Decompression Sickness – Harvard Health

What is it?

Decompression sickness, also called generalized barotrauma or the bends, refers to injuries caused by a rapid decrease in the pressure that surrounds you, of either air or water. It occurs most commonly in scuba or deep-sea divers, although it also can occur during high-altitude or unpressurized air travel. However, decompression sickness is rare in pressurized aircraft, such as those used for commercial flights.

When you scuba dive with compressed air, you take in extra oxygen and nitrogen. Your body uses the oxygen, but the nitrogen is dissolved into your blood, where it remains during your dive. As you swim back toward the surface after a deep dive, the water pressure around you decreases.

If this transition occurs too quickly, the nitrogen does not have time to clear from your blood. Instead, it separates out of your blood and forms bubbles in your tissues or blood. It is these nitrogen bubbles that cause decompression sickness. The condition is called the bends because the joint and bone pains can be so severe they double you over.

What happens inside your body during decompression sickness is similar to what happens when you open a carbonated drink. When you open the can or bottle, you decrease the pressure surrounding the beverage in the container, which causes the gas to come out of the liquid in the form of bubbles. If nitrogen bubbles form in your blood, they can damage blood vessels and block normal blood flow.

Factors that put you at higher risk of decompression sickness include:

• Heart muscle birth defects, including patent foramen ovale, atrial septal defect, and ventricular septal defect
• Being older than 30
• Being female
• Low cardiovascular fitness
• High percentage of body fat
• Use of alcohol or tobacco
• Fatigue, seasickness or lack of sleep
• Injuries (old or current)
• Diving in cold water
• Lung disease

Someone with an abnormal hole or opening in the heart from a birth defect is at especially high risk of developing serious symptoms from decompression illness. Because bubbles create high blood pressure in the lungs, blood and bubbles from your veins may flow more readily through the heart’s opening. This means your blood can re-circulate into arteries without first getting oxygen. An opening in the heart can also allow a relatively large air bubble (called an air embolism) to circulate into your arteries. An air embolism can cause a stroke.

People with asthma or another lung disease may have thin-walled air pockets in their lungs called bullae. These pockets do not empty quickly when the persons exhales. As they return to the surface after a deep dive, air in the bullae may expand. If a bulla ruptures, it could cause a collapsed lung or allow a large air bubble (air embolism) to enter the arteries.

Symptoms

Symptoms of decompression sickness include:

• Joint pain  
• Dizziness
• Headache
• Difficulty thinking clearly
• Extreme fatigue
• Tingling or numbness
• Weakness in arms or legs
• A skin rash

Diagnosis

Your diving history and symptoms are key factors in diagnosing decompression sickness. Blood tests and joint X-rays usually do not show any signs of the problem.

Expected duration

Joint pain, the most common symptom from decompression sickness, can last for days or weeks.

Prevention

To minimize the risk of decompression sickness while diving:

• Dive and rise slowly in the water, and don’t stay at your deepest depth longer than recommended. Scuba divers typically use dive tables that show how long you can remain at a given depth.
• Do not fly within 24 hours after diving.
• Don’t drink alcohol before diving.
• Avoid hot tubs, saunas or hot baths after diving.
• Make sure you are well hydrated, well rested and prepared before you scuba dive. If you recently had a serious illness, injury or surgery, talk to your doctor before diving.

Some people should avoid diving altogether, or should consider special risks. If you have a heart defect, it is not safe to dive. If you have asthma, a history of a ruptured lung at any time in your life or another lung disease, discuss diving safety with a doctor before deciding whether to dive. A person who requires insulin to treat diabetes may have wide swings in blood glucose levels during a dive, and caution is advised. Avoid diving if you have a groin hernia that has not been repaired, since expanding gas in the hernia can cause symptoms.

Treatment

Emergency treatment for decompression sickness involves maintaining blood pressure and administering high-flow oxygen. Fluids also may be given. The person should be placed left side down and if possible the head of the bed tilted down.

