Diving Safety
Myths & Misconceptions
Alex F. Brylske, Ph.D.
DAN Training Consultant
An Overview of Decompression
Signs & Symptoms of DCI
DCS
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Unusual fatigue
Skin itch
Pain in joints and/or muscles of the arms,
legs or torso
Dizziness, vertigo, ringing in the ears
Numbness, tingling and paralysis
Shortness of breath
Skin may show a blotchy rash
Paralysis, muscle weakness
Difficulty urinating
Confusion, personality changes, bizarre
behavior
Amnesia, tremors
Staggering
Coughing up bloody, frothy sputum
Collapse or unconsciousness
AGE
• Dizziness
• Visual blurring
• Areas of decreased sensation
• Chest pain
• Disorientation
• Bloody froth from mouth/nose
• Paralysis or weakness
• Convulsions
• Unconsciousness
• Cessation of breathing
• Death
Predisposing Factors
Host Factors
•
•
•
•
•
•
•
•
•
•
Lack of cardiovascular
fitness
Age
Alcohol or drug use
PFO
Obesity
Sleep deprivation
Dehydration
Inadequate Nutrition
Heavy exertion
History of DCI
Equipment
Environmental Factors failure/improper technique
•
•
•
•
•
Extremes of temperature
Rough seas
Flying after diving
Heavy exercise at depth
Nitrogen Narcosis
•
•
•
•
•
•
•
Violating decompression tables
Difficulty with buoyancy
Rapid ascent
Breath holding on ascent
Running out of air
Regulator malfunction
Unfamiliar/improper equipment
Source: The Neurologist. 2002 May;8(3):186-202. DECOMPRESSION ILLNESS IN DIVERS: A REVIEW OF THE LITERATURE
Diana Marie Barratt, MD, MPH*; Paul G. Harch, MD**; Keith Van Meter**, MD,
Patent Foramen Ovale (PFO)
A possible mechanism of so-called “unexplained” DCI?
Misconception #1
“While they may give slightly different
numbers, all decompression models
are pretty much based on the same
concepts and assumptions.”
Not True!
• Assumptions and
conceptual models
can differ greatly.
• Does gas remain in a
dissolved state
(“dissolved-phase
dynamics”) or do
bubbles inevitably
form (“free-phase
dynamics”)?
Haldane’s Model of
the Body
lung
5
min
10
min
20
min
40
min
75
min
1983 Orca EDGE
• Digital computer
• First practical &
successful dive
computer
• Tested in 100 trials
• No other dive
computers have
been tested
Orca EDGE Display
12 Haldane tissues
10
10
20
20
30
30
40
40
50
60
70
80
Depth
(fsw)
Halftimes = 5 ... 61 ... 480 min
50
maximum
allowable
surfacing
M-Values
60
70
80
90
90
100
100
At 90 fsw
Max
Depth
Ascent
to 30 fsw
Dissolved vs. Free Phase Gas Elimination
• Dissolved gas can diffuse
from the tissue into either
the circulation or bubbles.
• Dissolved gas in
circulation is easily
eliminated in the lungs.
• Free gas in bubbles
presents problems by
greatly increasing outgassing time.
Illustration: Eric Maiken
Free-Phase Model
• Reduced Gradient
Bubble Model
(RGBM)
• NAUI Dive Tables
• Some computers
• Deep stops
Misconception #2
“Deep safety stops (below 20 feet) add,
not reduce, nitrogen absorption, and
are therefore dangerous.”
Not True!
• Dissolved-phase Model: More
gas is absorbed but the tissues
affected never control,
provided it’s a nodecompression dive.
• Free-Phase Model: Better
nitrogen elimination with the
reduced-size bubble.
• “The secret of the deep stop
rests in the paradigm shift of
‘beating the bubble’ versus
"treating the bubble."
Evidence for Deep Stops
“The introduction of a deep stop during decompression ascent
appears to significantly decrease Doppler recorded bubbles and
predicted gas tensions in the fast ‘tissues’ which may relate to actual
gas exchange within the spinal cord. The authors conclude that such
a deep stop may therefore significantly reduce the incidence of
spinal cord-related decompression sickness.”
Source: Marroni, P. B. Bennett, F. J. Cronje, R. Cali-Corleo, P. Germonpre, M. Pieri, C.
