Problems On Ascent

As the diver begins to ascend. . . many changes begin to take place, as might be expected from what we've already discussed. It is these changes that we as divers are concerned with.

Henry's Law

To review for a moment, Henry's Law states that the solubility of a gas in a fluid is directly proportional to pressure. We have said previously that this will cause the blood stream of a diver to absorb larger amounts of nitrogen as he descends, thus causing a condition known as Nitrogen Narcosis. However, even if the diver does not go deep enough to incur Narcosis, it is obvious that his body contains much larger quantities of nitrogen than it did at surface.

Bends

As the diver ascends, the pressure decreases, and so, in accordance with Henry's Law, there is an over-abundance of nitrogen in the blood stream, for with a lessening of pressure the blood can keep in solution much less of this gas. Therefore, under normal conditions of depth and time, the excess nitrogen is carried to the lungs in solution, where it is passed into the alveoli as a gas and eliminated. Under conditions of either extreme depth, or extended time at depth, the body becomes so saturated with nitrogen, that normal ascent does not give the system time to eliminate the nitrogen in the blood stream in the normal way, but instead the nitrogen comes out of solution in the blood stream in the form of bubbles, due to the lessening pressure. When this happens, a very serious condition exists, known as the Bends, Compressed Air sickness, or Caisson Disease. The bubbles become lodged in the joints or muscle of the body, where they create great pain and deformation of tissue. Symptons will always appear within 24 hours after exposure to pressure, and the victim is in severe pain. The result of the bends is usually crippling depending upon where the bubbles lodge.

The method of preventing the bends is eminently simple, when you consider the cause, which is of course, lessening the pressure too rapidly, or in other words, decompressing too rapidly. The prevention is merely a matter of decompressing at a slow enough rate to allow this excess nitrogen to leave the body via the normal routes, the lungs. To do this, it is necessary to consult a series of tables called "decompression tables", which specify the rate of ascent for a diver who has been to a given depth for a given amount of time.

The treatment for the bends is a very difficult affair, for it requires a recompression chamber, which, as the name implies, recompresses the diver to a point where these bubbles go back into solution in the blood, thus relieving the bends. The diver is then brought "up" in the chamber at prescribed rates according to the treatment.

The reason we say that treatment is difficult for a sport diver, is that in many areas of the country a recompression chamber is not available, or if it is, it is so distant that by the time the victim is able to reach it the damage caused by the bends is permanent.

Repetitive Dives

One of the big dangers for sport divers is the fact that nitrogen accumulation is accumulative, in any one 24 hour period. What this means is that a sport diver making several brief, but deep dives, in any one 24 hour period may also incur the bends, for the nitrogen he has absorbed in his system becomes more and more saturate. A special set of decompression tables for successive dives exists, and a diver would do well to consult this table whenever a number of dives are contemplated in any one day.

Boyles Law

When we were discussing the problems on descent, we talked about Boyles Law, which essentially states that the volume of a gas is inversely proportional to pressure. During the descent we were primarily concerned with squeeze; brought about by the effects of this law. However, let us now consider the effects of this law upon ascent. Remember that the basic premise of scuba is that the diver is at all times breathing air at ambient, or surrounding pressure.

Air Embolism

Now, bearing this in mind, let us visualize the effects of a diver ascending from depth holding his breath. As we have said, pressure and volume of a gas are inversely proportional, which means that as you decrease the pressure exerted on a gas, its volume increases, which is precisely the situation when the diver ascends from depth holding his breath. What occurs physiologically is this: the air, trapped in the lungs, expands until finally the air sacs, or alveoli rupture. When the alveoli rupture they also rupture the blood vessels covering their walls, thus permitting air bubbles to enter the blood stream. These air bubbles follow the normal circulatory system through the heart, and usually up through the main aorta to the smaller blood vessels until they reach, at last, the capillaries there, because of their size they are unable to penetrate further and so lodge, creating a blockage or air embolism. The effect of this blockage, or embolism is that the tissue that is normally supplied with oxygen by these blocked vessels, now starves for lack of oxygen, and in a very few minutes dies from lack of it. If the embolism occurs in the cerebrum of the brain, death may be instantaneous. In any event, an air embolism is usually fatal, and is the most dreaded of divers ailments, with just cause.

