Activities The Great Outdoors All About Decompression Sickness Causes, Symptoms, and Prevention Share PINTEREST Email Print senerdesign/Getty Images The Great Outdoors Scuba Diving & Snorkeling Safety Gear Skills Hiking Climbing Skiing Snowboarding Surfing Paddling Fishing Sailing Learn More By Nicholas McLaren Nicholas McLaren is a professional scuba diver, first responder, and instructor of 17 scuba specialities. He also worked as an underwater videographer and scuba diving freelance writer. our editorial process Nicholas McLaren Updated February 11, 2019 Also known as "the bends" and Caisson Disease, decompression sickness affects divers or other people (such as miners) exposed to rapid changes in air pressure. In recent years, the medical term decompression illness has gained more traction—the term is technically more precise than decompression sickness, but it relates to the same condition. DCS, as it is commonly known, is caused by a build-up of nitrogen gas in the bloodstream. When we breathe at sea level, approximately 79 percent of the air we're breathing is nitrogen. As we descend in water, the pressure around our bodies increases at the rate of one unit of atmosphere for every 33 feet of depth, causing nitrogen to be forced from the bloodstream and into adjacent tissues. This process is not harmful, and it's entirely possible for the body to continue to absorb nitrogen until it reaches a point called saturation, which is the point at which the pressure in the tissues equals the surrounding pressure. Decompression Safety The problem arises when the nitrogen in the tissue needs to be released. To remove the nitrogen slowly from the body—a process called off-gassing—a diver must ascend at a slow, controlled rate and carry out decompression stops if necessary; this hovering in the water allows the nitrogen to slowly seep out of the body tissues and return to the bloodstream, where it's released from the body through the lungs. If a diver ascends too fast, the residual nitrogen in the tissues expands too quickly and forms gas bubbles. These bubbles must normally be on the arterial side of the circulatory system to be harmful—they are usually harmless on the venous side. Type I Decompression Sickness Type I decompression sickness is the least severe form of DCS. It usually involves only pain in the body and is not immediately life-threatening. However, the symptoms of Type I decompression sickness may be warning signs of more severe problems. Cutaneous Decompression Sickness: This condition arises when the nitrogen bubbles come out of solution in skin capillaries. This usually results in a red rash, often on the shoulders and chest.Joint and Limb Pain Decompression Sickness: This type is characterized by aching in the joints. It is not known precisely what causes the pain as bubbles in the joint would not have this effect. The prevailing theory is that it is caused by the bubbles aggravating bone marrow, tendon, and joints. The pain can be in one place, or it can move around the joint. It is unusual for bisymmetric symptoms to occur. Type II Decompression Sickness Type II decompression sickness is the most serious and can be immediately life-threatening. The main effect is on the nervous system. Neurological Decompression Sickness: When nitrogen bubbles affect the nervous system they can cause problems throughout the body. This type of DCS normally shows as tingling, numbness, respiratory problems and unconsciousness. Symptoms can spread quickly and if left untreated can lead to paralysis or even death.Pulmonary Decompression Sickness: This is a rare form of Decompression Sickness that occurs when bubbles form in lung capillaries. Although the majority of the time the bubbles dissolve naturally through the lungs; however, it is possible for them to interrupt blood flow to the lungs, which can lead to serious and life-threatening respiratory and heart problems.Cerebral Decompression Sickness: It is possible for bubbles that make their way into the arterial bloodstream to move to the brain and to cause an arterial gas embolism. This is extremely dangerous and can be identified by symptoms such as blurred vision, headaches, confusion, and unconsciousness. Other Forms of Decompression Sickness Extreme tiredness is very common in cases of DCS and can sometimes be the only symptom of decompression sickness present. It is also possible for decompression sickness to occur in the inner ear. This problem is caused by bubbles forming in the cochlea's perilymph during decompression. The result can be hearing loss, dizziness, ringing of the ears and vertigo. Symptoms Decompression sickness can manifest itself in many different ways and has many different symptoms, but the most common symptoms are: Extreme fatigueJoint and limb painTinglingNumbnessRed rash on the skinRespiratory problemsHeart problemsDizzinessBlurred visionHeadachesConfusionUnconsciousnessA ringing of the earsVertigoStomach sickness Risk Factors Every diver has a different level of risk of Decompression Sickness. Many risk factors are still not fully understood, but