Scientific papers 2000 - 2003
Abstract:
The risk of decompression sickness is a safety problem
related to offshore diving operations. Modem safety
management defines a systematic approach to such a
problem based on policy edition, support from an
organisation, planning and implementing, monitoring,
reviewing, and auditing. These activities are analysed in
light of the experience of a large diving company,
achievements are listed, and areas of improvement are
identfied. It is shown that the next edition of
decompression procedures will require hundreds of
thousands of dive records to identify the critical factors,
define models, and validate new procedures. This exceeds
the experience of a single diving company or even a
single nation, and it is believed that efforts of
decompression sickness management should be
coordinated at a European level.
This document is a presentation of a diving algorithm
based on the Reduced Gradient Bubble Model (RGBM).
This document is written in French by doctors from the
hospital group of reunion island. It discusses herniated
intervertebral disks and diving activities.
The authors recall basic spinal hygiene rules, expose
several neuro-radiological and therapeutic indications,
and make a brief review of the literature on the impacts of
diving on the spine. The differential diagnosis with a
decompression accident in the spinal cord is also
discussed.
The oxygen window. Inherent unsaturation. Partial
pressure vacancy. Most divers with an interest in
decompression diving have likely encountered one of
these terms at some time. All three terms are used to
describe the same physical phenomenon. For this article,
the term oxygen window will be used, as it appears to be
the most commonly applied term. However, the terms
inherent unsaturation and partial pressure vacancy more
correctly describe the physical phenomenon. Current
techniques of oxygen-facilitated decompression diving are
based on use of the oxygen window.
Despite common use by divers of the oxygen window, it
appears to be one of the least appreciated concepts in
decompression diving. Understanding the oxygen
window requires knowledge of circulatory and gas
transport physiology, and the best place to start is with
normobaric physiology.
Document written by Thomas, F. Floyd, James M. Clark,
Robert Gelfand, John A. Detre, Sarah Ratcliffe, Dimitri
Guvakov, Christian J. Lambertsen, and Roderic G.
Eckenhoff
Breathing 100% O2 at 1-atmosphere absolute (ATA) is
known to be associated with a decrease in cerebral blood
fow (CBF). It is also accompanied by a fall in arterial PCO2
leading to uncertainty as to whether the cerebral
vasoconstriction is totally or only in part caused by arterial
hypocapnia.
The team tested the hypothesis that the increase in arterial
PO2 while O2 was breathed at 1.0 ATA decreases the
cerebral blood fow (CBF) independently of a concurrent
fall in arterial PCO2 ..
This study was initiated to determine the effect of
decompression profiles on bubble formation following
surface decompression using oxygen.
Following an air dive to 496 kPa (130 fsw) for 90 minutes,
three different profiles were tested in the pig; a USN
staged decompression profile, a profile using linear
continuous decompression with the same total
decompression time as the USN profile, and a linear
profile with half the total decompression time compared
to the first two. The subsequent surface decompression at
220 kPa lasted 68 minutes for all three schedules.
The study demonstrated that, following final
decompression, the two linear profiles produced the
lowest amount of vascular gas, with the fastest profile
producing significantly less bubbles in the Pulmonary
artery than the other two. Similar results were obtained in
the jugular vein. The results are in qualitative agreement
with model simulation using the Reduced Gradient
Bubble Model (RGBM), demonstrating that the controlling
tissues are reduced from those with a half time of 40
minutes using the USN procedure to 5 minutes using the
fastest linear profile.
This report describes a case-control study of UK
compressed air workers in which subjects with repetitive
DCS during a single compressed air project were matched
to two control groups. Further to this, an analysis of the
Health and Safety Executive (HSE) Decompression
Database 1986-2000 was undertaken to examine the
relative contribution of those workers with repetitive DCS
to the overall number of DCS episodes in the UK during
the study period.
Cerebral gas embolism is a serious consequence of diving.
It is associated with decompression sickness and is
assumed to cause severe neurological dysfunction. A
mathematical model previously developed to calculate
embolism absorption time based on in vivo bubble
geometry is used in which various conditions of
hyperbaric therapy are considered… To continue…
Deep stops usually reduce overall decompression time
(hang time). And when coupled to the use of helium in
the breathing mixture (trimix) to reduce narcotic effects of
nitrogen, technical divers report feeling much better
physically today when they leave the water. The
reduction in hang time ranges from 10% to as high as
50%, depending on the diver, mix, depth, and exposure
time. Feeling better while decompressing for shorter
periods of time is certainly a win-win situation that would
have been thought an impossibility not too long ago.
