AHF 2203AVIATION HUMAN FACTORS Presentation 5: Hyperventilation and Cabin Pressurization
Recapitulate • Lets recap what we have done last session: • Atmospheric Layer • Variation of pressure and temperature with altitude • Physiological zone of atmosphere • Definition of Hypoxia • Physiological Process of Hypoxia • Types of Hypoxia • Stage of Hypoxia • Sign and symptoms of Hypoxia • Prevention and Correction of Hypoxia • EPT
Presentation Outline • Part 1: Hyperventilation • Part 2: Cabin Pressurization
Learning Outcomes • At the end of this session, student should be able to: • Identify and aware of Hyperventilation syndromes and their causes, effects, preventions and medical cure needed especially during flight. • Understand why aircraft cabin need to be pressurized especially at higher altitude.
How do you breathing? • Why do you breathing? • What gases do you consume during breathing? • What happen if you are stopped breathing? • Which one comfortable for you: Slow breathing? Rapid breathing?
Cont. • Breathing: Process of taking air (O2)into the lung and exchanging gas (CO2)to the environment. • CO2 is the gas produce by all living things as a WASTE PRODUCT.
Cont. • It is important for maintaining chemical balance in the body and control our breathing. • Access CO2 is eliminated by the lung during isolation (separation). • However, some amount of CO2 must remain in the body – to maintain chemical balance in the body.
Cont. • The concentration of gases in the body controlled by BRAIN. • Average adult breathing cycle: 12-16 breath per minute. • Rate of breathing can be rapid/slow down.
What happen to your breathing (slow/fast) when your get into emotional problem (angry/stress/anxiety/panic)?? Cont.
Hyperventilation • Hyperventilation (overbreathing) can be defineed as excessive rate and depth of respiration leading to abnormal loss of CO2 from the blood. • It causes the excessive loss of CO2from the blood. • This results to degrade the chemical balance in the blood
Cont. • The brain will react by restricting the blood flow. • By this restriction, the blood flow to the brain cause (result of Hyperventilation): • Poor judgment • Impaired memory • Performance impairment • Late of reaction time • Muscle coordination.
Cont. • If this chemical imbalance continue (not quickly cured) it might result: UNCONCIOUSNESS!!! • With the breath held the carbon dioxide levels build up once more and the symptoms disappear in reverse order.
Hyperventilation Process Imagine if the unconsciousness happens to the PILOT??
Cont. • Hyperventilation rarely painful. • Many symptoms and sign are similar to hypoxia. So this is the difficulty to recognize Hyperventilation.
Difference between Hypoxia and Hyperventilation Hyperventilation Hypoxia Skin may look blue (cyanosis). Can occur rapidly. Muscle soft and limp with little or no activity. • Skin may look pale. • As we ascend, it can occur slowly and gradually over time. • Muscle activity might becomes spastic
Cont. • To help differentiate between Hyperventilation and Hypoxia please monitor this element: • Flight attitude • Cabin altitude (if pressurized) • Oxygen system (if in use) • Emotional state • Awareness of your current flight environment.
Cont. • Hyperventilation and Hypoxia can occur simultaneously. This making it difficult to diagnose (analyze) the problem.
Causes of Hyperventilation • Main cause of Hyperventilation is EMOTIONAL PROBLEM What is emotional problem? Please give the example of emotional problem?
Cont. • Other causes of Hyperventilation that not caused by emotional problem: • Pain • Bleeding • Cardiac disease, such as congestive heart failure (abnormal collection of blood) or heart attack • Drugs (such as an aspirin overdose) • Respiratory disease: Infection such as pneumonia (infection of one or both lungs which is usually caused by bacteria, viruses, or fungi) or sepsis (toxins in the blood or tissues) • Lung disease such as asthma, • Pregnancy
Symptoms of Hyperventilation • Dizziness • Lightheadedness • Blurred Vision • Numbness • Tingling • Hot and cold sensations. • Muscle incoordination (cramps). • Shortness of breath • Unconsciousness *These symptoms also can be symptoms of Hypoxia *If you have hyperventilation syndrome, you might not be aware you are breathing fast. You might be aware of those symptoms above.
Prevention of Hyperventilation • Monitor your rate and depth of breathing. • Learn to recognize stressors that would cause you to over breath. • Avoid panic.
