[Section head]
21 Environmental Emergencies
[Chapter head]
21.xx the pt with a
Diving Emergency
Concepts used in this chapter include:
[sub head]
Overview

A large number of Australians engage in compressed gas diving for recreational,
scientific and occupational reasons.

All patients with complaints after diving should seek some form of medical
advice. Some of them will need specialist hyperbaric unit review.

Symptoms can range from minor ear pain to sudden death

Prehospital management of patients with significant diving related illness should
involve oxygen, positioning the patient supine, fluids and transport to a
recompression facility

Exposure of patients to altitude may worsen symptoms
[sub head 1]
Case Study
Case xxxx,15:30. Dispatch Details: A 24 year-old female was involved in a training
dive to 10 meters for 10 minutes, when she panicked and rapidly ascended to the
surface. She cried out on surfacing and lost consciousness immediately afterwards.
She was rescued into the boat and is returning to shore. The boat ramp is 20
minutes from the nearest tertiary hospital and 45 minutes from the nearest
hyperbaric chamber.
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Initial Presentation, 16:05: The ambulance crew finds the patient dressed in a
wetsuit lying on the deck of the boat receiving high flow oxygen via a face mask.
She is confused and agitated. She has a dense right hemiparesis. Her observations
are unremarkable apart from a GCS of 13.
[sub head 1]
Definition
need ref
[sub head 1]
Pathophysiology
Most diving related emergencies result from the consequences of a diver’s exposure
to air (or other gasses) at higher than normal pressure. There are two broad
categories of problems
1. Barotrauma
2. Decompression sickness (or the bends)
[margin note]
[end note]
1. Barotrauma
Barotrauma refers to physical damage to tissues caused by changes in volume of
gas filled spaces as a consequence of changes in pressure. It arises as a
consequence of Boyle’s law which states that at constant temperature, the volume of
a gas is directly proportional to the pressure of that gas. This means that if the
pressure of a gas doubles its volume will halve and vice versa. The pressure at sea
level is about 100 kilopascals or one atmosphere absolute (ATA). Pressure
increases by one atmosphere for every 10 meters a diver descends (see table).
Depth (meters
of seawater)
Pressure
(ATA)
Gas volume
Gas density
Surface
1
100%
1
10
2
50%
2
20
3
33%
3
30
4
25%
4
2
.
.
.
.
60
6
16%
6
etc
Barotrauma can occur as the diver is descending or ascending. Descent barotrauma
is caused by gas filled spaces becoming smaller as the pressure increases and
ascent barotrauma is caused by gas filled spaces becoming bigger as pressure
decreases. Any gas filled space in the body can be affected by barotrauma but the
most clinically significant things affected are the, sinus, face mask, ears and, most
importantly the lungs.
Sinuses
Sinus barotrauma occurs on descent. As the pressure surrounding the diver rises,
the volume of gas in the sinuses tends to decrease. Unless gas is added to the
sinuses, the decrease in volume will casue some tissue damage, namely oedema
and bleeding. Symptomatically the diver will experience pain in the sinuses which
may be relieved by ‘equalising’ the pressure. If the diver continues the dive the pain
will decrease as the sinuses become filled with oedema fluid and blood. On ascent
this fluid and blood will be expelled through the nose. Sinus barotrauma is self
limiting and does not cause serious morbidity.
Ears
Lungs
2. Decompression sickness
Decompressin sickness (DCS) is an acute condition that occurs following an acute
reduction in ambient pressure. It is caused by bubbles which form when the partial
pressure of a gas dissolved in the blood or a tissue exceeds the ambient pressure.
DCS was first described in compressed air workers in tunnels in the 19th centurty
(Caisson disease) and subsequently observed in divers, high altitue pilots and
astronauts.
Bubbles can form in the venous blood or in pretty much any tissue. Bubbles cause
symptoms by both direct mechanical effects and by acting at the cellular and tissue
level. Bubbles can cause endothelial disruption, complement activation, platelet
activation, nitric oxide production and leukocyte activation.
Commonly affected tissues include:
Tissue/organ affected
Effects
Joints/bones
Local pain (may be severe). Bone necrosis if repeated
Spinal Cord
Neurological symptoms
Veins
Spinal cord venous stasis and infarction. Cardiopulmonary
collapse with massive bubble load blocking the pulmonary
venous circulation. Arterial bubbles if there is a right to left
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shunt present
Brain
Any conceivable neurological symptom or sign
Inner ear
Vertigo and hearing loss
Skin
Rash and bruising
[box]
Definitions: Decompression sickness (DCS) is caused by bubbles forming from
gas coming out of solution. Arterial gas embolus (AGE) is caused by bubbles
moving directly from the alveolus to the arterial circulation. Decompression illness
(DCI) describes both decompression sickness and arterial gas embolus.