Bonuccelli1, C. Balestra. (2004). A deep stop during decompression from 82 fsw (25 m)
significantly reduces bubbles and fast tissue gas tensions. Undersea and Hyperbaric
Medicine, Vol. 31, No. 2, pp. 223-243. at:
www.diversalertnetwork.org/news/download/marronifinal1888acapcoraut.pdf)
Deep Stops: Can Adding Half the Depth of A Safety Stop Build in Another Safety Margin?
www.diversalertnetwork.org/news/Article.aspx?newsid=514
Take-Home Message
• DAN Online Seminar: “Inert Gas Exchange,
Bubbles and Decompression Theory” by Dr.
Richard Vann.
– Relatively safe decompression procedures can be
produced by models based on very different physical,
physiological, and pathophysiological mechanisms.
– Success in improving decompression safety and the
dictum “what works, works” are of obvious practical
importance, but relative success is by no means
sufficient to prove a model is based on valid theory.
Misconception #3
“I can’t get the bends if I follow my
tables or computer.”
My computer told me it was okay!
• 36 yr old female with 20 yrs of diving but no
dives in past 13 months.
• Dive vacation with husband
• Profile: (Dive 1) 120 feet for 20 minutes--
25 min SIT-- (Dive 2) 63 feet for 30 minutes.
• Immediately felt bad after dive, complained of
headache, pain and tingling in left arm and foot,
left shoulder weakness.
(continued)
• Husband felt it was due to carrying tanks, not
DCI.
• Symptoms improved somewhat, but did not
resolve, over next several hours.
• Called DAN to ask questions.
• Recommendation evaluation by local dive
physician, but advice declined by husband.
• Symptoms worsened on flight home, called DAN
again.
• Completely resolved on one Table 6 treatment.
I thought I had the flu!
• 44-year-old full-time Instructor
• Excellent health, back surgery more than year
prior to incident.
• Most diving in cold water (dry suit) and selfimposed limit of 115 feet.
• Profile Single multilevel dive: 90’ for 10”.--70
feet for 15”--45 feet for 26”--3” safety stop.
• Felt fine afterwards and rest of day.
(continued)
• Following morning awoke with headache, mild
nausea and slight burred vision.
• After several hours at work noted a “cool
sensation” in his right foot, bilateral shoulder
pain and dull ache in left hand and both wrists.
• Assumed he had the flu.
• Third day, right foot completely numb and called
DAN.
• Completely resolved on one Table 6 treatment.
Take-Home Message
• Few divers really “plan” their
dives today. Too many turn on
their computers and turn off their
brains.
• Use tables and computers
conservatively.
• Stay warm and well hydrated.
• Avoid excessive exercise
before, during and after diving.
Misconception #4
“Fewer cases of bends have been
reported since dive computers became
popular.”
“More cases of bends have been
reported since dive computers became
popular.”
Neither is true
• When dive computers were first
introduced, many diving physicians
believed that the DCS incidence
would increase drastically. This has
not happened.
• There is no evidence of any more—
or less—DCS for dive computers
than for dive tables.
• However, incidence of arterial gas
embolism among injured divers is
less among computer users.
Misconception #5
“Decompression sickness is an
‘all-or-none’ event.”
The Decompression Stress
Continuum
Areas of red skin without pain or swelling, skin itch, mild
pain in a joint that lasts less than one hour, and mild to
moderate fatigue after a dive are signs of mild decompression
stress and do not require treatment.
Is There Anyway to Quantify
Decompression Stress?
• Gas absorption is
based largely on
blood flow.
• A good measure of
blood flow is heart
rate.
Misconception #6
“The kind of bends that recreational
divers get isn’t the same—or as
serious—as that of commercial or
military divers.”
