Deep Sea

Deep Sea Physiology Introduction

In high altitude, the problem is with low atmospheric (barometric) pressure.

• In deep seas or mines, the problem is with high barometric pressure.
• The increased pressure creates two major problems:
• Compression effect on the body and internal organs
• Decrease in volume of gases.

Read And Learn More: Medical Physiology Notes

Barometric Pressure At Different Depths

• At sea level, the barometric pressure is 760 mm Hg, which is referred to as 1 atmosphere.
• At a depth of every 33 feet (about 10 m), the pressure increases by one atmosphere.
• Thus, at a depth of 33 feet, the pressure is two atmospheres. It is due to the air above the water and the weight of the water itself.
• The pressure at different depths is given in Table.

Effect Of High Barometric Pressure – Nitrogen Narcosis

Narcosis refers to unconsciousness or stupor (lethargy with suppression of sensations and feelings) produced by drugs.

• Nitrogen narcosis means the narcotic effect produced by nitrogen at high pressure.
• Nitrogen narcosis is common in deep-sea divers who breathe compressed air (air under high pressure).
• Breathing compressed air (air under high pressure) is essential for a deep sea diver or an underwater tunnel worker, it is to equalize the high pressure acting on the thoracic wall and abdomen in a deep sea or underwater tunnel.
• Eighty percent of the atmospheric air is nitrogen. Being an inert gas, it does not produce any known effect on the functions of the body at normal atmospheric pressure (sea level).
• When a person breathes pressurized air as in a deep sea, the narcotic effect of nitrogen appears. It produces an altered mental state similar to alcoholic intoxication.

Nitrogen Narcosis Mechanism:

• Nitrogen is soluble in fat. During compression by high barometric pressure in the deep sea, nitrogen escapes from blood vessels and gets dissolved in the fat present in various parts of the body, especially the neuronal membrane.
• The dissolved nitrogen acts like an anesthetic agent suppressing neuronal excitability. Nitrogen remains in dissolved form in the fat till the person remains in the deep sea.

Barometric pressure and the effects at different depth

Nitrogen Narcosis Symptoms:

• The first symptom starts appearing at a depth of 120 feet.
• The person becomes very jovial and careless. He does not understand the seriousness of the conditions
• At a depth of 150-200 feet, the person becomes drowsy
• At 200-250 feet depth, he becomes extremely fatigued and weak. There is a loss of concentration and judgment.
• The ability to perform skilled work or movements is also lost
• Beyond a depth of 250 feet, the person becomes unconscious.

Nitrogen Narcosis Prevention:

Helium may be used as a substitute for nitrogen to dilute oxygen during deep-water diving.

• Helium also produces some effects like nausea and dizziness. However, the adverse effects of helium are less severe than nitrogen narcosis.
• Nitrogen narcosis may be prevented by limiting the depth of dives.
• The effects of nitrogen narcosis may also be minimized by safe diving procedures such as proper maintenance of equipment and less work effort.
• In addition, alcohol consumption should be avoided 24 hours before diving.

Nitrogen Narcosis Treatment:

• The symptoms of nitrogen narcosis completely disappear when the diver returns back to a depth of 60 ft.
• There is no need for any further treatment since nitrogen narcosis does not have any hangover effect.
• However, the physician should be consulted if the diver loses consciousness.

Decompression Sickness

Definition:

Decompression sickness is the disorder that occurs when s person returns rapidly to normal surroundings (atmospheric pressure) from an area of high atmospheric pressure like the deep sea.

It is also known as dysbarism, compressed air sickness, caisson sickness, bends, or diver’s palsy.

Decompression Sickness Cause:

• The high barometric pressure at deep sea leads to the compression of gases in the body. Compression reduces the volume of gases.
• Among the respiratory gases, oxygen is utilized by tissues. Carbon dioxide can be expired.
• But, nitrogen, which is present in high concentration, i.e. 80% is an inert gas. So, it is neither utilized nor expired.
• When nitrogen is compressed by high atmospheric pressure in the deep sea, it escapes from blood vessels and enters the organs.
• As it is fat soluble, it gets dissolved in the fat of the tissues and tissue fluids. It is very common in the brain tissues.
• As long as the person remains in the deep sea, nitrogen remains in the solution and does not cause any problems.
• But, if the person ascends rapidly and returns to atmospheric pressure, decompression sickness occurs.
• Due to the sudden return to atmospheric pressure, the nitrogen is decompressed and escapes from the tissues at a faster rate.
• Being a gas, it forms bubbles while escaping rapidly. The bubbles travel through the blood vessels and ducts.
• In many places, the bubbles obstruct the blood flow and produce air embolism leading to decompression sickness.
• The underground tunnel workers who use the caissons (pressurized chambers) also develop decompression (caisson disease) sickness.
• The pressure in the chamber is increased to prevent the entry of water inside.
• Decompression sickness also occurs in a person who ascends rapidly from sea level in an airplane without any precaution.

Decompression Sickness Symptoms:

The symptoms of decompression sickness are mainly due to the escape of nitrogen from the tissues in the form of bubbles.

The symptoms of decompression sickness are:

• The presence of bubbles in the myelin sheath of sensory nerve fibers produces severe pain in the tissues, particularly in the joints.
• It also produces sensation of numbness, tingling or pricking (paresthesia), and itching
• The bubbles in the myelin sheath of motor nerve fibers produce temporary paralysis
• Muscles develop cramps associated with severe pain
• The bubbles in the blood occlude the coronary arteries and cause coronary ischemia
• Blood vessels in the brain or spinal cord are also occluded by the bubbles
• The tissues of the brain or spinal cord are damaged because of obstruction of blood vessels by the bubbles
• The condition leads to dizziness, paralysis of muscles, shortness of breath, and choking
• Finally, fatigue and severe pain develop leading to unconsciousness and death.

Decompression Sickness Prevention:

• Decompression sickness is prevented by taking proper precautionary measures.
• While returning to mean sea level, the ascent should be very slow with a short stay at regular intervals.

The stepwise ascent allows nitrogen to come back to the blood without forming bubbles. It prevents decompression sickness.

Decompression Sickness Treatment:

• If a person is affected by decompression sickness, the first recompression should be done. It is done by keeping the person in a recompression chamber.
• Then, he is brought back to atmospheric pressure by reducing the pressure slowly. Hyperbaric oxygen therapy may be useful.

 Scuba

• SCUBA (self-contained underwater breathing apparatus) is used by deep sea divers and underwater tunnel workers to prevent the ill effects of increased barometric pressure in deep sea or tunnels.
• This instrument can be easily carried and it contains cylinders, a valve system, and a mask.
• By using this it is possible to breathe air or gas mixture without high pressure.
• Also, because of the valve system only the amount of air necessary during inspiration enters the mask, and the expired air is expelled out of the mask.
• The disadvantage of this instrument is that the person using this can remain in the sea or tunnel only for a short period.
• Especially, beyond the depth of 150 feet, the person can stay only for a few minutes.