The optimal treatment is the use of a hyperbaric oxygen chamber, which is a high-pressure chamber in which the patient receives 100% oxygen. This treatment reverses the pressure changes that allowed gas bubbles to form in the blood stream. The treatment drives nitrogen back into its liquid form so that it can be cleared more gradually from the body over a period of hours.

It is not recommended that divers with decompression sickness attempt to treat themselves with deep diving.

When to call a professional

If you experience symptoms of decompression sickness after scuba diving or flying, get to a doctor as soon as you can. Hyperbaric treatment is most successful if given within several hours after symptoms start.

Prognosis

Most cases of decompression sickness respond well to a single treatment with hyperbaric oxygen. Your doctor may suggest repeated treatments if you continue to experience symptoms, especially neurological symptoms.

Additional info

Undersea & Hyperbaric Medical Society

https://www.uhms.org/

How To Identify Decompression Sickness — AKA The Bends

“I’m bent.” They’re the two hardest words any diver ever says. But denying the symptoms of decompression sickness (DCS) could mean you end up with the four hardest to hear: “Can never dive again. “

Relaxing at the pool after a morning of diving, you notice a nagging ache in your shoulder. Is it DCS or a muscle strain from lugging gear bags? Time for a little self-diagnosis:

Many divers make the mistake of ignoring DCS symptoms — don’t be that person.

PADI

Do I have any symptoms of DCS?

These include but are not limited to:

• Joint or limb pain
• Itching
• Skin rash
• Nausea and vomiting
• Dizziness
• Ringing in the ears
• Extreme exhaustion

Clearly, these symptoms are not specific to DCS, so move to the next question:

LEARN MORE: The ABCs of DCS

How Likely Are These To Be Symptoms of DCS?

You did only a single half-hour dive to 40 feet that morning — how could it be DCS? Easy: during the last five days you’ve done 15 dives. The more diving you’ve been doing, the more likely it is to be DCS. The more you’ve pushed the edge of no-decompression status, the more likely it is DCS. The more safety stops you’ve blown off, the more likely it is to be DCS. Any of those apply?

I’m Still Not Sure. What Can I Do?

This is easy: Call DAN’s emergency number (+1-919-684-9111) if you need some expert assistance in deciphering your symptoms. DAN has doctors on call 24 hours a day who can help you arrive at a decision about your symptoms.

I Know I Have The Bends. What Should I Do?

Start breathing oxygen and have someone call DAN’s emergency number immediately: (919-684-8111). The DAN staff can help you arrange for transportation to the nearest chamber. DAN will help you even if you have not purchased DAN insurance, but you won’t like the five-figure bill you may have to pay. Or the possible delay in emergency evacuation because the helicopter company wants its money up front since you don’t have insurance, Considering how little we actually know about the mechanism of DCS, anyone diving without dive accident insurance is taking unnecessary health and financial risks.

READ MORE: Scuba Hand Signals for Emergencies

Why Do Divers Deny DCS?

A mix of three reasons is usually involved. First, because the dive was well within the no-decompression limits of their computer or tables. However, divers can get bent even when they follow all the rules. Second, symptoms of the most common form of DCS, Type I, are similar to many of life’s aches and pains, especially as we grow older. But third, and most common, those in denial are afraid of being labeled a “lousy” diver.

The fact is, you can be the world’s greatest diver and do everything right that day, but still get bent. Your chances are greatly reduced by adhering to the guidelines of safe diving, but each time we expose our bodies to decreased pressure when returning from a scuba dive, we are risking DCS. The key is to recognize symptoms and have the courage to rake immediate action. Otherwise, you might never have to worry about denying again; you won’t be a diver any more.

How to choose the right fins for spearfishing

09-06-2023

Author:
Katran Gun

6664

How to choose fins for spearfishing?? choice of fins for freediving?? These questions are asked by many novice spearfishers and freedivers! Also, people with experience having tasted the taste of hunting and getting their first trophy should study this question enough to improve the quality of their hunts. And when they go to the online store of diving equipment in Ukraine, they have a huge choice with completely different types, models, materials, etc. Every year there are more and more new models and brands, etc.

