Compressed Gas Breathing First Aid And Resuscitation
Compressed gas breathing SCUBA divers breathe gas (usually air) while underwater. Most commonly, divers use self-contained underwater breathing apparatus (SCUBA) and breathe from cylinders containing oxygen and nitrogen carried underwater.
However, the breathing gas can also be supplied via a surface-supplied breathing apparatus (SSBA). Divers are vulnerable to various potential injuries and illnesses, including ear injuries, drowning, carbon monoxide poisoning, carbon dioxide poisoning, and heart attack.
These can be managed by the usual first aid and resuscitation protocols outlined in various ANZCOR Guidelines. However, breathing compressed gas underwater can lead to several unique medical problems, the most significant being decompression illness (DCI) and pressure damage of the lungs called pulmonary barotrauma (PBT).
Australian hyperbaric units treat an average of 125 cases of DCI a year. Twenty-nine per cent of calls to an Australian-based diving emergency hotline were due to suspected DCI, compared to 1% from PBT.
Decompression illness and pulmonary barotrauma require special first aid considerations, including the prompt and continued administration of near 100% oxygen. This is different from most other first-aid uses of oxygen, as detailed in ANZCOR Guideline 9.2.10, which should be read in conjunction with this guideline.
What Is Decompression Illness
Oxygen and nitrogen from the inhaled gas are dissolved in the diver’s blood and body tissues during an air dive. The body uses the oxygen, but the nitrogen remains dissolved in the diver’s blood and tissues. Unless the diver ascends slowly enough to allow excess nitrogen to leave the body gradually through the lungs, nitrogen comes out of the solution.
It may form bubbles in the diver’s blood and body tissues. The physical effects of these bubbles and their biochemical changes can cause a lack of blood supply (ischaemic) and inflammatory tissue damage. This is known as decompression sickness (DCS). Some deep divers breathe mixtures of gas containing helium and may face the same problems due to helium bubbles.
What Is Pulmonary Barotrauma
As a diver ascends, the gas in the lungs expands with reducing ambient pressure, and, unless expanding gas is adequately exhaled, the diver’s lungs can distend and tear. This can result in a collapsed lung (pneumothorax) and trapping of gas in the mediastinum (mediastinal emphysema) or under the skin (subcutaneous emphysema).
Escaped gas may also enter the arterial circulation and distribute to the cerebral circulation causing cerebral arterial gas embolism (CAGE), causing stroke-like symptoms and signs.
Defining Decompression Illness Terminology
The term decompression illness (DCI) collectively describes both DCS and CAGE. It is unnecessary to differentiate between these in the emergency setting as the First Aid and more advanced treatment are the same for both conditions.
Decompression Illness Signs And Symptoms To Look For
DCI is associated with a wide range of potential symptoms and signs, from minor to rapidly fatal. Common symptoms and signs include:
• Pain (often at or near joints)
• Extreme fatigue/feeling unwell
• Muscle weakness in one or both arms and legs
• Mottled skin rash
• Poor coordination
• Altered consciousness
Signs Of Pulmonary Barotrauma After Scuba Diving
• Chest pain
• Difficulty breathing
• Blueness of lips and tongue (cyanosis)
• Voice changes
• Difficulty swallowing
• ‘Crackly’ skin around the neck (crepitus)
• Symptoms and signs of decompression illness may also be present.
Management Strategies For Divers With Decompression Illness
• If the person is not responding and is not breathing normally, commence resuscitation following the ANZCOR Basic Life Support DRSABCD protocols. A person with DCI may regain consciousness and appear to have recovered but still needs to be managed for suspected DCI due to the possibility of relapse.
• Promptly provide as close to 100% oxygen as possible if available and trained to do so and continue to do so until the ambulance or evacuation personnel arrive and take over management. Near 100% oxygen should be administered even if pulse oximetry indicates a high oxygen saturation.
• If early-onset DCI is suspected (within 30 minutes of surfacing), lay the person flat if possible.
• Seek immediate diving medical advice by calling the nearest public hospital diving and hyperbaric medicine unit (in Australia) or the Diver Emergency Service (0800 4 DES 111 in New Zealand).
• Assist with any transfer to a recompression chamber if requested.
• The consulting diving doctor may advise that an alert and stable person thought to be suffering from DCI may freely drink non-alcoholic fluids, such as water or isotonic/electrolyte fluids (as long as they have no stomach cramps, nausea, urinary retention or paralysis).
• The person should be kept thermally comfortable (warm but not hyperthermic).
• Record details of the dive(s), the symptoms and signs (and their timing), the first aid given and the response to the first aid.
Rationale Behind Horizontal Positioning For Suspected DCI
A flat (horizontal) posture without leg elevation is recommended in persons suspected of DCI as it has been shown to increase the rate of inert gas elimination. It may also reduce the likelihood of arterial bubbles distributing to the brain. An unconscious diver should be managed in the ‘recovery position’.
However, a conscious person having increased difficulty breathing when supine can be placed in a position of comfort. The administration of 100% oxygen reduces the size and number of gas bubbles in the blood and tissues by helping to eliminate the inert gas.
The Australian and New Zealand Committee on Resuscitation (ANZCOR) makes the following recommendations in summary for First Aid and Resuscitation for divers who have breathed compressed gas:
1. Send for an ambulance early in the treatment of suspected decompression illness or pulmonary barotrauma and promptly contact the nearest public hospital Diving and Hyperbaric Medicine Unit (in Australia) or Diving Emergency Service Hotline (New Zealand) for specialist diving medical advice.
2. Provide near 100% oxygen to the person as soon as possible and continue oxygen administration until relieved by medical personnel. (Near 100% oxygen should be administered even if pulse oximetry indicates a high oxygen saturation).
3. Manage the person horizontally if early-onset decompression illness is suspected. Otherwise, and in the event of breathing difficulty, the person can be managed in a position of comfort.
4. Record details of the dive(s), the symptoms and signs, first aid provided and response.
5. An alert and stable person suspected of having decompression illness may drink non-alcoholic fluids as advised by the diving doctor.
6. Keep the person thermally comfortable.
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