Consensus guideline: Pre-hospital management of decompression illness: expert review of key principles and controversies.

(Mitchell SJ, Bennett MH, Bryson P, Butler FK, Doolette DJ, Holm JR, Kot J, Lafère P. Pre-hospital management of decompression illness: expert review of key principles and controversies. Diving and Hyperbaric Medicine. 2018 March;48(1):45е.doi.10.28920/dhm48.1.45-55.) Guidelines for the pre-hospital management of decompression illness (DCI) had not been formally revised since the 2004 Divers Alert Network/Undersea and Hyperbaric Medical Society workshop held in Sydney, entitled "Management of mild or marginal decompression illness in remote locations." A contemporary review was initiated by the Divers Alert Network and undertaken by a multinational committee with members from Australasia, the USA and Europe. The process began with literature reviews by designated committee members on: the diagnosis of DCI; first aid strategies for DCI; remote triage of possible DCI victims by diving medicine experts; evacuation of DCI victims; effect of delay to recompression in DCI; pitfalls in management when DCI victims present at hospitals without diving medicine expertise and in-water recompression. This was followed by presentation of those reviews at a dedicated workshop at the 2017 UHMS Annual Scientific Meeting, discussion by registrants at that workshop and, finally, several committee meetings to formulate statements addressing points considered of prime importance to the management of DCI in the field. The committee placed particular emphasis on resolving controversies around the definition of "mild DCI" arising over 12 years of practical application of the 2004 workshop's findings, and on the controversial issue of in-water recompression. The guideline statements are promulgated in this paper. The full workshop proceedings are in preparation for publication.

Identifying and acting on potentially inappropriate care? Inadequacy of current hospital coding for this task.

INTRODUCTION: Recent Australian attempts to facilitate disinvestment in healthcare, by identifying instances of 'inappropriate' care from large Government datasets, are subject to significant methodological flaws. Amongst other criticisms has been the fact that the Government datasets utilized for this purpose correlate poorly with datasets collected by relevant professional bodies. Government data derive from official hospital coding, collected retrospectively by clerical personnel, whilst professional body data derive from unit-specific databases, collected contemporaneously with care by clinical personnel. AIM: Assessment of accuracy of official hospital coding data for hyperbaric services in a tertiary referral hospital. METHODS: All official hyperbaric-relevant coding data submitted to the relevant Australian Government agencies by the Royal Hobart Hospital, Tasmania, Australia for financial year 2010-2011 were reviewed and compared against actual hyperbaric unit activity as determined by reference to original source documents. RESULTS: Hospital coding data contained one or more errors in diagnoses and/or procedures in 70% of patients treated with hyperbaric oxygen that year. Multiple discrete error types were identified, including (but not limited to): missing patients; missing treatments; 'additional' treatments; 'additional' patients; incorrect procedure codes and incorrect diagnostic codes. Incidental observations of errors in surgical, anaesthetic and intensive care coding within this cohort suggest that the problems are not restricted to the specialty of hyperbaric medicine alone. Publications from other centres indicate that these problems are not unique to this institution or State. CONCLUSIONS: Current Government datasets are irretrievably compromised and not fit for purpose. Attempting to inform the healthcare policy debate by reference to these datasets is inappropriate. Urgent clinical engagement with hospital coding departments is warranted.

The use of portable 2D echocardiography and 'frame-based' bubble counting as a tool to evaluate diving decompression stress.

INTRODUCTION: 'Decompression stress' is commonly evaluated by scoring circulating bubble numbers post dive using Doppler or cardiac echography. This information may be used to develop safer decompression algorithms, assuming that the lower the numbers of venous gas emboli (VGE) observed post dive, the lower the statistical risk of decompression sickness (DCS). Current echocardiographic evaluation of VGE, using the Eftedal and Brubakk method, has some disadvantages as it is less well suited for large-scale evaluation of recreational diving profiles. We propose and validate a new 'frame-based' VGE-counting method which offers a continuous scale of measurement. METHODS: Nine 'raters' of varying familiarity with echocardiography were asked to grade 20 echocardiograph recordings using both the Eftedal and Brubakk grading and the new 'frame-based' counting method. They were also asked to count the number of bubbles in 50 still-frame images, some of which were randomly repeated. A Wilcoxon Spearman ρ calculation was used to assess test-retest reliability of each rater for the repeated still frames. For the video images, weighted kappa statistics, with linear and quadratic weightings, were calculated to measure agreement between raters for the Eftedal and Brubakk method. Bland-Altman plots and intra-class correlation coefficients were used to measure agreement between raters for the frame-based counting method. RESULTS: Frame-based counting showed a better inter-rater agreement than the Eftedal and Brubakk grading, even with relatively inexperienced assessors, and has good intra- and inter-rater reliability. CONCLUSION: Frame-based bubble counting could be used to evaluate post-dive decompression stress, and offers possibilities for computer-automated algorithms to allow near-real-time counting.