Physical readiness and body makeup are considered
fundamental attributes of U.S. Navy divers. Methods to
objectively determine body makeup are fraught with
shortcomings and can be technically challenging,
particularly in field operations.
Two potential field methods of determining body
composition, densitometry and deuterium oxide dilution,
were assessed and compared in the laboratory.
Authors:
R.G. Dunford, R.D. Vann , W.A. Gerth, C.F. Pieper, K.
Huggins, C. Wacholtz, and P.B. Bennett.
Decompression sickness (DCS) is a pathological event
thought caused by intravascular and extravascular gas
bubbles. The bubble theory of DCS is supported by
empirical evidence, and venous gas emboli (VGE) can be
detected after diving using non-invasive Doppler
ultrasonic methods, but the etiology of DCS is complex,
and VGE are frequent after symptom-free dives. High VGE
levels, however, are associated statistically with increased
DCS incidence suggesting that VGE and DCS may share a
common origin. Further, VGE might initiate DCS should
they cross or bypass the pulmonary capillary filter and be
transported by the arterial circulation to organs such as
the brain or spinal cord.
Du 6 au 10 juin 1988 eut lieu à Kongsvoll, en Norvège, un
symposium international consacré au thème de la
sursaturation et la formation de bulles dans les fluides
et les organismes.
La première partie du document présentent les
participants et le thème qu’ils ont développés. ).
La deuxième partie du document est la traduction d’un
article du Dr Hennessy qui présente une hypothèse
concernant la décompression en plongée. A la suite de
cet article, figure la retranscription de la discussion qui
suivit entre les participants à propos de cette nouvelle
hypothèse.
Cells from virtually all organisms respond to various
stresses by the rapid synthesis of a highly conserved set of
polypeptides termed heat shock proteins (HSPs). The
precise functions of HSPs are unknown, but there is
considerable evidence that these stress proteins are
essential for survival at both average and elevated
temperatures. HSPs also appear to play a critical role in
developing thermotolerance and protection from cellular
damage associated with stresses such as ischemia,
cytokines, and energy depletion. These observations
suggest that HSPs play an essential role in normal cellular
homeostasis and the stress response. This mini-review
examines recent evidence and hypotheses suggesting
that the HSPs may be important modifying factors in
cellular responses to various physiologically relevant
conditions such as hyperthermia, exercise, oxidative stress,
metabolic challenge, and aging.
It is accepted that gas bubbles grow from pre-existing gas
nuclei in tissue. The possibility of eliminating gas nuclei
may be of benefit in preventing decompression sickness.
The present study examined the hypothesis that
hyperbaric oxygen may replace the resident gas in the
nuclei with oxygen and eliminate the nuclei themselves
because of its metabolic role.
Authors: Kun-Lun Huan, Chin-Pyng Wu, Yin-Li Chen, Bor-
Hwang Kang, & Yu-Chong Lin
Diving acclimatization refers to reduced susceptibility to
acute decompression sickness (DCS) in individuals
undergoing repeated compression-decompression cycles.
The authors postulated that mechanisms responsible for
acclimatization are similar to that of stress preconditioning.
In this study, we investigated the protective effect of prior
heat shock treatment on air embolism-induced lung injury
and DCS incidence in rats.
Authors: M. B. Harris, M. A. Blackstone, Hong Ju, V. J.
Venema, & R. C. Venema.
Endothelial nitric oxide (NO) synthase (eNOS) is the
primary source of NO production in the cardiovascular
system. It is a key regulator of systemic blood pressure,
blood vessel proliferation, and vascular lesion formation.
eNOS is regulated by numerous mechanisms, including
subcellular location, phosphorylation, and protein-protein
interactions. This study is the continuation of previous
experiences regarding this point. Understanding the
phenomenons described is essential to understand divers'
physical condition and some phenomena linked to
decompression accidents.
Authors: Jay B. Dean, Daniel K. Mulkey, Alfredo J. Garcia,
Robert W. Putnam, and Richard A. Henderson
As ambient pressure increases, hydrostatic compression of
the central nervous system, combined with increasing
levels of inspired PO2, PCO2, and N2 partial pressure, has
deleterious effects on neuronal function, resulting in O2
toxicity, CO2 toxicity, N2 narcosis, and high-pressure
nervous syndrome. The cellular mechanisms responsible
for each disorder have been difficult to study by using
classic in vitro electrophysiological methods, due to the
physical barrier imposed by the sealed pressure chamber
and mechanical disturbances during tissue compression.
