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Diving Medicine

Dive medicine for the ED Reg's, Royal Hobart Hospital
by

Chris Holden

on 6 May 2014

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Transcript of Diving Medicine

Diving and Dive Medicine
Chris Holden
ED Registrar - Royal Hobart Hospital
History Of Diving
We
Love
Physics

Physiology
Simulated Dive
Pre-Clime Era
900 BC
1511
1749
1829
1840
1878
Bert - Caisson Disease
1907
Haldane's Goats
1930
Nitrogen Narcosis
Henry's Law
Amount of gas dissolved in a solvent is proportional to the partial pressure of the gas
So higher pressure = more dissolved gas
Dalton's Law
Total pressure = sum of all the individual gas pressures in a mixture
Ptot = ppGas A + ppGas B....
Boyle's Law
Press x Vol = Constant
Volume is proportional to 1/Pressure
Gas Tension
Henry's Law takes time!
In the mean time...
ppGas - ppDissolved gas = Pressure Gradient
Atmosphere
Pascal = 1 Newton / Sq.Metre
1 ATM = 101325 Pa
1 extra ATM for each 10msw
So at 30msw the pressure is...
4 ATMs
Thats why this bubble is small...
Types of Diving
Breath Hold
Surface Fed
Diving Bell
Saturation
SCUBA
Re-Breathers
Words...
Decompression Sickness (DCS)
Arterial Gas Embolism (AGE)
Decompression Illness (DCI)
DCS and / or AGE
Pulmonary Overinflation Syndromes
Barotrauma
Oxygen Toxicity (too much Oxygen)
Nitrogen Narcosis
Hypoxia (too little)
The Badness
Barotrauma
Ze Bubbles!
CO2
Oxygen
Barotrauma
Boyle's Law: PV=K
Going down?
Pressure increasing
Volume must decrease
Fixed containers = badness
SQUEEZE!
Coming up?
Pressure decreasing
Volume must increase
Fixed containers = badness
Reverse Squeeze
Herbert Nitsch - 214msw
22 ATM
Technical
Decompression Sickness - The Bends
Inert Gas bubbles in tissue
Any inert - He, N, H, Ne...
On-gassing
pp.Inert in Lungs > Gas Tension
Inert gas dissolves into tissues
Rate depends on pp.Gradient, Solubility, Perfusion
Off-Gassing
Gas tension > pp.Inert in Lungs
Inert gas leaves solution
Allowable supersaturation
Depends on gas solubility, tissue type
Bubbles form in tissue = Bends
Classified by location
Type 1
D
CS
Skin
Lymph
Muscle
Joint
Type 2
DCS
Inner ear "Staggers"
Cardiopulmonary "Chokes"
CNS
DCS - Clinical Features
Neurological:
77%
Limb Pain:
48%
Constitutional:
29%
Skin:
10%
Respiratory:
4%
Girdle/Back pain
3%
Lymphatic:
1%
Whats so bad about bubbles?
Seriously...
Tissues
Direct Trauma
Nerve compression
Increased tissue pressure (reduced perfusion)
Venous
Flow flow obstruction
Venous gas emboli in lungs
Indirect
Immune mediated
Constitutional symptoms
Type 1 DCS
Musculoskeletal Pain
Deep dull ache
Progressive
Unaffected by movement
Guarding position
Upper > Lower limbs
Skin
Pruritus
Orange Peel Skin (lymphatics)
Rash inc. Cutis marmorata
Lymphatic
Localised lymphadenopathy
Lymphoedema
Type 2 DCS
Neurological
Inner ear ("The Staggers')
Cardiopulmonary ("The Chokes")
Neurological
Inner Ear
Cardiopulmonary
Most common: Paraesthesia
Any neurology is possible
Disturbance of higher function
Delayed micturition
Paralysis, death
Hearing loss, tinnitus, vertigo, dizziness, nausea, vomiting
More common in heliox dives
Pathophysiology unclear - slow N washout?
Difficult to distinguish from barotrauma
Vertigo the most common complaint
Profuse intravascular bubbling
Bubbles filtered out in lungs
Retrosternal burning discomfort
Worse on deep inspiration
Non-productive cough
Severe respiratory distress, circulatory collapse, death
Arterial Gas Embolism
Pulmonary Overinflation Syndrome (POS)
Boyle's Law ("Reverse squeeze")
Large gas emboli in the pulmonary veins
Emboli expand and ambient pressure declines
Cerebral arteries
Coronary arteries
Usually within 10-20 minutes from surfacing
Difficult to distinguish from Type 1 DCS...
...but it doesn't matter anyway
Too much of a good thing..
Oxygen toxicity
: partial pressure and time dependent
CNS oxygen toxicity "Paul Bert Effect"
Pulmonary oxygen toxicity "Lorraine Smith Effect"
Ocular oxygen toxicity (prem's don't dive)
Pulmonary Oxygen Toxicity
Toxic Dose:
pO2 > 0.5ATA (ie. Air at 14msw)
12hrs at pO2 = 1 ATA
4hrs at pO2 = 2 ATA
Clinical Presentation:
Burning pain on inspiration
Cough
Respiratory distress
Measurable decline in lung function
CNS Oxygen Toxicity: Bad news for Divers
pO2 and time dependent
pO2 > 1.3ATA (wet) vs. pO2>2.4ATA (dry)
PADI recommended maximum: 1.4ATA
That's 55msw on air
Risk Factors
Individual susceptibility
Immersion in water
Exercise
Depth (independent of pO2)
Continuous exposure (hence air-breaks)
CNS Oxygen Toxicity: Signs and Symptoms
V
isual disturbance
E
ar symptoms
N
ausea / Vomiting
T
witching / Tingling
I
rritability
D
izziness
C
onvulsions (may come first!)
1945
Costeaus's Aqua Lung
Hypoxia
Hypoxic symptoms begin at piO2 < 0.16ATA
Helpless at piO2 < 0.11ATA
Hypoxic diver is often unaware of the problem
Causes:
Failed re-breather equipment
Switching to the wrong mix
Shallow-water blackout during breath-hold dive
Hypercapnia
Symptoms
Dyspnoea
Confusion
Headache
Seizure
Causes
High inspired CO2
Scrubber failure
Inadequate ventilation
Inert Gas Narcosis
Martini's law
Adaptation probably not possible
He2 is almost non-narcotic
Lipid solubility predicts narcotic potential
Common below 30msw on air
Alcohol, benzodiazepenes, CO2 all increase narcosis
Task fixation, euphoria, paranoia, hallucinations, LOC
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