diving injury led to a fatality in seven cases (2%). The most frequent predisposing factor was health conditions (58%). Exertion (19%), primary diver errors (18%), and faulty equipment (17%) were the most frequently identified triggers. The ascent was the most frequent disabling agent (52%).

Conclusions

The CEA framework was found to be a valuable tool in this analysis. Health factors present before diving were identified as the most frequent predisposing factors. Arterial gas emboli were the most lethal injury mechanism.

A retrospective review of divers treated for inner ear decompression sickness at Fiona Stanley Hospital hyperbaric medicine unit 2014-2020

Introduction

Inner ear decompression sickness (IEDCS) is increasingly recognised in recreational diving, with the inner ear particularly vulnerable to decompression sickness in divers with a right-to-left shunt, such as is possible through a persistent (patent) foramen ovale (PFO). A review of patients treated for IEDCS at Fiona Stanley Hospital Hyperbaric Medicine Unit (FSH HMU) in Western Australia was performed to examine the epidemiology, risk factors for developing this condition, the treatment administered and the outcomes of this patient population.

Methods

A retrospective review of all divers treated for IEDCS from the opening of the FSH HMU on 17 November 2014 to 31 December 2020 was performed. Patients were included if presenting with vestibular or cochlear dysfunction within 24 hours of surfacing from a dive, and excluded if demonstrating features of inner ear barotrauma.

Results

There were a total of 23 IEDCS patients and 24 cases of IEDCS included for analysis, with 88% experiencing vestibular manifestations and 38% cochlear. Median dive time was 40 minutes and median maximum depth was 24.5 metres. The median time from surfacing to hyperbaric oxygen treatment (HBOT) was 22 hours. Vestibulocochlear symptoms fully resolved in 67% and complete symptom recovery was achieved in 58%. A PFO was found in 6 of 10 patients who subsequently underwent investigation with bubble contrast echocardiography upon follow-up.

Conclusions

IEDCS occurred predominantly after non-technical repetitive air dives and ongoing symptoms and signs were often observed after HBOT. Appropriate follow-up is required given the high prevalence of PFO in these patients.

Decompression Sickness Risk in Parachutist Dispatchers Exposed Repeatedly to High Altitude

INTRODUCTION: Occurrences of severe decompression sickness (DCS) in military parachutist dispatchers at 25,000 ft (7620 m) prompted revision of exposure guidelines for high altitude parachuting. This study investigated residual risks to dispatchers and explored the potential for safely conducting repeat exposures in a single duty period.METHODS: In this study, 15 healthy men, ages 20-50 yr, undertook 2 profiles of repeated hypobaric chamber decompression conducting activities representative of dispatcher duties. Phase 1 comprised two ascents to 25,000 ft (7620 m) for 60 and then 90 min. Phase 2 included three ascents first to 25,000 ft for 60 min, followed by two ascents to 22,000 ft (6706 m) for 90 min. Denitrogenation was undertaken at 15,000 ft (4572 m) with successive ascents separated by 1-h air breaks at ground level.RESULTS: At 25,000 ft (7620 m), five cases of limb (knee) pain DCS developed, the earliest at 29 min. Additionally, multiple minor knee "niggles" occurred with activity but disappeared when seated at rest. No DCS and few niggles occurred at 22,000 ft (6706 m). Early, heavy, and sustained bubble loads were common at 25,000 ft, particularly in older subjects, but lighter and later loads followed repeat exposure, especially at 22,000 ft.DISCUSSION: Parachutist dispatchers are at high risk of DCS at 25,000 ft (7620 m) commensurate with their heavy level of exertion. However, the potential exists for repeated safe ascents to 22,000 ft (6706 m), in the same duty period, if turn-around times breathing air at ground level are brief. Older dispatchers (>40 yr) with functional right-to-left (intracardiac or pulmonary) vascular shunts will be at risk of arterialization of microbubbles.Connolly DM, D'Oyly TJ, Harridge SDR, Smith TG, Lee VM. Decompression sickness risk in parachutist dispatchers exposed repeatedly to high altitude. Aerosp Med Hum Perform. 2023; 94(9):666-677.

Does Decreased Diffusing Capacity of the Lungs for Carbon Monoxide Constitute a Risk of Decompression Sickness in Occupational Divers?

Long-term alterations of pulmonary function (mainly decreased airway conductance and capacity of the lungs to diffuse carbon monoxide (DLCO)) have been described after hyperbaric exposures. However, whether these alterations convey a higher risk for divers' safety has never been investigated before. The purpose of the present pilot study was to assess whether decreased DLCO is associated with modifications of the physiological response to diving. In this case-control observational study, 15 "fit-to-dive" occupational divers were split into two groups according to their DLCO measurements compared to references values, either normal (control) or reduced (DLCO group). After a standardized 20 m/40 min dive in a sea water pool, the peak-flow, vascular gas emboli (VGE) grade, micro-circulatory reactivity, inflammatory biomarkers, thrombotic factors, and plasmatic aldosterone concentration were assessed at different times post-dive. Although VGE were recorded in all divers, no cases of decompression sickness (DCS) occurred. Compared to the control, the latency to VGE peak was increased in the DLCO group (60 vs. 30 min) along with a higher maximal VGE grade (p < 0.0001). P-selectin was higher in the DLCO group, both pre- and post-dive. The plasmatic aldosterone concentration was significantly decreased in the control group (-30.4 ± 24.6%) but not in the DLCO group. Apart from a state of hypocoagulability in all divers, other measured parameters remained unchanged. Our results suggest that divers with decreased DLCO might have a higher risk of DCS. Further studies are required to confirm these preliminary results.

A review of 149 Divers Alert Network emergency call records involving diving minors

INTRODUCTION

Minors have been scuba diving for decades, and while the initial concerns about potential long-term complications related to bone development appear to be unfounded, the incidence of scuba diving injuries among them has been poorly studied.

METHODS

We reviewed 10,159 cases recorded in the DAN Medical Services call centre database from 2014 through 2016 and identified 149 cases of injured divers younger than 18 years. Records were analysed for case categorisation on the most common dive injuries. Information about demographics, level of training, risk factors, and relevant behavioural aspects were collected when available.

RESULTS

While the most common reason for the call was to rule out decompression sickness, the majority of cases pertained to ear and sinus issues. However, 15% of the dive-related injuries involving minors had a final diagnosis of pulmonary barotrauma (PBt). While no reliable data is available on the incidence of PBt in adult divers, the authors' impression based on personal experience suggests that the number of cases of PBt in minors trends higher than in the general diving population. The narratives on some relevant records describe unmanageable levels of anxiety leading to panic.

CONCLUSIONS

Based on the results and narratives on these cases, it is reasonable to infer that psychological immaturity, suboptimal management of adverse situations, and inadequate supervision might have led to severe injuries among these minor divers.

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

INTRODUCTION

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.

METHODS

Past medical records of patients with decompression illness from 2015 to 2021 were retrieved and analysed.

RESULTS

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.

CONCLUSIONS

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.

Decompression illness in Finnish technical divers: a follow-up study on incidence and self-treatment

INTRODUCTION

Technical diving is increasing in popularity in Finland, and therefore the number of decompression illness (DCI) cases is also increasing among technical divers. Although hyperbaric oxygen treatment (HBOT) remains the standard of care, there are anecdotal reports of technical divers treating mild DCI symptoms themselves and not seeking a medical evaluation and possible recompression therapy. This study aimed to make an epidemiologic inventory of technical diving-related DCI symptoms, to establish the incidence of self-treatment and to determine the apparent effectiveness of different treatment methods.

