All humans tend to fear the unknown, and for first-time night divers that means what we cannot see in the water. For starters, it's actually rare to find a night dive site that is truly pitch-black. Once your eyes have adjusted to the conditions, you'll be amazed at what you can see with no light at all. You don't need the biggest and brightest light you can find. Most fish and critters will flee from an oversized light, and you'll miss the action. Relying on too much artificial light can ruin your night vision and prevents your eyes from acclimating to the conditions. Some night diving tips: Be sure to review night diving signals and procedures, so you can communicate without blinding your fellow divers. Shine your light downward on your signalling hand to illuminate the conversation. Review signals using the light (a circle means OK, rapid side to side movement means attention!, etc.). And never, ever shine your light in another diver's eyes. Also think about how you will attach your light to your gear. A wrist lanyard means you won't lose the light if you accidentally let it go. And don't forget the backup light. A small light that fits in a BC pocket is a good idea, just in case.
Excerpts from newsletter Diving with the “A” Team Geoffrey Burton
By: Colleen Muskat On: Wednesday, December 17, 2008, 3:09 am
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I hope this isnt a stupid question? How do the symptoms of "the bends" or AGE present? Does a diver bleed internally, externally, I can imagine there is great pain? in other words, can anyone explain how it feels when you have decompression sickness?
Also does a diver become paralyzed?
By: Lori-lee Henderson On: Tuesday, December 2, 2008, 3:13 am
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Decompression Illness - Johan Olivier
How to get it, and what to do with it?
DCI or Decompression illness is the general name given for diving disorders. It can mainly be broken up into 2 main disorders.
1- DCS(compression sickness), better known as “the bends” and
2 - AGE (arterial gas embolism). There are many sub classifications for both of these disorders, but is not important for this discussion.
DCS – is caused when tissues “fizz” like a carbonated drink. The “fizz” is caused by an inert gas, which was dissolved into the tissues while the diver was under pressure. An inert gas is usually nitrogen, helium or hydrogen.
In air we roughly get 20% oxygen and 80% nitrogen. At the coast, that gives us 0.2 atmospheres (ATA) oxygen and 0.8ATA nitrogen. Add the two up (0.2 + 0.8 = 1) then we get 1 ATA air.
There is the same pressure of nitrogen in the body’s tissues than what is in the surrounding air, which is being breathed. When a diver dive’s down to 20m (3ATA) the nitrogen pressure changes from 0.8 ATA to (0.8 x 3 = 2.4) 2.4 ATA. Over time the diver’s tissues will dissolve enough nitrogen, so that the nitrogen pressure in the tissues are the same as in the surroundings or breathing mix. The diver is now in a state of “saturation”.
If the diver starts to ascend to a shallower depth, say 10m, the diver’s tissues will be in a state of “super saturation”. This means that there is more gas pressure in the tissues than in the surroundings. This is tolerable to a certain point, but must be carefully monitored and controlled, by doing stops at certain depth levels. The diver is now busy de-gassing. If the diver goes up to fast, or misses his stops, the tissues will start to “fizz”. The level of toleration for “de-gassing” is affected by various factors, including, fitness, dehydration, temperature and the type of inert gas. Diving tables or dive computers are used to try and prevent a diver to exceed the level of tolerance. A diver can get DCS without even realizing it whilst diving, and only start noticing it after a few hours.
AGE – is somewhat different to DCS in how you get it, but can in some cases present with the same problems as DCS. The main differences are:
The diver doesn’t need a gas load to get it.
It is associated with barotrauma. (trauma caused by pressure)
Boyles law states: “Double the pressure – half the volume”. The same is true vice versa. “half the pressure – double the volume”
If a diver takes a lift bag full of air down to 10m, the bag will be half full at 10m. If the diver fills the lift bag at 10m and takes it to the surface, some air will escape on the way up. The reason for that is that the compressed air is expanding as the pressure is decreased. Same is true if the same diver takes a full breath at 10m and holds his breath as he swims up to the surface. At 10m, a diver with 6 liters of lung capacity will have 12 liters of air in the lungs, if it could hold the pressure. The lungs will burst at a pressure between 8 – 10 kpa (one 10th of a bar)
*(T.J.R Frances & D.G.Gorman) The gas that was in the lungs moves into the circulation system of the diver. The bubbles now starts to block circulation in the arteries where it is too small to pass through. The diver usually presents with severe symptoms, just after it happens, or very shortly after the dive.
