The Complete Diver's Guide to Decompression Sickness: Prevention, Recognition, and Treatment

Decompression sickness is one of the most serious threats to scuba divers worldwide, yet it is also one of the most preventable diving injuries. Regardless of whether you are a recreational diver or a technical diver, decompression sickness is something you need to understand to stay safe underwater.

Decompression sickness, also known as "the bends," occurs when nitrogen gas that has been trapped in body tissues under pressure forms bubbles during an ascent from a dive. Bubbles can clog blood vessels and burst tissues. Symptoms include joint and skin rashes, extreme neurological problems, paralysis, or even death, depending on where the bubbles form in your body.

This post provides you with all the necessary information about decompression sickness, how to avoid it, and what to do if you do suffer from it.

Decompression Sickness: The Science Behind the Bubbles

As you descend during scuba diving, the air in your lungs gets compressed due to the increased water pressure, and it forces more nitrogen from your breathing gas to be dissolved in your blood and tissues. Usually, during a controlled, gradual ascent to the surface, this dissolved nitrogen is gradually released from your tissues and transported by your blood into your lungs, where it's exhaled.

However, if you climb too quickly or skip required decompression stops, the rapid drop in surrounding pressure causes the dissolved nitrogen to escape from your tissues and blood as bubbles, much like opening a carbonated beverage too quickly releases the dissolved gases.

These bubbles may lead to blockage of blood vessels, tissue destruction, and interference with regular physiological processes. The location and size of bubbles determine the extent and nature of symptoms. Decompression illness is divided into two broad categories: Type I DCS affects the skin, muscles, and joints. Type II DCS involves the nervous system, lungs, or other vital organs and is considered more severe.

Preparing for Your Dive: The Foundation of Decompression Safety

Proper dive planning is necessary to avoid decompression sickness. Before you even get wet, consider the following key factors to minimize your risk of DCS.

Physical conditioning begins well ahead of your dive day. Good cardiovascular fitness helps your body's ability to transport and eliminate dissolved gases. The quality of your sleep also impacts your decompression risk. Fatigue can impair judgment and make it tougher to follow safe diving practices.

Dive planning must always begin with a thorough review of your intended dive profile. Use dive tables or dive computers to determine no-decompression limits for your planned depth, and always plan for a dive profile that's well within these limits.

For multi-dive profiles, plan the sequence of your dives carefully, as the residual nitrogen from previous dives will affect the decompression commitment for subsequent dives. Allow the body to release built-up nitrogen by including surface intervals between dives. Your dive computers or dive tables should take residual nitrogen into account.

Environmental factors also affect decompression planning. Cold water diving increases your risk of decompression sickness because it can affect circulation and gas elimination.

Finally, prepare your equipment carefully. Make sure that your dive computer is in proper working condition and that you are familiar with its functions, including decompression stop calculations and safety stop reminders. If using dive tables, make sure that you have the correct tables for the conditions in which you will be diving and that you understand how to use them properly.

How to Avoid Decompression Sickness: Safe Diving Practices

The single most significant principle to avoid decompression sickness is managing your rate of ascent, which should never exceed 30 feet per minute. Indeed, most dive computers now suggest even more cautious rates of 10-20 feet per minute for the last 60 feet of ascent.

Rapid ascents come with a risk of bubble formation, but modern dive computers provide you with both audible and visual warnings when you are ascending too rapidly. Respond immediately to these warnings!

Also, respect safety stops. Even when diving within no-decompression limits, perform a safety stop at 15-20 feet for three to five minutes so that nitrogen has some additional time to be eliminated from the body. It serves as a final check of your buoyancy control before surfacing. This practice should be considered mandatory rather than optional.

If decompression stops are required, treat them as absolute requirements, not suggestions. Do not skip or shorten required decompression stops. If you fail to respect these stops, you are increasing your risk of severe decompression sickness.

Extend the surface intervals between consecutive dives to a minimum of one hour, and preferably longer for deeper dives to allow extensive nitrogen elimination. The majority of experienced divers make it a practice to use the "deepest dive first" rule for several dives on a single day, as this procedure generally generates more conservative nitrogen loading.

Altitude diving is made more complex by the fact that the reduced atmospheric pressure at altitude affects decompression calculations. Dive computers and tables are calibrated for sea level conditions; therefore, you should use special procedures or altitude-adjusted dive tables.

