Article

Fatal accidents among deep sea fishermen in Singapore

January 1976

Authors:

As part of a survey into the occupational health of deep sea fishermen in Singapore, retrospective study of death due to acute decompression was done. A total of 8 cases was recorded in the Department of Pathology from 1954 to 1974. These involved male Chinese fishermen from 18 to 36 yr with an average age of 28 yr. All had a common history of diving into the water at a depth of 60 to 100 feet to free the anchor. They were either pulled out from the sea unconscious or felt uneasy and died soon after. At postmortem 5 of them exhibited gas bubbles in subcutaneous tissues, heart or veins.

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Article

Reduced gradient bubble model

December 1990 · International Journal of Bio-Medical Computing

B. R. Wienke

An approach to decompression modeling, the reduced gradient bubble model (RGBM), is developed from the critical phase hypothesis. The phase limit is introduced, extended, and applied within bubble-nucleation theory proposed by Yount. Much is different in the RGBM algorithm, on both theoretical and applied sides, with a focus on permissible bubble excesses rather than just dissolved gas buildup, ... [Show full abstract] something of a departure from traditional models. Overall, the approach is conservative, with changes in parameter settings affording flexibility. Marginal profiles permitted by tables and meters are restricted by the bubble algorithm. Highlighted features of the conservative algorithm include: (1) reduced no-stop time limits from the varying-permeability model (VPM); (2) short safety stops (or shallow swimming ascents) in the 10-20 feet of sea water (fsw) zone; (3) ascent and descent rates of 60 fsw/min, or slower; (4) restricted repetitive exposures, particularly beyond 100 fsw, based on reduced permissible bubble excess; (5) restricted spike (shallow-to-deep) exposures based on excitation of additional micronuclei; (6) restricted multi-day activity based on regeneration of micronuclei; (7) consistent treatment of altitude diving within model framework; (8) algorithm linked to bubble-nucleation theory and experiment. Coupled to medical reports about the long term effects of breathing pressurized gases and shortcomings in dissolved gas models, conservative modeling seems prudent.

Article

Full-text available

DCS RISK ESTIMATORS FOR DIVE COMPUTERS AND DIVEWARE

October 2017 · Computers in Biology and Medicine

Dive computers and diveware are important underwater tools and staging devices across sport, technical, commercial , military, scientific, exploration and research diving sectors. They are supplanting traditional dive tables and their use is growing as decompression activities grow. While important computer parameters are displayed thoughout a dive, risk associated with surfacing and arbitrary ... [Show full abstract] ascents to depths above the diver are not yet encoded into underwater devices and divewear and that is the focus here. Risk estimation is needed for diver safety and sensible dive planning. We discuss (two) basic biophysical models, oxygen toxicity and then methodology for risk estimators that can be employed in present generation dive computers and dive planning software for end of dive (EOD) and on the fly (OTF) risk at any point on a dive. Exponential risk functions are defined for dissolved gas and bubble models using profile data correlated with the LANL Data Bank, a collection of computer downloaded mixed gas decompression profile with DCS outcomes across OC and RB diving. Risk functions are based on profile supersaturations in excess over permiss-ble supersaturations which are a standard metric. Comparative results and applications are given for both nonstop and deep decompression diving on OC and RB systems. Computer implementation is easily accomplished within existing dive computers and diveware platforms. Techniques are underscored and results are discussed. References detail background information and analyses and work extends earlier published analyses for EOD risk estimation. It is hoped that this methodology is useful, well defined and pertinent for the dive computer and dive software industry. Standard (SI) and English units are employed. By convention, by usage or for ease, some nonstandard units are employed. Pressure and depth are both measured in feet of sea water (f sw) and meters of sea water (msw), with 1 atm = 33 f sw = 10 msw to good approximation. Acronyms are used herein. They are standard throughout the dive community with definitions:

Article

[A critical assessment of Trendelenburg's position in the acute phase after a diving accident]