Another way to get AGE is by having a PFO (Patent Foramen Ovale). Roughly 37% of all humans have it; therefore it is assumed that 37% of all divers have it too. It is a small flap between the left & right atriums of the heart. The blood flows into the heart at the (1) right atrium, to the (2) right ventricle, to the lungs to get oxygen, (3)to the left atrium,(4) to the left ventricle, then into the rest of the body. All humans had it whilst in their mother’s womb. The baby cannot breathe before birth, so the blood bypasses the lungs, by going directly from the right atrium to the left atrium. It usually closes completely, shortly after birth.
It is normal for a small amount of bubbles to form in the blood of a diver as they decompress. These bubbles are usually filtered out by the lungs. Having a flap between the 2 atriums, small bubbles formed with decompression cannot be filtered out by the lungs. They therefore go straight back into the arterial side of the circulation and starts blocking like AGE.
As an industry standard, all divers who have any diving emergency or medical queries should call the DAN-SA Hotline on 0800020111. It is not a prerequisite to be a DAN member to use the call center, but it will cover your medical bill if you get DCI. The main reason is, they are a 24hr call centre and not all the chambers are open 24/7.
The first thing to be done in all cases of DCI is to give 100% oxygen as soon as possible for as long as possible. This could be the most critical part of the diver’s treatment. You immanently start to oxygenate the tissues and help prevent the manifestation of new nitrogen bubbles. The diver should also be given clear liquids like water or juice. No coffee or anything that would dehydrate the diver.
At the chamber
A lot of divers are not sure what happens at the decompression chamber where they actually get treated. All cases are different from each other, and each case must be handled on own merit. Here is but a rough outline.
The DMO (Dive Medical Officer) is charged with the task of assessing the diver and make a decision on the dive history. It will be a bad idea to pressurize a diver for AGE and finding out at 50m that the diver has a ruptured lung. What to do if the diver gets oxygen toxicity in the beginning of the treatment?
If all complications are assessed - the diver will go through the following procedure –more or less.
Diver will go on 100% O2 down to 2.8ATA. After 10 min the diver is examined. If all the problems are resolved, the diver will continue with a USN TT 5 (2hr15min) dive.
If all the problems are not resolved, the diver will continue with USN TT6.
The dive can be made longer as the diver responds to the treatment. The severity of the diver will also determine how aggressive the treatment will be. If the diver feels 100% “cured” it doesn’t mean that the bubbles have all disappeared. The effect of the pressure has squeezed the bubble smaller, combined with the increased oxygen effect, may lead the diver to think that the bubble is gone. This is not always the case, as the bubble must now over time, slowly be dissolved back into the tissue that surrounds it. The table 6 could give a 95% improvement, and sometimes it is difficult to pick up subtle abnormalities. Some abnormalities could also be due to fatigue, cold etc.
Sometimes it could be necessary to do follow-up hyperbaric treatments, based on the normal table 9.
This could be done over several days, or possibly weeks, until full recovery is noted.
All these factors are dependent on:
1) How long after the diver surfaced, was oxygen administered?
2) How long did it take before the diver received decompression treatment?
3) How well is the diver hydrated between the dive and decompression treatment?
This paper is but a guide to give a diver a better understanding of DCI and the treatment of it. Hopefully it will also point out to have as much information available about the dive, so that the DMO can have a better idea of the dive profile. This will assist the DMO to make more proactive decisions on a treatment plan. It is also important to give all the information. Some people think that they would get banned from diving if they didn’t plan their dive properly and had to miss a deco stop because they ran out of air. Even if there were a couple too many beers the previous night, it will not help to lie to the DMO. Chances are better to get back into the water, if there is a logical explanation why a diver got DCI. A DMO will think twice to clear a diver if he/she got DCI for no reason.
