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Learning Outcomes?
- • Describe how oxygen can be stored or generated onboard aircraft.
- • Describe how oxygen can be delivered to aircrew.
- • Explain how a pressure demand oxygen regulator works.
- • Demonstrate the functions of an ADF panel mounted regulator.
- • State the safety rules relating to oxygen.
- • Describe the types of aircraft pressurisation systems.
- • Describe the physical and the physiological effects of a loss of cabin pressurisation.
- • State the actions required in event of decompression.
- • Describe the effects of pressure breathing.
- • Demonstrate the pressure breathing cycle.
- • Describe systems which protect against hypoxia in military and civilian aviation.
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Hypoxia protection?
- • Ambient pressure (cabin pressurisation)
- • Supplemental oxygen
- • Pressure breathing
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Aircraft Pressurisation?
- • Unpressurised
- • Cabin = ambient
- • ‘High differential’
- • Cabin >> ambient
- • ‘Low differential’
- • Cabin > ambient
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High differential cabins High Differential Systems?
- • Advantages
- •‘Shirt sleeve’ environment
- • Comfortable temperature
- • wearing street clothes.
- •Reduced pressure changes
- •No O2 requirement
- •No DCI risk
- • Disadvantages
- •Performance penalty
- •Large decompression risk
- • Hypoxia prevention
- • Breathe cabin air, supplementary oxygen if cabin fails
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Low differential cabins Low Differential Systems?
- • Advantages
- •Optimum endurance
- •Decompression risk
- •Military population
- • Hypoxia prevention
- • Disadvantages
- •Risk of hypoxia
- •Risk of DCI
- •Temperature
- •Supplemental O2requirement
- • Supplemental oxygen supply
- • Delivery system
- • Continuous use
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Loss of Cabin Pressure?
- • Engine failure
- • Control system failure
- • Leaks
- • Loss of canopy
- • Loss of doors or windows
- • Structural failure
- • Weapons
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Decompression
- • Size of defect
- • Pressure differential
- • Volume of cabin
- • Descent profile
- • Aerodynamic effects
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Physiological Effects of Rapid Decompression?
- • Pressure changes
- • ears, sinuses, gut
- • Hypoxia
- • DCI
- • Cold
- • Noise
- • Air blast
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Aircrew Actions in the Event of a Decompression?
- • Don oxygen immediately
- • Select 100 % oxygen
- • Select emergency pressure
- • Check connections-push
- • Breathe at normal rate and depth
- • Initiate emergency descent <10000 ft CABALT
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Possible involvement of AVMO?
- • (ASOR)
- • PM220 Physiological Incident Form
- • Consider DCI
- • HD130 if DCI suspected
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Hypoxia protection?
- • Ambient pressure (cabin pressurisation)
- • Supplemental oxygen system
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Oxygen system?
- • Oxygen source
- • Regulator
- • Mask
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Summary of Aircrew O2 Requirements?
- Altitude (ft) Breathing Gas
- 0 – 10,000 Air
- 10 – 33,700 Increasing % O2
- 33,700 – 40,000 100% O2
- > 40,000 100% O2
- Pressure breathing
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Ideal Oxygen System?
- • Oxygen purity
- • Minimal dead space
- • Acceptable temperature
- • Dispersion of expirate
- • Reliable
- • Automatic
- • Minimum vs maximum acceptable oxygen
- • Matches high peak inspiratory flow rates
- • Comfortable
- • Minimal resistance to breathing
- • Copes with RD
- • Pressure breathing
- • Leakage and safety pressure
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Oxygen Supply?
- • Solid
- • Oxygen Candle
- • Gaseous
- • Liquid Oxygen
- • LDBO or LOX
- • On Board Oxygen Generation
- • OBOGS or MSOC
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Solid Oxygen?