Therefore, we have made a brief overview of modern fins. Of course, the best way would be to watch our video how to choose fins for spearfishing video As they say, it’s better to see once than hear a hundred times.

But still, a fresh look will be as follows: fins for spearfishing in Ukraine are definitely recommended to take with interchangeable blades, with a closed heel, 70-90 cm long. You can easily install galoshes yourself without a specialist.

The fins with straps (diving) do not fix your leg enough, and the energy that should be transferred from the leg to the shovel is wasted on leg play. Accordingly, the hunter spends more oxygen, which reduces the duration of the dive and gets tired faster. Also, straps clinging to the grass, cramps and snags will interfere with movement and delay the hunter in motion.
Long fins allow the hunter to move forward and give him momentum for a long distance and the underwater hunter does not make noise in the water, does not make noise and does not frighten the fish.

These fins include Sporasub Spitfire, Omer Stingray, Mares Razor Pro, Bs diver Orca, Cressi Sub Gara Modular ), Omer Stingray Short (omer stingray short), Scorpena B (scorpion B).

The advantage of fins with interchangeable blades is that they have a special breaking angle from 17 to 29degrees which helps the fin to function better both in horizontal swimming (and you have to swim over considerable distances) and when diving in depth. The next advantage of fins with interchangeable blades is that when we can change the standard plastic blade for fiberglass, carbon fiber, or the same plastic but with a different stiffness. For example, softer for spearfishing in winter when the plastic hardens and becomes plywood.

Oak blades do not work in bending and we spend a lot of effort on moving. Blades for spearfishing made of fiberglass and carbon fiber do not change properties with temperature, in addition, they have a much higher efficiency. That is, with all other things being equal, on such blades we will swim a greater distance, spending the same effort as in plastic. Since such blades are not cheap at the edges, they are equipped with a special protective flange.

There are also transitional options from glass carbon to carbon, these are blades for Sandwich carbon fins. Inside, the basis of the blade is plastic, and on the surface of the carbon coating.

How to choose carbon fins for spearfishing? fiberglass? or glass-carbon sandwich? the answer is that for deep-sea it is better, of course, carbon fiber is more efficient, but fiberglass is less killed, therefore it lasts longer, therefore, carbon fiber is more often used for swimming in rivers among writhing, karyag where the blades are subjected to great mechanical stress. Yes, and it’s cheaper. The second swimming in carbon to a depth of no more than 10 meters you will not feel the difference (except psychologically =))

It is also a good option and not expensive to buy Leaderfins Ice or Leaderfins Black Ice fins. These are fins with a glass-plastic blade, but at the same time they are not expensive. The only downside is that they are small. the size of the galoshes leaderfinz ice 44-45 corresponds to the usual galoshes 43-44 bs-diver. And the size of galoshes 46-47 corresponds to 45-46. And if you need a thin sock, this is the best option for a beginner.

Now about the selection of the stiffness of the blades – a whole art.

1. The softer the galoshes mustache, the better the blade works, some galoshes mustaches are generally trimmed. Without an erroneous option, galoshes Mares Razor, galoshes Bs-diver , Omer Stingray Short – I do not recommend all other galoshes from other manufacturers. Their mouths are coarse. Especially Picasso and Omer Stingray .

2. Hunting conditions: the formula is as follows – the flow, we take harder stagnant water is softer, we take it harder in cold weather, since there are more loads on us, but if plastic is softer, because plastic changes properties with temperature and can break. Regular formula up to 70-80 kg soft paddles, 80-95 kg is average, more than 100 kg is hard, but taking into account the season of temperature and current. The best way is to take a friend and swim in his equipment and compare. A comrade can be found on our spearfishing forum katrangun.com in live communication or by visiting the spearfishing festival held three times a year .

Next, it is very important that the spearfishing sock on the leg is anatomical. In this version, in addition to better warming, it sits better in the galosh, the leg is better fixed and feels the fin. Therefore, accordingly, the energy transmitted from the foot to the blade will be maximum. It is not for nothing that they release all sorts of bizarre fins with sneakers, like sporasab revolutionary. This is not a divorce of suckers, for novelties, but real improved fixation of the foot. Special stars or stirrups for fins also help to fix the foot well.

