What is Decompression Illness?

There are two mechanisms that fall under the broad term of DCI.  Both may result in bubble formation during or after an ascent from a dive when compressed gas is used.  These are Arterial Gas Embolism (AEG) and Decompression Sickness (DCS).

AEG is caused when gas in the lungs expands and cannot escape quickly enough causing areas of the lung to overstretch and rupture.  The gas is forces into the surrounding blood vessels in the lungs where it is carried to the heart and then directly to the arterial blood supply of the brain, heart and other organs.

DCS occurs when a diver ascends too quickly for the nitrogen in their tissues to pass through the lungs in an orderly way.  This nitrogen forms bubbles in the tissue or in the veins during and following an ascent.

Let’s reinforcing this important point: Pay attention to symptoms presenting within 24-48 hours after diving. These should be considered diving-related until demonstrated to be otherwise. Oxygen first aid should be commenced immediately if available and expert medical advice sought promptly by calling a DAN Hotline. The sooner this is done, the better.

Risk Factors of DCI:

A number of predisposing factors are thought to increase a diver’s chances of suffering DCI. On most dives, much more dive time is spent absorbing nitrogen than is allowed for it to be eliminated during the ascent phase. Any factor that will increase nitrogen uptake and distribution during the dive, such as those causing an increase in circulation is likely to increase the risk of DCI. In addition, anything that reduces nitrogen elimination during the ascent phase, including factors that reduce circulation during this phase, may also increase the likelihood of DCI.

There are good data to support some of these predisposing factors. Others are theoretically likely to increase the risk and appear to be supported by anecdotal reports, but remain unproven through lack of appropriate studies. Some of the risk factors of DCI relate to the physical and medical condition of the diver (i.e. body fat, age, previous DCI, dehydration), some to the dive itself (i.e. depth, repetitive diving, rate and frequency of ascent), while others to activities after the dive (i.e. exercise, altitude exposure).

What Can I Do to Try to Avoid Getting DCI?

There are some strategies that divers can use to try to minimize the risks, these include:

• Don’t dive if you are not medically or physically fit enough to do so.
• Ensure you are well-hydrated.
• Avoid dives close to the limits of the dive computer or table used.
• Ascend slowly and avoid multiple ascents.
• Complete safety stops.
• Avoid deep or very long dives.
• Avoid dives that require mandatory decompression stops.
• Plan repetitive dives conservatively and maximize surface intervals.
• Use nitrox.
• Avoid going to altitude too soon after diving, including flying after diving and driving over mountains after diving.

Common Signs and Symptoms of DCI:

Common Signs and Symptoms of DCI include numbness / tingling, nausea, headache, feeling unwell, rash, weakness, pain/discomfort at the joint, dizziness, chest/torso or back pain; and extreme fatigue. Numbness and tingling are very common symptoms as is extreme fatigue. Such symptoms, if relatively mild, are often overlooked or thought to be due to something other than DCI, such as muscle strain; as a result first aid and treatment is often delayed.

Other signs and symptoms include blotchy skin, confusion, convulsions, coughing, death, difficulty breathing, difficulty passing urine, hearing loss, lack of coordination, itch, loss of balance, loss of bladder/bowel control, paralysis, personality change, ringing in ears, impaired responsiveness, speech disturbances, visual disturbances.

Did you know:

The signs and symptoms of decompression illness (DCI) are many and varied as bubbles can affect a variety of body organs, including the brain, spinal cord, nerves, lungs, heart, tendons, muscles, bones, skin, bladder and inner ear.  The severity can range from almost undetectable minor symptoms, such as mild tingling in a fingertip, to severe life threatening symptoms such as unconsciousness and absent breathing.

The development of symptoms of decompression illness (DCI) can be progressive. For example, what starts as tingling in the feet can sometimes develop into weakness or even paralysis in the legs, so it’s important to start appropriate first aid quickly rather than ignoring the symptoms.

DCI Treatment:

Emergency treatment for DCI is immediate 100% Oxygen as soon as symptoms are noticed.   Seek expert professional medical attention immediately by calling the DAN Hotline.  Don’t rely on a Dive Master making a judgement.

The proper treatment for DCI is recompression in a chamber whilst breathing 100% Oxygen. Recompression provides a number of benefits which include:

• It immediately reduces the size of the bubbles in the diver’s blood and tissues. If bubbles in the blood are blocking blood vessels, reducing their size can help restore better blood flow. If bubbles are pressing on nerves and other body systems, compressing them can help to relieve this.
• Recompression greatly increases the pressure difference between the inert gas in the bubbles and in the surrounding tissues and the lungs which encourages the inert gas to move out of the bubbles, into the tissues and into the lungs where it is exhaled.
• Recompression also causes more oxygen to dissolve in the blood and be delivered to body tissues in need of it, as well as reducing inflammation.

Adapted from John Lippmann’s book Decompression Illness