An Overview of Decompression

Transcription

1 Diving Medicine just add water An Overview of Decompression Vandenhoven Guy, M.D., Ph.D. BVOOG Belgische Vereniging voor Overdruk en Onderwater Geneeskunde HEPHS - ISEK - Environmental, Ageing & Occupational Physiology (Integrative) Lab. - Brussels - Belgium DAN Europe - Benelux - Research - Brussels - Belgium SKA - Congres 2016 On the Edge GrensverleggendeSportgeneeskunde Antwerpen Paul Bert ( )

2 John Scott Haldane ( ) Ite Boerema ( ) DECOMPRESSION ILLNESS DECOMPRESSION ILLNESS

3 «Life Without Blood» Boerema 1960 Signs & Symptoms of DCI Hyperbaric oxygen 20 m depth 0,5 % Hematocrit Actual human record 1,7 gr/100 ml Hb DCS Unusual fatigue Skin itch Joint and/or muscle pain of arms, legs or torso Dizziness, vertigo, ringing in ears Numbness, tingling and paralysis Shortness of breath Skin may show 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 Environmental Factors Equipment Failure / Improper Technique 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 Patent Foramen Ovale (PFO) A possible mechanism of so-called unexplained DCI? Source: The Neurologist May;8(3): DECOMPRESSION ILLNESS IN DIVERS: A REVIEW OF THE LITERATURE Diana Marie Barratt, MD, MPH*; Paul G. Harch, MD**; Keith Van Meter**, MD,

4 Patent Foramen Ovale (PFO) A possible mechanism of so-called unexplained DCI? Patent Foramen Ovale (PFO) A possible mechanism of so-called unexplained DCI? Not True! Misconception #1 While they may give slightly different numbers, all decompression models are pretty much based on the same concepts and assumptions. 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 )?

5 Haldane s Model of the Body 1983 Orca EDGE Digital computer (Haldane decompression model with M-value ascent criteria) lung 5 min 10 min 20 min 40 min 75 min First practical & successful dive computer Tested in 100 trials No other dive computers have been tested EDGE : Electronic Dive Guide Experience Orca EDGE Display 12 Haldane tissues Halftimes = min Structure of Decompression Models Depth (fsw) maximum allowable surfacing M-Values At 90 fsw Max Depth Ascent to 30 fsw Dive parameters Gas exchange model Parameters Bubble growth model Parameters What is happening? 1 fsw = m

6 Right heart Left heart Lungs Brain Spinal cord Articulations Other tissues Aorta Venous Bubble Scenario Right heart Left heart Lungs Brain Spinal cord Articulations Other tissues Aorta Arterial Bubble Scenario Neurological symptoms Articular pain Right heart Left heart Lungs Brain Spinal cord Articulations Other tissues Aorta Heart Shunt Neurological symptoms Cerebral Symptoms Right heart Left heart Lungs Brain Spinal cord Articulations Other tissues Aorta Pulmonary Shunts Neurological symptoms Cerebral Symptoms

7 Pulmonary Shunts תסחיפי אויר בכלי דם במוח Venous Blood Alveolar System Non ventilated Non Perfused Ventilated perfused Non Ventilated Perfused Arterial Blood Dissolved vs Free Gas Elimination Free Phase Model 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. Reduced Gradient Bubble Model (RGBM) NAUI Dive Tables Some computers Deep stops Illustration: Eric Maiken

8 Not True! Misconception #2 Deep safety stops (below 20 feet) add, not reduce, nitrogen absorption, and are therefore dangerous. 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." 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. 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. 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 at: Deep Stops: Can Adding Half the Depth of A Safety Stop Build in Another Safety Margin?

9 My computer told me it was okay! Misconception #3 I can t get the bends if I follow my tables or computer. 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. 1 ft = m (continued) I thought I had the flu! 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. 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. 1 ft = m

10 (continued) Take-Home Message 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. 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. Neither is true 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. 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.

11 The Decompression Stress Continuum 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. Is There Anyway to Quantify Decompression Stress? Misconception #6 Gas absorption is based largely on blood flow. A good measure of blood flow is heart rate. The kind of bends that recreational divers get isn t the same or as serious as that of commercial or military divers.

