Sea water is approximately 800 times more dense than air. Therefore, it exerts much greater pressure on the body of a diver. The weight exerted by the atmosphere on an area of 1m2, is approximately 10,000kg at sea level. This value of pressure (10,000 kg m-2) is thus referred to as 1 atmospheric absolute (1 ATA), or 1 atmospheric pressure. For every 10m(~32feet) below the surface a person dives, he is subjected to an additional pressure of 1ATA. Therefore, at 30m, a diver will experience a pressure of 4 ATA (1 ATA exerted by the atmosphere, & 3 ATA exerted by the 30m of water above him).

2.  Sea water is approximately 800 times more dense than air. Therefore, it
exerts much greater pressure on the body of a diver.
 The weight exerted by the atmosphere on an area of 1m2, is
approximately 10,000kg at sea level. This value of pressure (10,000 kg m-2)
is thus referred to as 1 atmospheric absolute (1 ATA), or 1 atmospheric
pressure.
 For every 10m(~32feet) below the surface a person dives, he is subjected
to an additional pressure of 1ATA. Therefore, at 30m, a diver will
experience a pressure of 4 ATA (1 ATA exerted by the atmosphere, & 3 ATA
exerted by the 30m of water above him).

3.  Pressure at sea level is 760mmHg or 1Atm
 Gases inhaled at high pressure to equalize the
external pressure on thorax, so that adequate
expansion occurs
 These inhaled gases at high pressure dissolves in
body fluids at high quantity

4.  Dysbarism / Caisson’s disease
 Nitrogen narcosis
 Acute oxygen toxicity
 Air embolism

5.  Also known as dysbarism ,the bends , diver’s
palsy , decompression sickness
 Due to rapid shift of a person from a high
atmospheric pressure area to low pressure area
 Eg :- person working in caisson , deep sea divers

7. Defination
Decompression sickness (DCS) is a condition that
occurs when divers come back to the surface too
quickly after being deep under water. It is caused by
the formation of nitrogen bubbles in the blood
stream and, in the worst cases, can cause death.

8.  Divers breath 80% nitrogen under water
 Nitrogen under such high pressure gets dissolved
in blood
 Gets accumulated in tissues and fats
 During slow ascends these dissolved gas gets
eliminated by lungs slowly
 But rapid ascend causes formation of nitrogen
bubbles
 Which produces symptoms

9. Inflammation
 The gas: tissue interface can activate
complement, other inflammatory pathways &
inflammatory cells, leading to an acute
inflammatory response
Ischaemia
 Blood flow obstruction can lead to ischaemia &
infarction of tissue/organs
Coagulation
 The gas:blood interface can activate clotting
factors, leading to intravascular coagulation

10. Emboli
 Bubbles forming in the blood can disrupt blood
flow
Cell Disruption
 Bubbles forming within cells can damage their
internal structure & lead to loss of function
Tissue Rupture
 Large bubbles forming in the vasculature may
cause vessels to rupture. Similarly, bubbles
forming in other spaces (e.g. The lungs) may
cause them to rupture

11. Mechanical Compression
 Large bubbles may compress surrounding
structures, causing damage & leading to loss
of function

12.  Usually appear after half hour after reaching sea
level
 Due to bubbles in musculoskeletal system
 Bubbles in circulation to brain , spinal cord , heart
 Bubbles in pulmonary circulation
 Fat people more prone to dysbarism
 Pain in joint and muscles (called Bend)
 Numbness
 Coronary Ischemia- Myocardial infarction (blockage
of coronary arteries)
 Neurological symptoms- dizziness, unconsciousness,
paralysis

13. Musculoskeletal Pain
 The most common symptom, occurring in up to 80%
of patients. May range from ‘niggling aches’ to
severe joint pain & muscle cramp. Most commonly
affects the upper limbs.
Neurological Symptoms
 Symptoms are varied, and may be dynamic. Spinal
symptoms are most common, including lower back
pain & lower body paraesthesia /paralysis. Other
symptoms include psychological changes,
intellectual/visual impairment and ataxia.