there are a few basic factors that doctors agree increase the chance of developing Decompression Sickness: Body Fat: The theory is that nitrogen absorbs more easily into fat, so an overweight diver is at a higher risk of decompression sickness.Exercise: Interestingly, exercise has both a positive and negative effect. Exercise at least 12 hours before a dive seems to produce proteins that protect the body and decrease the risk of decompression sickness. On the other hand, exercise less than 12 hours before a dive can raise the number of gas micronuclei on which bubbles form, and this increases the risk of decompression sickness. Exercise immediately after a dive increases the risk of bubbles forming as blood pressure is increased and bubbles can more easily be transferred from the venous to the arterial side of the circulatory system.Gender: Theoretically women should have a higher risk of Decompression Sickness because women typically have a higher body fat percentage. However, this has not been proven in studies, and it's possible that gender does not affect the chances of suffering from decompression sickness.Age: Generally, older people are at an increased risk of decompression sickness. This is due to less efficient circulatory and respiratory systems.Fitness: Fitness decreases the risk of decompression sickness. A fitter body can tolerate more physical stress, including decompression sickness.Dehydration: Dehydration causes less blood to be available for gas exchange which makes it more difficult for the body to off-gas, increasing the risk of decompression sickness.Injury and Illness: Injury and illness can affect normal circulation, increasing the risk of decompression sickness.Alcohol: Consuming alcohol before or after a dive accelerates circulation which helps tissues to load with gas. Alcohol also dilates capillaries which can increase the rate of nitrogen released.Carbon Dioxide: Improper breathing can lead to elevated levels of carbon dioxide, which interferes with the bodies ability to transport gas. This will lead to an increased chance of decompression sickness.Cold: Doctors generally believe that diving in cold water increases the risk of decompression sickness. This is due to the body working harder to keep warm as it becomes colder, which means that when the body is warmer it can absorb gas normally, but as it becomes cold, it has difficulty offing the gas.Altitude and Flying After Diving: When ascending on land or in a plane, the atmospheric pressure changes, and this increases the chances of decompression sickness. It is best not to ascend above 300 meters (1000 feet) or fly after diving. Patent Foramen Ovale (PFO) - Hole in the Heart: As a fetus, a baby doesn't breathe and needs a way for blood to bypass the lungs until it is born. The body achieves this by having a small opening in the middle of the heart that allows blood to bypass the lungs. Normally, this hole would close within a year of birth, but in approximately 20-34 of people, this does not happen, leaving a permanent opening in the heart. Usually, a flap grows over the opening, and there is no effect. However, in some cases the flap allows blood to pass through the opening. This means that bubbles are more easily able to pass from the venous to the arterial side of the circulatory system, significantly increasing the risk of decompression sickness. It has been found that a large proportion of divers who suffered from decompression sickness had a PFO.Reverse Profiles: The jury is still out on reverse profiling, or making a deeper dive after a shallower dive. Theoretically, it should increase the risk of decompression sickness, but this has not been proven scientifically. It would still be better to err on the side of caution. Prevention As there are many risk factors, there are also many methods of prevention. Here's a basic checklist that will help you lower your risk of suffering from Decompression Sickness: Always ascend slowly and safely from every diveDon't push your limits and do all required decompression stopsKeep physically fit and within a healthy weight rangeDon't exercise within 12 hours of divingDon't ascend to altitude or fly immediately after divingBreathe normally throughout the dive, don't exert yourself or skip breatheMake sure you're adequately hydrated before every diveDon't drink alcohol before or after diving and never dive when hungoverGet checked out by a doctor to find out if you have a PFOAvoid reverse profiling—just in case Treatment Medical professionals with oxygen may treat minor cases of DCS; in time, the excess nitrogen in the body will naturally off-gas. More serious situations, including rapid uncontrolled ascents from significant depth, usually require re-pressurization in a hyperbaric oxygen chamber. Immediate on the scene treatment consists of oxygen therapy and basic first aid. This should be followed as quickly as possible by recompression treatment in a recompression chamber. When treating decompression sickness, the delay in beginning recompression treatment can be the biggest single cause of residual effects.