The treatment for an air embolism is to immediately elevate the feet of the victim in order to try to get the air bubbles to flow away from the brain, treat him as though in shock, and call a doctor, who will, if possible, put his victim in a recompression chamber to recom-press these bubbles until they go into solution in the blood or are reduced in size enough to allow them passage through the blood vessels. The only treatment then consists of surgery. Due to the very short time required for permanent brain damage to be incurred, most air embolisms are fatal.

Pneumothorax

Another separate ailment caused by ascending while holding the breath is Pneumothorax, where the lung wall actually ruptures, filling the pleural cavity with air, and sometimes collapsing the lung. The treatment for this is the insertion by a doctor of a syringe to remove the air from the pleural cavity and reinflate the lung.

The third ailment incurred by ascent from depth while holding the breath is Mediastinal Emphysema. In this situation again the alveoli rupture allowing air to flow into the mediastinal area. If the air rises up the neck and lodges under the skin it results in a condition called subcutaneous (sub—meaning under; cutaneous meaning skin) emphysema.

All of these ailments are caused by either a voluntary or involuntary blockage of the airway upon ascent. The lung tissue is capable of withstanding about 2 pounds of pressure differential, so it can readily be seen that a diver ascending from barely over four feet of water holding his breath can very well incur an air embolism, a pneumothorax, or an emphysema. The prevention is obvious, of course. ALWAYS EXHALE UPON ASCENT. Tilt the head back, exhale, and ascend, taking care to rise slower than your smallest bubbles. If you are ascending from a depth and exhaust all of your air before reaching the surface, or if you feel the need for another breath before reaching the surface, inhale and then proceed to exhale immediately.

As long as there is no blockage of the airway, either voluntary or involuntary, there is no danger of embolism, pneumothorax, or emphysema in diving. One of the primary rules of scuba is "Never, under any circumstances, hold your breath. Always breathe normally, or exhale continuously upon ascent."

Remember, so critical is this matter of pressure and volume that an embolism can be incurred in as little as four feet of water.

Some hazards of diving are somewhat separate from those considered heretofore, and so are treated in a separate manner. These include! such things as Carbon Monoxide poisoning, lipoid pneumonia, carbon dioxide poisoning, anoxia, vertigo, and panic. We shall deal with them in turn.

Carbon Monoxide Poisoning

Carbon Monoxide poisoning is a problem incurred by scuba diver, not skin divers, and is caused by breathing impure air. Sometimes an air station operator will have his exhaust from his gas engine located in such a manner that it will be taken into the intake of his compressor, and so compressed along with the air. Carbon Monoxide is a gas that cannot be tolerated by the human body, and so the diver is afflicted with carbon monoxide poisoning. The primary symptoms of carbon monoxide poisoning are nausea, distortion of vision, and eventual unconsciousness. Treatment is to bring the diver to the surface immediately upon appearance of the first symptoms, keep him at rest, if available let him breathe oxygen, if not, air. A doctor should be summoned. One of the telltale symptoms of carbon monoxide poisoning is the red coloration of the victim's skin.

Another ailment due to breathing impure air is lipoid or lipid pneumonia. This is caused by breathing air with a high concentration of oil, usually due either to poor filtering of the air, or due to the dieselizing of an oil lubricated compressor. The symptoms of lipoid pneumonia are identical to those of so called "Walking Pneumonia", and are not generally severe enough to warrant hospitalization. The diver usually detects the presence of oil in his air by its very distinctive and unpleasant taste. It tastes like hot or burnt oil fumes, which, of course, it is. The prevention for this is to get your air only from reliable and reputable air stations.