METHODS

A one-year prospective survey with online questionnaires was conducted. Fifty-five experienced and highly trained Finnish technical divers answered the survey and reported their diving activity, DCI symptoms, symptom treatment, and treatment outcome.

RESULTS

Of the reported 2,983 dives, 27 resulted in symptoms of DCI, which yielded an incidence of 91 per 10,000 dives in this study. All of the reported DCI symptoms were mild, and only one diver received HBOT. The most common self-treatments were oral hydration and rest. First aid oxygen (FAO₂) was used in 21% of cases. Eventually, none of the divers had residual symptoms.

CONCLUSIONS

The incidence of self-treated DCI cases was 27 times higher than that of HBO-treated DCI cases. There is a need to improve divers' awareness of the importance of FAO₂ and other recommended first aid procedures and to encourage divers to seek medical attention in case of suspected DCI.

Intra-Individual Test-Retest Variation Regarding Venous Gas Bubble Formation During High Altitude Exposures

INTRODUCTION: Hypobaric decompression sickness remains a problem during high-altitude aviation. The prevalence of venous gas emboli (VGE) serves as a marker of decompression stress and has been used as a method in evaluating the safety/risk associated with aviation profiles and/or gas mixtures. However, information is lacking concerning the variability of VGE formation when exposed to the same hypobaric profile on different occasions. In this paper, intra-individual test-retest variation regarding bubble formation during repeated hypobaric exposures is presented. The data can be used to determine the sample size needed for statistical power.METHOD: A total of 19 male, nonsmoking subjects volunteered for altitude exposures to 24,000 ft (7315 m). VGE was measured using ultrasound scanning and scored according to the Eftedal-Brubakk (EB) scale. Intraindividual test-retest variation in bubble formation (maximum VGE) was evaluated in subjects exposed more than once to hypobaric pressure. The statistical reliability was examined between paired exposures using the Intraclass Correlation test. G*Power version 3.1.9.6 was used for power calculations.RESULTS: During repeated 20-30 and 70-min exposures to 24,000 ft, 42% (N = 19, CI 23-67%) and 29% (N = 7, CI 5-70%) of the subjects varied between maximum EB scores < 3 and ≥ 3. The sample size needed to properly reject statistical significance of 1 EB step nominal difference between two paired exposures varied between 29-51 subjects.CONCLUSION: The large intraindividual test-retest variations in bubble grades during repeated hypobaric exposures highlight the need for relatively large numbers of subjects to reach statistical power when there are no or small differences in decompression stress between the exposures.Ånell R, Grönkvist M, Eiken O, Elia A, Gennser M. Intra-individual test-retest variation regarding venous gas bubble formation during high altitude exposures. Aerosp Med Hum Perform. 2022; 93(1):46-49.

Acclimatization to diving: a systematic review

Multiday hyperbaric exposure has been shown to reduce the incidence of decompression sickness (DCS) of compressed-air workers. This effect, termed acclimatization, has been addressed in a number of studies, but no comprehensive review has been published. This systematic review reports the findings of a literature search. PubMed, Ovid Embase, The Cochrane Library and Rubicon Research Repository were searched for studies reporting DCS incidence, venous gas embolism (VGE) or subjective health reports after multiday hyperbaric exposure in man and experimental animals. Twenty-nine studies fulfilled inclusion criteria. Three epidemiological studies reported statistically significant acclimatization to DCS in compressed-air workers after multiday hyperbaric exposure. One experimental study observed less itching after standardized simulated dives. Two human experimental studies reported lower DCS incidence after multiday immersed diving. Acclimatization to DCS has been observed in six animal species. Multiday diving had less consistent effect on VGE after hyperbaric exposure in man. Four studies observed acclimatization while no statistically significant acclimatization was reported in the remaining eight studies. A questionnaire study did not report any change in self-perceived health after multiday diving. This systematic review has not identified any study suggesting a sensitizing effect of multiday diving, and there is a lack of data supporting benefit of a day off diving after a certain number of consecutive diving days. The results suggest that multiday hyperbaric exposure probably will have an acclimatizing effect and protects from DCS. The mechanisms causing acclimatization, extent of protection and optimal procedure for acclimatization has been insufficiently investigated.

Hyperoxic Effects on Decompression Strain During Alternating High and Moderate Altitude Exposures

INTRODUCTION: In fighter aircraft, long-duration high-altitude sorties are typically interrupted by refueling excursions to lower altitude. In normoxia, excursions to moderate cabin altitude may increase the occurrence of venous gas emboli (VGE) at high cabin altitude. The aim was to investigate the effect of hyperoxia on VGE and decompression sickness (DCS) during alternating high and moderate altitude exposure.METHODS: In an altitude chamber, 13 healthy men were exposed to three different conditions: A) 90 min at 24,000 ft (7315 m) breathing normoxic gas (54% O₂; H-NOR); B) 90 min at 24,000 ft breathing hyperoxic gas (90% O₂; H-HYP); and C) three 30-min exposures to 24,000 ft interspersed by two 30-min exposures to 18,000 ft (5486 m) breathing 90% O₂ (ALT-HYP). VGE occurrence was evaluated from cardiac ultrasound imaging. DCS symptoms were rated using a scale.RESULTS: DCS occurred in all conditions and altogether in 6 of the 39 exposures. The prevalence of VGE was similar in H-NOR and H-HYP throughout the exposures. During the initial 30 min at 24,000 ft, the prevalence of VGE was similar in ALT-HYP as in the other two conditions, whereas, after the first excursion to 18,000 ft, the VGE score was lower in ALT-HYP than in H-NOR and H-HYP.DISCUSSION: Hyperoxic excursions from 24,000 to 18,000 ft reduces VGE occurrence, presumably by facilitating diffusive gas exchange across the bubble surfaces, increasing the share of bubble content contributed by oxygen. Still, the excursions did not abolish the DCS risk.Ånell R, Grönkvist M, Gennser M, Eiken O. Hyperoxic effects on decompression strain during alternating high and moderate altitude exposures. Aerosp Med Hum Perform. 2021; 92(4):223230.

Decompression Sickness Risk Assessment and Awareness in General Aviation

INTRODUCTION: Decompression sickness (DCS) can occur during unpressurized flight to altitudes >18,000 ft (FL180; 5486 m). To our knowledge, this has not been studied in general aviation (GA). This knowledge gap may have public health and safety implications because the most popular models of GA aircraft by sales volume are capable of flying >FL180.METHODS: Data from a 1-yr period in a commercial flight tracking database were analyzed to identify flights >FL180 in unpressurized, piston aircraft in the United States. Peak altitude and duration at that altitude were used to calculate DCS risk employing the U.S. Air Force (USAF) Altitude Decompression Sickness Risk Assessment Computer (ADRAC). Registration numbers were cross referenced in publicly available federal databases to identify any events that might be attributable to impairment due to DCS. A web-based survey of practices and associated symptoms was also made available to GA pilots through an online discussion forum.RESULTS: During the data collection period, 1696 flights occurred. The DCS risk was calculated to be 1.9 4.2%. There were 42 responses to the survey. Of these, 25 (59.5%) pilots reported having flown at altitudes >FL180 and 21 (84%) of them reported symptoms possibly attributable to DCS. None sought medical attention. No safety events were identified for any of the aircraft during the study period.CONCLUSION: The risk of DCS in the GA community is not zero. As GA aircraft performance profiles advance and sales increase, this may have significant implications from a public health and safety perspective. Further study is warranted.Harrison MF, Butler WP, Murad MH, Toups GN. Decompression sickness risk assessment and awareness in general aviation. Aerosp Med Hum Perform. 2021; 92(3):138145.