There are also fins with anatomical galoshes and laces, for example C4 Wahoo or C4 NTT . They are ideal for deep sea hunting beyond 20-30 meters.

The choice of fins for spearfishing according to the size of the galoshes is an important point, but it’s very simple, you can just watch our video on how to choose the size of fins for spearfishing and figure it out once or twice.

Carbon is cheaper than plastic: Freediving Edition fins

A lot has been written and said about fins, and even the disputes that arise among hunters cannot even be counted. But despite their importance in diving and hunting, fins are still chosen on the basis of appearance or on the advice of a friend, and all comparisons in the press or in conversations remain subjective. This is undoubtedly used by large branded firms, slipping their products to the hunter at exorbitant prices. We trust, we pay, and then for years we swim shod in plywood, break the swimming technique, or, conversely, expend a lot of effort, but swim a little. I will try to state my opinion in order, without crumbling everything into a salad. So, separately and slowly:

Fins

A fin is a kind of symbiosis of a plate and a footsock, used to achieve maximum pushing force, or maximum coefficient of performance (COP), with a dosed application of force. Simply put, the fin must swim. Materials that are better suited to this task: textolite and other composite materials that increase their stiffness or resistance incrementally. They should carry the main load in the stroke. I think that the optimal load distribution between the plate and galoshes is 80% by 20% or 70% by 30%, here we use the experience of our speed athletes, who have no shortage of experience.

Papa Carlo’s galoshes

The galoshes should definitely be made of rubber, and not of cheaper plastic, like in “BEUCHAT” or “asphalt” with the addition of rubber, as is often found in the company “OMER”. “OMER” – the most common galoshes at the moment, but for some reason the lottery version, 50/50, either normal, or from the Chinese dad Carlo, if you’re not lucky. Of course, Pinocchio would be happy with such a gift, but we have to take a knife and intuitively plan these logs. “OMER” brand is very promoted. He is a leader in many positions. For example, their guns are probably one of the most successful ones, so they can afford misses in galoshes. It is for these reasons that we had to change the brand to H.Desault, where in galoshes the thickness of the side whiskers involved in the stroke increases depending from the size of the galoshes. And it’s not trifles. A size 46 fin with the same blade will be stiffer than a size 40.

Plates

Plates are made of a composite material: bauxite resin + fiberglass or carbon fiber (carbon). The point in this process is put by a vacuum press. In the manufacture of plates, fiberglass is stacked in layers so that the plate is soft at one end and fairly stiff at the other. The main merit of these materials is that they have a return energy. When we load the plate, it tends to return to its original shape, producing a push. Here the properties of carbon can be higher. The soft end of the plate can work out the lightest stroke. Let me give you an example: leadership in such a stroke can certainly be assigned to rubber fins “Dolphin” or “Aquanaut”. The hunter uses such a stroke when he approaches the trophy, while the hunter’s trophy does not see. The task is not to create water vibrations that the fish feel well. Or let’s take an anti-example: the recently promoted OMER millenium blades, models: “runner” and “ice”. In the section, this blade resembles slate and, with such a design, cannot provide a proper change in stiffness from the galoshes to the end of the blade. “Slate” he does not twist slate. I think that the manufacturer had to resort to this technique in order to protect the blade from breaking more strongly. I don’t see any other reason. The other extreme of the stroke is power: we often see on video recordings when, at the beginning of the ascent, the diver’s blade breaks under the toe of the galoshes, reducing all efficiency to nothing. Knead at the bottom with such flippers)))). Here we are faced with examples such as molding (plastic). In such fins it is simply dangerous to invest in the stroke. Molded thermoplastic fins are cheap to manufacture, have high repeatability, but require the most careful handling. It happens that such blades are not enough for one season, or even they break down completely in one competition. As a result, you lost.

Endurance

I’ve only seen one broken composite plate in five years, broken around the bolts, most likely because they were simply overtightened. Composite material, unlike plastic, does not change its properties at different temperatures and does not become brittle in the cold.

