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Diving disorders

Divers face specific physical and health risks when they go underwater or use high pressure breathing gases.

Injuries and disorders

Relying on underwater breathing equipment

Being unable to breath fresh air naturally whilst submerged and relying on limited breathing gas supplies and fallible breathing equipment can result in:

• Drowning : being unable to inhale anything but water
• Secondary drowning : can occur hours after a near drowning
• Hypoxia : inhaling a breathing gas that contains insufficient oxygen to support normal activities or consciousness
• Anoxia : inhaling a breathing gas that contains no oxygen or being unable to inhale and breathing gas
• Salt water aspiration syndrome : the diver inhales a mist of sea water from a fault demand valve causing a reaction in the lungs

Barotrauma or pressure damage on descent

Air spaces within the body provide no support against greater outside pressure:

• Tympanum damage (damage to the eardrum caused by failing to equalize pressure in the inner ear).
• Damage to the body's other air spaces, such as the paranasal sinuses
• Squeeze damage to tissues adjacent to equipment air spaces, such as the eyes inside the air space of the mask

Barotrauma on ascent

Air spaces within the body expand when the outside pressure decreases:

• Pulmonary barotrauma - commonly known as "burst lung" by divers:
  • Pneumothorax - collapsed lung
  • Interstitial emphysema - gas trapped in the chest after lung barotrauma
  • Gas embolism - air or other gas bubbles in the blood stream
• Decompression sickness ("the bends") is caused by ascending too quickly to be able to eliminate excess nitrogen that had been adsorbed at depth
• Nitrogen narcosis is caused by using breathing gases that contain nitrogen at depth
• Oxygen toxicity is caused by using breathing gases that contain oxygen at depth
• HPNS, High Pressure Nervous Syndrome or Helium Tremors caused by using breathing gases that contain helium at depth

Decompression sickness, arterial gas embolism, and barotrauma are all dysbarism.

Impurities and poisons that may be present in breathing gas

• Carbon monoxide poisoning is due to compressor maintenance errors or input of impure air to the compressor
• Carbon dioxide poisoning is due to incomplete elimination of carbon dioxide produced by the diver's own metabolism. This gas is normally safely exhaled to the environment and not re-inhaled in significant volumes.

Causes of injuries and diseases

Major causes of diving and underwater injuries include:

• Running out of breathing gas underwater, for reasons such as poor dive discipline, equipment failure or secondary factors such as getting trapped by nets, rocks or inside caves or inside wrecks
• Losing control of buoyancy results is excessive vertical speed during descent and ascent causing barotrauma to air spaces within the body
• Breath holding on ascent can cause barotrauma to the diver's lungs
• Missing decompression stops or ascending faster than inert gases can be eliminated from the tissues can cause decompression sickness
• Breathing poisonous gases or contaminants present in a diving cylinder
• Long exposure to cold water may cause hypothermia
• Bites and strings from marine animals such as coral, electric eels, jellyfish, orca, lionfish, blue ringed octopus, sharks, sting rays and stonefish
• Exposure to disease carried by organisms, for example Weil's disease and Bilharzia