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.

Transportation of divers with decompression illness on the west coast of Scotland.

INTRODUCTION: There is a time line for divers who develop decompression illnesses (DCI) from the completion of their dive to the initiation of recompression. The time to treatment is influenced by many factors; two being the time before acknowledgement that the diver has a pressure-related illness and the time taken for transfer from that point to commencment of recompression. METHOD: Time to onset of symptoms, and time from onset of symptoms to treatment were analysed for 233 divers, 202 recreational and 31 professional, presenting within 24 h of onset of symptoms to the Dunstaffnage Hyperbaric Unit between 1990 and 2009, who were transported by air, sea or road. RESULTS: Divers with severe DCI had significantly shorter times for onset of symptoms (95% confidence intervals 0.9 to 2.3 h longer for mild/moderate compared to severe DCI) and were transferred for treatment approximately twice as fast as those with mild/moderate symptoms (inter-quartile ranges: recreational divers, 2.25-5.63 h for mild/moderate DCI versus 1.54-3.25 h for severe DCI; professional divers, 2.63-11.13 h for mild/moderate DCI versus 2.25-2.92 h for severe DCI). Although choice of transport was most likely influenced both by location and disease severity, transfer modality did not significantly affect time to treatment for divers with severe DCI. In addition, no differences in time to treatment were observed between professional and recreational divers irrespective of disease severity. CONCLUSIONS: The data suggest that transport was optimised to fit the particular circumstances of the patient and that divers treated for DCI in Scotland may benefit from there being a single, integrated, co-ordinated clinical service.

Risk of misclassification of decompression sickness.

Decompression sickness (DCS) is classified on the basis of which organ system is affected, and neurological DCS is considered more severe than DCS in joints and skin with respect to response to recompression treatment and risk of long-term sequelae. Gas bubble formation interstitially in the tissues or in the circulation is considered to be the mechanism for all types of DCS. Ten patients diagnosed as having DCS in joints or skin, by doctors experienced in diving medicine, underwent clinical examination by a neurologist and had an electroencephalogram. Eight of the ten subjects had findings suggesting central nervous system deficits. The findings indicate that DCS of the central nervous system often accompanies DCS of the joints and skin, and that local skin and joint symptoms may draw attention away from cerebral symptoms. We recommend that all cases with DCS should initially be treated as neurological DCS.

Decompression illness medically reported by hyperbaric treatment facilities: cluster analysis of 1929 cases.

INTRODUCTION: The term decompression illness (DCI) describes maladies resulting from inadequate decompression, but there is little consensus concerning clinically useful DCI subclasses. Our aim was to explore an objective DCI classification using multivariate statistics to assess naturally associated clusters of DCI manifestations. We also evaluated their mapping onto other DCI classifications and investigated the association with therapeutic outcome. METHODS: We defined the optimal number of clusters using "two-step" cluster analysis and Bayesian information criterion with confirmation by hierarchical clustering with squared Euclidian distances and Ward's method. The data were 1929 DCI cases reported by hyperbaric chambers to the Divers Alert Network (DAN America) from 1999-2003. RESULTS: Four robust and highly significant clusters of DCI manifestations were demonstrated containing 300, 741, 333, and 555 patients. Each cluster had characteristic manifestations. Cluster 1 was effectively pain only. For Cluster 2, characteristic manifestations included numbness, paresthesia, and decreased skin sensitivity; for Cluster 3, malaise, paralysis, muscular weakness, and bladder-bowel dysfunction; and for Cluster 4, hearing loss, localized skin swelling, tinnitus, skin rash and mottling, confusion, dyspnea/chokes, muscular problems, vision problems, altered consciousness, headache, vertigo, nausea, fatigue, dizziness, and abnormal sensations. DISCUSSION: Internal reliability was confirmed by arbitrarily dividing the dataset into two parts and repeating the analysis. The clusters mapped poorly onto traditional DCI categories (AGE, Type I DCS, Type II DCS), but more specifically onto the Perceived Severity Index (PSI). All three classification methods (DCI, Cluster, PSI) predicted complete relief of manifestations equally well. We conclude that cluster analysis is an objective method for classifying DCI manifestations independent of clinical judgment.

Viewpoint: the type A- and the type B-variants of Decompression Sickness.

