1. Hypoxia Dr Simon Brown
Title slide

2. Decompression & Hypoxia
The Prevalence
The Problem
The Physiology
The Prevention

3. The Prevalence of Decompression

4. Decompression Occurrence
UK [ ]:
Canada [ ]: 164
Australia [ ]:
Collection of reports from around the world.
Nb dates – not comparative – not factor’d - Western nations well reported and documented.
Works out roughly at 35/40 per year worldwide (probably more of these going on than engine shutdowns).
USA [ ]: 355
GREECE [2005]: At least 1

5. Decompression Occurrence
UK [ ]:
Canada [ ]: 164
Australia [ ]:
8 pressurisation related incidents since 11 Jan 99.
Including the excessive cabin altitude incident 8 Oct 05.
USA [ ]: 355
Your Company ?

6. Selected Incidents Greece 2005 - Boeing 737 121 Fatalities
Cabin probably did not pressurise in climb
F/D crew did not don masks
Cabin Crew and pax did don drop-down masks
Autopilot levelled aircraft at 34,000 ft
Interceptor saw FO “slumped” over controls Captain not seen on flight deck
121 Fatalities
The Helios Accident.
Still under investigation.

7. Selected Incidents USA 1996 - Boeing 727
33,000 ft (cabin altitude horn warning sounded)
Cabin altitude climbed to 14,000 ft, masks deployed
Flt Eng inadvertently opened outflow valve - cabin alt increased
Captain, Flt Eng and No1 unconscious
First Officer donned mask at first warning
Captain, Flt Eng and No1 regained consciousness in descent
Similar to the previous incident. Only one flight deck member carried out their drills correctly and saved the aircraft. If they hadn’t, it would have been another “Helios”.
Worth mentioning how aircraft pressurise (inflow/outflow) – possible 2 min syndicate work.

8. Selected Incidents UK 1998 - Boeing 737
35,000 ft (cabin altitude 20,000 ft)
Captain couldn’t don oxygen mask quickly enough
Senior cabin crew took off her mask to help Captain
Captain and cabin crew member unconscious
F/O Had Donned Mask & Descended Aircraft
Captain unaware he had been unconscious
Made various incorrect switch selections
Sabre
Capt proved that mental faculties don’t come back immediately – more later.

9. “. it is possible that neither fully appreciated the nature of hypoxia
“ . . .it is possible that neither fully appreciated the nature of hypoxia.” [UK AAIB, referring to the unconscious Captain and No1]
Refers to the Sabre incident Captain and Number 1

10. Cabin Decompression How Cabin Pressurisation Works
[Picture of aircraft outflow valve]
[Animation of aircraft pressurisation system]
Ask pilots the reasons for cabin decompressions
Get them to explain ‘packs / bleeds’ etc to CC

11. Cabin Decompression Causes Include: Not As Uncommon As You Think
A/C Pack or Bleed Failures
Outflow Valve Failures
Door Seal/Latching Failures
Structural Failures
Not As Uncommon As You Think

12. The Problem
“ . . .it is possible that neither fully appreciated the nature of hypoxia.”
Read out Feedback Glider Pilot Incident

13. What is Hypoxia?

14. Definition:
Hypoxia is a condition when oxygen available to tissues is insufficient to meet their needs
Hypoxia is recognised to be the most serious single physiological hazard during flight at altitude
Brief description of what hypoxia actually is.
The second paragraph is a quote from Ernsting (researcher from 40s/50s) and remains true to this day – in other words – ‘if you can’t breath you die’ – no food or water, you have 40 days / no air, you have 40 secs.

15. What Is Hypoxia Insufficient Oxygen for the Tissues
Brain tissues most sensitive to lack of oxygen
Therefore, first symptoms of hypoxia are related to higher mental function
What is Hypoxia?