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.

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.

Acclimatization to diving: a systematic review

Multiday hyperbaric exposure has been shown to reduce the incidence of decompression sickness (DCS) of compressed-air workers. This effect, termed acclimatization, has been addressed in a number of studies, but no comprehensive review has been published. This systematic review reports the findings of a literature search. PubMed, Ovid Embase, The Cochrane Library and Rubicon Research Repository were searched for studies reporting DCS incidence, venous gas embolism (VGE) or subjective health reports after multiday hyperbaric exposure in man and experimental animals. Twenty-nine studies fulfilled inclusion criteria. Three epidemiological studies reported statistically significant acclimatization to DCS in compressed-air workers after multiday hyperbaric exposure. One experimental study observed less itching after standardized simulated dives. Two human experimental studies reported lower DCS incidence after multiday immersed diving. Acclimatization to DCS has been observed in six animal species. Multiday diving had less consistent effect on VGE after hyperbaric exposure in man. Four studies observed acclimatization while no statistically significant acclimatization was reported in the remaining eight studies. A questionnaire study did not report any change in self-perceived health after multiday diving. This systematic review has not identified any study suggesting a sensitizing effect of multiday diving, and there is a lack of data supporting benefit of a day off diving after a certain number of consecutive diving days. The results suggest that multiday hyperbaric exposure probably will have an acclimatizing effect and protects from DCS. The mechanisms causing acclimatization, extent of protection and optimal procedure for acclimatization has been insufficiently investigated.

Diving Accident Evacuations by Helicopter and Immersion Pulmonary Edema

BACKGROUND: Scuba diving activities expose divers to serious accidents, which can require early hospitalization. Helicopters are used for early evacuation. On the French Mediterranean coast, rescue is made offshore mainly by a French Navy Dauphin or at a landing zone by an emergency unit EC 135 helicopter.METHODS: We retrospectively analyzed diving accidents evacuated by helicopter on the French Mediterranean coast from 1 September 2014 to 31 August 2016. We gathered data at the Center for Hyperbaric Medicine and Diving Expertise (SMHEP) of the Sainte-Anne Military Hospital (Toulon, France), the 35 F squadron at Hyres (France) Naval Air Station, and the SAMU 83 emergency unit (Toulon, France).RESULTS: A total of 23 diving accidents were evacuated offshore by Dauphin helicopter and 23 at a landing zone on the coast by EC 135 helicopter without hoist. Immersion pulmonary edema (IPE) accounted for one-third of the total diving accidents evacuated by helicopter with identified causes. It was responsible for at least half of the deaths at the dive place. A quarter of the rescued IPE victims died because of early cardiac arrest.DISCUSSION: Helicopter evacuation is indicated when vital prognosis (IPE and pulmonary overpressure in particular) or neurological functional prognosis (decompression sickness) is of concern. IPE is the primary etiology in patients with serious dive injuries that are life-threatening and who will benefit from helicopter evacuation. A non-invasive ventilation device with inspiratory support and positive expiratory pressure must be used, in particular for IPE.Corgie L, Huiban N, Pontier J-M, Brocq F-X, Boulard J-F, Monteil M. Diving accident evacuations by helicopter and immersion pulmonary edema. Aerosp Med Hum Perform. 2020; 91(10):806811.

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 (2.97/1010⁴). (c) For daily repetitive dives (≺12-hour surface intervals (SI)), DCS occurred only following one or two dives (4.3/1010⁴ 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).

CONCLUSION

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.

Incidence of decompression sickness in hypobaric hypoxia training

Simulated flight in a hypobaric chamber is a fundamental component in the physiological training of aviators. Although rare, there is always a risk of decompression sickness (DCS) in trainees during hypobaric hypoxia training. In this study we aimed to determine the incidence of altitude-induced DCS and the symptoms manifested in trainees and inside chamber observers (ICOs) during the training sessions. We retrospectively reviewed the records of DCS cases during the period of January 1, 2011, and October 1, 2018. The records of 6,657 trainees and 615 ICOs were evaluated. The gender distribution in 6,657 trainees was 6,578 (98.81%) male and 79 (1.19%) female. The numbers of DCS cases in trainees and ICOs were six (0.09%) and two (0.33%), respectively [(ICOs versus trainees - odds ratio (OR): 3.574; 95% CI 0.720-17.744; (p > 0.05)]. All ICOs were male; no DCS incident was observed among female trainees. Recompression treatments were applied on site, and complete recovery was achieved in all cases. Overall DCS incidence was found to be 0.11% among the 7,193 male subjects, which included trainees and ICOs. The higher incidence of DCS in ICOs was attributed to the physical activities performed at altitudes by ICOs. In such training, established instructions have to be strictly followed by physicians, ICOs and trainees. All trainees and ICOs should be aware of the symptoms and signs of DCS, and medical support including a recompression facility, should be provided on site during hypobaric hypoxia training.

Nitrogen Washout and Venous Gas Emboli During Sustained vs. Discontinuous High-Altitude Exposures

INTRODUCTION: The frequency of long-duration, high-altitude missions with fighter aircraft is increasing, which may increase the incidence of decompression sickness (DCS). The aim of the present study was to compare decompression stress during simulated sustained high-altitude flying vs. high-altitude flying interrupted by periods of moderate or marked cabin pressure increase.METHODS: The level of venous gas emboli (VGE) was assessed from cardiac ultrasound images using the 5-degree Eftedal-Brubakk scale. Nitrogen washout/uptake was measured using a closed-circuit rebreather. Eight men were investigated in three conditions: one 80-min continuous exposure to a simulated cabin altitude of A) 24,000 ft, or four 20-min exposures to 24,000 ft interspersed by three 20-min intervals at B) 20,000 ft or C) 900 ft.RESULTS: A and B induced marked and persistent VGE, with peak bubble scores of [median (range)]: A: 2.5 (1-3); B: 3.5 (2-4). Peak VGE score was less in C [1.0 (1-2), P < 0.01]. Condition A exhibited an initially high and exponentially decaying rate of nitrogen washout. In C the washout rate was similar in each period at 24,000 ft, and the nitrogen uptake rate was similar during each 900-ft exposure. B exhibited nitrogen washout during each period at 24,000 ft and the initial period at 20,000 ft, but on average no washout or uptake during the last period at 20,000 ft.DISCUSSION: Intermittent reductions of cabin altitude from 24,000 to 20,000 ft do not appear to alleviate the DCS risk, presumably because the pressure increase is not sufficient to eliminate VGE. The nitrogen washout/uptake rate did not reflect DCS risk in the present exposures.Ånell R, Grönkvist M, Eiken O, Gennser M. Nitrogen washout and venous gas emboli during sustained vs. discontinuous high-altitude exposures. Aerosp Med Hum Perform. 2019; 90(6):524-530.

