Diving SafetyMyths & Misconceptions

Alex F. Brylske, Ph.D.DAN Training Consultant

An Overview of Decompression

Signs & Symptoms of DCI

• 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

• Dizziness• Visual blurring• Areas of decreased sensation• Chest pain• Disorientation• Bloody froth from mouth/nose• Paralysis or weakness• Convulsions• Unconsciousness• Cessation of breathing• Death

DCSAGE

Predisposing Factors

• Lack of cardiovascular fitness

• Age

• Alcohol or drug use

• PFO

• Obesity

• Sleep deprivation

• Dehydration

• Inadequate Nutrition

• Heavy exertion

• History of DCI

• 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

Host Factors Environmental FactorsEquipment failure/improper technique

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

5min

10min

20min

75minlung 40

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

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100

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100Depth(fsw)

MaxDepth

maximum allowablesurfacing

M-Values

At 90 fswAscent

to 30 fsw

Halftimes = 5 ... 61 ... 480 min12 Haldane tissues

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 out-gassing 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 no-decompression 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."

“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

Evidence for Deep Stops

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 self-

imposed 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.”

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.

The Decompression Stress Continuum

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.”

Skin bends

Symptoms ofDecompression 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)

Maximum Depth in Series by Diagnosis

Maximum Depth in Series (fsw)

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< 30 30-59 60-89 90-119 120-149 150-179 > 180

DCS IAGEDCS II

Frequency of Reported Problems During Dive

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Rapid Ascent

ExertionCold

Missed DecoEquipmentBouyancy

NauseaOut of Air

Short of Breath

Injury

Low on Air

% o

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N = 3461. Environmental

factors

2. Medical & health issues

3. Procedural problems

Individual Symptoms for Injured Divers

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CardioPulmonary

Headache

Dizziness

Skin Changes

Fatigue

Muscular Weakness

Pain

Paresthesia

First Symptom

All Symptoms

% of Cases

Symptom Onset Time by Diagnosis

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Missing

Before Last DiveDuring Last Dive

< 1 hr1-2 hrs3-6 hrs7-12 hrs13-24 hrs25-48 hrs

> 48

DCS IAGEDCS II

% o

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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.

“Diving is more dangerous than ever.”

Misconception #9

Not true…we think

Annual Record of Diver Injuries

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87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04

Dan Notified

Report Submitted

US & Canadian Residents

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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 ContinuesWhat 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

Alex Mustard photo

Any Questions?

239-471-7824239-471-7824

abrylske@dan.orgabrylske@dan.org

Dive Safety: New Insights and Fresh

Perspectives

Alex F. Brylske, Ph.D.DAN Training Consultant