16. Loss of Self-criticism Mental Incoordination
HYPOXIA
Higher Functions
Lack of Insight
Loss of Judgement
Loss of Self-criticism
Euphoria
Feelings of Unreality
Mental Incoordination
Loss of Memory
Physical Signs
Muscular Incoordination
Increased Heart Rate
Cyanosis (Blue Lips)
Hyperventilation +
Unconscious
DEATH

17. HYPOXIA Susceptibility to hypoxia increased by: - final altitude
- time taken to climb
- exercise
- cold
- illness
- fatigue
- drugs/alcohol
- smoking
Facilitate first
Important points: time taken to climb. Any aircraft decompression, rapid or slow, gets you to a high altitude in relatively quick time. (The body can adapt quite a bit when climbing, or even driving, up a mountain. Aircraft ascent is a different ball game).
Cabin crew are more susceptible because they are standing up and moving. Even standing up makes a big difference to your oxygen requirements. The pilots are sitting down and may have been on oxygen from 9,000 ft cabin altitude. The pax are generally sitting down.
Smoking: smokers are already at 3-5,000 ft before take off because their oxygen carrying capacity is less (carbon monoxide in ciggies). They may notice the symptoms first or, suffer the consequences first.

18. Signs & Symptoms of Hypoxia
Above 20,000 ft
Exaggeration of all signs and symptoms
Comprehension and mental performance decline rapidly
Unconsciousness occurs with little or no warning
Points: many pilots, especially those who have received training in the forces, still think that 20,000 ft is not too high an altitude. Hypoxia symptoms start above 10,000 ft but you are unaware of them (rather like your first drink). This is why the warnings come on at 9,500 ft , minus 500 ft, plus zero - doh!

19. Cabin Decompression May be Slow or Fast Cabin Noise Fogging/Dust
Temperature
Masks
Body
Ears/Sinuses
Hyperventilate
Faintness
Unconsciousness
A slow, insidious decompression may mask some of the body’s symptoms, notably the ears and sinuses.
May be Slow or Fast

20. Physiology of Hypoxia
How does oxygen get from the lungs into the bloodstream?
Answer = Air Pressure
Analogy = Car Fuel Tank – If you have fuel in your fuel tank the car isn’t going to run – You need the fuel pressure to push the fuel to the engine

21. Physiology of Hypoxia
Respiration
Alveolus
Capillaries

22. Physiology of Hypoxia
Respiration
Alveolus O2
CO2
Capillary

23. Gas Exchange Takes Place by Diffusion Only
Physiology of Hypoxia
Respiration
Gas Exchange Takes Place by Diffusion Only
Alveolus O2
CO2
Capillary

24. This Requires Pressure
Physiology of Hypoxia
Respiration
This Requires Pressure
Alveolus O2
CO2
Capillary

25. Pressure [Film clip demonstrating pressure.] Answer = Air Pressure
Analogy = Car Fuel Tank – If you have fuel in your fuel tank the car isn’t going to run – You need the fuel pressure to push the fuel to the engine

26. The Atmosphere 40,000 feet 1/5 sea level pressure 34,000 feet
14 psi (760 mm Hg or 1 bar)
18,000 feet
1/2 sea level pressure
34,000 feet
1/4 sea level pressure
40,000 feet
1/5 sea level pressure
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27. The Volume of a Gas Increases as the Pressure Drops
Gas Expansion SL 1x
The Volume of a Gas Increases as the Pressure Drops
8,000 ft
1.5x

28. This Requires Pressure
Physiology of Hypoxia
Respiration
This Requires Pressure
Alveolus O2
CO2
Capillary

29. This Requires Pressure
Physiology of Hypoxia
Respiration
This Requires Pressure
Alveolus
Sea Level
14 psi(760 mm Hg or 1 bar)
18,000 feet
1/2 sea level pressure
34,000 feet
1/4 sea level pressure
40,000 feet
1/5 sea level pressure
CO2 O2
Capillary

30. . . . but not up here Holding your breath works down here . . .
Remember – holding your breath won’t work at Altitude