- • Oxygen Candle
- • Used as oxygen supply in commercial aircraft for PAX
- • Oxygen is held in chemical combination
- • Reaction initiated with rapid liberation of gaseous oxygen
- • NAClO3 + Fe FeO + NaCl + O2
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Solid Oxygen Problems?
- • Continuous supply
- •Low pressure
- • Runs until exhausted
- •Finite storage
- • Many advantages:
- • Small and light
- • Easy supply
- • Reliable
- • Low risk
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Gaseous Oxygen?
- • Aviator’s dry breathing oxygen
- • CIG gas codes 420 or 430
- • 99.7% oxygen
- • Moisture <7ppm
- • Colourless, odourless, tasteless
- • Common, simple, cheap, available
- • No ongoing losses when unused
- • Bulky, heavy
- • Usually 1800 psi (221 bar)
- • 10 litre cylinder-2210 litres
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Liquid Oxygen?
- • Saves space and weight
- • Low risk of explosive hazard
- • Inefficient, expensive, complex
- • Hard to get, dangerous to handle
- • Contamination a problem
- • Limited mostly to military use
- • 1 litre LOX yields 840 litres (NTP) O2
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Constant Flow Systems?
- • Direct flow
- • Oxygen store, mass flow regulating device, simple hose and mask
- • 100% oxygen all the time
- • Inefficient and wasteful
- • Inspiration is only 40-50% of the respiratory cycle
- • Volume flow is inversely proportional to ambient pressure
- • Reservoir systems
- • Excess oxygen collected during expiration, so less wasteful
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Demand Regulators?
- • Automatic air dilution
- •Economical
- •100% oxygen possible
- • Barostatic control
- • safety pressure
- • Inspiratory demand
- Delivery Interface
- • Oxygen delivered by
- • Nasal cannulae
- • Pulsed delivery
- • Simple mask
- • Oronasal mask
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Military Aviation Oronasal Masks?
- • Inspiratory valve
- • Expiratory valve
- •Split compensation
- • Anti-suffocation valve
- • PB toggle
- • Reflected seal
- • Quick don, constant use
- • 100% O2, constant flow
- • One size fits all
- •Leaks, air dilution
- • Duration
- •10 min for all pax
- •10% of pax, >14,000 ft
- • Tethered, no mobility
- • Maintain PTO2 83mmHg
- •15 000 ft
- •As high as 20-22 000 ft
- • Incremental O2, to 100%
- • Well-fitting mask
- •No leaks or dilution
- • Long duration (hours)
- •Demand regulator
- • Can be attached to POS
- • Maintain PTO2 148 mmHg
- •MSL
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Summary of Aircrew O2 Requirements?
- Altitude (ft) Breathing Gas
- 0 – 10,000 Air
- 10 – 33,700 Increasing % O2
- 33,700 – 40,000 100% O2
- > 40,000 100% O2
- Pressure breathing
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Aircrew O2 Requirements 0 – 10,000 ?
- Altitude (ft) Breathing Gas
- 0 – 10,000 Air
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Aircrew O2 Requirements 10 – 33,700?
- Altitude (ft) Breathing Gas
- 10 – 33,700 Increasing % O2
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Aircrew O2 Requirement 33,700 – 40,000 ?
- Altitude (ft) Breathing Gas
- 33,700 – 40,000 100% O2
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Aircrew O2 Requirements > 40,000?
- Altitude (ft) Breathing Gas
- > 40,000 100% O2
- Pressure breathing
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Pressure breathing Breathing technique?
- ‘In for 2… Hold for 2… Out for 4…’
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Problems with Pressure Breathing?
- • Need increased mask tension
- • Distension of upper airways & middle ear
- • Irritation of eyes
- • Distension of lungs and chest
- • Increased effort of breathing
- • Hyperventilation
- • Circulatory effects & syncope
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Quiz question 10?
- • A physiological requirement for pressure breathing exists above what altitude?
- a. 10,000 ft b. 33,700 ft c. 40,000 ft d. 50,000 ft
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