[Diving and asthma: Literature review]

INTRODUCTION

Scuba diving has long been contraindicated for asthmatics. Recommendations are evolving towards authorisation under certain conditions. Our objective was to review the literature on the risks associated with scuba diving among asthmatics and about recommendations on this subject.

MATERIALS AND METHODS

We used the MEDLINE and LiSSa databases, until June 2018, in French, English or Spanish language, with the keywords "asthma AND diving" and "asthme plongée" respectively. References to the first degree were analyzed.

RESULTS

We have included 65 articles. Risk of bronchospasm is well documented, particularly in cold and/or deep water, or in the event of exposure to allergens (compressor without filter). Nonasthmatic atopic divers may be at greater risk of developing bronchial hyper-reactivity. Although the theoretical risk exists, epidemiological studies do not seem to show an over-risk of barotrauma, decompression sickness or arterial gas embolism in asthmatics. French, British, American, Spanish and Australian societies agreed on the exclusion of patients with moderate to severe persistent asthma, FEV1<80%, active asthma in the last 48hours, exercise/cold asthma and poor physical fitness.

CONCLUSION

A diver's examination should include a triple assessment: asthma control, number of exacerbations and treatment compliance. Homogenizing the recommendations would improve the framework for the practice of diving among asthmatics and allow larger studies in this population. Communicating the current recommendations remains important to divers, dive instructors and doctors in the context of the development of scuba diving.

A Systematic Review and Meta-Analysis of Decompression Sickness in Altitude Physiological Training

INTRODUCTION: A review of decompression sickness (DCS) cases associated with the NASA altitude physiological training (APT) program at the Johnson Space Center (JSC) motivated us to place our findings into the larger context of DCS prevalence from other APT centers.METHODS: We reviewed JSC records from 1999 to 2016 and 14 publications from 1968 to 2004 about DCS prevalence in other APT programs. We performed a meta-analysis of 15 APT profiles (488 cases / 385,116 exposures). We used meta-regression to evaluate the relation between estimated exposures and probability of DCS in a test group, accounting for the heterogeneity between studies.RESULTS: Our in-house review identified 6 Type I DCS (1 from an inside observer) and 1 Type II DCS. There were 6 cases in 9560 student hypobaric exposures from 3 NASA training flights; a student pooled prevalence rate of 0.44 cases / 1000 exposures compared to 1.44 cases / 1000 from 12 published APT profiles. The overall pooled DCS prevalence rate was 1.16 cases / 1000 exposures. There was substantial heterogeneity in DCS prevalence across studies. Denitrogenation time, exposure pressure, and exposure time were associated with probability of DCS in the meta-regression model.CONCLUSIONS: While the overall DCS prevalence rate is relatively low, there is marked heterogeneity among profiles. The pooled DCS prevalence rate estimate for the NASA profiles was lower than the overall rate. Variability in APT profile DCS prevalence could be further explained given student level and additional test-level covariates.Conkin J, Sanders RW, Koslovsky MD, Wear ML, Kozminski AG, Abercromby AFJ. A systematic review and meta-analysis of decompression sickness in altitude physiological training. Aerosp Med Hum Perform. 2018; 89(11):941-951.

Body mass index in association with decompression sickness events: cross-sectional study among small-scale fishermen-divers in southeast Mexico

INTRODUCTION

Decompression sickness is endemic to small-scale fishermen-divers from coastal communities in southeast Mexico; overweight and obesity are also highly prevalent in the region. Existing literature suggests it is possible that fat tissue could play a role in decompression sickness pathophysiology. Our aim in this study is to describe the association between the number and severity of DCS events treated at the hyperbaric program and fishermen-diver body mass index.

METHODS

In this cross-sectional study, we obtained anthropometric measurements of 105 fishermen-divers and reviewed clinical records of each participant at a hyperbaric program.

RESULTS

Average BMI among participants was 34.5 ± 4.7, while 9.5% (n=10) were healthy-weighted, 28.6% (n=30) were overweight and 42.8% (n=65) were obese. Number of DCS events per diver was associated with BMI and severity of DCS in linear regression models.

CONCLUSIONS

Overweight and obesity are highly preventable health problems; our results suggest that an association between these conditions and the frequency and the severity of DCS are an important topic to be further considered in longitudinal prospective studies.

A historical review of the U.S. Navy's busiest recompression chamber in the Pacific theater with a current perspective on caring for civilian divers within its area of responsibility: short communication

On the island Nation of Guam, the United States Department of Defense has stationed military personnel from every service branch. Guam is utilized as a strategic waypoint for the U.S. military in the Pacific theater. As the largest service branch in the region, the Navy has placed a few Diving Medical Officers in Guam to collectively manage and treat patients with recompression therapy. Guam is also a popular tourist destination, with multiple recreational diving companies certifying individuals who are looking to take advantage of the beautiful warm water and exotic marine life. Unfortunately, with an increase in training and certifying inexperienced divers, came an increase in the operational tempo of the U.S. Navy's recompression chamber on Guam. The recompression chamber on Naval Base Guam (NBG) has been treating patients since 1971. With the only multiplace chamber in the Mariana Islands, Diving Medical Officers, with the accompanying chamber staff, treat military personnel, active-duty sponsored patients and civilian patients. Treating civilian patients by military providers through military treatment facilities presents multiple issues that must be addressed in an effort to provide efficient quality medical care. This article reviews the records, documents, and activity of the NBG chamber over the last four decades. Through the obtained data the information provides projected financial reimbursement from civilian patients. The article also sheds light on areas of needed improvement with regard to data collection, third-party financial collection efforts and the necessity of an inclusive electronic health record (EHR) for military and civilian patients.

[Diving Accidents in Lakes - a Retrospective Study of a Level-1 Emergency Centre in Switzerland]

Diving Accidents in Lakes - a Retrospective Study of a Level-1 Emergency Centre in Switzerland Abstract. Switzerland is a country in the middle of Europe without access to an open sea. Here one does not assume a noteworthy number of diving accidents. However, this study shows a large number and attempts to explore the main risks of diving accidents. The data from 2001 to 2016 of patients had been collected und retrospectively evaluated using the electronic database of the emergency center of the university hospital in Bern, Switzerland. Barotrauma of the ear (69.0 %), decompression accidents (20.7 %) as well as cardiovascular complications (13.8 %) appeared quite frequently during scuba diving in Switzerland. In contrast, otitis occurred only at a very low percentage (3.5 %). The risk of diving accidents is clearly underestimated. Preventative measures should include more emphasis on the vertical diving profile with increasing diving depths and on the hazards of cardiovascular diseases with increasing age.

Health care worker decompression sickness: incidence, risk and mitigation

Inadvertent exposure to radiation, chemical agents and biological factors are well recognized hazards associated with the health care delivery system. Less well appreciated yet no less harmful is risk of decompression sickness in those who accompany patients as inside attendants (IAs) during provision of hyperbaric oxygen therapy. Unlike the above hazards where avoidance is practiced, IA exposure to decompression sickness risk is unavoidable. While overall incidence is low, when calculated as number of cases over number of exposures or potential for a case during any given exposure, employee cumulative risk, defined here as number of cases over number of IAs, or risk that an IA may suffer a case, is not. Commonly, this unique occupational environmental injury responds favorably to therapeutic recompression and a period of recuperation. There are, however, permanent and career-ending consequences, and at least two nurses have succumbed to their decompression insults. The intent of this paper is to heighten awareness of hyperbaric attendant decompression sickness. It will serve as a review of reported cases and reconcile incidence against largely ignored individual worker risk. Mitigation strategies are summarized and an approach to more precisely identify risk factors that might prompt development of consensus screening standards is proposed.

