Dysbarism (Decompression Illness)

Background

Please discuss ALL cases of possible barotrauma or drowning with the EM Consultant on call.

The Irish Naval Service provides a recompression service to civilian divers. We (CUH Emergency Medicine Service) will be providing clinical advice and support. Doing this will involve the following:

• Divers requiring recompression will first be assessed at CUH emergency department
• Any investigations or clinical interventions (e.g. chest drains etc) will be done here prior to transferring the patient to the RCC at Hawlbowline
• The Irish Naval Service will be alerted by us (Medico Cork) as per their SOP
• The chamber will take about one hour to be readied
• The diver will be accompanied to Hawlbowline by a nurse at least, and by the clinician (those on this list and/or Dr John Murphy INS) if necessary
• It will not usually be necessary for the clinician to be in attendance on site for the treatment

Clinical advice and support are available from the Royal Navy Duty Diving Medical Officer in Portsmouth 0044 7831 151 523. We should of course be in a position to support each other.

It may be necessary to enter the chamber on occasion. Each clinician must have a ‘diving medical’ (including spirometry and audiometry) and have experienced of being compressed to 18m.

Air Ambulance Ops Notice 3/08

Diving Emergencies Contact No. and protocol

Dive Chamber Regions and Information:

Initiating Control, please check if Ambulance is required at receiving Dive Chamber location.

Southern Region;

All Hospitals south of: Athlone-Dublin-Galway

Contact Ambulance Control; (021) 4546418.

Northern Region;

All Hospitals north of Athlone-Dublin-Galway

Contact Coastguard Control, (01) 6620922

United Kingdom Chamber;

Plymouth: +44 (1752) 209999

Out of Hours; +44 (870) 2385001

Aero-medical Support Services;

Irish Air Corps; (01) 4037502/4037800

Irish Coastguard; (01) 662092

Decompression sickness clinical

Is caused by accumulation of nitrogen (bubbles) in tissues. Suspect decompression sickness, (the "Bends", dysbarism) in any patients with a history of a dive within last 48 hours who presents with:

• Joint pains (dull ache, unaffected by movement, "niggles" may flit between joints)
• Neurological symptoms (however vague). Particularly changes in mentation, sensation, coordination, audiovestibular function, cerebellar symptoms or fatigue. Neurological signs (equivocal or definite, particularly cranial nerve deficits)
• Skin rashes (pruritis, erythema, marbling of the skin)
• Constitutional symptoms (malaise, extreme fatigue, the shivers)
• Lymphatic oedema (esp. face, neck or breast)
• SOB - (the "chokes") - caused by massive embolisation of the pulmonary vasculature by venous bubbles

Have a low threshold for diagnosing decompression sickness, even in those with safe diving practice. Beware of those who have transient neurological symptoms ("TIAs"), as these may resolve then progress to full neurological deficit with an inflammatory response and clot formation at the site of the original transient bubble.

Boyle's law

The the volume of a fixed mass of gas is inversely proportional to the absolute pressure (assuming constant temperature)

Henry's law

At a constant temperature the amount of gas that will dissolve in a liquid is proportional to the partial pressure of the gas over the liquid("Heineken law")

Dalton's law

In a mixture of gases, the partial pressure of each gas present is equal to the pressure that gas would exert if it alone occupied the original volume. P(total) = P(1) + P(2) +.....P(n)

Pulmonary barotrauma (POIS = Pulmonary Over Inflation Syndrome)

Results in:

1. Arterial Gas Embolism
2. Pneumothorax
3. Mediastinal or surgical emphysema
4. Pneumoperitoneum

History

• Get as detailed dive history as possible - particularly gas mixtures used, depth and duration, decompression stops
• Record if symptoms occurred on descent or ascent or how long after dive completed
  • Inner or middle ear (tympanic membrane) trauma usually have difficulty clearing on descent
• Note past medical history (particularly previous Decompression Illness), respiratory and ENT status

Management

Initial measures aim to increase oxygenation (hasten removal of nitrogen from tissues and treat tissue hypoxia) and hydration (dehydration and haemoconcentration occur due to insensible losses to the environment).

AVOID ENTONOX

Airway

• 100% oxygen by face mask, to hasten inert gas elimination
• Rapid sequence intubation (RSI)if airway not protected
• Left lateral position (not "head down" as may raise intracranial pressure)

Breathing

• Chest drain if pneumothorax, surgical emphysema or pneumomediastinum
• Even if only problem appears to be pulmonary barotrauma, refer to diving medicine unit anticipating 2° deterioration)

Circulation

• IV fluids (increased vascular permeability causes third space losses)
• ± urinary catheter

Disability

• Neurological examination (including gait assessment if possible)
• Diazepam for fitting