If you need to travel by air after diving, follow proper surface intervals to prevent decompression sickness from the reduced cabin pressure during flight.

How to Recognize the Signs and Symptoms of Decompression Sickness

For the best treatment and outcome, you must know how to recognize the signs and symptoms of decompression sickness. From a clinical point of view, DCS can present itself in a highly diverse manner, ranging from mild joint pain to potentially fatal neurologic forms. Symptoms may appear from shortly after surfacing to 24 hours later, but are usually seen within six hours.

Type I decompression sickness most commonly presents itself with musculoskeletal signs. Shoulder, elbow, knee, and ankle pain are the most common symptoms. Skin signs can also present as itch, rash, or mottled discoloration of the skin, particularly over the upper arms and torso. Lymphatic involvement can lead to swelling of lymph nodes or extremities. Such symptoms, though uncomfortable, are usually not immediately life-threatening. Even so, they require prompt medical care and recompression therapy to avoid progression to more severe forms.

Type II decompression illness involves the central nervous system, lungs, or cardiovascular system and is an emergency medical condition. Neurological symptoms can include headache, dizziness, confusion, speech difficulties, extremity weakness or paralysis, loss of coordination, seizures, or loss of consciousness. Visual disturbances, hearing loss, or alterations in sensation can also occur.

Pulmonary decompression sickness, or "the chokes," involves chest pain, shortness of breath, or a non-productive cough. The cause of these symptoms is the presence of gas bubbles in the pulmonary circulation, which can rapidly progress to respiratory failure.

Vestibular decompression sickness affects the inner ear and can lead to extreme dizziness, vertigo, nausea, vomiting, or hearing loss.

Other divers develop prodromal symptoms, which are early warning signs that may develop into full-blown manifestations. They may include an inexplicable tiredness, mild confusion, or the feeling that something is slightly off. Frequent divers learn to develop an intuitive sense of such subtle changes and must never ignore them after a dive.

The Causes of Decompression Sickness

The most direct cause of decompression sickness is rapid ascent. Missed or inadequate decompression stops allow too little time for nitrogen off-gassing, particularly on technical dives where required decompression is mandatory. Even brief interruptions of required decompression stops can cause dangerous bubble formation. The deeper and longer the dive, the more you need proper decompression.

Yo-yo diving, where a diver completes more than one ascent and descent during a single dive, can create unpredictable nitrogen loading patterns that increase the risk of decompression. This type of dive profile is challenging for dive computers to track in terms of nitrogen buildup and can result in unexpected decompression requirements.

Pushing no-decompression limits is another risk factor. You may be staying within published no-decompression limits, which should theoretically eliminate DSC. However, these limits have inherent safety factors that fail to account for individual variations in physiology or environmental conditions.

Another complication may arise from reverse dive profiles. A diver who dives at increasingly deeper depths faces an increased risk of decompression sickness unless they maintain adequate surface intervals. While reverse profiles are not inherently bad, you must plan them well to prevent problems.

Gas switching during technical diving is another factor that complicates decompression management. The use of incorrect gas mixtures, gas switching at the wrong depths, or failure to follow planned gas switch procedures can result in inadequate decompression or oxygen toxicity, both of which contribute to diving injuries.

Finally, equipment failure, specifically dive computer failure, can result in improper decompression if divers lack backup strategies or alternative means of monitoring their obligations.

Predisposing Factors That Increase Your Risk

Age and physical fitness can influence decompression risk, with increasing susceptibility to DCS in older divers. This is because of age-associated changes in circulation, lung function, and tissue composition. Conversely, cardiovascular fitness improves circulation, thereby increasing the body's ability to move and eliminate dissolved gases.

Obesity contributes to the risk of decompression through various mechanisms, including altered patterns of blood flow, increased solubility of nitrogen in fat tissues, and reduced exercise capacity.

Dehydration is one of the most avoidable and common decompression sickness risk factors. Caused by a diminished blood volume, it lowers circulation and nitrogen elimination.

Repeated attacks of decompression sickness increase the risk of future attacks, perhaps due to residual tissue damage or hypersusceptibility to bubble formation. Patients with a history of DCS must work with diving medicine specialists to define appropriate diving limitations and may need to adopt more conservative dive profiles on a permanent basis.