31. Physiology of Hypoxia Breathing Rate Oxygen Saturation Cabin Altitude
Subject stops breathing
10 secs
100 %
50 %
Cabin Altitude
8,000 ft
25,000 ft
This slide illustrates a guy who didn’t continue breathing for approx 15 secs after a rapid decompression and look at the oxygen saturation level

32. A Bit More on Pressure - The Atmosphere
Nitrogen
78%
Other
Gases 1%
Oxygen
21%
Only 1/5 of the pressure is Oxygen
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Use the Promote and Demote buttons on the toolbar to change automatically between level settings and bullet points.
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Add in the correct Section number above the Title or a sub-title if required.
The only font that should be used in the presentation is TheSans Q5 Plain.
All text should be left aligned, other than titles in diagrams and tables.
Animation
No animation effects should be used on body text slides. If you wish to build bullet points as you discuss them, then use the Appear effect.
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33. A Bit More on Pressure - The Atmosphere
Now ALL of the pressure is Oxygen
More Oxygen
Nitrogen
78%
Other
Gases 1%
Oxygen
21%
Nitrogen
78%
Oxygen
21%
Other
Gases
Bullet point and paragraph slide
Replace the existing text contents by highlighting and typing over.
Use the Promote and Demote buttons on the toolbar to change automatically between level settings and bullet points.
If all your information will not fit onto the slide, challenge its length or run onto two slides using the same slide Title followed by: - continued.
Add in the correct Section number above the Title or a sub-title if required.
The only font that should be used in the presentation is TheSans Q5 Plain.
All text should be left aligned, other than titles in diagrams and tables.
Animation
No animation effects should be used on body text slides. If you wish to build bullet points as you discuss them, then use the Appear effect.
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34. A Bit More on Pressure + = = + 40° 8° Answer = Air Pressure
Analogy = Car Fuel Tank – If you have fuel in your fuel tank the car isn’t going to run – You need the fuel pressure to push the fuel to the engine +

35. A Bit More on Pressure - The Atmosphere
Now ALL of the pressure is Oxygen
More Oxygen
Nitrogen
78%
Other
Gases 1%
Oxygen
21%
Nitrogen
78%
Oxygen
21%
Other
Gases
Bullet point and paragraph slide
Replace the existing text contents by highlighting and typing over.
Use the Promote and Demote buttons on the toolbar to change automatically between level settings and bullet points.
If all your information will not fit onto the slide, challenge its length or run onto two slides using the same slide Title followed by: - continued.
Add in the correct Section number above the Title or a sub-title if required.
The only font that should be used in the presentation is TheSans Q5 Plain.
All text should be left aligned, other than titles in diagrams and tables.
Animation
No animation effects should be used on body text slides. If you wish to build bullet points as you discuss them, then use the Appear effect.
No slide transition effects (animation moving between slides) should be used on any slide.
Do not use sound effects on any slide. 1%

36. Time of Useful Consciousness (TUC)
ALTITUDE
SITTING QUIETLY
MODERATE ACTIVITY
RAPID DECOMPRESSION
35,000 FT
45 SECONDS
30 SECONDS
20 SECONDS
Just a reminder for everyone – CC are moderate activity vs FD/Pax

37. Hypoxia Video
[Video clip of rapid decompression and hypoxia at 25,000 ft in QinetiQ’s hypobaric chamber.]

38. Time of Useful Consciousness (TUC)
ALTITUDE
SITTING QUIETLY
MODERATE ACTIVITY
RAPID DECOMPRESSION
35,000 FT
45 SECONDS
30 SECONDS
20 SECONDS
Just a reminder for everyone – CC are moderate activity vs FD/Pax

39. Prevention
Stay Below 10,000 ft!

40. Prevention Cabin Decompression . . .
. .or if you suspect hypoxia ? . . .
CARRY OUT THE ACTIONS IN THE SAFETY MANUAL

41. GET ON OXYGEN AND STAY ON IT
DON’T HOLD YOUR BREATH

42. . . . but not up here Holding your breath works down here . . .
Remember – holding your breath won’t work at Altitude

43. Questions?