Decompression sickness among diving fishermen in Mexico: observational retrospective analysis of DCS in three sea cucumber fishing seasons

The probabilities of decompression sickness (DCS) among diving fishermen are higher than in any other group of divers. Diving behavior of artisanal fishermen has been directed mainly to target high-value species. The aim of this study was to learn about the occurrence of DCS derived from sea cucumber harvesting in the Yucatán Peninsula, Mexico. We conducted a retrospective chart review of diving fishermen treated at a multiplace hyperbaric chamber in Tizimín, Mexico. In total, 233 recompression therapies were rendered to 166 diving fishermen from 2014 to 2016. The average age was 36.7 ± 9.2 years (range: 20-59 years); 84.3% had experienced at least one DCS event previously. There was a correlation between age and DCS incidents (F: 8.3; R2: 0.07) and differences in the fishing depth between seasons (H: 9.99; p⟨0.05). Musculoskeletal pain was the most frequently reported symptom. Three divers, respectively, suffered permanent hearing loss, spinal cord injury and fatal outcome. Diving fishermen experience DCS at an alarmingly high rate, probably due to the type of species targeted, given the requirements in each case. Understanding divers' behaviors and their incentives while in pursuit of high-value species such as sea cucumber could help to find ways to mitigate health risks and help enforce regulation.

The demographics and diving behaviour of DAN Asia-Pacific members with and without pre-existing medical conditions

INTRODUCTION

This report examines Diver Alert Network Asia-Pacific (DAN AP) members with and without cardiac or respiratory conditions, diabetes or hypertension and compares their demographics, health and diving activities.

METHODOLOGY

Two online cross-sectional surveys of DAN AP members were conducted. The first sought information from 833 divers who applied for membership between July 2009 and August 2013 and who had declared the targeted medical conditions. The second, conducted between December 2014 and April 2015, was sent to 9,927 current members with known email addresses. The groups were compared for age, gender, body mass index, fitness, smoking and diving qualifications, history, currency and practices.

RESULTS

Of 343 (41%) respondents to the first survey, 267 (32%) provided sufficient information for inclusion. Of 1,786 (18%) respondents to the second survey, 1,437 (15%) had no targeted medical condition and were included in the analysis. Those with medical conditions were on average 4.7 years older (P 〈 0.001); more overweight or obese (68% versus 57%, P = 0.001); took more medications (57% vs. 29%, P 〈 0.001), smoked less (4% vs. 7%, P = 0.02) and did less repetitive diving (median 75 vs 90, P 〈 0.001). Other diving demographics were similar.

CONCLUSIONS

A substantial number of people are diving with medical conditions and there is a need to better understand the associated risks. Divers need to be well-educated about the potential impact such conditions may have on diving safety and should monitor their health status, especially as they age.

Acute and Chronic Gas Bubble Lesions in Cetaceans Stranded in the United Kingdom

The first evidence suggestive of in vivo gas bubble formation in cetacea, including eight animals stranded in the UK, has recently been reported. This article presents the pathologic findings from these eight UK-stranded cetaceans and two additional UK-stranded cetacean cases in detail. Hepatic gas-filled cavitary lesions (0.2-6.0 cm diameter) involving approximately 5–90% of the liver volume were found in four (two juvenile, two adult) Risso's dolphins ( Grampus griseus), three (two adult, one juvenile) common dolphins ( Delphinus delphis), an adult Blainville's beaked whale ( Mesoplodon densirostris), and an adult harbour porpoise ( Phocoena phocoena). Histopathologic examination of the seven dolphin cases with gross liver cavities revealed variable degrees of pericavitary fibrosis, microscopic, intrahepatic, spherical, nonstaining cavities (typically 50–750 μm in diameter) consistent with gas emboli within distended portal vessels and sinusoids and associated with hepatic tissue compression, hemorrhages, fibrin/organizing thrombi, and foci of acute hepatocellular necrosis. Two common dolphins also had multiple and bilateral gross renal cavities (2.0–9.0 mm diameter) that, microscopically, were consistent with acute ( n = 2) and chronic ( n = 1) arterial gas emboli-induced renal infarcts. Microscopic, bubblelike cavities were also found in mesenteric lymph node ( n = 4), adrenal ( n = 2), spleen ( n = 2), pulmonary associated lymph node ( n = 1), posterior cervical lymph node ( n = 1), and thyroid ( n = 1). No bacterial organisms were isolated from five of six cavitated livers and one of one cavitated kidneys. The etiology and pathogenesis of these lesions are not known, although a decompression-related mechanism involving embolism of intestinal gas or de novo gas bubble (emboli) development derived from tissues supersaturated with nitrogen is suspected.

Inner-ear decompression sickness in nine trimix recreational divers

INTRODUCTION

Recreational technical diving, including the use of helium-based mixes (trimix) and the experimentation of new decompression algorithms, has become increasingly popular. Inner-ear decompression sickness (DCS) can occur as an isolated clinical entity or as part of a multi-organ presentation in this population. Physiological characteristics of the inner ear make it selectively vulnerable to DCS. The inner ear has a slower gas washout than the brain thus potentially making it more vulnerable to deleterious effects of any bubbles that cross a persistent foramen ovale (PFO) and enter the basilar artery, whilst the inner ear remains supersaturated but the brain does not.

METHODS

A questionnaire was made widely available to divers to analyse the incidence of inner-ear DCS after technical dives. One-hundred-and-twenty-six divers submitted completed questionnaires, and we studied each incident in detail.

RESULTS

Nine (7.1%) of the 126 responders reported to have had at least one episode of inner-ear DCS, of which seven occurred without having omitted planned decompression stops. Of these seven, four suffered from DCS affecting just the inner ear, while three also had skin, joint and bladder involvement. Five of the nine divers affected were found to have a PFO. All affected divers suffered from vestibular symptoms, while two also reported cochlear symptoms. Three divers reported to have balance problems long after the accident.

CONCLUSIONS

This small study is consistent with a high prevalence of PFO among divers suffering inner-ear DCS after trimix dives, and the pathophysiological characteristics of the inner ear could contribute to this pathology, as described previously. After an episode of DCS, vestibular and cochlear injury should always be examined for.

Decompression illness treated in Denmark 1999-2013

INTRODUCTION

The incidence, diver characteristics and symptomatology of decompression illness (DCI) in Denmark has not been assessed since 1982, and the presence of long-term residual symptoms among divers receiving hyperbaric oxygen therapy in Denmark has never been estimated to our knowledge.

METHODS

We undertook a retrospective study of the incidence and characteristics of DCI cases in Denmark for the period of 1999 to 2013. Medical records and voluntary questionnaires were reviewed, extracting data on age, gender, weight, height, diver certification level, diving experience, number of previous dives, type of diving, initial type of hyperbaric treatment and DCI symptoms. Trend in annual case numbers was evaluated using run chart analysis and Spearman's correlation. Age, height, weight, and BMI were evaluated using linear regression. The presence of long-term residual symptoms was investigated by phone interviewing the subgroup of divers treated in 2009 and 2010.