BACKGROUND: Symptoms of neurological decompression incidents (DCS/AGE) can be severe or mild. It is unknown if these differences of symptom presentation represent different clinical entities or if they represent just the spectrum of DCS/AGE. METHODS: 267 cases with DCS/AGE were compared retrospectively and classified into two subgroups, the Type A-DCS/AGE for cases with a severe and often stroke-like symptomatology and the Type B-DCS/AGE for those with milder and sometimes even doubtful neurological symptoms. The main outcome measures were the number of hyperbaric treatments (HTs) needed and the clinical outcome. RESULTS: 42 patients with DCS/AGE were classified as Type A- and 225 patients met the criteria for a Type B-DCS/AGE. Patients with Type A-lesions were more severely affected, needed more hyperbaric treatments and had a less favorable outcome than patients with the Type B-variant. CONCLUSIONS: The Type A- and the Type B-DCS/AGE are likely to be different entities with better clinical outcome in the Type B-variant and possibly significant differences in the underlying pathophysiologies of both variants. Future studies with a particular focus on the up to now inadequately investigated Type B-DCS/AGE are necessary to elucidate such differences in the pathophysiology.

Clasificación de la patología de buceo / Classification of diving disorders

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Type II decompression sickness in naval hypobaric chambers: A case of mistaken identity?

INTRODUCTION: Historically, U.S. Navy clinicians have used the U.S. Navy Dive Manual for guidance in the diagnosis and treatment of injuries incurred during hyper- or hypobaric operations. Based on this manual, paresthesias are considered to be central nervous system manifestations and thus are classified as Type II (severe) decompression sickness (DCS). Yet given the highly successful response to treatment of peripheral nervous system manifestations of DCS in the literature, both the diving and aviation communities have questioned its classification as "severe" DCS. This record review was undertaken to examine U.S. Naval severe cases of altitude DCS with the goal of identifying dissimilarities between hypobaric facilities in classification and incidence. METHODS: Hypobaric exposures and cases were reviewed from quarterly training reports maintained at the Naval Operational Medicine Institute, Pensacola, FL, between January 1993 and April 2004. Cases were analyzed for age, gender, flight profile, symptom complex, type of DCS, and treatment provided. RESULTS: There were 50,355 hypobaric exposures resulting in 97 cases of altitude DCS. Of the 97 cases of diagnosed DCS, 58 were classified as Type II, while 39 were Type I. Of the 58 cases of Type II DCS, 29 were diagnosed as Type II by the sole finding of non-dermatomal paresthesias. DISCUSSION: Type II DCS, a designation traditionally reserved for severe DCS, is frequently diagnosed by the sole finding of non-dermatomal paresthesias in Naval hypobaric training. A review and revision of the U.S. Naval Aviation classification system for altitude DCS should be undertaken with emphasis on severity not symptomatology.

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Central nervous system decompression sickness and venous gas emboli in hypobaric conditions.

INTRODUCTION: Altitude decompression sickness (DCS) that involves the central nervous system (CNS) is a rare but potentially serious condition. Identification of early symptoms and signs of this condition might improve treatment. METHODS: We studied data from 26 protocols carried out in our laboratory over the period 1983-2003; all were designed to provoke DCS in a substantial proportion of subjects. The data set included 2843 cases. We classified subject-exposures that resulted in DCS as: 1) neurological DCS of peripheral and/or central origin (NEURO); 2) a subset of those that involved only the CNS (CNS); and 3) all other cases, i.e., DCS cases that did not have a neurological component (OTHER). For each case, echo imaging data were used to document whether venous gas emboli (VGE) were present, and their level was classified as: 1) any level, i.e., Grade 1 or higher (VGE-1); and 2) high level, Grade 4 (VGE-4). RESULTS: There were 1108 cases of altitude DCS in the database; 218 were classified as NEURO and 49 of those as CNS. VGE-1 were recorded in 83.8% of OTHER compared with 58.7% of NEURO and 55.1% of CNS (both p < 0.001 compared with OTHER). The corresponding values for VGE-4 were 48.8%, 37.0%, and 34.7% (p < 0.001, compared to OTHER). Hyperbaric oxygen (HBO) was used to treat about half of the CNS cases, while all other cases were treated with 2 h breathing 100% oxygen at ground level. DISCUSSION: Since only about half of the rare cases of hypobaric CNS DCS cases were accompanied by any level of VGE, echo imaging for bubbles may have limited application for use as a predictor of such cases.

Cigarette smoking and decompression illness severity: a retrospective study in recreational divers.