Alcohol consumption also affects the risk of decompression. Alcohol dehydrates, inhibits mental functions, and may alter circulatory patterns. That’s why most diving medicine experts recommend alcohol abstinence for at least 12-24 hours before diving.

Smoking also significantly increases the risk of decompression sickness, as it impairs lung function and reduces the efficiency of gas exchange. The carbon monoxide from your cigarette smoke reduces the oxygen-carrying capacity of blood and may impair the regular elimination of gases.

Also, environmental factors can influence decompression risk. Cold water diving increases the susceptibility to DCS by circulatory and gas evacuation effects. Heavy underwater labor, whether caused by strong currents, equipment failure, or strenuous efforts, can increase the hazard of nitrogen uptake and bubble formation. And high-altitude diving requires specific precautions due to the reduced atmospheric pressure.

Finally, the use of medication can affect the risk of decompression in different ways. Some drugs alter circulation, while others may affect gas exchange or bubble formation. Divers on medication must ask diving medicine specialists for advice regarding potential interactions with diving.

What to Do If You Suspect Decompression Sickness

Immediately stop all operations and assess the situation upon receiving an alert. If you are still in the water when symptoms develop, slowly and safely resurface, and maintain close monitoring of the affected diver. Do not attempt in-water recompression as the maneuver is extremely dangerous and can worsen the condition or create further complications.

What can you do to help divers with DSC symptoms? After they are taken out of the water, place them in a comfortable, flat position if possible. This position maintains blood pressure and circulation to vital organs. If the diver is not responsive or having respiratory distress, place them in the recovery position to hold the airway open and do the following:

Administer 100% oxygen, if possible, as high-dose oxygen helps remove nitrogen from the body and can significantly improve the outcome.
Call emergency medical services.
Do not give the affected diver anything to eat or drink, as they may require surgery and anesthesia.
Keep detailed records of the diving activities, including depths, bottom times, surface intervals, and any equipment problems.
Monitor the injured diver closely for any changes in their status. Decompression illness can progress quickly, and symptoms can shift from mild to lethal.
If evacuation to a recompression center is likely to be delayed, continue supportive treatment until transportation can be provided.
Do not attempt to transport the affected diver to the hospital yourself unless there is no other way.
Do not fly or expose the diver to lowered atmospheric pressure until the diver is medically cleared by diving medicine specialists.

Diagnosis of Decompression Sickness

Diagnosis of decompression sickness is primarily based on clinical tests, since no laboratory test or imaging study formally establishes the diagnosis. Physicians make a diagnosis based on a culmination of detailed diving records, symptom presentation, physical health examinations, prior health status, and response to therapy.

Full dive history

The healthcare team will require full details of all dives over the preceding 48 hours, including depths, bottom times, ascent rates, decompression stops, surface intervals, and other relevant information.

Duration and evolution of symptoms

Most instances of decompression sickness happen within six hours of surfacing, but delayed presentations up to 24 hours following surfacing may occasionally occur.

Physical examination

Focus on neurological function, joint mobility, skin integrity, and respiratory status. The neurological exam may include testing of coordination, sensation, reflexes, and cognitive function.

Imaging studies

Imaging studies such as MRI or CT scans can be performed to rule out other conditions or to assess the extent of tissue damage. Imaging studies are instrumental when neurological symptoms are present.

Differential diagnosis

Differential diagnosis is necessary since numerous other conditions can mimic the symptoms of decompression sickness.

Other considerations

Response to treatment often helps to establish the diagnosis. Improvement with hyperbaric oxygen therapy is highly suggestive of decompression sickness, but lack of immediate improvement does not rule out the diagnosis. The threshold for diagnosing and treating presumed decompression sickness is low because the condition can have severe complications if treatment is delayed.

Onsite Treatment and First Aid

The primary focus of on-site medical treatment is to ensure adequate oxygenation, promote circulation, prevent further damage, and provide immediate evacuation to appropriate medical care. This protocol must be started immediately if any decompression illness is suspected. It must be maintained through the evacuation process, along with the following:

Oxygen therapy

Oxygen must be administered at a maximum concentration, ideally 100% via a demand valve or non-rebreather mask. Continue oxygen treatment until the patient receives medical attention.

Position of the diver

Position the affected diver properly to help maintain circulation and prevent complications. Avoid the head-down position unless you are specifically trained in its use, as improper positioning can exacerbate certain types of DCS. If the diver is unconscious or vomiting, place them in the recovery position to maintain airway patency and prevent aspiration.

