3.  Pressure at sea level is 760mmHg or 1Atm
 For every 10M descent pressure increases
by 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
 Nitrogen narcosis
 High pressure nervous syndrome
 Acute oxygen toxicity
 Air embolism

5.  Inhalation of mixture of 80% Nitrogen and
20% oxygen at high pressure
 Nitrogen narcosis at high pressure
 Euphoria at 100 ft
 Narcosis starts at 120 ft and 250ft (severe)
 Narcosis because of anesthetic effect of
nitrogen
 Narcosis :- stage of unconsciousness and
stupor

6.  Advantages of heliox
narcotic effect of helium is one fifth of
nitrogen
reduces work of breathing due to low
resistance
less soluble

7.  High pressure nervous syndrome due to
helium
 HPNS is due to anesthetic effect of helium in
high pressure
 Lipid soluble
 Direct effect of helium in cns membranes
 Drowsiness , tremors , in coordination
 Eeg changes

8.  Due to inhalation of 100% under high
pressure
 Nausea , dizziness , irritability , disorientation
,disturbed vision , convulsions , pulmonary
damage

9.  Aka 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 , or in unpressurized airplane cabinets

11. 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.

12.  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

13.  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

14.  Can be prevented by slow gradual ascend to
sea level
 The reduction in pressure should not be
more than 50%

15.  Slow decompression
 Decompression chamber
 Hyperbaric oxygen

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

17.  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

18.  Self contained underwater breathing
apparatus
 Tank and valve system used by deep sea
divers