12 % of Injured Divers % of Injured Divers Symptoms of Decompression Illness Maximum Depth in Series by Diagnosis DCS Type 1- (JOINT) Pain only DCS Type 2 - Any neurological symptom anywhere in the body DAN accident data : 25% of DCS is Type I (pain or rash only) and 65% is Type II (neurological) Skin bends DCS I AGE DCS II < > 180 Maximum Depth in Series (fsw) Frequency of Reported Problems Individual Symptoms for Injured Divers Rapid Ascent Exertion Cold Missed Deco N = Environmental factors 2. Medical & health issues 3. Procedural problems Equipment Bouyancy Nausea Out of Air Short of Breath Injury Low on Air Paresthesia Pain Muscular Weakness Fatigue Skin Changes Dizziness Headache CardioPulmonary First Symptom All Symptoms % of Cases

13 Symptom Onset Time by Diagnosis Take-Home Message Missing Before Last Dive During Last Dive < 1 hr 1-2 hrs 3-6 hrs 7-12 hrs hrs DCS I AGE DCS II hrs > 48 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! Not true! Misconception #7 DCI involves a lot more than just bubbles Bends is just a bubble disorder so if you get rid of the bubbles your problems are over.

14 transversal diameter (mm) % of pre dive values General Overview of DCI Physiology DCI A lot more than just bubbles Physiological variations after a dive (n=90) *** pre dive level *** ** * ** * Urine specific gravity Hematocrit ECW ICW FMD Arterial baseline diameter Skin temperature DCI A lot more than just bubbles DCI A lot more than just bubbles Spleen Transversal diameter variation during Dry Voluntary Apnea (After 3weeks Training) (5 maximal apneas every day) ** Bubble grade Total Bubbles grades comparison *** Apnea duration (sec) No Vib Vib Pre Dive Vibration

15 % of control value % of pre dive values DCI A lot more than just bubbles DCI A lot more than just bubbles % Variation on Bubble count 30 min. after diving (34 m depth 20 min.) visually measured on 10 heart beats (echographic images) same divers (bubblers n=7) ns Flow Mediated Dilation 25m 25 min. ns ** * * 100 ** 50 ** 0 Vibration Sauna Chocolate 100% = mean of bubble count during 3 control dives without chocolate with chocolate All Not true! Misconception #8 If I get the bends I should immediately rush off to the nearest recompression chamber. What if the chamber isn t operational? Medical support is as important as recompression perhaps more so. Always contact DAN first.

16 Number of Cases Misconception #9 Diving is more dangerous than ever. Misconception #9 Diving is more dangerous than ever. Not true we think Annual Record of Diver Injuries Annual Record of Divers Fatalities Dan Notified Report Submitted US & Canadian Residents Year

17 Incidence of DCI DAN Europe study on effectiveness of diving fitness examinations Incidence of DCI DAN Europe study on effectiveness of diving fitness examinations Design : retrospective longitudinal study Time period : Study group : Maltese registered divers (n = 6267) Control group : DAN Europe divers (n = 49146) Outcome: number of DCI incidents compared to number of dives in the two groups Study Group : Incidence rate : 1 DCI per 16,420 dives Absolute risk : 0.006% (95% CI 0.004% %) Control Group : Incidence rate : 1 DCI per 6,400 dives Absolute risk : 0.016% (95% CI 0.014% %) The difference between the two rates is statistically significant (p < 0.001) Take-Home Message DAN PDE Extravaganza 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. 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. Fitness to dive assessment is important in preventing diving illness

18 How Can You Reduce Your Risk? Encourage to Pursue Training 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 (10 m/minute). Always do safety stops, and add a deep stop (5 min. at 20 feet or 15 meter and 20 feet or 5 meter) on deeper divers (below 82 feet or 25 meter). 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. 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 1 ft = m Encourage to Pursue Training Encourage to Pursue Training BVOOG SBMHS EUBS ECHM VUB NELOS ULB - ESP BVOOG - SBMHS Belgische Vereniging voor Overdruk en Onderwater Geneeskunde Société Belge de Médecine Hyperbare et Subaquatique

19 Diving Medicine safe down deep