Decompression Sickness Signs, Symptoms

Updated February 5, 2022

Decompression Sickness Signs, Symptoms & Prevention

With proper training and a responsible approach, you have a pretty strong probability of diving safely. That is not to say, though, that there are not inherent dangers to prepare for. If you are an inexperienced diver or have been away from it for a while and are thinking about jumping back in there for a liveaboard to the Galapagos or the Red Sea, it would be well worth your while to get a little refresher on how to dive safely in order to avoid one of the biggest hazards in scuba diving, decompression sickness. Here we will take a close look at it and its implications, and present some tips to prevent it from happening to you.

What is Decompression Sickness?

Air is made up of approximately 78% nitrogen and 21% oxygen. On descent under increasing pressure nitrogen is taken into the body’s tissues. The deeper and longer the dive the more nitrogen is taken up by the body. While maintaining a position at depth the nitrogen poses no threat. Then on the ascent, the pressure decreases, and nitrogen is released through the lungs by breathing out. If the ascent is faster than the rate of nitrogen release through breathing, bubbles will form in the tissues and blood like the classic example of opening a soft drink too quickly.

In order to avoid this dangerous situation, dive tables and dive computers with algorithms based on the tables were created to provide guidelines to show divers how long to stay at various depths to decrease the risk of these bubbles forming when pressure is decreased on an ascent. If the no-decompression limits from tables and dive computers are followed, divers use a safe ascent rate (revised by many training agencies to no faster than 10 meters (33 feet) per minute), and also include a safety stop of 3 minutes at 5 meters (15 feet) for additional outgassing, the risk of decompression sickness is greatly reduced.

Signs and Symptoms of Decompression Sickness

The is a great variety of signs and symptoms of decompression sickness with a range of severity depending on where the nitrogen bubbles have migrated to. The range goes from relatively minor joint pain, numbness, or tingling to death.

This list contains the most common signs and symptoms of decompression sickness:

pain in joints, arm and leg muscles, and/or torso
itch, rash, mottling of the skin
headache, lightheadedness, fatigue, malaise, nausea/vomiting
numbness, tingling, paralysis
dizziness, vertigo, ringing in the ears
motor weakness
confusion, personality changes, memory loss, bizarre behavior
impaired coordination
hearing problems
lymphatic swelling
bladder and bowel dysfunction
the “chokes,” breathing problems, pain in the chest, coughing, shortness of breath
coughing up blood, frothy sputum
uncontrollable shaking

These signs and symptoms of decompression sickness often appear between 15 minutes to 12 hours after surfacing. In extreme cases, they may appear even before reaching the surface or immediately thereafter. The onset of signs and symptoms after 12 hours does happen on rare occasions, especially if diving is followed by air travel.

Other Factors Influencing the Onset of Decompression Sickness

General physical fitness, amount of exertion, environmental factors, and consumption behavior are all factors that can influence susceptibility to decompression sickness.

More specifically here are some of those factors:

Dehydration reduces blood circulation slowing nitrogen elimination.
Injuries or illness can reduce circulation leading to the affected parts of the body decreasing the speed of nitrogen elimination.
Being overweight – Nitrogen elimination is slower from fat than muscle.
Age – Circulation slows down as you get older making gas exchange slower as well.
Cold water reduces circulation to the extremities as a diver gets colder during a dive slowing nitrogen elimination there.
Alcohol – Consuming alcoholic beverages affects nitrogen elimination by changing circulation patterns, encouraging dehydration, and dilating capillaries.
Excess carbon dioxide in the system alters circulation and gas exchange. This is achieved by skip breathing which should not be done under any circumstances.
Heavy exercise before, during, and after diving speeds up circulation so that more nitrogen than normal dissolves in the body and alters nitrogen elimination.

Treatment For Decompression Sickness

If you observe any of the signs or symptoms and suspect it may be decompression sickness, emergency medical services should be contacted immediately. If additional help or advice is needed, you can contact the DAN (Divers Alert Network) hotline 24 hours a day at +1-919-684-9111. Even minor symptoms should be treated seriously and first aid administered. First aid for any case of suspected decompression sickness regardless of the severity of symptoms is the same. The affected diver should lie down on the left side with head and neck supported by some sort of cushion and kept warm. The victim should be administered 100% O2 and rest in position until emergency services arrive.

Hopefully, a hyperbaric chamber is available nearby where the patient can be put back under pressure while continuing to breathe 100% O2. Back under increased pressure again the excess nitrogen can be reabsorbed into the tissue and slowly released. For severe cases recompressing in a chamber is the only effective means of treatment. It can take many hours to complete. In cases of minor symptoms, emergency medical personnel and doctors may decide the chamber is not necessary.

Do not under any circumstances take the victim back into the water to recompress. It could exacerbate the situation and put the victim at greater risk.

To increase your skills and confidence in emergency situations you could consider taking a rescue diver course where you learn about and get practice in simulated emergency conditions. A part of the process includes diving first aid and O2 usage.

Prevention Measures

Plan your dive and dive your plan within the recreational no-decompression limits.
Make your ascents at a rate of 10 meters (33 feet) per minute or less. Remember the air in your BCD will expand so make sure to maintain neutral buoyancy by releasing air before and as you ascend.
Do a safety stop of at least 3 minutes at 5 meters (15 feet) to provide an extra margin of time to safely off-gas nitrogen. Release more air from your BCD if necessary to maintain neutral buoyancy.
Plan your dive so that you will have enough air in your tank to accomplish your ascent and your safety stop without any worries of running out.
An ascent line, if available, can provide an extra measure of security to help maintain the prescribed ascent rate as you move toward your safety stop. If you have become positively buoyant, you can grab the line on the ascent and at the safety stop depth.
If you have done a deep dive or been in cold water or unusually rigorous conditions, adding extra time to the safety stop provides an extra margin of safety.
Do not fly or drive to a higher elevation within 12 hours if you have done a single dive. For multiple dives, PADI recommends waiting for 18 hours minimum and 24 hours ideally.

Dive Safely and Confidently Enjoy Your Diving

Please keep in mind the dangers of decompression sickness, follow these guidelines, and you can help assure a safe and satisfying experience diving.

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