Transcript AHF 2203 AVIATION HUMAN FACTORS

AHF 2203
AVIATION HUMAN FACTORS
Presentation 2: The Atmosphere and
Hypoxia
Recapitulate
• Lets recap what we have done last session:
– Definition of Physiology and Flight Physiology.
– Importance of Flight Physiology.
– Basic Concept of The Nervous System.
– Basic Concept of The Respiratory System.
– Basic Concept of The Circulatory System.
Presentation Outline
• Part 1: Introduction to Earth’s Atmosphere
• Part 2: Hypoxia
Learning Outcomes
• At the end of this session, student should be
able to:
– Know that pressure plays the important role
during altitude changes
– Classify the types of hypoxia, it causes, symptoms,
and prevention steps through the explanation.
Presented by Mohd Amirul for AMC
4
EARTH’S
ATMOSPHERE
Earth’s Atmosphere
• Air is one of the primary
things that makes life on
Earth possible. Air is a
synonym for
atmosphere. The Earth’s
atmosphere or air is
made up of a variety of
gases and other
particles.
Cont.
• What is the Atmosphere??
– layer of gases surrounding the planet Earth that is
retained by Earth's gravity.
• Gases in atmosphere:
– 78% - Nitrogen
– 21% - Oxygen
– 1% - Other gases (Argon,
Carbon Dioxide, Neon,
Helium)
Layers (Structure) of Atmosphere
Cont.
• Troposphere
– Temperature will decrease
constantly with altitude.
– 75% of weight of atmosphere.
– Contains almost all weather
– Altitude (height) vary with:
• Latitude: lower at poles and
higher at equatorial
• Seasons: higher in summer than
winter
– Almost all clouds in this layer.
– Almost commercial aircrafts fly
in this layer.
Cont.
• Stratosphere
– Very small increase in
temperature (almost
constant) except at the
top where temperature is
zero at 50 kms.
– Little water vapor @
turbulence
Functions of the Atmosphere
• Source of oxygen and carbon dioxide
• Protection for the human on the Earth from
the harmful cosmic ray, solar radiation and
ultraviolet (UV) ray.
• Source of rain
• Maintains the temperature and climate that
sustain life on earth
Variation in Atmosphere
• The earth’s atmosphere varies in
– Temperature
– Pressure
– Density
– Humidity
Atmospheric Pressure
• Atmospheric pressure is the combined weight of all
the atmospheric gases, creating a force upon the
surface of the earth – the cause of this force is gravity
• The atmospheric pressure can be measured in force /
unit area (Pounds per square inch [Psi] or Millimeters
of mercury [mm/Hg])
• The standard atmospheric pressure at sea level is 760
mm/Hg.
• It is the combination of:
Gases
Pressure [mm/Hg]
Oxygen
100
Carbon dioxide
40
Nitrogen
573
Water Vapor
47
Total
760
Pressure and Temperature Decrease
with Altitude
Altitude (Feet)
Pressure
(mm/ Hg)
0
760
Temperature
(degree
Celsius)
15.0
18,000
380
-5.3
34,000
190
-62.3
48,000
95
-67.3
63,000
47
-67.04
Pressure & Temperature
• Air Pressure
– At sea level, the air pressure is about 760 mm/Hg.
– As the altitude increases, the air pressure decreases (and
there is less oxygen to breathe).
• Temperature
– As we ascend from the surface, the temperature falls
steadily with altitude.
– Temperature decreases at about 2°C per 1,000 feet .
Physiological Zones of the Atmosphere
• Atmosphere can be divided into 2 physiological
zones, which are efficient and deficient.
• These zones can affect us medically and
physiologically.
63,000 ft
DEFICIENT ZONE: 10,000 to 50,000 feet
18,000 ft
EFFICIENT ZONE: Sea level to 10,000 feet
Cont.
Physiological-efficient
zone
Physiological-deficient
zone
• Between sea level to
•
approximately 12,000
feet
•
• Represents10,000
where the
FT MSL
human body can adapt
the environment.
•
• The oxygen levels are
usually sufficient for
human body
requirements.
Between 12,000 feet to
about 50,000 feet.
Human cannot adapt
unless they are in a
pressurized cabin.