Symptoms of
Decompression Illness
• DCS Type 1- (JOINT) Pain only
• DCS Type 2 - Any neurological
symptom anywhere in the body
• DAN accident data shows: 25% of
DCS is Type I (pain or rash only),
and 65% is Type II (neurological)
Skin bends
% of Injured Divers
Maximum Depth in Series
by Diagnosis
45
DCS I
AGE
DCS II
40
35
30
25
20
15
10
5
0
< 30
30-59
60-89
90-119 120-149 150-179 > 180
Maximum Depth in Series (fsw)
Frequency of Reported
Problems During Dive
% of Injured Divers
25
20
N = 346
2. Medical &
health issues
15
10
3. Procedural
problems
5
De
co
ui
pm
Bo en
uy t
an
c
Na y
us
ea
O
Sh
ut
or
o
to fA
f B ir
re
at
h
In
ju
Lo
ry
w
on
Ai
r
ld
Eq
d
Co
se
Ex
er
tio
n
M
is
pi
d
As
ce
nt
0
Ra
1. Environmental
factors
Individual Symptoms for
Injured Divers
Paresthesia
Pain
Muscular Weakness
First Symptom
Fatigue
All Sym ptoms
Skin Changes
Dizziness
Headache
CardioPulmonary
0
20
40
% of Cases
60
80
40
48
50
>
Be
M
fo
is
re
si
ng
La
Du
rin st
D
g
La iv e
st
Di
ve
<
1
hr
12
hr
s
36
hr
s
712
hr
13
s
-2
4
hr
25
s
-4
8
hr
s
Symptom Onset Time by Diagnosis
70
60
DCS I
AGE
DCS II
30
20
10
0
Take Home Message
• DCS isn’t just the result of “deep” diving.
• A rapid ascent is the most commonly reported
problem associated with a DCI incident, but
exertion and cold are also common.
• Recreational divers tend to present with more
serious forms of DCI (Type II) than either
commercial or military divers.
• “Denial ain’t just a river in Egypt.” DON’T DIVE
IF YOU EXPERIENCE POSSIBLE SYMTOMS
OF DCI!
Misconception #7
“Bends is just a ‘bubble
disorder’ so if you get rid of the
bubbles your problems are
over.”
Not True
• DCI involves a lot more than just bubbles
Misconception #8
“If I get the bends I should immediately
rush off to the nearest recompression
chamber.”
Not True!
• What if the chamber isn’t operational?
• Medical support is as important as
recompression—perhaps more so.
• Always contact DAN first.
Misconception #9
“Diving is more dangerous than ever.”
Not true…we think
Number of Cases
Annual Record of Diver Injuries
1400
Dan Notified
1200
Report Submitted
US & Canadian Residents
1000
800
600
400
200
0
87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04
Year
Annual Record of Diver Fatalities
Take Home Message
• The overall rate of DCI from Project Dive Exploration in
2007 was a little less than 3.1 cases per 10,000 dives
(down from 3.6 cases per 10,000 dives reported in
2006).
• There are actually fewer diving fatalities today than in the
past, although we still don’t know the denominator of
how many dives are made nor how many divers there
are.
PDE Extravaganza:
May 25-September 7, 2009
• Go to the DAN homepage
and click the PDE
Extravaganza icon.
• Follow instructions to
complete a donor profile
and receive an ID.
• Go diving
• Use your dive log
software to donate your
profile.
• Receive a free t-shirt and
automatically enter a
prize drawing.
How Can You Reduce Your Risk?
• Whatever dive table or computer you use, use it
conservatively (stay well within maximum limits).
• Pay close attention to ascent rates, never exceeding 30
feet-per-minute.
• Always do safety stops, and add a deep stop (half the
maximum depth for two to threes) on deeper divers
(+40’).
• Dive only when well rested, nourished and hydrated (and
stay warm and well hydrated).
• Avoid heavy exercise before, during and immediately
after diving.
• Stay fit for diving, and adjust your diving according to
your level of fitness.
Encourage Divers to Pursue Training
• Eight dive-specific first aid courses
• Oxygen First Aid for Scuba Diving Injuries
– First program, still largest and most popular
• On-Site Neurological Assessment for Divers
– Designed as a next step beyond oxygen
• Automated External Defibrillators for Scuba Diving
Encourage Divers to Pursue Continuing
Education
DES Quest III – The Quest Continues
What Is It?
– The DES Quest is an annual
challenge to all divers to achieve
the level of Diving Emergency
Specialist (DES)
– DES is a recognition program
designed to commend divers who
have continued their education and
training in order to increase their
safety and improve their ability to
assist in an emergency.
When Is It?
– June 1 – December 31, 2008
Any Questions?
239-471-7824
abrylske@dan.org
Alex Mustard photo
Dive Safety:
New Insights and Fresh
Perspectives
Alex F. Brylske, Ph.D.
DAN Training Consultant