DCI – Signs and Symptoms

Symptoms and SignsDEMP of DCI

General – Anorexia, Excessive fatigue, Malaise, Headache, Vomiting

Pain – Joint pains, Ear pain, Chest pain

Skin – Itching, Redness, Marbling

Level of consciousness – Strange speech and thoughts, Disorientated in time and place, Personality change, Dysphasia (difficulty speaking)

Hearing and vision – Hearing loss, Vertigo, Tinnitus, Visual impairment

Strength – Weakness of limbs, Sensation, Paraesthesia (pins and needles), Numbness

Co-ordination – Unusual gait, Poor balance

Bladder and bowels – Incontinence

Pulmonary – Cough, Shortness of breath, Voice changes, Haemoptysis (coughing up blood)

Who do I call for Advice ? Call London Hyperbaric Medicine on(+44) 020 8539 1222  if you are within easy striking distance of London or the Royal Navy Helpline on 07831 151 523  (24 hours)

What is DCI?

Decompression Illness(DCI) is a term used to describe both Decompression Sickness (DCS) and Cerebral Arterial Gas Embolism (CAGE). It is caused by the expansion of inert gas bubbles (Nitrogen) into tissues on decreasing pressure. The tissues affected tend to be those tissues with a poorer blood supply, as the nitrogen is less readily removed. Three gas laws are of particular importance with regard to DCI;

Boyle’s Law states “for any gas at a constant temperature, the volume of a gas will vary inversely with the absolute pressure”.
Dalton’s Law states “the total pressure exerted by a mixture of gases is equal to the sum of the pressures of each of the different gases making up the mixture, with each gas acting as if it alone was present and occupied the total volume”.
Henry’s Law states “the amount of any given gas that will dissolve in a liquid at a given temperature is a function of the partial pressure of that gas in contact with the liquid and the solubility coefficient of the gas in the particular liquid”.

As can be seen from the above at deeper depths more nitrogen will be dissolved in tissues, on ascent the nitrogen will come out of solution forming bubbles which if they cannot be removed will cause the symptoms of DCI. It is the bubble size rather than the fact that they are nitrogen that causes the problems.

Decompression Illness First Aid

Initial treatment for decompression illness (DCI) or arterial gas embolism (AGE) is the same for either condition.
Remember:
Airways
Breathing
Circulation
(Defibrillation)

  • Give 100% oxygen (by means of a tight fitting mask).
  • Lay the casualty down and keep them horizontal.This prevents conditions worsening with bubbles traveling to the brain. If the diver loses consciousness put the diver into the recovery position.
  • Give fluids orally (aim for 1 litre an hour and no alcohol or caffeine). Only give if the casualty is able to take them unaided and ideally the fluid should be isotonic.
  • Keep the patient comfortable.
  • Protect against Hypothermia. Cover with blankets or thermal shields.
  • Consider the buddy, are there two or more casualties?
  • No in-water recompression.
  • The only effective treatment is recompression, seek medical help immediately.
  • Never give Entonox to suspected DCI / AE cases.

Contact London Hyperbaric Medicine for training in DAN or BSAC Oxygen Administration and DAN Automated External Defibrillation (AED). Call 020 8539 1222 for your training needs.

Risk Factors for DCI

The following are examples of factors that can increase the chance of DCI and is not meant as an all-inclusive list.
Depth of dive – Dives deeper than 40m are an independent risk factor for DCI
Inadequate decompression – Remember most computers are based on theoretical data. Tables are often based on fit young men (e.g. USN tables based on Navy divers), most recreational divers do not fall into this category! It is always safer to do slightly longer decompression than is the minimal requirement according to the computer/tables.
Repeated dives – Following a dive the body will have a residual nitrogen load, this needs to be taken into account when planning the following dive(s).
Patent Foramen Ovale (PFO) – This is a communication between the right and left side of the heart through the wall between the two upper chambers (atria). Due to pressure changes at birth, in the majority of the population it closes and seals. If it remains open blood can be shunted from the right (deoxygenated) side to the left (oxygenated) side of the heart bypassing the lungs, any nitrogen bubbles in the blood will not be filtered out by the lungs and will be able to pass into the arterial circulation and to the brain.
25% of the general population have a PFO but up to 75% of those with unexplained DCI have a PFO. A test involving an ultrasound scan of the heart (echocardiogram) and injecting a saline solution that has been vigorously mixed with blood can be performed in divers with unexplained DCI to determine whether they have a PFO.
Equipment failure – Not always avoidable but check kit thoroughly before diving and ensure you know how to use any new kit and have checked it at shallow depth.
Alcohol – A frequent contributing factor for DCI, consumption the night prior to a dive causes a degree of dehydration which will increase the chance of DCI.
Smoking – Causes blood vessels to vasoconstrict which will reduce tissue perfusion. Increases amount of CO (carbon monoxide) in the blood which reduces the bodies oxygen carrying capacity.
Temperature – Cold water increases the oxygen demand on the body.
Obesity  – Fat is five times more soluble to nitrogen than muscle, so there is an increased nitrogen load.
Gender – There is some evidence to suggest that there is an increased chance of DCI for women mid-menstrual cycle. Men are more likely to have an episode of DCI than women due to risk taking behaviour.
Flying – At altitude there is a lower partial pressure of each gas. According to Boyle’s Law the volume of a gas will therefore increase. If nitrogen bubbles are present their volume will increase, worsening any symptoms of DCI. In view of this it is recommended that flying be avoided until 12-24 hours after a dive.

Treatment

Hyperbaric oxygen therapy is required, until a hyperbaric facility is reached, oxygen via a mask with a reservoir bag and re-hydration should be commenced.
Hyperbaric oxygen causes a reduction in the size of the bubbles by increasing the pressure (Boyle’s Law) and an increase in the rate of removal of the nitrogen by increasing the concentration gradient (Henry’s Law).
Different facilities will use different recompression tables. At London Hyperbaric Medicine we use the COMEX 30 table, and US Navy Tables 5 and 6 for the treatment of DCI.
Divers with DCI require multiple treatments depending on their degree of symptoms. Divers are generally treated until all symptoms have resolved or until further treatments do not produce any further improvements in symptoms.