Treatment of Hyperventilation • FAA Checklist (usually when occur simultaneously with hypoxia): • Wear Oxygen Mask • Check the oxygen regulator is turned on • Check all connection are secure • Slow down your breathing rate and depth • Descend to suitable altitude (10000 ft and below)
Cont. • Other treatment: • Best method is to voluntarily reduce rate of breathing (Normal rate is 12-16 breaths per minute) • Go to 100% O2(if available) • Talk or sing (to increase CO2 level) • Breathing into a bag.
Cont. • Pressure is decrease when altitude is increase. • Outside pressure (atmospheric pressure) could be harmful in the high altitude to human body. • So to maintain pressurization in the cabin at high altitude is important.
What is Cabin Pressurization? Cont. • Cabin pressurization is the active pumping of compressed air into an aircraft cabin . • The purpose of these systems is to provide a safe and comfortable cabin environment, and to protect all cabin occupants from the physiological risks of high altitudes (e.g. hypoxia, decompression sickness).
Cont. • It involves simultaneous control on: • Temperature • Humidity • Air Circulation • Cabin Pressure • Pressurization is essential above 10,000 feet
Cont. • Most pressurize aircraft today cruise at altitude of 25000 ft - 51000 ft while keeping cabin at comfortable pressurize altitude as in 6500 ft - 8000 ft.
Cont. Basic Mechanic of Cabin Pressurization System
Cont. • Outside air continuously enters engine. • Air is compressed by the compressor in the engine and then passes through cooling packs. • Cool outside air goes into mixing chamber and mixed with re-circulated air from the tanks. • Air from mixing chamber then continuously supplied to the cabin. • Outflow valve then control the air flow by open and close the valve to maintain the suitable pressure.
Cont. Outflow Valve
Advantage of Pressurized Flight • Oxygen mask no need to be worn • Risk of decompression sickness minimized • Decompression sickness caused by nitrogen forming as bubbles in the blood • Less noise and vibration during flight. • Better control of temperature and air ventilation (system supply fresh air) . • Fewer trapped gas problem. • The gas can’t be released especially by our body cavities part.
Disadvantages of Pressurized flight • Always a chance of DECOMPRESSION.
Cont. What is Decompression?? • Decompression means aircraft loss of cabin pressurization. • It can occur because cabin pressurization system not functioning well, the damage to the aircraft that causes a breakin the aircraft structure which enabling cabin air to escape outside the aircraft
Cont. • THREE major types of decompression: • Slow Decompression • Rapid Decompression • Explosive Decompression Vary with TIME!
Cont. Slow Decompression • When the cabin loss pressure greater than 10 seconds. • It happens in case of a small air leak. • Potential to be most dangerous types of decompression when unaware cabin altitude is going up (since it happen very slow).
Cont. Rapid Decompression • Total loss of cabin pressurization within 1-10 seconds. • It happens in case of big air leak.
Cont. Explosive Decompression • When cabin pressurization loss in less than 1 second!!! • This rapid change can occur faster than our lungs can decompress. Lung damage possible to occur. • It happens in case of big air leak.
Cont. Qantas Flight Decompression, Big Hole in the Fuselage
Factors AffectingSeverity and Times of Decompression • Size of cabin • the larger the cabin, the longer the decompression time (slower decompression) • Size of the opening (air leak) • the larger the opening, the faster the decompression time.
Cont. • Differential ratio • the greater the pressure differential between the cabin pressure and the external environmental pressure, the more forceful the decompression. • Flight altitude • higher altitudes create greater threats for physiological consequences (see *Time of useful Consciousness (TUC)) *TUC also known as Effective Performance Time (EPT).
Cont. Times of Useful Consciousness • TUC or EPT is the period of time that a pilot has from the time oxygen become less available until the time when he or she loses the ability to recognize and take action • If someone goes beyond TUC, then he or she isn’t even aware of the problem and will not take corrective action • The keyword is EFFECTIVE or USEFUL (He or she might be conscious but not making expected useful or effective decision). • TUC decrease as altitude increases.
Effects of Decompression • Physical effects : • Noise: • Noise from decompression can increasing to very loud explosive sound. • Communication can be disturbed. • Fog: • Form when decreasing in temperature and pressure associated with decompression • Effect visual problem • Flying Debris (dust/dirt) • Dust and dirt cause visual problem. • Cooler Temperature • Pressure or air departs the cabin • Hypothermia (abnormal body temperature) can occur.
Cont. • Physiological effect: • Trapped Gas • The gas can’t be released especially by our body cavities (hole) part (e.g. middle ear, teeth etc.) • Certain gases that will expand with decreasing in pressure • Decompression sickness • Occur due to nitrogen in the body coming out as solution and forming bubble. • Hypothermia • Cause by cooler temperature at high altitude