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

Dysbarism

Nitrogen narcosis

High pressure nervous syndrome

Acute oxygen toxicity

Air embolism

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

Advantages of heliox

narcotic effect of helium is one fifth of

nitrogen

reduces work of breathing due to low

resistance

less soluble

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

Due to inhalation of 100% under high

pressure

Nausea , dizziness , irritability , disorientation

,disturbed vision , convulsions , pulmonary

damage

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

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.

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

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

Can be prevented by slow gradual ascend to

sea level

The reduction in pressure should not be

more than 50%

Slow decompression

Decompression chamber

Hyperbaric oxygen

Hyperbaric chamber:

A sealed compartment used to treat

Air Embolism and decompression

sickness, in which pressure is first

increased and then gradually

decreased.

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

Self contained underwater breathing

apparatus

Tank and valve system used by deep sea

divers