October 1993 · Schweizerische Zeitschrift für Sportmedizin

G de Watteville

For several years now, a controversy has developed on how to position a patient after a decompression accident with acute gas embolism. The usefulness of the so-called Trendelenburg position, based on experimental evidence gathered on dogs, has recently been challenged. The basis assumption was that cerebral embolism may be reduced by the hydrostatic effect of putting the head below the body's ... [Show full abstract] center of gravity. This position however required much technical resourcefulness and often delayed the first therapeutic intervention. Newer experimental research shows that, contrary to the old theory, positioning the head below feet level increases the intra-cranial pressure, injuring the blood-brain barrier, even when done under hyperbaric oxygen therapy. A wide consensus has now emerged, which should be communicated to first-aid personnel, so that no more time is being lost in trying to position the accidented diver by unduly complicated means. The current recommendations asks for laying the injured diver horizontally on its back, or sideways, if he is unconscious. It is by far more important to control its vital functions, give first-aid, administer oxygen in closed circuit, and shorten as much as possible transport time to the next center for hyperbaric therapy.

Article

Research on Nitrogen-Oxygen Saturation Diving with Repetitive Excursions.

April 2000 · Journal of PHYSIOLOGICAL ANTHROPOLOGY and Applied Human Science

Zhong-yuan Shi

For some tasks of underwater operation the need for longer dive duration and more working divers necessitates the use of saturation diving techniques with excursions. Saturation diving with excursion has high working efficiency. A collaborative experiment with Chinese Underwater Technology Institute, American National Office of Research Undersea Program and Hamilton Research Ltd. was conducted at ... [Show full abstract] our Institute in Shanghai. The main experiment objectives were to assess the longer, deeper repetitive excursions during nitrogen-oxygen saturation situation, oxygen exposure management, nitrox saturation decompression after excursions and performance aspects. Four Chinese professional experienced divers were saturated at 25 msw for 5 days at the hyperbaric facility, where they did 15 air excursions to depths between 50 and 75 msw, for duration up to 240 min. Decompression from excursions to the storage were mostly no-stops, but 5 required stops for 3 to 116 min. Saturation decompression began with the "precursory" ascent following a brief return to 25 msw. Doppler bubble detection showed some bubbles of Spencer Grade II and occasionally III, following excursions and during saturation decompression, especially after muscle flexing. No symptoms of decompression sickness were reported: one diver was more of fatigued on one occasion than other times. Oxygen exposure reached its peak of 3103 Oxygen Toxicity Units on Day 6. The only subjective symptom of oxygen toxicity was mild and transient numb fingertips. No significant change was seen in vital capacity.

Article

Full-text available

Extreme survival: A serious technical diving accident

March 2005

Trytko B, Mitchell S. Extreme survival: a serious technical diving accident. SPUMS J. 2005; 35: 23-7.) A 34-year-old technical diver involved in a dive to 105 metres' sea water incorrectly assembled his rebreather and suffered carbon dioxide toxicity at depth. He developed anxiety, confusion and dyspnoea resulting in a rapid ascent with loss of consciousness. In the process, he omitted 51 minutes ... [Show full abstract] of decompression time. His subsequent presentation with life-threatening decompression illness and salt-water aspiration, and the management of these problems are discussed. A note on terminology: In this paper we follow Francis and Mitchell 1 in utilising the term 'decompression sickness' (DCS) to refer specifically to the consequences of bubble formation from dissolved inert gas, and the term 'decompression illness' (DCI) to refer to the broad spectrum of bubble-induced symptoms that may arise from DCS and arterial gas embolism.

Conference Paper

Full-text available

DIVE COMPUTER PROFILE DATA AND RISK ESTIMATORS

December 2017

Dive computers and diveware are important underwater tools and staging devices across sport, technical, commercial , military, scientific, exploration and research diving sectors. They are supplanting traditional dive tables and their use is growing as decompression activities grow. While important computer parameters are displayed thoughout a dive, DCS risk associated with surfacing and ... [Show full abstract] arbitrary ascents to depths above the diver are not yet encoded into underwater devices and diveware and that is the focus here. Risk estimation is needed for diver safety and sensible dive planning. We discuss (two) basic biophysical models, oxygen toxicity and then methodology for risk estimators that can be employed in present generation dive computers and dive planning software for end of dive (EOD) and on the fly (OTF) risk at any point on a dive. Exponential risk functions are defined for dissolved gas and bubble models using profile data correlated with the LANL Data Bank, a collection of computer downloaded mixed gas decompression profile with DCS outcomes across OC and RB diving. Risk functions are based on profile supersaturations in excess over permiss-ble supersaturations which are a standard metric. Comparative results and applications are given for both nonstop and deep decompression diving on OC and RB systems. Computer implementation is easily accomplished within existing dive computers and diveware platforms. Techniques are underscored and results are discussed. References detail background information and analyses and work extends earlier published analyses for EOD risk estimation. It is hoped that this methodology is useful, well defined and pertinent for the dive computer and dive software industry. Animal Disclaimer-Humans and animals were not used for testing in this paper. Certainly animals and humans were employed in cited References. DEFINITIONS AND ACRONYMS Standard (SI) and English units are employed. By convention, by usage or for ease, some nonstandard units are employed. Pressure and depth are both measured in feet of sea water (f sw) and meters of sea water (msw), with 1 atm = 33 f sw = 10 msw to good approximation. Acronyms are used herein. They are standard throughout the dive community with definitions:

