What are the bends when scuba diving?

Answer 1

When you are diving the nitrogen in an air supply dissolves into the blood and tissues due to the high pressure. When you start to come up the pressure decreases and the nitrogen comes out or "undissolves" (like fizz in a bottle of pop) and forms bubbles in your blood vessels and tissues. This stops the blood from flowing and forms bubbles, which expand the vessels, causing a painful condition known as "the bends". Bends can also happen if divers fly immediately after diving. The pressure in airplanes is even less than that at sea level.

Answer 2

People underwater breath air at an increased pressure (to counter the water pressure) and under higher pressure, nitrogen becomes more soluble and dissolves in the blood. When a diver returns to the surface and is breathing air at a normal pressure, the nitrogen in his blood is no longer as soluble, and it therefore comes out of the blood, forming bubbles. It is very unhealthy to have bubbles in your blood, hence, this causes a very serious and potentially fatal condition known as the bends.

Answer 3

The short answer: The bends (just one possible form of decompression illness) are caused when gas that is dissolved in the body comes out of solution due to reduced pressure on the body, and forms gas bubbles in various body tissues. The most commonly affected tissues are the skin, blood, brain, and around the joints. Joint pain accounts for the origin of the name "bends". This can happen to divers when the pressure decreases as they ascend towards the surface, and can also happen to those who are exposed to the low pressures found at high altitudes, such as astronauts. Reducing pressure on the body must be done at a controlled rate that accounts for how much gas is dissolved in the body and how much the pressure changes.

The detailed answer: Any material that can absorb gas will accumulate some of whatever gas it comes in contact with. Just as the oceans have oxygen and other gases dissolved in the water, our bodies also have some gases dissolved in them from breathing the air. The air is 21% oxygen and 79% nitrogen (plus small amounts of other gases). Since our bodies metabolize oxygen it doesn't accumulate in significant amounts, but nitrogen (and other breathing gases, such as helium) can.

How much gas can be absorbed is proportional to pressure, and as the pressure increases as you descend in the water you absorb additional gas. In salt water every 33 feet (or 10 meters) adds another atmosphere of pressure to the one atmosphere we experience at sea level. If a person stays at increased pressure long enough their body will continue to absorb nitrogen until it has absorbed as much as it is capable of absorbing at that pressure. At that point the dissolved gas will be at equilibrium, and the amount of dissolved gas in the body will remain constant. Thus, a diver at 66 feet could accumulate three times as much dissolved gas as they have at sea level. Different tissues will absorb gas at different rates, and tissues such as blood and your brain will absorb gas fairly quickly, while your teeth and bones will absorb it more slowly. This is accounted for by "decompression algorithms" that determine how much time a diver can spend at any given depth before they must start back to the surface, or how long they must wait before continuing towards the surface.

Reducing pressure reduces the amount of gas that can remain dissolved in the body. As a diver ascends back towards the surface (or a person increases their altitude above sea level) the pressure decreases. When this happens any tissue "compartment" that is already saturated will start to lose the dissolved gas, a process called "offgassing". A tissue compartment that is not yet saturated and is still absorbing additional gas when a diver starts towards the surface may become saturated during ascent, when the pressure is reduced to the point that the tissue then has as much gas as it can absorb. When the pressure is reduced at a modest rate the dissolved gas will be lost by remaining dissolved as it is transported through the blood until it reaches the lungs where it it exhaled. As a general rule the pressure on a saturated tissue can be halved and the gas will still remain dissolved. That means that a diver can stay at 33 feet for as long as their air lasts and then return directly to the surface, because they are only halving the pressure on their body.

When the pressure is decreased too much and too rapidly the gas can come out of solution and form bubbles of gas. When a diver goes deeper than 33 feet some of the tissues in their body may absorb more than twice as much gas as can be absorbed at sea level if they remain at that depth long enough. Since they can reduce the pressure on their body to less than half when they ascend, there is a risk of dissolved gases coming out of solution and forming bubbles if they ascend too soon or too rapidly. That means that for any depth below 33 feet there are time limits for a dive that will not require a "decompression stop." The deeper a diver goes the less time they can remain at that depth. Different algorithms suggest slightly different times, but a diver can stay at 40 feet for about two hours (longer than a typical Scuba tank is likely to last), but only about 20 minutes at 100 feet.

When a diver stays longer than those "no deco" time limits they must ascend to a somewhat shallower depth (known as a "deco ceiling")and then wait while they lose some of the dissolved gas before ascending further. When a diver ascends too far or too soon for the amount of dissolved gas they will have exceeded the no deco limits and gas bubbles may form. While following the decompression algorithms makes it very unlikely that a diver will suffer decompression sickness, individuals may experience different results, and people do rarely experience problems despite staying within those theoretical limits.

Answer 4

Under "HENRY'S GAS LAWS" he found that GAS under PRESSURE would dissolve in a liquid. On the converse, when the pressure is relieved the dissolved gas in the liquid will become gas once again. Think of a Carbonated soda. It has Carbon Dioxide gas in solution and under pressure. When you open the soda slowly, the pressure is released and You have fizz or bubbles. If you release the pressure to quickly you have an uncontrolled release of gas. As related to diving the bubble or fizz is gas in the BLOOD (liquid) and if you return too quickly to a less ambient pressure You have an uncontrolled release of the gas from solution. This gas then becomes trapped in the joints and surrounding tissue causing great pain. i.e.: THE BENDS I hope this clears up Your question on what and how the BENDS occur

Answer 5

The bends are where too much nitrogen builds up in your blood stream. It is painful and can be deadly if not addressed immediately. Don't let this discourage you because you learn all about it when you get certified.

Answer 6

ALL gasses can cause the bends (even oxygen in extreme levels). But for most divers it is nitrogen and for deep mixed gas technical divers it can also be helium that they added to their gas mix. However, it is not the blood divers are worried about (even though that is the transport mechanism), it is the gas that expands in the cells and tissues.

Answer 7

It is caused by gas dissolved in bodily tissues (usually nitrogen) coming out of solution too rapidly when the diver ascends, and creating bubbles in the bloodstream. Symptoms can range from mild discomfort to permanent paralysis and death.

Answer 8

There is no 100%, sure-fire way to prevent the bends. The following recommendations have been found to be helpful: Always ascend slowly and safely from every dive; breathe normally throughout the dive; don't exert yourself or skip breathe; don't push your limits; don't exercise within 12 hours of diving; don't drink alcohol before or after diving and never dive when hungover; do all required decompression stops; keep physically fit and within a healthy weight range; make sure you're adequately hydrated before every dive; and don't ascend to altitude or fly immediately after diving.