[end box]
[sub head 1]
Clinical Reasoning 1: Assessment
Patient History
This patient has serious neurological symptoms and signs following a rapid ascent
form a short, shallow dive. She almost certainly has a cerebral arterial gas embolus.
Given that the diagnosis is not in doubt the issues for the paramedics are about how
to prevent the situation from deteriorating and what is the most appropriate transport
destination.
An initial set of vital signs will act as a baseline against which to measure any
changes.
[box]
HISTORY
Ask!
Details of the dive (depth, duration, first dive of the day?)
Are the symptoms better or worse?
[sub head 1]
Clinical Reasoning 2: Confirm!
Are You Sure?
Part of the clinical reasoning process is to take your initial hypothesis and seek to
confirm of challenge it by finding clinical signs that should occur with your provisional
diagnosis.
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What other possibilities are there? It is unlikely that the presentation could be due to
another diving related cause (and unimportant given that the prehospital treatment
doesn’t change. A non diving related cause is also unlikely given the history.
[box]
DIFFERENTIAL DIAGNOSIS
Cerebral arterial gas embolus, or
Trauma
Toxins
Hypoxia
CVA
Subarachnoid haemorrhage
Hypoglycaemia
Cardiovascular
[sub head 1]
Clinical Reasoning 3: Treatment
Emergency Management
Safety
Pissing in boats
Positioning
If the patient has circulating arterial bubbles then these bubble may travel against the
direction of blood flow to whichever area of the body is highest (ie they will ‘float’).
So if the patient is positioned with the head up bubbles will go to the brain and
worsen the damage.
Because of this it is vital that patients with possible CAGE are kept supine at ALL
times.
[box]
DISCUSSION TOPIC: If bubbles travel to whichever part of the body is the
highest, why not transport them feet up?
[end box]
Detail yes
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Oxygen
Oxygen is indicated for all patients with significant diving related illness. Bubbles are
in equilibrium with gas dissolved in the surrounding tissues, so, in patients breathing
air, they are composed mainly of nitrogen..why (with smaller amounts of oxygen,
carbon dioxide and water). By eliminating nitrogen from the inspired gas the nitrogen
in the bubbles will be reabsorbed into the venous circulation and the bubbles will
shrink. So some oxygen is good, more is better and 100% inspired oxygen is best.
Transport
Definitive management of cerebral arterial gas embolus is recompression in a
hyperbaric oxygen facility, and transport should not be delayed in these patients. If
possible the patient should be transported to a hosital with a hyperbaric facility and
other hospitals should be bypassed, unless there are procedures such as
endotracheal intubation and resuscitation that are immediately required and are
beyond the skills of the crew in attendance. Notification of the receiving hospital with
patient details (including the details of the dive) can assist in preparing the hospital.
A phone call to the Diver’s Emergency Service can help the paramedics with
treatment advice and contact with hyperbaric staff at the treating facility.
[box]
The Diver’s Emergency Service: The Royal Adelaide hospital Hyperbaric Unit
provides a 24 hour medical specialist cover of the Divers Emergency Service (DES)
telephone. This can be accessed by calling:
Within Australia (Toll Free) 1800 088 200
Outside Australia +61-8-8212 9242
The service primarily acts as a consultation service for diving-related emergencies.
The hyperbaric specialist on the DES phone can provide diagnostic and treatment
advice as well as liason with local hyperbaric facilities
[end box]
[sub head 1]
On-Going Management Definitive treatment for decompression
illness is obviously not usually available in the prehospital environment so
management of conscious patients should be supportive of symptoms and all efforts
focussed on delivering the patient to definitive care.
[insert clinical reasoning model]
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Fluids
Endothelial damage caused by bubbles causes vasodilation and increased capillary
permeability leading to loss of circulating blood volume see SIRS. Administration of
fluids to support perfusion should be commenced according to local guidelines.
Consulting with the receiving hospital is recommended and transport must not be
delayed in order to gain IV access.
Pain Relief
Opioid pain relief should be considered according to local guidelines for patient
comfort but with careful consideration of side-effects.
[box]
PRINCIPLES OF MANAGEMENT
Decompression illness
POSITIONING: Keep the patient supine at ALL times
OXYGEN: 100%.
FLUIDS: To maintain perfusion
TRANSPORT: To recompression facility
SUPPORTIVE: Manage pain, nausea as required.
