2. Diving Safty and Decompression Meter
(Dive Computer, Decompression Computer (
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Dr.A.EBADI.AEROSPACE & DIVING MEDICINE,ARMY UNIVERSITY OF MEDICAL SCIENCE.
4. CERTIFICATES
-Professional Association of Diving Instructors
(PADI)
-National Association of Underwater
Instructors (NAUI)
-British Sub-Aqua Club (BSAC)
-Confederation Mondiale des Activites
Subaquatiques (CMAS)
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11. A:Decompression Sickness (DCS)
History:
-DCS recognized in divers and compressed air workers
since late 1800s
-Prevailing guideline was to ascend slowly
Standards ranged from 1.5 ft/min to 5 ft/min
-DCS still occurred but less frequently
-DCS associated with nitrogen bubbles
-Haldane: Shorter/shallower dives associated with less
frequent/less severe DCS
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12. Decompression Theory
-Body tissues absorbs nitrogen at depth
-Each tissue type absorbs nitrogen at different rate
-Slow, staged ascent (“decompression”) releases nitrogen
harmlessly and is exhaled Stages determined by time/depth of
each dive
-Ascent without adequate decompression causes nitrogen bubble
formation
Clinical manifestations = “Decompression Sickness”
(Destructive,compressive,obstructive)
-Typically presents minutes to hours after dive-95% within 6
hours
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13. Type I DCS
-Musculoskeletal pain (Limb bends)
Most common manifestation of DCS
Dull pain, not well localized; no change with
movement
Knees, elbows, or shoulders most commonly
involved
-Cutaneous DCS (Skin bends)
Pruritis and erythema of trunk
-Treatment: Recompression
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14. Type II DCS
-Risk of permanent disability or death
-Pulmonary DCS (“Chokes”)
-Venous gas emboli clog pulmonary arterial
circulation
-Rare; occurs with rapid ascent from deep dive
-Substernal discomfort, cough; worse with deep
inspiration
-May lead to right-sided heart failure and
cardiovascular collapse
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15. Type II DCS (con’t)
Neurologic DCS
-Predilection for spinal cord
-Recreational divers doing short, deep dives
-Syndrome – over minutes to hours after ascent
-Tingling in trunk
-Progressive numbness and paresthesias
-Ascending motor weakness
-Bowel/bladder incontinence
-Severe cases may present with LOC/paraplegia
-Cerebral manifestations: memory impairment, aphasias,
visual disturbances, personality changes
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16. Type II DCS (con’t)
Vestibular DCS (“Staggers”)
-Sudden onset of dizziness, nausea, vomiting,
nystagmus, +/- hearing loss and tinnitus
-Not common in recreational divers
-Confused with middle ear barotrauma
Treatment of Type II DCS:
-Rapid recompression with hyperbaric oxygen
Supportive care: Fluids
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19. Dive Tables
-Traditionally dive tables are used for planning dives to
avoid risk of DCI
-Dive tables contain safety limits of depth and time
-There are many standard dive tables,
Original UK, US Navy etc.
-Dive tables can be generated by an algorithm (many
variations possible)
-Dive computers run these algorithms(Different
Algorithm*)
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23. Decompression Meter
(Dive Computer)
• Sensors send data to the
•
•
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Analog to Digital (A/D)
Converter.
A/D Converter changes
analog data to digital
signals.
The Micro Processor
calculates the data and
presents it to the diver via
the LCD Display.
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24. Depth-Time Profile
Surface
00
'2
0
01 "
'4
0
03 "
'0
0
04 "
'2
0
05 "
'4
0
07 "
'0
0
08 "
'2
0
09 "
'4
0
11 "
'0
0
12 "
'2
0
13 "
'4
0
15 "
'0
0
16 "
'2
0
17 "
'4
0
19 "
'0
0
20 "
'2
0
21 "
'4
0
23 "
'0
0
24 "
'2
0
25 "
'4
0
27 "
'0
0
28 "
'2
0
29 "
'4
0
31 "
'0
0
32 "
'2
0
33 "
'4
0
35 "
'0
0
36 "
'2
0
37 "
'4
0
39 "
'0
0
40 "
'2
0
41 "
'4
0
43 "
'0
0
44 "
'2
0
45 "
'4
0
47 "
'0
0"
0
-5
-10
-15
0.85% MaximumDepth
MaximumDepth
Depth
-20
-25
-30
-35
Bottom Zone
-40
A
-45
A
Bottom Time
-50
Time
Risky dive with some minor problems. Because your bottom time of 12.0min
exceeds no-stop limit by 4.0min this dive is risky. But you performed the ascent
well. Your buoyancy control in the bottom zone was poor as indicated by ‘saw
tooth’ patterns marked ‘A’ on the depth-time profile.
