Air Embolism

Excessive intra-lung or intra-pulmonary pressure can be the most serious of all diving accidents. This occurs only when the diver holds his breath when ascending for example when he panics. As explained by Boyle's Law, gases expand within the Lungs as a diver ascends. If a diver at 66 ft. (3 atmospheres absolute) came to the surface holding his breath, his lungs would expand to three times the normal volume. In making an ascent always expel the air from the lungs. If ascending with SCUBA make sure you breath regularly on surfacing. If making a free ascent, blow bubbles so that they are ahead of you as you ascend. This insures that you are not rising to quickly. To be doubly sure that you have reduced the volume you can expel all the air loft as you surface. If the diver does not exhale continuously upon ascending, three things may occur.

• Air may push through the lung tissues and enter the skin about the neck
• Air may push through the lung tissues and into the spaces between the lungs and cause a pneaumothorax.
• Air embolism may also result when air from the lung is forced into the blood vessels.

This air is then carried to the brain and other vital organs. This could cause circulatory blockage and will result in convulsions and unconsciousness. If not treated immediately with re compression, death will result. Should a diver become unconscious his buddy should hit him in the stomach when bringing him to the surface. This will expel the air from his lungs and prevent excessive pressure due to air expansion. Air embolism should be thoroughly understood by all underwater swimmers and with proper training an accident of this type will not occur. Most people will feel the pressure building up in their lungs and will automatically expel some air. However, under panic and ignorance of the dangers, serious injury could result.

Squeeze

One of the most common examples of barotrauma "squeeze" is the inability to equalize ear pressure. Even in very shallow water the diver may feel the "squeeze", which is nothing more than the additional pressure of the water on the air spaces of the body, such as the ear, sinuses, lungs and the face when wearing a mask.
If the diver experiences any pain in the ears he should ascend to a point where he experiences relief. To equalize the pressure he should valsalva i.e. hold the nose with the mouth closed and forcefully exhale. One should never continue a descent when experiencing pain. In doing so several degrees of eardrum damage may result. The final and most damaging consequence is that of perforation. When the eardrum breaks there will be a relief of pain as the pressure is suddenly equalized. Rupture of the membrane is usually followed by bleeding and an infection often occurs within the ear due to contaminants in the water. Cold water will act on the middle ear to produce rather severe dizziness.
The sinuses can also be affected by the "squeeze". A diver who feels pain above and below the eyes and behind the nose should not continue descending. Further pressure on the blocked sinuses can cause damage to the mucus membranes. A lung "squeeze" may occur to a SCUBA diver if their is a failure of the air supply at very great depths.
A skin diver may also experience a lung "squeeze" when diving too deeply. The skin diver has no way to equalize the pressure and therefore the lung space is decreased as the water pressure is increased. Severe lung "squeeze" may rupture the small capillaries and the diver may spit up a small amount of blood when reaching the surface. The depth to which an individual may skin dive is dependent on his total lung capacity and is, therefore, variable.
Ear plugs are never worn when diving. A closed pocket of air is created and with increasing external pressure the ear plug may be pushed into or through the drum, resulting in severe damage. Goggles for the eyes are also not recommended for diving as there is no means of equalizing the pressure within them. With a face mask air from the nose equalizes the pressure and prevents the "squeeze".

Affects of Cold Weather

It has been found that swimmers working in water below 60 degrees Fahrenheit often experience a marked reduction in efficiency due to loss of concentration and fatigue. Wet suits are extremely helpful in retaining body heat, however, after prolonged periods in very cold water the diver will begin to feel the affects of the cold and should remain in the water only as long as he is fairly comfortable.

Carbon Monoxide Poisoning

Carbon Monoxide fumes can be extremely dangerous to the diver. If breathed in a sufficient quantity unconsciousness occurs. For this reason the diver must make sure his compressor supplies clean filtered air when filling air tanks. When using a compressor be sure that the air intake draws suction from a pure atmosphere and is well away from the engine exhaust.

Oxygen Poisoning

In the closed circuit type of SCUBA pure oxygen is the breathing media most often used. Breathing oxygen eliminates the medical problem of decompression sickness and nitrogen narcosis. However the problem of oxygen toxcidity becomes acute. It has been found that breathing pure oxygen under pressure has a toxic effect on the brain. This is subject to individual variations but occurs with great frequency past 60 ft. The symptoms are twitching of the muscles (usually the face), ringing in the ears, visual disturbances or dizziness and the end result is convulsions similar to that of the epileptic type. Oxygen poisoning itself leaves no permanent injury, however, the consequences may. The diver who uses closed circuit type breathing apparatus should ascend immediately if any of the symptoms occur. The reduction of the partial pressure of oxygen is the only remedy. Most recreational divers don't use closed circuit breathing apparatus and therefore the above mentioned problem doesn't pertain to them. However oxygen toxity can occur using open circuit breathing apparatus if the partial pressure of oxygen rises to high. This has occurred in divers at a partial oxygen pressure of 1.2 atmospheres (at a depth of approx. 165 ft.). Most divers regard a a partial oxygen pressure of 1.4 atmospheres (approx. 198 ft.) as a safe upper limit during periods of physical exertion, and 1.6 atmospheres (approx. 232 ft.) during periods of rest.

Anoxia

Anoxia is a lack of oxygen. The underwater swimmer using compressed air is concerned only in that he should know that without enough oxygen a person is overcome with asphyxiation. Anyone who begins to run out of air should ascend immediately. The reserve mechanism ensures that there is enough air left to reach the surface without difficulty. With closed circuit breathing apparatus anoxia is a more serious problem.

This information was obtained from The Dive Locker