BACKGROUND: Severe decompression illness (DCI) could be more likely in cigarette smokers because of airway obstruction or vascular disease. The present study evaluated the severity of DCI as a function of cigarette smoking in recreational divers. METHODS: We examined all DCI reports recorded in the Divers Alert Network (DAN) database from 1989 through 1997. Smoking history was quantified as heavy (>15 pack-years), light (0 to 15 pack-years), and never smoked. DCI symptoms were classified as severe (alteration in consciousness, balance or bladder/bowel control, motor weakness, visual symptoms, convulsions), moderate (other neurological symptoms), or mild (pain, skin, or nonspecific symptoms). The proportional odds model and generalized logits were used for the adjusted analysis when accounting for other covariates. RESULTS: There were 4,350 patients included in the analysis. After adjustment for confounding variables, heavy smokers were more likely to have severe vs. mild symptoms than nonsmokers (OR = 1.88) (95% CI 1.36, 2.60) or light smokers (OR = 1.56) (95% CI 1.09, 2.23). Heavy smokers and light smokers were more likely to have severe vs. moderate symptoms than nonsmokers (OR = 1.36) (95% CI 1.06, 1.74) and (1.22) (1.02, 1.46), respectively. Although these data do not reveal whether smoking predisposes to DCI, the results are consistent with a tendency, when DCI occurs, for cigarette smoking to trigger more severe symptoms. CONCLUSIONS: The data suggest that when DCI occurs in recreational divers, smoking is a risk factor for increased severity of symptoms.

Epidemic decompression sickness: case report, literature review, and clinical commentary.

BACKGROUND: Decompression sickness (DCS) is a syndrome of symptoms caused by bubbles of inert gas. These bubbles are produced by a significant ambient pressure drop. Although cases are usually solitary there have been several episodes of DCS clusters. This paper reports an episode of epidemic decompression sickness and reviews the literature. METHODS: The case reported describes six aircrewmen with DCS following an unpressurized AC-130 flight (maximum altitude 17,000 ft). Two obvious concerns-the low altitude at which DCS was encountered and the potential for epidemic hysteria-are discussed and discounted. In addition, factors contributing to this case are recounted in depth. Moreover, the literature was examined for similar cases of epidemic decompression sickness. Four other instances were discovered. Detailed qualitative analysis of these five reports was performed. RESULTS: With this information epidemic decompression sickness is defined and classified. Two types are described-individual-based (Epi-I) and population-based (Epi-P). Epi-I is a cluster of DCS following a solitary exposure; whereas, Epi-P is a cluster of DCS following multiple exposures over time. Investigation of Epi-P follows the classical rules of outbreak investigation (time, place, person, and environment); whereas, Epi-I does not. In fact, the focus in Epi-I is almost entirely the environment. Following this outline should produce an etiology that control measures can be directed against. However, it is prudent to look beyond the etiology. Enter the Haddon Matrix, a classic public health tool that considers counter-measures before, during, and after the event. CONCLUSION: These many concepts are illustrated with the presented case. Following this template, both the expert and the novice flight surgeon have a systematic and reproducible approach to these difficult puzzles.

[Decompression sickness in divers treated at the Israel Naval Medical Institute between the years 1992 to 1997].

Clinical characteristics of 125 divers treated for decompression sickness (DCS) in the hyperbaric multiplace chambers of this Institute during 1992-1997 were analyzed retrospectively. In 62 (51%) the diagnosis was DCS Type I (joint pain or skin involvement) and in 60 (49%) DCS Type II (neurological, inner ear or pulmonary disease). Risk factors for the evolution of DCS were depth and duration of the dives involving accidents, violation of recommendations of the decompression tables, and repeated dives. Results were available for 112 of the 125 patients. 54 of them (48%) recovered completely, and another 54 recovered partially; 4 did not respond to treatment. Inner ear DCS was less responsive to hyperbaric oxygen treatment (p = 0.0001). There was significant improvement of neurological function in those with severe neurological injury (p = 0.0001). Rapid diagnosis and transportation of divers with DCS to a hyperbaric chamber is of crucial importance.

Management of decompression sickness in Jordan.

This study, conducted at Princes Haya Hussein Hospital Hyperbaric Department, examined 23 cases (22 males, 1 female), diagnosed with decompression sickness (types I and II) and treated with hyperbaric therapy. The results showed 61% of dive accidents were decompression sickness type II; 26% of treated patients had residual symptoms after the first session of recompression treatment and 74% made a full recovery. There were no deaths and no complications were observed. The study concludes that decompression sickness type II is the most common type, found mainly in sports divers. Early recognition of symptoms and commencement of treatment lead to a much better outcome.

[Incidence and prevention of space decompression sickness].

To expound the necessity that space decompression sickness (SDCS) should be separated from altitude DCS, comparison was made between the features of space DCS and altitude DCS. The etiology and pathogenesis of the space DCS and altitude DCS were the same, but the features of the rules leading to their incidences (included influencing factors etc.) were different. For the convenience of getting better systemic and definite knowledge about SDCS, and making effective preventive plans and theoretical expositous, SDCS should be taken as an independent professional term.