Article

Research on Deep Submergence Diving Physiology and Decompression Technology Utilizing Swine: Evaluat...

May 1971

Murlin F Gillis

Attempts to define the no-decompression air limits for miniature swine were complicated by individual variance and bends tolerance development, but, based solely on clinical signs, they appear more resistant to bends than man except perhaps at depths beyond 140 feet. Although 100 feet/90 minutes, 140 feet/60 minutes and 180 feet/30 minutes produces an 80% incidence of bends, they generally ... [Show full abstract] tolerate dives to from 60 to 180 feet for bottom times three times greater than the no-decompression limits for man. Temporary signs of middle ear distress are seen almost exclusively on ascent.

Article

Effect of N2-He-O2 on decompression outcome in rats after variable time-at-depth dives

June 1988 · Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology

R. S. Lillo

No study of decompression sickness has examined both variable gas mixtures and variable time at depth to the point of statistical significance. This investigation examined the effect of N2-He-O2 on decompression outcome in rats after variable time-at-depth dives. Unanesthetized male albino rats were subjected to one of two series of simulated dives: 1) N2-He-O2 dives (20.9% O2) at 175 feet of ... [Show full abstract] seawater fsw) and 2) N2-O2 dives (variable percentage of O2; depths from 141 to 207 fsw). Time at depth ranged from 10 to 120 min; rats were then decompressed within 10 s to surface pressure. The probability of decompression sickness (severe bends symptoms or death) was analyzed with a Hill equation model, with parameters for gas potency and equilibrium time for the three gases and weight of the animal. Relative potencies for the three gases were of similar magnitude for bends and statistically different for death in ascending order: O2 less than He less than N2. Estimated gas uptake rates were different. N2 took three to four times as long as He to reach full effect; the rate of O2 appeared to be considerably shorter than that of N2 or He. The large influence of O2 on decompression outcome questions the simplistic view that O2 cannot contribute to the decompression requirement.

Article

Inner Ear Decompression Sickness

October 1976 · The Laryngoscope

With recent increases in commercial, military, and sport diving to deeper depths, inner ear injuries during such exposures have been encountered more frequently and noted during several phases of diving: during compression, at stable deep depths, with excessive noise exposure in diving, and during decompression. The pathophysiology of these injuries differs, depending upon the phase of diving in ... [Show full abstract] which the injuries occur. In this report, 23 cases of hearing loss, tinnitus, and/or vertigo occurring during or shortly after decompression are presented. Thirteen of these cases occurred in helium-oxygen dives involving a change to air during the latter stages of decompression. A significant correlation is present between prompt recompression treatment, relief of symptoms, and lack of residual deficits. Current knowledge indicates that the management of otologic decompression sickness should include: 1. prompt recompression to at least 99 feet deeper than the symptom onset depth; 2. recompression using the previous helium-oxygen mixture when the injuries occur during or shortly after a switch from helium-oxygen to air during the latter stages of decompression; 3. the use of parenteral diazepam for symptom relief and cyclic inhalations of oxygen enriched treatment gases; and 4. the avoidance of further diving by divers who exhibit permanent inner ear injuries after the acute symptoms have subsided.