RESULTS

Two-hundred-and-five DCI cases were identified. The average annual case load was 14 with no significant trend during the study period (P = 0.081). Nor did we find any trend in age, weight, height or BMI. The most frequent symptoms were paraesthesia (50%), pain (42%) and vertigo (40%). Thirteen out of the subgroup of 30 divers had residual symptoms at discharge from hospital, and six out of 24 of these divers had residual symptoms at the time of follow-up.

CONCLUSIONS

We observed a more than ten-fold increase in DCI-cases since the period 1966-1980. In the subgroup of divers treated in 2009/2010, a quarter had long-term residual symptoms as assessed by telephone interview, which is in keeping with the international literature, but still a reminder that DCI can have life-long consequences.

Does self-certification reflect the cardiac health of UK sport divers?

BACKGROUND

Since 2009, the United Kingdom diving incident data show an increasing number of fatalities in the over-50s age group. Previous studies also suggest some divers take cardiac medications. Since 2001, diving medicals have not been mandatory for UK sport divers. Instead, an annual medical self-certification form, submitted to their club/school or training establishment, is required. We documented in a survey of UK sport divers the prevalence of cardiac events and medications and the frequency of medical certifications.

METHODS

An anonymous on-line questionnaire was publicised. Measures included diver and diving demographics, prescribed medications, diagnosed hypertension, cardiac issues, events and procedures, other health issues, year of last diving medical, diagnosed persistent foramen ovale (PFO), smoking and alcohol habits, exercise and body mass index.

RESULTS

Of 672 completed surveys, hypertension was reported by 119 (18%) with 25 of these (21%) having not had a diving medical. Myocardial infarction 6 (1%), coronary artery bypass grafting 3 (< 1%), atrial fibrillation 19 (3%) and angina 12 (2%) were also reported. PFOs were reported by 28 (4%), with 20 of these opting for a closure procedure. From 83 treated incidences of decompression illness (DCI), 19 divers reported that a PFO was diagnosed.

CONCLUSIONS

Divers inevitably develop health problems. Some continue to dive with cardiac issues, failing to seek specialised diving advice or fully understand the role of the diving medical. Physicians without appropriate training in diving medicine may inform a diver they are safe to continue diving with their condition without appreciating the potential risks. The current procedure for medical screening for fitness to dive may not be adequate for all divers.

A 10-year estimate of the incidence of decompression illness in a discrete group of recreational cave divers in Australia

INTRODUCTION

The vast majority of freshwater cave diving in Australia occurs within the limestone caves of the Gambier karst in the south-east of South Australia. The incidence of decompression illness (DCI) in cave divers is presumed to be higher than open-water recreational divers because of the greater depths involved, but has not previously been reported. Our aim was to determine the incidence of DCI in cave divers, the patterns of diving and the outcome of hyperbaric treatment.

METHODS

This was a retrospective cohort study of cave divers with DCI presenting to the Royal Adelaide Hospital or The Alfred Hospital over a 10-year period between 2002 and 2012. We reviewed case notes of cave divers who were treated for DCI after diving in the Mt Gambier karst. As there are no records of the number of dives performed during the study period we generated a denominator for the incidence of DCI by extrapolating available data and making a number of assumptions about the number of dives per dive permit issued.

RESULTS

Sixteen patients were treated for DCI during the study period. The precipitating dive was a single deep decompression dive in seven cases, multiday repetitive dive sequences in eight and a non-decompression dive in one. Three of the 16 cases of DCI involved dives in excess of 90 metres' fresh water (mfw) using trimix. As the total estimated number of dives in the study period was approximately 57,000 the incidence of DCI in Australian cave divers was estimated to be 2.8:10,000 (0.028%). It is possible that the overall incidence of DCI is as high as 0.05%, and even higher when dives to depths greater than 90 mfw are involved.

CONCLUSIONS

The estimated incidence of DCS in this series is lower than expected but consistent with other series describing DCI in cold-water recreational diving.

Simvastatin decreases incidence of decompression sickness in rats

Decompression sickness (DCS) is a specific diving injury which sometimes may be life-threatening. Previous studies suggested that simvastatin (SIM) can protect against pathological inflammation and tissue damage. This study aimed to investigate whether SIM pretreatment could exert its beneficial effects on DCS. SIM was administered orally to adult male Sprague-Dawley rats for two weeks (2 mg/kg/day), then rats were subjected to a simulated dive at 700 kPa air pressure for 100 minutes before rapid decompression. After 30 minutes of symptom observation, lung tissue and blood samples were collected for further analysis. Compared to the vehicle-control, SIM pretreatment significantly decreased the incidence of DCS and ameliorated all parameters of pulmonary injuries, including lung dry/wet weight ratio, bronchoalveolar lavage fluid protein concentration, lung tissue malondialdehyde level and morphology. Moreover, SIM pretreatment abolished increases in systemic and pulmonary inflammation by reducing tumor necrosis factor-α levels in blood plasma and lung tissue. The results indicate that SIM may offer a novel pharmacological protection against injuries in DCS rats by inhibiting inflammatory responses. Further study is needed to understand the exact mechanisms.

[Fewer cases of decompression sickness in Västra Götaland. Eight years of statistics show a reduced number of consultations and treatments]

During the period 2005 to 2012, a total of 340 consultations (phone calls and/or visits) regarding possible decompression illness were recorded at the two hospitals with recompression chambers in the Västra Götaland region, Sweden. An analysis of the data showed a trend towards fewer consultations and recompression treatments. A similar trend has been observed in many other countries. Possible reasons for this reduction in the number of cases are discussed. Most of the patients only present relatively mild signs and symptoms at the time of consultation. This, together with the fact that the number of patients is low, involves a risk that awareness and knowledge regarding correct handling and care in diving accidents might be lost. Since rapid and correct care of decompression illness is important to avoid later sequeale it is important that competence in diving medicine is maintained at hospitals Nationwide.

Decompression illness in goats following simulated submarine escape: 1993-2006

The United Kingdom Ministry of Defence commissioned work to define the relationship between the internal pressure of a distressed submarine (DISSUB), the depth from which escape is made and the risk of decompression illness (DCI). The program of work used an animal model (goat) to define these risks and this paper reports the incidence and type of DCI observed. A total of 748 pressure exposures comprising saturation only, escape only or saturation followed by escape were conducted in the submarine escape simulator between 1993 and 2006. The DCI following saturation exposures was predominantly limb pain, whereas following escape exposures the DCI predominantly involved the central nervous system and was fast in onset. There was no strong relationship between the risk of DCI and the range of escape depths investigated. The risk of DCI incurred from escape following saturation was greater than that obtained by combining the risks for the independent saturation only, and escape only, exposures. The output from this program of work has led to improved advice on the safety of submarine escape.

Scuba diving injuries among Divers Alert Network members 2010-2011

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.

A study on dysbaric osteonecrosis in caisson workers

PURPOSE

To study the effects of exposure to compressed air on tunnel workers' health and to investigate the prevalence of dysbaric osteonecrosis (DON) in caisson workers.

METHODS

128 tunnel workers were divided into the exposed group (n = 58) and the control group (n = 70), and their shoulders, hips and knees were examined with X-ray, computed tomography (CT) and magnetic resonance imaging (MRI).

