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Hypoxia Dr Simon Brown

Hypoxia Dr Simon Brown. Decompression & Hypoxia . The Prevalence The Problem The Physiology The Prevention. The Prevalence of Decompression. GREECE [2005]: At least 1. Decompression Occurrence. UK [1990-99]: 77. Canada [1985-99]: 164. Australia [1990-99]: 5.

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Hypoxia Dr Simon Brown

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  1. Hypoxia Dr Simon Brown

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

  3. The Prevalence of Decompression

  4. GREECE [2005]: At least 1 Decompression Occurrence UK [1990-99]: 77 Canada [1985-99]: 164 Australia [1990-99]: 5 USA [1974-83]: 355

  5. Decompression Occurrence UK [1990-99]: 77 Canada [1985-99]: 164 Australia [1990-99]: 5 USA [1974-83]: 355 Your Company ?

  6. Selected Incidents • Greece 2005 - Boeing 737 • 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

  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

  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

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

  10. Cabin Decompression • How Cabin Pressurisation Works • [Picture of aircraft outflow valve] • [Animation of aircraft pressurisation system]

  11. Cabin Decompression • Causes Include: • 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.”

  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

  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

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

  17. HYPOXIA Susceptibility to hypoxia increased by: • - final altitude • - time taken to climb • - exercise • - cold • - illness • - fatigue • - drugs/alcohol • - smoking

  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

  19. Cabin Decompression • May be Slow or Fast • Cabin • Noise • Fogging/Dust • Temperature • Masks • Body • Ears/Sinuses • Hyperventilate • Faintness • Unconsciousness

  20. Physiology of Hypoxia • How does oxygen get from the lungs into the bloodstream?

  21. Physiology of Hypoxia Respiration Alveolus Capillaries

  22. Alveolus CO2 O2 Physiology of Hypoxia Respiration Capillary

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

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

  25. Pressure [Film clip demonstrating pressure.]

  26. 40,000 feet 1/5 sea level pressure 34,000 feet 1/4 sea level pressure 18,000 feet 1/2 sea level pressure Sea Level 14 psi (760 mm Hg or 1 bar) The Atmosphere

  27. 1.5x 8,000 ft 1x SL Pressure Gas Expansion The Volume of a Gas Increases as the Pressure Drops

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

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

  30. . . . but not up here • Holding your breath works down here . . .

  31. Subject stops breathing Breathing Rate 10 secs Oxygen Saturation 100 % 25,000 ft 50 % Cabin Altitude 8,000 ft Physiology of Hypoxia

  32. Nitrogen 78% Oxygen 21% Other Gases 1% A Bit More on Pressure- The Atmosphere Only 1/5 of the pressure is Oxygen

  33. Nitrogen 78% More Oxygen Now ALL of the pressure is Oxygen Oxygen 21% Other Gases 1% A Bit More on Pressure- The Atmosphere Nitrogen 78% Oxygen 21% Other Gases 1%

  34. 40° = + 8° = + + + + A Bit More on Pressure

  35. Nitrogen 78% More Oxygen Now ALL of the pressure is Oxygen Oxygen 21% Other Gases 1% A Bit More on Pressure- The Atmosphere Nitrogen 78% Oxygen 21% Other Gases 1%

  36. SITTING QUIETLY MODERATE ACTIVITY RAPID DECOMPRESSION ALTITUDE 45 SECONDS 30 SECONDS 35,000 FT 20 SECONDS Time of Useful Consciousness(TUC)

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

  38. SITTING QUIETLY MODERATE ACTIVITY RAPID DECOMPRESSION ALTITUDE 45 SECONDS 30 SECONDS 35,000 FT 20 SECONDS Time of Useful Consciousness(TUC)

  39. Stay Below 10,000 ft! Prevention

  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 . . .

  43. Questions?

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