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Diving Safety Myths & 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 DCS AGE
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 Factors Equipment 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 5 min 10 min 20 min 75 min lung 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 10 20 30 40 50 60 70 80 90 100 10 20 30 40 50 60 70 80 90 100 Depth (fsw) Max Depth maximum allowable surfacing M-Values At 90 fsw Ascent to 30 fsw Halftimes = 5... 61... 480 min 12 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) 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 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 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)
Maximum Depth in Series by Diagnosis Maximum Depth in Series (fsw) % of Injured Divers
Frequency of Reported Problems During Dive % of Injured Divers N = 346 1.Environmental factors 2.Medical & health issues 3.Procedural problems
Individual Symptoms for Injured Divers % of Cases
Symptom Onset Time by Diagnosis % of Injured Divers
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 Year Number of Cases
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
Alex Mustard photo Any Questions? email@example.com
Dive Safety: New Insights and Fresh Perspectives Alex F. Brylske, Ph.D. DAN Training Consultant