Article

A Working Week at 840 Feet In the Open Sea

January 1972

In Sept., 1970, three COMEX divers worked twice a day for 8 days at 840 ft in the open sea, up to 3 hours at a time. The necessary methods and equipment were developed during a prior series of experimental simulated saturation dives. Further improvement of these techniques has enabled man to work for extended periods of time, down to 1,000 ft even in arctic conditions. INTRODUCTION In early ... [Show full abstract] 1970, the COMEX Co. undertook, as main operator, the series of saturation deep diving experiments known as the JANUS II operation. This experimental program, jointly sponsored by the Centre National pour l' Exploitation des Oceans and the French oil company, ELF-ERAP, was the logical follow -up to the JANUS I operation, which in 1968, had permitted us to develop and perfect the necessary methods and techniques for bringing saturated divers to work on a routine basis at a depth of 500 ft in the open sea. The purpose of the JANUS II program was to extend the possibilities of this method to a depth in the range of 800 to 850 ft and to test its industrial practibility under real conditions in the open sea. The whole operation was divided into three main phases to ensure a logical progression toward the final objective of the program. PHASE ONE The first phase, which took place in April and May, 1970, in the pressure chambers complex of COMEX Hyperbaric Research Center, was mainly devoted to the detailed study of the various physiological parameters that governed the entire experiment. First of all, we verified the hypothesis that men, saturated at a simulated depth of 660 ft, could work twice a day for 2 hours at a time at a depth of 840 ft and return safely to their habitat, pressurized at 660 ft, without any intermediate decompression stops. This was realized through an 8-day saturation period by progressively increasing the duration of the 840-ft exposures from 1 to 2 hours, then shifting the evening dive to match the required working periods of 8 to 10 a.m. and 6 to 8 p.m. as shown in Fig. 1. This basic hypothesis proved to be absolutely correct. At the same time, we verified that the total pressure exposure was physiologically harmless to the three divers and that their living and working capabilities were absolutely unaffected by these unusual conditions. This was effected by means of a series of intensive biological and physiological tests including (1) blood and urine sampling and analysis, (2) dietetic monitoring and control, (3) electro encephalographic and electrocardiographic monitoring, (4) respiratory measurements at rest and under effort by the use of a specially designed ergometric chair, (5) psychomotor tests and (6) study of the reflexes. This first phase additionally permitted us to start the evaluation of a new final decompression method intended to reduce significantly the duration of the return to normal atmospheric pressure.

Article

Patent Foramen Ovale as a Risk Factor for Altitude Decompression Illness

June 2001

The relation between the presence of a patent foramen ovale (PFO) and the risk of decompression illness (DCI) remains controversial. PFO is a common finding in the general population with an autopsy prevalence of about 25%. Recent review articles in the diving literature have concluded the presence of a PFO may increase the relative risk for DCI but the absolute risk remains low. In space ... [Show full abstract] operations DCI is a significant concern for extravehicular activities (EVA) because of the low Suit pressure (the NASA EMU-suit pressure is 4.3 psia equivalent to about 30,000 feet).

Article

Full-text available

Diving behavior and fishing performance: The case of lobster artisanal fishermen of the Yucatan coas...

September 2015 · Undersea and Hyperbaric Medicine

An average of 209 cases of decompression sickness (DCS) have been reported every year among artisanal fishermen divers of the Yucatan Peninsula, Mexico. DCS is a major problem among fishermen divers worldwide. This paper explores how diving behavior and fishing techniques among fishermen relate to the probability of experiencing DCS (Pdcs). Fieldwork was conducted in two communities during the ... [Show full abstract] 2012-2013 fishing season. Fishermen were classified into three groups (two per group) according to their fishing performance and followed during their journeys. Dive profiles were recorded using Sensus Ultra dive recorders (Reefnet Inc.). Surveys were used to record fishing yields from cooperative and individual fishermen along with fishing techniques and dive behavior. 120 dives were recorded. Fishermen averaged three dives/ day, with an average depth of 47 ± 2 feet of sea water (fsw) and an average total bottom time (TBT) of 95 ± 11 minutes. 24% of dives exceeded the 2008 U.S. Navy nodecompression limit. The average ascent rate was 20 fsw/minute, and 5% of those exceeded 40 fsw/minute. Inadequate decompression was observed in all fishermen. Fishermen are diving outside the safety limits of both military and recreational standards. Fishing techniques and dive behavior were important factors in Pdcs. Fishermen were reluctant to seek treatment, and symptoms were relieved with analgesics.