diving+medicine

clinical > environmental medicine toc =Diving medicine = This page provides a brief introduction to medicine relating to //recreational// diving for clinicians who have no personal knowledge or experience of diving.

Clinicians seeking medical advice should seek this from experts. In an emergency clinicians in the UK should contact the Royal Navy Duty Diving Medical Officer (NB this provides medical advice - **if rescue is needed contact the emergency services**: coastguard offshore, police inland).

Recreational divers use a supply of compressed air which is supplied through a mouthpiece, which is likely to fall out if the diver is unconscious.

Decompression illness
Decompression illness (DCI) includes decompression sickness (DCS) and arterial gas emobilsm (AGE)

Boyle's law
At a constant temperature the product of a gas's pressure and volume remains constant: P x V = k When a diver rises to the surface the pressure drops; the volume of gases in their body will increase.

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Decompression sickness ("the bends")
In DCS nitrogen bubbles form on moving to the surface. As the depth increases nitrogen, which is breathed in, is dissolved - especially in fatty tissues. As the diver begins to surface pressure decreases and, as per Boyle's law, gas volume will increase, and form bubbles. DCS can occur up to 36 hours after surfacing.

The clinical features will depend on the site of the nitrogen bubbles: - pain in large joints (joints) - chest pain, dyspnoea, SOB, haemoptysis (venous blood, going to lungs) - neurological deficit (spinal cord or brain)

<span style="font-family: Verdana,Geneva,sans-serif;">Arterial gas embolism
<span style="font-family: Georgia,serif;">As predicted by Boyle's law, as a diver ascends the air they breathe will expand (since pressure is decreasing and P x V is constant). If the diver holds their breath air expands in the alveoli for which it can enter the venous circulation in the lungs. From their the gas can pass to the left side of the heart and then to systemic circulation.

<span style="font-family: Georgia,serif;">The clinical features are determined by the site of the gas embolism but while the diver is vertical the brain is most at risk - a typical presentation is diver surfacing without problem and then becoming unconscious within a few minutes.

<span style="font-family: Verdana,Geneva,sans-serif;">Barotrauma
<span style="font-family: Georgia,serif;">The air in air-containing parts of the body (e.g. lungs, middle ear, sinuses) will reduce in volume when descending (Boyle's law) and expand when ascending. Injuries (such as ruptured tympanic membrane) due to this mechanism are classed as barotrauma.

<span style="font-family: Verdana,Geneva,sans-serif;">Nitrogen Narcosis
<span style="font-family: Georgia,serif;">At increasing depth, the amount of nitrogen dissolved in the blood starts to act as an anaesthetic. Compressed air should not be used for dives deeper than 50m (this is into the realm of professional divers).

<span style="font-family: Verdana,Geneva,sans-serif;">links
<span style="font-family: Georgia,serif;">[|Dive Medicine] <span style="font-family: Georgia,serif;">[|4 Rs of managing decompression illness] <span style="font-family: Georgia,serif;">[|US Navy Diving Manual] <span style="font-family: Georgia,serif;">[|Undersea Medicine] <span style="font-family: Georgia,serif;">[|Diving medicine for SCUBA divers]