14. Aural Symptoms
 Labyrinthine symptoms, including nausea, vertigo &
nystagmus, may be combined with hearing
symptoms, including hearing loss & tinnitus
Skin Rashes
 Mottling & marbling of the skin may occur,
occasionally progressing to an ‘orange peel’-like
discolouration. May be associated with itching or
burning sensations.

15. Respiratory Symptoms
 Chest pain & non-productive coughing are the
most common respiratory symptoms, and may
progress to severe dyspnoea & respiratory
distress. Haemoptysis may also occur.

16.  Slow decompression
 Decompression chamber
 Hyperbaric oxygen
 Recompression followed by slow decompression in
Compression chamber--
 10 minutes at 50 feet depth
 17 minutes at 40 feet depth
 19 minutes at 30 feet depth
 50 minutes at 20 feet depth
 84 minutes at 10 feet depth
 Total 3 hours

17. Hyperbaric chamber:
A sealed compartment used to treat Air Embolism
and decompression sickness, in which pressure is
first increased and then gradually decreased.

18. Severe decompression sickness can be a medical
emergency. Prompt resuscitation measures can
therefore save lives.
Administration Of O2
 100% oxygen should be administered via a
mask. This will improve O2 saturations and
thus supply to any ischaemic tissues.

19. Warming
 Wetsuits should be removed & passive re-
warming of patients should be commenced to
prevent hypothermia.
Lie Patient Horizontally
 Lying patient horizontally limits air emboli
rising, and therefore may reduce the chances of
emboli reaching the brain. The recovery position
should be utilised in the event of vomiting.

20. Fluid Resuscitation
 Hypovolaemia often occurs in divers suffering
decompression sickness due to dehydration,
increased capillary permeability caused by
inflammation & increased diuresis due to
cold. IV crystalloids should therefore be given
.

21.  Inhalation of mixture of 80% Nitrogen and 20% oxygen at
high pressure
 At 120 feet feels joviality & careless (rapture of the deep)
 At 150 to 200 feet, the diver becomes drowsy.
 At 200 to 250 feet, loss of strength.
 Beyond 250 feet, becomes unconsciousness
Nitrogen narcosis similar like alcohol intoxication
Nitrogen reacts with fatty acids in cell membrane of neurons and
impairs the conduction like gas anesthetics

22.  Due to inhalation of 100% under high pressure
 Breathing high partial pressures of O2 for prolonged time
periods can produce acute CNS toxicity.
 Symptoms include behaviour disturbance, hallucinations,
syncope & convulsions.
 Oxygen toxicity may be fatal when underwater, and so care
must be made to reduce O2 content of gas mixtures for deep
dives.
 In recompression chambers, O2 toxicity can be treated by
withdrawing O2 & administering benzodiazepines to prevent
convulsions.

23.  When diver suddenly returns to surface holding
breath
 Air in the lungs increases causing expansion and
rupture of pulmonary veins
 This occurs due to rapid loss of external pressure
on chest which leads to expansion of gas inside
lungs

24.  Self contained
underwater breathing
apparatus
 Tank and valve system
used by deep sea divers
 Contains oxygen &
helium (Heliox)

25.  Has only about one fifth the narcotic effect of
nitrogen
 Only about one half volume of helium dissolves in
the body tissues as nitrogen
 Low density of helium (one seventh the density of
nitrogen) keeps the airway resistance for breathing at
a minimum work of breathing

26.  High pressure nervous syndrome due to helium
 HPNS is due to anesthetic effect of helium in
high pressure
 Lipid soluble
Symptoms-
 Drowsiness , tremors , in coordination
 EEG changes

27.  The deepest SCUBA dive record-Ahmed
Garb, 1090 ft in Red sea