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25. Decompression Meter
(Dive Computer)
1- Mechanical models of gas uptake and release, such as the
movement of gas through restricted orifices.(SOS -1960s)
2-Electronic models of the established decompression tables( Suunto
USN meter.)-unilevel diving
3-Electronic models using the decompression theories on which
different tables.(VEO 100 Nx)-multi-level diving
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28. Unsafe dives*
The following patterns in dive profiles are known
to cause DCI
-Rapid ascent(Detect)
-Sawtooth
-Reverse dive profile etc.
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29. Rapid Ascent
-A pattern in the dive profile caused by the diver
rising rapidly to the surface
-Rapid ascent is the most critical factor causing
bubbles in body tissues
-Therefore has higher chance of causing DCI
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-Most dive computer software detect rapid
ascents and sound alarms
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30. Sawtooth
-A pattern in the dive profile caused by the diver
going down and up in quick succession
-This may not happen very frequently, but when
it happens it may cause the tissues to absorb
excess gas bubbles
-Therefore may cause DCI
-Dive computer software does not detect them
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31. Reverse Profile
-This is a pattern observed at the level of a
whole dive profile.
-Ideally a diver is required to initially reach the
planned maximum depth and then all the
subsequent dive should be performed at a
depth shallower than the maximum
-A reverse profile is a dive profile where the
diver performs the reverse of the ideal
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32. Personal Charactristics*
1- Age
2- Sex
3-BMI-(Fatty Tissue Percent)
4-Health State (DM-HLP-Nutrition-Metabolism)
5-Body Position & Activity
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34. با توجه به کاهش زمان صعود غواصان استفاده کننده از
DECOMPRESSION COMPUTERSوبنابراین افزایش احتمال
بروز عالیم بالینی DCSونیاز به Hyperbaric Chamber
توصیه می شود :
1- غواصان به صورت کمکی وبه همراه جداول برداشت فشار
استاندارد از این دستگاه ها استفاده نمایندو این موضوع را
بخصوص در غوص های بیش از 03 متر مد نظر قرار دهند.
2- درصورت استفاده ازاین دستگاه ها می بایست به منظورکنترل
وبهبود عالیم بیماری برداشت فشاراحتمالی Hyperbaric
Chamberدرمحل غوص حاضرباشد.
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35. 4- همانند استاندارد کردن زمان براساس ساعت گرینویچ
،غوص استاندارد بر اساس یک مبدا قابل قبول بین المللی وبا
حداقل ریسک بیماری برداشت فشاربرای غواصان مطرح،
وازسوی سازمان های مرتبط مورد تایید جهانی قرارگرفته
وانواع مختلف DECOMPRESSION COMPUTERSبراساس
آن تنظیم گردد.
5- لزوم انجام تحقیقات بیشتر دراین زمینه درجهت ارتقائ ایمنی
غواصی با DECOMPRESSION COMPUTERS
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36. SAFETY GUIDELINES
1-Fully understand how to use the Dive Computer(instruction/ Authorized
Oceanic Dealer )
2- Any display or function varies from the information presented in the Operating
Manual
(Authorized Oceanic Dealer )
3- Low battery condition (do not dive until the battery is replaced)
4- Each Nitrox dive(Dive Computer must be verified, or set)
5- The bar graphs (if available) in normal zones throughout your dives.
6- Always make your deepest dive first
7- Always limit your dive to the level of your training and experience
8- Allow an adequate surfacegasabeh.com between each dive
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37. SAFETY GUIDELINES
9-Decompression diving, or diving deeper than 130 FT (39 M)(greatly
increase your risk of decompression sickness
10-Decompression diving is inherently hazardous and greatly increases
your risk of decompression sickness, even when performed according
to the Dive Computer’s calculations.
11- Using a Dive Computer, just as dive tables, is no guarantee of
avoiding decompression sickness
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38. Refrences
1- Petar J. Denoble, MD., D.Sc Alessandro Marroni, MD. D.S Richard
D. Vann, Ph.D.Common Factors in Diving Fatalities Fatality Workshop,
Durham April 8-10, 2010
2-www. DivingCaribbeanNicheMarkets.
3-www. Wikipedia, the free encyclopedia- Dive computer
4- Carl Edmonds M.B., B.S. (Sydney), Christopher Lowry M.B., B.S.,
John Pennefather B.SC. Robyn Walker M.B., B.S., Dip. D.H.M. Diving
and Subaquatic Medicine 4th Edition 2002
5-Wilmshurst peter.Technological advances in scuba diving do not
always increase safety.Bjsm.bmj.com.2011
.
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