RESULTS

1) 34.5% of the exposed group were diagnosed with DON based on the national diagnostic criteria of decompression sickness. 2) The incidental difference of skeletal cystic changes between the exposed group and the control group was highly statistically significant (p < 0.01). 3) CT and MRI examination could detect early onset of DON lesions, and the cystic changes shown in CT and abnormal signals in MRI were diagnostic indicators in cases.

CONCLUSION

Cystic changes in CT and abnormal signals in MRI are key imaging findings of early DON.

Decompression illness in divers treated in Auckland, New Zealand, 1996-2012

INTRODUCTION

The treatment of divers for decompression illness (DCI) in Auckland, New Zealand, has not been described since 1996, and subsequent trends in patient numbers and demographics are unmeasured.

METHODS

This was a retrospective audit of DCI cases requiring recompression in Auckland between 01 January 1996 and 31 December 2012. Data describing patient demographics, dive characteristics, presentation of DCI and outcomes were extracted from case notes and facility databases. Trends in annual case numbers were evaluated using Spearman's correlation coefficients (ρ) and compared with trends in entry-level diver certifications. Trends in patient demographics and delay between diving and recompression were evaluated using regression analyses.

RESULTS

There were 520 DCI cases. Annual caseload decreased over the study period (ρ = 0.813, P < 0.0001) as did entry level diving certifications in New Zealand (ρ = 0.962, P < 0.0001). Mean diver age was 33.6 (95% confidence limits (CI) 32.7 to 34.5) years and age increased (P < 0.0001) over the study period. Median (range) delay to recompression was 2.06 (95% CI 0.02 to 23.6) days, and delay declined over the study period (P = 0.005).

CONCLUSIONS

Numbers of DCI cases recompressed in Auckland have declined significantly over the last 17 years. The most plausible explanation is declining diving activity but improvements in diving safety cannot be excluded. The delay between diving and recompression has reduced.

The relationship of decongestant use and risk of decompression sickness; a case-control study of Hawaiian scuba divers

Exposure to cold, dehydration, and aging are known to contribute to the development of decompression sickness (DCS) in divers. Hypertension and nicotine usage have also been suggested as risk factors. Vasoconstriction is an underlying mechanism associated with all of these risk factors. Vasoconstriction increases the degree of bubble formation which is believed to be the cause of DCS. Formed bubbles interfere with the production of nitric oxide which modulates vascular tone resulting in vasoconstriction. Divers commonly use sympathomimetic decongestants which induce vasoconstriction to prevent barotrauma of the ears and sinuses while diving and thus theoretically may contribute to the risk for developing DCS. The purpose of this case-control study was to explore the association between decongestant usage and development of DCS in 400 divers treated/evaluated at the University of Hawai'i, John A. Burns School of Medicine between 1983 and 2010. Bivariate and logistic regression analyses were employed to evaluate differences between cases and controls. In addition to the variable of interest, other co-variables known to have significant influence in the development of DCS were appropriately controlled for during the analyses. In this study population, dehydration (OR = 2.7; 95% CI: 1.1, 7.4), repetitive diving (OR = 2.8; 95% CI: 1.8, 4.4), and violation of dive profiles (OR = 4.9; 95% CI: 3.1, 7.9) contributed independently and significantly to the development of DCS. The co-variables of cold, gender, obesity, and rapid ascents were not significant contributors to developing DCS in this study. There was a small but statistically insignificant risk associated with decongestant use (OR = 1.4; 95% CI: 0.8-2.6; P = .22). The inherent limitations associated with records-based studies may have underestimated this risk. It is important therefore that future research be undertaken to help clarify this concern.

Barodontalgias, dental and orofacial barotraumas: a survey in Swiss divers and caisson workers

Changing ambient pressure can lead to medical conditions in body cavities filled with air. Intraoral pain elicited by changes in pressure is referred to as barodontalgia. Dental barotraumas are defined as pressure-induced damages of teeth and restorations. The pathophysiologic background so far is not completely clear. The present study deals with dental and orofacial symptoms which can occur as a result of pressure variations. With the aid of cantonal administrations, diving associations, and tunnel construction firms, 520 pressure-exposed individuals (499 scuba/ professional divers, 21 caisson workers operating at excess pressure) were questioned regarding dental problems. A personal interview was conducted with affected individuals. Problems in the dental area were experienced by 15% of all respondents. Toothaches were suffered by 10.2% of the participants. Tooth injuries occurred in 6.3% of all interviewees (26 fractured amalgam restorations, 4 crown fractures, 3 losses of tooth fragments). A proportion of 11.3% among the respondents complained about temporomandibular joint problems or mucosal irritations (for example aphthae) related to the mouthpieces. Barotraumas outside the dental area were incurred by 31.9% of the divers. Of these, 69.9% concerned the ears and 65.6% occurred during the descent. Based on the results obtained from the survey and taking into account the current literature, recommendations for the prevention of barotraumas in divers and caisson workers were prepared. Diagnostic exclusion of dental pathologies and avoidance of retentive reconstruction materials are important factors for the prevention of barodontalgias and dental barotraumas.

Incidence of DCS and oxygen toxicity in chamber attendants: a 28-year experience

Decompression sickness (DCS) and central nervous system oxygen toxicity are inherent risks for "inside" attendants (IAs) of hyperbaric chambers. At the Hyperbaric Medicine Center at the University of California San Diego (UCSD), protocols have been developed for decompressing IAs. Protocol 1: For a total bottom time (TBT) of less than 80 minutes at 2.4 atmospheres absolute (atm abs) or shallower, the U.S. Navy (1955) no-decompression tables were utilized. Protocol 2: For a TBT between 80 and 119 minutes IAs breathed oxygen for 15 minutes prior to initiation of ascent. Protocol 3: For a TBT between 120-139 minutes IAs breathed oxygen for 30 minutes prior to ascent. These protocols have been utilized for approximately 28 years and have produced zero cases of DCS and central nervous system oxygen toxicity. These results, based upon more than 24,000 exposures, have an upper limit of risk of DCS and oxygen toxicity of 0.02806 (95% CI) using UCSD IA decompression Protocol 1, 0.00021 for Protocol 2, and 0.00549 for Protocol 3. We conclude that the utilization of this methodology may be useful at other sea-level multiplace chambers.

Current status of decompression illness in China: analysis of studies from 2001-2011

OBJECTIVE

To analyze the studies on decompression illness (DCI) in China in the past 10 years.

METHODS

We searched three Chinese databases and collected studies on DCI for further analysis. On the basis of findings, we proposed the issues on DCI in China.

RESULTS

There are more than 50,000 active divers in China, the majority of whom are fishing divers. Among them, the incidence of DCI is still at a high level because they have little or no knowledge of diving and diving medicine, the quality of diving equipment is poor, and divers generally do not follow the regulations of diving. There are few dive physicians in China, and the general clinicians have poor knowledge about, or pay little attention to, dive medicine. This might be the major cause of the poor quality of studies on DCI. There is no consensus in the classification of DCI and treatment tables for DCI treatment. These are factors affecting systemic review and further meta-analysis of available studies on DCI.

CONCLUSION

It is imperative to generalize knowledge in not only divers and diving-related practitioners but general practitioners as well.