Carbon Dioxide Poisoning

This is an ailment primarily encountered in the use of closed circuit scuba, where the carbon dioxide absorbent is saturated and so allows a build up of excessive carbon dioxide in the breathing gas. However, it is also encountered sometimes in the use of a full face mask by a user of an open circuit scuba. Due td lack of ventilation of the full face mask, carbon dioxide is able to accumulate and so cause the diver to be breathing a too high percentage of carbon dioxide. The symptoms of carbon dioxide poisoning are; impairment of vision, nausea, and finally loss of consciousness. The distinctive symptom is the blue coloration of the victims skin.

The treatment is the same as that for carbon monoxide poisoning, surfacing and the administration of oxygen or fresh air.

Anoxia

Anoxia is a lack of oxygen in the system. It is primarily encountered by the diver in skin diving. For instance, when a person holds his breath, his body tissues continue to use up the oxygen supply contained in the air supply in the lungs. However, as this oxygen is used the tissues are giving off as a waste gas carbon dioxide. When the level of carbon dioxide reaches a given point in the blood stream it stimulates the diaphram and causes it to spasm, thus initiating the respiratory cycle. However, a person who has practiced breath holding can ignore this "kick" of the diaphram and continue holding his breath. Unfortunately, this is the last warning the diver gets and his next reaction is unconsciousness. Once unconscious his involuntary system takes over and he begins breathing. This is fine, at the surface on dry land, but under water it is fatal, and causes the victim to drown. One place where anoxia can be encountered in the use of scuba is in the practice of "skip breathing". This is a practice of some divers attempting to get more underwater time from their tanks, and is simply the device of skipping one or more breaths regularly. It is easy to see that this could develop into an oxygen deficiency in the diver and finally lapse into anoxia. Again we run into the rule of breathing normally.

Vertigo

Vertigo is a phenomena of balance and confusion of the mind in relation to a reference point. It occurs when the mind is confused as to the direction of the body. Literally, the diver suffering from vertigo doesn't know up from down. In some instances this occurs when the diver loses his point of reference, that is, he is unable to see anything that tells him "which way is up". This is often encountered when a diver is out of sight of both the surface and the bottom and in many instances he sees his bubbles and is confused to see them going sideways rather than upward. Once the diver is able to convince himself that the bubbles are indeed going up, and orients his body, then this bewildering sensation of vertigo vanishes and all is once again well. This sensation of vertigo has a tremendously upsetting effect upon the mind, and, is often accompanied by nausea.

Panic

One of the greatest factors in diving, both skin and scuba, is panic. Panic has been defined as "... .being overcome by an unreasoning fear, robbing the individual of the processes of logical thought and reducing him to act instinctively. " As you have learned in the foregoing, instinctive actions are not always the safest in the use of scuba. It is more or less instinctive, for instance, for a person whose air supply is suddenly cut off to attempt to race to the surface holding his breath. As you know, this would be certainly fatal to the scuba diver. Also, a person stricken with panic at the surface is concerned only with keeping his head above water., and so does not usually employ his fins in the proper manner, doesn't use his snorkel, and often does not cooperate with his "buddy", and so may be a very real menace to them both. Panic is one of the primary reasons for the use of the buddy system in diving. If one person has difficulties, his buddy can assist him to save his own life, or if necessary, can act the part of the rescuer. The cardinal rule of diving is NEVER DIVE ALONE, and this will be gone into much more thoroughly later.

The one main contributing factor to panic is the exceeding of one abilities. Know your own limitations, and stay within them. Never put yourself in a position from which you cannot extricate yourself. If you are not as strong a swimmer as you might be, do not go farther from shore or your boat than you are certain you can swim. Everyone can panic, so swimming ability alone is not enough of a prevention. The best preventitive of panic is to learn the use and limitations of your equipment and yourself, and to know your emergency procedures so well that you automatically do the proper things and so fight down and overpower the rise of panic. If the dangers of diving were to be listed in order of frequency and fatality, panic would head the list. Remember, you need not be in a dangerous situation to panic, but if you think it is dangerous, then it becomes so. Your life is in very capable hands so long as you do not succumb to panic.

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