The documents are classified chronologically from 2000 to 2003.
Click on their descriptions to open and download them.
Many divers report less fatigue following diving, breathing
oxygen-rich N2 - O2 mixtures than breathing air. In this
double-blinded, randomized controlled study, 11 divers
breathed either air or enriched Air Nitrox 36% O2 during
an 18 msw chamber dive for a bottom time of 40
minutes. Two periods of exercise were performed during
the dive. Divers were assessed before and after each dive.
This experiment examined the involvement of the
autonomic nervous systems and intrinsic components in
the occurrence of hyperbaric bradycardia. Eight male
divers were exposed to an N2 - O2 (Nitrox) environment
at 3 atmospheres (ATA). The heart rate (HR), plasma
norepinephrine (NE), and spectral power of the variability
of the cardiac interval were measured during a 4-day pre-
dive control period, a seven-day saturation period at 3
ATA, and a 4-day post-dive period.
There is a dispute as to whether paradoxical gas embolism
is an important aetiological factor in neurological
decompression illness, particularly when the spinal cord is
affected. The authors performed a blind case-controlled
study to determine the relationship between
manifestations of neurological decompression illness and
causes in 100 consecutive divers with neurological
decompression illness and 123 unaffected historical
control divers. The clinical effects of neurological
decompression illness (including the sites of lesions and
onset latency) were correlated with right-to-left shunts,
lung disease, and a provocative dive profile.
Authors: A. Hjelde, s. Kotengz, 0. Eftedalz, at A. 0. Brubakk
There is a considerable difference in detected venous gas
emboli (VGE) between individuals following
decompression. This study explores the role surface
tension that may play in the differences. The authors
measured serum surface tension in 26 anesthetized pigs
before (predive) and after a dive (postdive) to 300 kPa for
3 hours. Gas bubbles in the pulmonary artery were
monitored continuously from the beginning of
decompression and continued throughout 120 minutes
after the dive.
Authors: P. T. Wilmshurst, M. J. Pearson, K. P. Walsh, W. L.
Morrison, and P. Bryson.
A large right-to-left shunt is associated with neurological
decompression illness after non-provocative dives,
resulting from paradoxical gas embolism. A few
observations suggest that cutaneous decompression
illness is also associated with a right-to-left shunt, although
an embolic aetiology of a diffuse rash is more diffcult to
explain. The authors performed a retrospective case-
control comparison of the prevalence and sizes of right-to-
left shunts determined by contrast echocardiography
performed blind to history in 60 divers and one caisson
worker with a history of cutaneous decompression illness
and 123 historical control divers.
Authors: Carturan, D., A. Boussuges, P. Vanuxem, A. Bar-
Hen, H. Burnet, and B. Gardette.
This study aimed to assess the effects of ascent rate, age,
maximal oxygen uptake (VO2 max), and percent body fat
on the production of bubbles after diving. Fifty male
recreational divers performed two dives at 35 m during 25
min and then ascended in one case at 9 m/min and in
the other case at 17 m/min.
They performed the same decompression stops in the two
cases. Twenty-eight divers were Doppler monitored at 10-
min intervals until 60 min after surfacing, and the data
were analyzed by Wilcoxonsigned-rank test to compare
the effect of ascent rate on the kinetics of bubbles.
Twenty-two divers were monitored 60 min after surfacing.
Authors: Ulrik Wisløff , Russell S. Richardson, and Alf O.
Brubakk
This study determines the effect of inhibiting nitric oxide
synthase (NOS) on bubble formation in acutely exercised
and sedentary rats exposed to hyperbaric pressure.
Author: Shi Zhong-yuan
A collaborative experiment with Chinese Underwater
Technology Institute, American National Office of
Research Undersea Program, and Hamilton Research Ltd.
was conducted at 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.
Authors: Anuj Chawla & Ak Lavania
This short paper is not a study, but a document used to
teach divers and specialists about oxyfen toxicity
Authors: Russell P. Bowler & James D. Crapo
This document is purely medical. It has been integrated to
provide information on the effect of oxidative stress,
Published by: Unimed Scientific Limited for the UK HSE
This study was commissioned to compare a number of
tables used for oxygen decompression in compressed air
tunneling work. It was undertaken by Unimed Scientific
Limited at the request of UK Health and Safety Executive.