Edge

The edge is the necessary element of the blade. Kant centers the stroke, directs the discharge of water, but there is one thing here: with the front stroke (extension of the leg), in which the quadriceps triceps of the thigh participates and which is 2-3 times stronger than the biceps of the thigh, the edging is undoubtedly needed. On a return or backstroke, the sooner the water leaves the blade, the better. The blade does not get stuck, but quickly returns to its original position. Let me give you an example of C4: in addition to the fact that the edge of these blades does not go along the very edge, it is higher than necessary, and even has the same height on the lower and upper sides of the blade. With such performance characteristics, the return stroke turns out to be too difficult, this causes a feeling that the blade is stuck in the water, lives its own life, or works out the stroke belatedly.

Rigidity

Rigidity is the cornerstone of all hunter disputes. I will make a reservation right away, the terms “hard”, “soft” or “medium” are subjective concepts and they have no reference point. The fact that the Portuguese are soft, the Italian – tin. The weight range of hunters is also large, from 60 to 120 kg, but the stiffness cannot be selected based on such a progression: 60×2 = 120. If your weight is twice as much, this does not mean that your stroke is twice as strong. It is enough for a large hunter to increase the rigidity of the blades by 20-30%. Let me give you an example: new blades are released, another athlete sets a record in them, and this model is put into production, but the champion knows what he needs, and you buy only the appearance and the legend. One of these blades, when tested in a 25 meter pool, showed 32 strokes instead of 21-24 to reach the same time as well-swimming fins.

In order not to argue about fins, it is better to test them. How to do it: At 25 meters, take measurements, the number of strokes and the time. If the blade is soft, it will only be possible to meet at the same time due to additional strokes. If the blade is stiff, the number of strokes may be the same, but the amount of oxygen you “burn” more and score your legs. As a rule, excessive rigidity breaks the swimmer’s knees and kills the technique. Of course, a constantly floating and experienced person should test. So you can determine a successfully working flipper. Tip: often the mistake is choosing too hard fins and leads to the fact that after many hours of swimming, the swimmer swims not technically, clogs his legs and strokes become ineffective.

Bend. 90% for or 90% against

A little earlier, I was a clear opponent of blade bending. The flipper should be a continuation of a straight line drawn from the top of the head to the end of the foot, if we are looking at the swimmer from the side (in profile). Insufficient bending of the foot requires bending of the blade, but here we must not forget that the swimmer still slightly bends the knee during the stroke, and this bend again brings the blade to the same straight line. The main disadvantage of the flex is that the flex prevents the blade from extending, and this is one third of the area of ​​the fin, which, instead of the stroke, creates resistance in the case of a back weak return stroke. Here it is a huge minus canceling all the pros. Let’s go on the other hand, when swimming on the surface, the hunter, as a rule, rows from the knee and rarely does anyone manage to use the back stroke, it is very difficult to keep the foot in an extended position – anatomy interferes. So decide for yourself how much you benefit from the bend. Example: fins «Cressi Gara 3000» the thickness of the mustache at the bottom of the galoshes is much greater than the thickness at the top, which makes it impossible to technically return this fin to the initial phase of the stroke. The load on the return stroke is too high. I happened to be on Italian freediving courses at the Apnea Academy, and so, among 40 or even more Italians, only Pelitari swam in such fins, the rest, apparently, were not paid for it.

Money

So why is carbon cheaper than plastic? This is entirely the merit of the blade manufacturer, Leaderfins, who over the past few years have not denied joint experiments with us and the search for materials with the necessary properties, which has led to the development of a very successful range of fins for freediving and spearfishing.

Choice of 4 firmness: medium (#2, weight up to 65-70kg), medium-hard (#3, weight 70-90/95kg), hard (#4, weight over 100kg), extra-hard ( #5, weight 120-130+).

The most common option is a medium hard plate + Omer Stingray overshoes. The foot pocket fixes the plate very securely, and at the same time allows you to quickly and easily disassemble the fin, if necessary.