Safe Diving!!
Johan Olivier
By: Normalair On: Sunday, November 30, 2008, 6:16 am
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Basic Etiquette for Scuba Divers
Written by Johan Swart and published in Diving Dynamics Magazine
In the good old days when Scuba diving was an infant sport, all divers were a hairy lot, and many of them belonged to, or had been kicked out of motorcycle gangs.
Anyone whose hairline was more than two centimeters above his eyebrows was considered an intellectual. The question of diving etiquette was never raised because nobody knew what etiquette was, or how to spell it.
The world turns and times change. Now our beloved sport is being infiltrated by strangers such as yuppies, schoolchildren, wives, family-to-be, politicians, “dominies”, doctors, professors and students……people who worry more about such things as whether the boat has a head (“toilet” for all the landlubbers) on it and, if so, whether or not it actually has a door. The time has therefore come to formulate some standards of decorum to cope with the social problems associated with our liquid orientated sport.
Let’s face it. Diving is a disgusting hobby. It gets disgusting even before you jump into the water, and it gets worse as the dive progresses.
First, there is the problem of applying anti-fogging compound to the lenses of your diving mask. Since man was designed to evolve into a scuba diver, “mother nature” thoughtfully provided him with an excellent on-board source of anti-fogging compound. Various commercial substitutes are available for the totally finicky, but beware, the day will come when the little expensive bottle has been lost, crushed or forgotten at home and you will have to resort to “mother nature’s” way. Here are some pointers:
“Gghwwauuk-phu!!” is out! Saliva is the proper substance and you should, as far as possible, avoid involving your post-nasal drip. Saliva should be applied in the least noisy manner possible and with as little foreign matter (coffee grinds, boerewors or other materials normally associated with unbrushed teeth) as possible.
The mask should be held in your own hands, close to your own face, while applying the compound. Since tobacco chewing has long gone out of style, the public seems to have lost its appreciation for the great skill involved in accurately spitting from a distance.
Use only one of your own hands to evenly spread the anti-fogging compound on the lenses of your mask and rinse that hand over the side before attempting last-minute cheek pinches, pats, squeezes or hugs.
Do rinse your mask after spreading the compound. The newby divers do not consider it good form if you glare at them through smeared lenses.
While on the subject of spitting, perhaps mentioning another related topic or function would not be amiss, which, if not performed with decorum, may contribute to the general onset of “mal de mer” amongst those of your companions with unstable digestive systems. If you have to expulse some unmentionable substance orally over the side, always do it to the leeward (“with the wind” landlubber!!). This applies to any natural function, for that matter, including throwing up if you turn out to be the one with the unstable digestion. The object of any such expulsion activity is after all to rid yourself permanently of whatever is being expelled and not to end up wearing it or decorating the boat or your buddies with it.
Since many divers are prone to seasickness, I will hereby offer a few free guidelines to help you carry off your bouts of this affliction with decorum, if not with dignity:
Never eat scratchy stuff. Stick to smooth, pleasant tasting basics that will not ferment or multiply in your stomach.
If possible, remove yourself from the company of others. They may be occupied with their own affairs and may even fail to notice your most obvious symptoms. Thus, it may eventually even be necessary to inform them of your delicate condition. They will only be too happy to cooperate with your request for solitude and if they do choose to assist you in a very supportive and understanding manner you could count them amongst the dearest of your friends.
Enduring your misery up on deck, in the fresh air, is usually more practical than below deck where the atmosphere may be contaminated with diesel fumes, fish bait or cooking odours. Also when your time comes, you will find it easier to hit the ocean than the ship’s head (“toilet” landlubber)which is usually rather small and located in cramped quarters, where someone else might have had the same problem before you.
Remember that divers usually get picked up on the leeward side (downwind) of the boat as the skipper normally uses the wind to drift onto the waiting divers. These swimmers would appreciate your warning them well in advance of your impending crisis.