[end of box]
On-Going Management
Recompression therapy for decompression illness
Patients with DCI need recompression to resolve symptoms and help prevent long
term morbidity. All Australian and New Zealand tertiary hospital hyperbaric facilities
can offer full intensive care treatment and monitoring to patients in the hyperbaric
chamber.
Once assessed patients are placed in the chamber on 100% oxygen. The chamber
is then pressurised to at least 2.8 ATA (the equivalent of 18m of seawater) so the
patient has an FIO2 of 2.8ATA (compared with 0.2 in a patient breathing air at sea
level). The increased pressure will cause bubbles to shrink (in accordance with
Boyle’s law), and increase the partial pressure of nitrogen in the bubbles. The 100%
oxygen will create a large gradient for the nitrogen in the bubbles to be reabsorbed.
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The hyperbaric oxygen has a number of beneficial physiologic effects including
changes in neutrophil marginalisation, changes in nitric oxide levels and many
others.
Evaluate
[box]
EVALUATE
IS YOUR PT . . .
Protecting their airway and ventilating adequately?
Consider intubation to ensure airway protection and adequate ventilation.
Adequately perfused?
Commence or increase IV fluid infusion rate.
Ensure receiving hospital is notified.
[box]
SITUATIONAL AWARENESS
Suspect
call
[end box]
[sub head 1]
Long term Impact
[sub head 1]
Summary
Case Study 2
[sub head]
12:20. Dispatch: “Case xxxx, A 38 year-old male collapsed after climbing steps
following surfacing from a 30 minute dive to seven meters. Breathing but coughing
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pink, frothy sputum
[sub head]
ASSESS
12:33. Arrival at scene:
Patient is lying on a jetty at the top of a flight of steps.
He is anxious and looks unwell
12:40. Primary Survey:
Pt has a GCS of 13 (E3, V4, M6)
12.42. Pertinent Hx: Diving with a friend with a maximum depth of 7 meters. He
made four or five rapid ascents to the surface during the dive.
He developed severe shortness of breath after the last ascent
and collapsed walking up the stairs.
12.30. Vital Signs Survey: Difficult assessment due to the presence of a wetsuit
PEFUSION STATUS: HR 135 thready, Skin cool, pale
and clammy
RESP STATUS: RR 45 BPM, coughing. Pink frothy
sputum
CONSCIOUS STATE: GCS = 13, eyes closed,
confused
12:33. Secondary Survey: - No abnormalities found
12:34. Past Hx:
Heavy smoker, BMI 40.
[sub head]
CONFIRM
What is your provisional diagnosis?
1. Cardiovascular
2. DCI
3. Near drowning
4. Envenomation
5. Anaphylaxis
6. Poisoning
HOW WOULD YOU NARROW THESE?
[sub head]
ARE YOU SURE?
9
Explore your hypothesis and try to narrow it
[box]
Planning
Is this patient time critical?
Is this patient transport critical?
What other assessments do you need to consider?
Have you got enough history and scene assessment?
What are you management regimes you are considering?
[sub head]
TREAT
How would you treat this patient?
Consider your clinical decision making for this case and then turn the page.
[sub head]
ARE YOU SURE?
What else could it be?
1. Cardiovascular: A primary cardiac event is possible in an obese heavy smoker.
2. DCI: Coronary AGE is another possibility.
3. Near drowning: Near drowning does not fit the symptoms particularly well given
the rapidity of deterioration after the man exited the water by himself. Possible
4. Envenomation: The only envenomation which would fit this man’s presentation is
Irukandjii syndrome. This diagnosis needs to be considered if the incident occurred
in the Irukandjii jellyfishes distribution
5. Anaphylaxis: Allergen exposure underwater would be quite unusual but
anaphylaxis cannot be excluded.
6. Poisoning: Poisoning by contaminated gas is a possibility, a combination of
carbon monoxide and inhaled hydrocarbons could explain his symptoms.
This is a case where it is impossible to definitely make a diagnosis in the field and
the paramedics must manage the patient symptomatically and resolve the basic
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issues of airway, breathing and circulation before reassessing to see if the
underlying cause has become clearer.
[sub head]
TREAT
Oxygen @ 8l/min via BVM and breathing supplemented to 1212:40. Treatment:
16BPM @ 8-10mls/kg
Remove the patient’s wesuit
12:45. Evaluate:
PEFUSION STATUS: HR 124, Sinus Tach, BP
75/50, Skin cold and clammy
RESPIRATORY STATUS: RR 40 BPM, Air Entry L =
R, increased work of breathing, widespread fine crepitations
CONSCIOUS STATE: GCS = 9 (E2 V2 M5)
.