Fluids

Be very careful with fluids. A small amount of water is safe if the diver is conscious and can swallow without risk, but use neither high volumes of water nor anything other than water.

Pain management

In most instances, limit pain management to comfort measures rather than medication.

Temperature regulation

Temperature regulation is necessary because hypothermia and hyperthermia both exacerbate decompression sickness. Keep the injured diver warm but not overheated.

Vital sign monitoring

Continuously monitor the patient's status and detect any deterioration; note and record pulse, respiratory rate, blood pressure, and other vital signs. Document any change in symptoms or neurological status.

Contact medical services

You must contact medical services as soon as possible. Some areas have diving emergency hotlines manned by diving injury-aware medical professionals who can give advice on treatment and assist with evacuation planning to suitable facilities.

Medical Treatment and Hyperbaric Therapy

The definitive medical treatment for decompression illness is hyperbaric oxygen therapy, in which the patient inhales 100% oxygen in a pressure chamber. Treatment acts through bubble reduction, increased tissue oxygenation, and increased removal rate of nitrogen from body tissues.

Treatment protocols for hyperbaric treatment follow standard procedures based on the type and degree of decompression sickness. Type I DCS tends to have shorter, less severe treatment protocols, whereas Type II DCS has more prolonged and intense treatment. The most common protocol for severe decompression sickness involves administering 100% oxygen at an absolute pressure of 2.8 atmospheres for approximately 4-5 hours, with precise breathing cycles to prevent oxygen toxicity.

You must constantly monitor Type II decompression sickness patients. Neurological evaluation tracks improvement or deterioration, which the doctors will need to determine how to treat the patient.

Complications of decompression sickness can include permanent neurological damage, osteonecrosis (bone death), or chronic pain syndromes. That’s why all decompression sickness cases require follow-ups. The protocol includes neurological observation, monitoring for delayed complications, and determining fitness and whether to return to diving.

Prevention is still much better than treatment for decompression sickness. Although present-day hyperbaric therapy is quite successful in the majority of instances, permanent disability may occur in some patients even with the best treatment. This reality underscores the importance of adhering to safe diving procedures and maintaining conservative decompression management.

Returning to Diving After Decompression Sickness

The decision to return to diving after suffering decompression sickness needs diligent medical assessment and consideration of various factors. There is no consensus among diving professionals regarding return-to-diving standards. Divers must undergo a complete neurological recovery before returning to diving can even be considered. Residual neurological symptoms or signs significantly increase the risk for future decompression sickness events and can be worsened by additional diving activity. Always consult with diving medicine physicians before making your decision.

The time required for decompression sickness treatment to return to diving varies according to the severity of the incident and individual recovery. Mild Type I DCS can allow a return to diving in weeks, whereas severe Type II DCS can require months of recovery or may require stopping diving altogether. Even in mild cases, most diving medicine specialists recommend waiting at least a few weeks.

Decompression sickness may result in medical conditions that can permanently disqualify individuals from diving. These can include severe residual neurological damage, specific cardiac abnormalities discovered on examination, or results that would point to increased susceptibility to future events. Divers who return to diving after experiencing decompression sickness require ongoing medical monitoring and surveillance to detect delayed complications and assess their ongoing fitness for diving activities. Any new symptoms or issues justify prompt medical evaluation.

Conclusion: Prioritize Safety in Every Dive

Decompression sickness is perhaps the most serious risk associated with diving, but it is also largely preventable through proper education, conservative dive planning, and sticking to established safety protocols. Take the time to research DCS physiology, learn how to recognize predisposing characteristics, and familiarize yourself with proper treatment of suspected cases, as it can be a matter of life and death.

The key message to all divers is that conservative diving methods provide maximum protection against decompression sickness. These include conservatively planning dives within no-decompression limits, controlling ascent rates, performing safety stops, maintaining physical fitness, and staying properly hydrated. While these practices are no guarantee against DCS, they significantly reduce risk and provide safety buffers for unforeseen events.

Every dive must begin with a commitment to safety that prioritizes the long-term enjoyment of diving over short-term thrills. The ocean will always be there, but taking unnecessary risks with decompression can end your diving career permanently or even cost your life. Conservative diving practices, continued education, and respect for the physical limitations of human physiology under pressure provide the foundation for a safe and long diving career.