Those who are not seasick have no sympathy at all with those who are. Unless you have a gun among your dive gear, no amount of pleading will influence them to cut short their diving or spearfishing excursion. So, shut up and suffer in silence. This requires true nobility of spirit since your heroism and sincere humanism might not even be noticed, to say nothing of being appreciated, by your companions.
One trick could however swing things in your favour. This trick is so bad that even I hesitate to mention it, but persons of very low moral character or persons in the dire straights of desperation can consider it. This trick takes advantage of what is commonly called the “Avalanche effect”. For every person who is really seasick, there are usually several others who are bravely battling the symptoms and who, in the normal course of events, might even be able to complete the mission of the day without succumbing to their worst fear. If the weather or the petrol fumes are pretty bad, there is a good possibility that you could trigger the” avalanche effect” by seeking out the most densely populated part of the boat when you surrender the contents of your stomach. Utter a few loud moans and groans to make sure all attention is focused on you. Lose your balance and be violently sick in full sight of everybody.
If this lowlife, underhanded trick works, you will achieve an easy majority and the diving day will be over.
But remember ,you will lose most of your friends and your name will be cursed amongst divers until your fins rot and your cylinders rust through.
Amongst the latest developments in diving equipment is the hot water heated wetsuit. Once again “mother nature” was way ahead of technology. Not only is “homo scubiens” equipped with his or her own hot water system but he or she even has an inborn reflex that gives them an overpowering urge to micturate (“make water” according to any good dictionary) as soon as he or she is totally encased in a wetsuit. The use of the system is a personal matter between the diver and his wetsuit and I will not comment on it other than to suggest that, should you notice your buddy pausing for a moment with a far away look in his eyes and a smile so wide that the danger of losing his mouthpiece becomes a reality, you might stop and wait at a discreet distance, up current from him or her.
Rinsing your wetsuit out as soon as you have taken it off, and taking it off without assistance, if you happened to be the one who had the faraway look in your eyes, is, indeed, a hygienic and genteel practice.
Since man has not yet completed his evolution into a scuba diver, he is troubled by airspaces in his head, called sinuses. Indeed, there are those who maintain that divers have more airspaces in their heads than other people, but this slander has never been substantiated.
These sinuses are fortunately connected to passages opening into the diver’s general ventilating system. As it is well known, the sinuses provide ideal nesting sites for almost every miserable, freeloading type of bacteria ever found in air or in water.
The creator was surely tired when he finished designing man’s wonderful brain, because he apparently left the rest of the head to an apprentice draftsman in the back of the room. This kid goofed up both the ears and the sinuses by making their tissue, which swells like mad and starts oozing sticky stuff whenever it is exposed to even the most insignificant irritant. As a result divers often have problems balancing the pressure inside their heads with the pressure outside.
Most of this difficulty with air passages occurs on the way down through the water. It however never seems to raise any questions of etiquette as all your buddies realize that you are holding your nose in an effort to force air into your sinuses or middle ears, and not to express your opinion of the company you find yourself in.
It is however on the way back up that things really become bad from an etiquette point of view. As the pressure outside decreases, the air, which so painfully introduced into these air spaces, must find its way out again. It usually escapes rather easier then it went in, but it is the stuff that it brings out with it that causes the social problem. Don’t be lulled into a false sense of security by the fact that you haven’t had a cold or sinus trouble for ages. That might only mean that your contribution to the ocean or your upper lip will be vintage stuff and of a much more interesting colour.
As soon as you reach the surface, after each and every dive, remove your mask and rinse it thoroughly. Then blow your nose, check your eyebrows, cheekbones and lips and wash your face. Do this with your face in the water and as quietly as possible, but make sure that you do a good job. Abalone can be real sneaky!! Keep a box of tissues with your gear for use after you dived. Your mother should have told you that blocking one nostril with your finger and snorting over the side is uncouth.
The diver is a primitive beast, hell-bent on regressing to the primordial sea. It is probably futile to go much beyond the above basics of social conduct, the observance of which may render the average diver at least tolerable to his fellow human beings.
By: Normalair On: Friday, November 21, 2008, 1:17 am
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