Authors: Mirit Eynan, Yehuda Arieli, Ran Arieli, & Arieth
Bomzon
The purpose of this study was to measure the effect of 24
h breathing 100% O2 in normobaric conditions on
energetic efficiency in the trained rat. The results suggested
that prolonged exposure to hyperoxia induces a reduction
in the energetic efficiency of trained rats.
Thirteen cases of decompression sickness (DCS) occurred
during the construction of the 8-km long railway tunnel
under the Great Belt in Denmark between January 1992
and February 1996.
320 compressed air workers were subjected to 9018
pressure exposures in four tunnel boring machines.
Overall DCS incidence was 0.14%.
Working pressures ranged between 0.25 bar (1.25 atm
abs or 126.3 kPa) and 2.95 bar (3.91 atm abs or 396.3
kPa) and working times ranged between 2 minutes and
339 minutes.
Research on the validation of decompression tables is one
of common subject area of the cooperation undertaken
between the defense and civil institute of environmental
medicine, Toronto, Canada, and the Naval academy of
Gdynia - Poland
This document from Unimed Scientific Ltd, written in 2002
by Valerie Flook for “Well Ops UK Ltd”, is a theoretical
study of heliox excursion, evaluating the extent of bubble
formation and suggesting changes that would reduce
decompression bubbles. To complete the analysis quickly,
only the depths of 75 msw, 100 msw, and 130 msw have
been considered, and the maximum downward
excursions considered for each was 25, 29, and 33 msw.
Author: Valerie Flook
The work described in this report continues the one
published by Unimed Scientific Ltd in December 2002 for
“Well Ops UK Ltd”. In this report, Valerie Flook describes
changes to procedures for upward excursions, that were
not discussed in the previous document.
Authors: R. S. Lillo, & E. C. Parker
A mixed-gas model for rats was developed to further
explore the role of different gases in decompression and
to provide a global model for possible future evaluation of
its usefulness for human prediction. A Hill equation dose
response model was fitted to over 5,000 rat dives by using
the technique of maximum likelihood. These dives used
various mixtures of He, N 2 , Ar, and O2 and had times at
depth up to 2 h and varied decompression profiles.
Publisher: Divers Alert Network (DAN), Durham
This document is the proceedings of a nitrox workshop
organized by the Diver Alert Network (DAN) in
November 2000.
DAN is a non-profit organization associated with Duke
University Medical Center in Durham, North Carolina,
USA. The organization operates as a lifeline for
scuba/recreational divers with a 24 hours hotline. It is
registered in our website (see in “Entertainment”)
Authors: Z. Nachum, A. Shupak, O. Spitzer, Z. Sharoni, Y.
Ramon, A. Abramovich, I. Doweck, C.R. Gordon
Inner ear decompression sickness (IEDCS) may result in
permanent, severe cochleo-vestibular deficits, unless
immediate diagnosis is reached and the correct treatment
is commenced early. Previously reported IEDCS cases
were mostly associated with deep mixed helium diving,
whereas after sport air diving this entity is considered to
be rare.
Authors: Frederick W. Rudge
This document, explains that decompression sickness may
occur during flights due to the problems posed by the
pressurization of airplane cabins. It is initially written for
aviation personels. However, it should be considered to
understand the guidelines DMAC 7.
Authors: A Onoo, M Kiyosawa, H Takase, Y Mano
Pneumatic caisson engineering has been developed for
large civil engineering constructions. Because of
complaints of blurred vision by personnel working in
pneumatic caissons, the development of myopia was
suspected. The aim of this study was to determine the
cause of the blurred vision and the mechanism
underlying the changes.
12 caisson workers underwent a complete
ophthalmological examination after completing up to 11
weeks of work (4 days/week) in a pneumatic caisson. Six
months later, nine of the workers were examined again.
Authors: David J Doolette and Simon J Mitchell)
Isolated inner ear decompression sickness (DCS) is
recognised in deep diving involving breathing of helium-
oxygen mixtures, particularly where breathing gas is
switched to a nitrogen-rich mixture during
decompression. The biophysical basis for this selective
vulnerability of the inner ear to DCS has not been
established. A compartmental model of inert gas kinetics
in the human inner ear was constructed from anatomical
and physiological parameters described in the literature
and used to simulate inert gas tensions in the inner ear
during deep dives and breathing gas substitutions that
have been reported to cause inner ear DCS.