The incidence of decompression illness in 10 years of scientific diving

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.

Lower risk of decompression sickness after recommendation of conservative decompression practices in divers with and without vascular right-to-left shunt

INTRODUCTION

A vascular right-to-left shunt (r/l shunt) is a well-known risk factor for the development of decompression sickness (DCS). No studies to date have examined whether divers with a history of DCS with or without a r/l shunt have a reduced risk of suffering recurrent DCS when diving more conservative dive profiles (CDP).

METHODS

Twenty-seven divers with a history of DCS recommended previously to dive more conservatively were included in this study and retrospectively interviewed by phone to determine the incidence of DCS recurrence.

RESULTS

Twenty-seven divers performed 17,851 dives before examination in our department and 9,236 after recommendations for conservative diving. Mean follow up was 5.3 years (range 0-11 years). Thirty-eight events of DCS occurred in total, 34 before and four after recommendation of CDP. Four divers had a closure of their patent foramen ovale (PFO). A highly significant reduction of DCS risk was observed after recommendation of CDP for the whole group as well as for the sub-groups with or without a r/l shunt. A significant reduction of DCS risk in respect to r/l shunt size was also observed.

DISCUSSION

This study indicates that recommendations to reduce nitrogen load after DCS appear to reduce the risk of developing subsequent DCS. This finding is independent of whether the divers have a r/l shunt or of shunt size. The risk of suffering recurrent DCS after recommendation for CDP is less than or equal to an unselected cohort of divers.

CONCLUSION

Recommendation for CDP seems to significantly reduce the risk of recurrent DCS.

A review of 17 years of telephone calls to the Australian Diver Emergency Service (DES)

INTRODUCTION

The Diver Emergency Service (DES) in Australia provides specialised medical advice on diving incidents 24 hours a day to divers, dive operators, families and health professionals. It is operated from the Hyperbaric Medicine Unit of the Royal Adelaide Hospital where the physician-on-call also carries the DES phone (1800-088200 or +61-8-8212-9242).

METHODS

Data from calls to the service have been compiled into a computer database since 1991. Calls for the 17 years from 1991 through 2007 were analysed.

RESULTS

A total of 6,083 calls were logged, an average of 358 calls a year. Calls from Queensland and New South Wales each accounted for 25% of calls. Calls originating from outside Australia have been increasing and now make up 25% of calls. The diver themselves initiated the call 50% of the time and 66% of the calls were about male divers. The age range of divers was 12 to 95 years old. The mean age has increased from 30 to 36 years, with a greater proportion of calls from divers aged 50 years or older (from 2% to 14%). The largest group of calls (37%) related to whether symptoms might be the result of decompression illness (DCI). DCI was considered to be the probable diagnosis in 17% of calls, and possible in a further 12%. Other common findings were barotrauma (11%) and questions regarding fitness to dive (15%). Older divers were more likely to call in relation to a medical problem.

CONCLUSION

Interpretation of these data is qualitative but the prolonged collection period of 17 years allows some consideration of trends as to who calls the DES and why.

The epidemiology of injury in scuba diving

The epidemiology of injury associated with recreational scuba diving is reviewed. A search of electronic databases and reference lists identified pertinent research. Barotrauma, decompression sickness and drowning-related injuries were the most common morbidities associated with recreational scuba diving. The prevalence of incidents ranged from 7 to 35 injuries per 10,000 divers and from 5 to 152 injuries per 100,000 dives. Recreational scuba diving fatalities account for 0.013% of all-cause mortality aged ≥ 15 years. Drowning was the most common cause of death. Among treated injuries, recovery was complete in the majority of cases. Dive injuries were associated with diver-specific factors such as insufficient training and preexisting medical conditions. Environmental factors included air temperature and flying after diving. Dive-specific factors included loss of buoyancy control, rapid ascent and repetitive deep diving. The most common event to precede drowning was running out of gas (compressed air). Though diving injuries are relatively rare prospective, longitudinal studies are needed to quantify the effects of known risk factors and, indeed, asymptomatic injuries (e.g. brain lesions). Dive injury health economics data also remains wanting. Meanwhile, health promotion initiatives should continue to reinforce adherence to established safe diving practices such as observing depth/time limits, safety stops and conservative ascent rates. However, there is an obvious lack of evaluated diving safety interventions.

Per-capita claims rates for decompression sickness among insured Divers Alert Network members

Decompression sickness (DCS) in recreational diving is a rare and usually self-limiting injury, but permanent disability can occur. Incidence rate estimates are difficult to establish because the number of divers at risk is usually unknown in population samples with well-documented DCS. We estimated the annual per-capita DCS incidence rates for 2000-2007 based on insurance claims submitted by members of the Divers Alert Network (DAN), Durham, N.C., with dive accident insurance. The overall per-capita DCS claims rate (DCR) was 20.5 per 10,000 member-years. Based on the age-adjusted DCR, males submitted 28% more claims than females. Male-to-female difference was greatest between 35 and 40 years of age and disappeared by the mid-50s. Highest rates were observed in the 30- to 39-year age category, after which DCR declined with increasing age. Highest yearly DCR was estimated in 2002. Insurance dropout rate was greater among those who had DCS in the first year of their insurance compared to those who did not have DCS in their first year.

Diver Health Survey score and probability of decompression sickness among occupational dive guides and instructors

INTRODUCTION

This study attempted to correlate self-reported post-dive Diver Health Survey (DHS) scores with computed daily probability of decompression sickness (pDCS) values as a measure of decompression stress in occupational divers in the recreational diving industry.

METHODS

Divers completed the DHS form and their dive profiles were recorded electronically. The pDCS for each dive was calculated using the LE1 probabilistic model. Data were analysed using a mixed effects model.

RESULTS

DHS was not significantly associated with pDCS. Mean DHS on non-diving days was 1.6 and increased by 0.8 for each dive made during any day. Mean number of daily dives was 1.9 and mean DHS on diving days was 3.1.

CONCLUSION

Utility of the DHS for monitoring daily decompression stress among occupational divers working in the recreational diving industry in New Zealand remains unproven.

Decompression sickness in urban divers in France

BACKGROUND

Decompression sickness (DCS) can occur in SCUBA divers. DCS is treated with oxygen, preferably given under hyperbaric conditions. Although Paris (France) is located at a distance from the sea or lakes, some injured divers require hyperbaric oxygen treatment (HBOT) in this city, sometimes within a specific time frame. Thus, this study investigated the epidemiology and outcomes of such urban divers.

AIM

We conducted an observational study of SCUBA divers admitted to the Raymond Poincaré Hyperbaric centre near Paris from 1993 to 2003.

MATERIALS AND METHODS

We prospectively enrolled 69 consecutive SCUBA divers presenting DCS. Common risk factors were reported, especially aeroplane flight and training dives. Symptoms are very often atypical (63%) and onset time of symptoms is often too long (59% after 2 h) due to denial of symptoms. First aid is generally inadequate, with only 23% of victims receiving oxygen, fluid loading and aspirin together. HBOT was given for 42 (61%) patients although their examination results were considered as normal.

CONCLUSIONS

Diving pits and diving travel agencies should do more to warn divers of the need for treatment with normobaric oxygen and hydration pending HBOT. Moreover, hyperbaric physicians should better clarify HBOT indications for both symptoms of late onset and atypical presentations.