[head]
Case Study 3
[sub head]
A 40 year-old male complains of severe dizzyness and vomiting
following a 90 meter cave dive near Mt Gambier
11:15. Dispatch: “Case xxxx, A 40 year-old male has surfaced after a 90 meter
dive and developed vertigo and vomiting shortly afterwards. He is lying in a
paddock. Mt Gambier is a large town in the South East of South Australia. It is 4
hours by road from the nearest hyperbaric facilities in Adleaide and Melbourne. The
local hospital has an Emergency Department with 24 hour staffing and a High
Dependency Unit.
[sub head]
ASSESS
11:48. Arrival at scene: Crew are met at the paddock gate by a group of divers and
escorted to the patient, who is lying on the ground wearing a drysuit. The crew are
told that the diver became unwell shortly after climbing 15 meters up a rope ladder
following a 120 minute, 90 meter decompression dive using a closed circuit
rebreather, breathing trimix (a mixture of helium, oxygen and air). The other divers
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are adamant that the patient cannot be suffering from DCI because they dived
strictly according to the profiles provided by their computers.
Pt is lying supine and is conscious, but very
11:50. Primary Survey:
distressed. He says that the world is spinning around and he is very nauseous,
retching frequently.
11.51. Vital Signs Survey: PERFUSION STATUS: HR 115, Sinus, BP difficult to
assess due to clothing, Skin cold, clammy
RESPIRATORY STATUS: RR 24 BPM, SpO2 96%
(Air)
GCS: = 15
11:53. Pertinent Hx: The patient denies any significant past medical history or
allergies. He had a small amount of trouble clearing his ears at the start of the dive,
which was otherwise uneventful. He felt well until just after he finished climbing the
ladder.
11:54. Secondary Survey: Head - Profound nystagmus with rapid phase to the
left.
Neck - Nil abnormalities found
Chest - Nil abnormalities found
Abdo
- Nil abnormalities found
Pelvis - Nil abnormalities found
Limbs - Nil abnormalities found.
Back - Nil abnormalities found.
BSL - 6.1
Temp - 36.2 degC
[box]
HISTORY
Ask!
Medical Hx
Any illicit drugs or ETOH
12
[box]
SCENE MANAGEMENT:
Does the patient need immediate management? (Are A, B and C adequate?)
Is the patient time critical?
Do you have the resources you need to manage this patient?
Are you going to seek specialised hyperbaric advice or simply transport the patient to the
regional hospital?
[end box]
[sub head]
TREAT
11:55. Treatment:
Oxygen @ 15l/min via BVM
[sub head]
CONFIRM
What is your provisional diagnosis?
1. DCI
2. Inner ear barotrauma
3. Labyrinthitis
4. Stroke/SAH
HOW WOULD YOU NARROW THESE?
What else could it be?
1. DCI: The patient has neurological symptoms after a very deep dive.
Whilst AGE is unlikely in an experienced diver, DCI is certainly possible, even likley
2. Inner ear barotrauma: The patient’s symptoms are also entirely
consistent with inner ear barotrauma. The history of some difficulty with his ears at
the start of the dive supports this diagnosis
3. Labyrinthitis: Again the symptoms are consistent with labyrinthitis as a
diagnosis, although he would have to be a bit unlucky to develop symptoms
immediately after the dive!
4. CVA/SAH: Are possible but much less likely. Cannot, however, be
completely excluded.
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[sub head]
CONFIRM
This case has the potential to challenge the pre-hospital care provider who may not
be familiar with the intricacies of mixed gas, closed circuit decompression diving.
The diagnostic uncertainty in this patient is a major issue, in that recompression is
mandatory to prevent significant disability if the patient does have DCI, but will
possibly do more harm if the diagnosis is inner ear barotrauma. The main issue in
this patient is to involve people with the expertise to resolve this uncertainty as soon
as possible. This expertise may well not exist in a regional hospital.
[sub head]
TREAT
12:01. Treatment:
CRYSTALLOID FLUID, 20ml/kg
12:02. Treatment:
Intravenous antiemetic
SCENE MANAGEMENT:
After the hyperbaric unit was notified, fixed wing aircraft evacuated the patient sea
level. He remained very symptomatic until he was recompressed to 18 meters on
oxygen, but his symptoms did not completely resolve until the treatment was
increased to 30 meters. He made a full recovery.
The patient requested investigation for a possible patent foramen ovale? Why?
[end box]
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