Oxygen –
the ‘Breath
of Life’
“How high can I make
it without extra O2?”
harry oxer
How much oxygen in air?
At ground level:
• Nitrogen
78%
• Oxygen
21%
• Others
copyright Harry Oxer 5/2003
1% (mostly Argon)
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How much oxygen in air?
At 30,000’:
• Nitrogen
78%
• Oxygen
21%
• Others
1% (mostly Argon)
Same percentages, BUT:
copyright Harry Oxer 5/2003
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But……
• Oxygen needs pressure to get into
solution in the body
• And the pressure is MUCH lower as you
get higher!
• Need a partial pressure of at least
60mmHg to force oxygen into solution
in the body
copyright Harry Oxer 5/2003
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Compare carbon dioxide
• 1000 L of CO2 in an average room
• But all water doesn’t turn to soda water!
• CO2 only dissolves if injected under
PRESSURE
• If reduce the pressure enough – i.e. take the
top off – all the CO2 comes out of solution
• In space, even if lungs full of oxygen, you
would suffocate, because all oxygen comes out
of solution – no pressure to keep it dissolved!
copyright Harry Oxer 5/2003
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Relevance of this?
• As you climb in sailplane, or any
unpressurised a/c, the ambient pressure
FALLS, and so does the partial pressure
of oxygen
• Partial pressure – that % of the total
pressure exerted by the oxygen, i.e. 21%
• CO2 and water vapour further reduce the
pressure available for oxygen
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Pressure available to push
oxygen into solution
Pressure
altitude – (ft)
Atmospheric
Ambient O2
pressure mmHg pressure
Alveolar(lung)
O2 pressure
0
5000
10,000
760
632
523
159
133
110
103
81
61
12,000
13,000
14,000
483
465
447
101
97
94
54
51
48
15,000
20,000
25,000
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429
350
282
90
73
59
45
34
30
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Oxygen pressure cascade
• Air
150 mmHg
• Alveolae
100 mmHg
▼
▼
• Tissues average 40mmHg
• If inspired pressure of O2 < 40mmHg,
O2 comes OUT of body!
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flying
• Must maintain alveolar partial pressure of O2
at least 60mmHg (more than 40 to push)
• How?
• Increase inspired partial pressure, by
increasing %.
• e.g. 50% O2 pressure 760/2 = 380 mmHg –
300mmHg in lungs! Plenty of pressure.
• Add oxygen to increase the driving pressure
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10,000’
• Lung O2 pressure 61 mmHg – above the
tissue 40mmHg
• OK if you are fit and healthy!
12,000’
• Lung O2 pressure 54 mmHg – just above
the tissue 40mmHg – not much force to
get O2 in to solution!
• Above this level, RAPID decline!
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Effects of hypoxia
– low oxygen
•
•
•
•
•
•
•
Insidious
First to go is the ability to assess oneself
Over-confidence and under-competence!
Like alcohol
CAN’T detect own symptoms!
Use oxygen always, and early
No room for under-performing pilots who
don’t realise it - or dead heroes!
copyright Harry Oxer 5/2003
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hypoxia
• Up to 10,000’ - normal individual:
effects rarely significant
• 10,000-12,000’ – rapid decrease:
– Complex eye-hand coordination decreases
10-12% @ 12,000’, 30% @ 15,000’.
– Vision decreases from 8,000’
– Some > unconscious @ 16,000’!
AND YOU DON”T KNOW!
copyright Harry Oxer 5/2003
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hypoxia
The most dangerous aspect of
hypoxia is that the individual
experiencing it does not and
can not detect the decrement
in function, and loses the
ability for critical judgement
copyright Harry Oxer 5/2003
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When to use oxygen
•
•
•
•
You should consider it at 10,000’
You MUST use it from
12,000’
All the time
If oxygen fails, or any doubts,
DESCEND!
Fly another day
copyright Harry Oxer 5/2003
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When should I
consider oxygen earlier?
• Anaemia, lung disease, older, heart
problems, smoking, hang-over.
• Cold (Shivering increases O2
consumption up to 20 times!)
• Illness
• Medications?
copyright Harry Oxer 5/2003
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Summary
Above 10,000’ consider oxygen
If climbing, commence oxygen
On oxygen by 12,000’
Maintain until below 10,000’
Check flow and contents often
If in doubt about flow, duration,
DESCEND!
KNOW YOUR EQUIPMENT THOROUGHLY
before you fly.
copyright Harry Oxer 5/2003
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Using oxygen for gliding
EDS-D1 system
EDS-D1
Aviation
Oxygen
system
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Using oxygen
Check:
• Cylinder – security, sufficient contents,
turned ON
• Battery in unit and working. Cold
reserve?
• Unit connected to O2 and to nasal
prongs or mask – reachably stowed
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Using oxygen
• All settings will automatically give sufficient
oxygen – or more – for the flight altitude
• F 10 settings ADD a flow equivalent to that
which you’d get at 10,000’
‘D’ settings:
D 5 - - - O2 comes on at 5000’
D 10 - - - O2 comes on at 10,000’
D 12 - - - O2 comes on at 12,000’
Flow increases automatically with height
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Press to set
Oxygen
flow alarm
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Nonbreathing
alarm
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Using oxygen
• MUST be on by 12,000’
• Above 18,000’ FAI recommend full mask
rather than just nasal prongs
• MUST trigger oxygen with each breath – this
usually means breathe IN through nose
• Alarms sound if 45 seconds with no flow –
either not sniffing, not breathing, oxygen run
out, battery run out.
copyright Harry Oxer 5/2003
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Press nose
clip to fit
Pull elastic
both sides
to snug fit
Place elastic
below ears
copyright Harry Oxer 5/2003
Only mask above 18.000 with EDS 1
25
• If you wear a beard, a
good mask seal is difficult
• You risk hypoxia at
altitude!
copyright Harry Oxer 5/2003
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Using oxygen
• If alarm sounds, and oxygen not
flowing,
• press to last button position – R/M
mode (reserve/manual) – gives half
second oxygen pulses (longer)
• airbrakes, and GET DOWN!
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Using oxygen - summary
Use “D” from 10,000’
If older, chest problems etc.
use “F” settings
Check and KNOW your
Oxygen system
It is your LIFE
above 12,000’.
Harry Oxer
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