Here, there is increased
risk of problems,
especially hypoxia,
trapped-gas, and
evolved-gas situations.
Definition of Hypoxia
• Syndromes of lack of oxygen in blood
• Effect mainly the brain and other nervous
system
How it can be happened??
(Physiologycal Process)
• Hemoglobin is primary
transport to carry oxygen
through blood.
• The ability of hemoglobin to
carry oxygen is called as:
Blood Oxygen Saturation
(normally 95%-98% at sea
level). It is measurable as
we ascend.
Cont
• When altitude is increase, the pressure of oxygen
decrease.
• Caused the lower pressure in lungs
• Transfer process of carrying oxygen affected
• As a result, not enough oxygen to the brain and
affect other part of human body.
• Death will follow if lack of oxygen continues.
Time of Oxygen
1 Minute
2 Minutes
3 Minutes
4 Minutes
5 Minutes
6 Minutes
Put Back on Oxygen
Types of Hypoxia
hypoxic
hypoxia
hypemic
hypoxia
stagnant
hypoxia
histotoxic
hypoxia
Hypoxic Hypoxia (Altitude Hypoxia)
A
deficiency
in Alveolar
oxygen
exchange
Reduced
pO2
in the
lungs
(high
altitude)
Red
blood cells
Body tissue
Cont.
• Most common type of Hypoxia occur in aviation.
• Hypoxic hypoxia occurs when not enough oxygen is
in the air or when decreasing atmospheric pressures
prevent the diffusion of O2 from the lungs to the
bloodstream.
• The partial pressure of oxygen as it is presented to
the blood within the lungs is too low to effectively
carry and transfer enough oxygen to the cells of the
tissues.
Cont.
Cont.
• Can be resulted from:
– Altitude exposure
– Strangulation (compression of air passage cause
the respiration arrest)
– Other:
• Failure of oxygen system in aircraft
• Improper use of equipment
• Failure of depressurization system
Adequate
oxygen
Blood
moving
slowly
Stagnant
Hypoxia
Reduced
blood
flow
Red blood cells
not replenishing
tissue needs
fast enough
Cont.
• Occurs at circulatory level
• A condition that interferes within the normal
circulation of blood arriving at the cells.
• An arm or leg going to sleep because the
blood flow has accidentally been shut off is
one form of stagnant hypoxia.
Cont.
• Can occur as the result of:
– G forces from maneuvers (mostly aerobatic
aircraft)
– Disease of the blood vessels
– Cardiac (Heart) Arrest
– Shock
– Exposure to Cold
– Sudden change in posture
Cont.
The g-force, on something is its acceleration relative to
free-fall.
This acceleration experienced by an object is due to the
vector sum of non-gravitational forces.
Accelerations not produced by gravity are termed
proper accelerations, and cause stresses and strains
on objects. Because of these strains, large g-forces
may be destructive.
Hypemic Hypoxia
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Cont.
• Occurs at blood level.
• An oxygen deficiency due to reduction in the
oxygen carrying capacity of the blood (Low
Hemoglobin)
Cont.
• Caused by:
– Anemia (A deficiency of red blood cells)
– Bleeding
– Taking some prescription drug.
– *Blood donation
– Other:
Carbon Monoxide
• Smoking ;
• cabin contamination with
engine exhaust fume
interferes with oxygen
binding to the blood
Cont.
• *Blood Donation:
Symptoms of hypoxia at lower altitudes
Most airlines:
– No flight for 72 hours after donation of whole
blood
– No flight for 12 hours after donation of plasma
Histotoxic Hypoxia
Adequate
oxygen
Inability of the
cell to accept
or use oxygen
Red blood cells
retain oxygen
Poisoned tissue
Cont.
• Occurs at cell level
• Interferes with the normal utilization of
oxygen into the cells.
– plenty of oxygen is being transported to the cells
that need it, but they are unable to make use of it.
• Tissue cells are poisoned and unable to use
oxygen
• Caused by Alcohol and Drug
Why important to recognize?
• If hypoxia is prolonged, serious problems develop with
ultimate death . In extreme cases (prior to death), some brain
cells are actually killed, and they cannot be regenerated.
• The single most dangerous characteristic of hypoxia is that if
the crewmember is hypoxic and engrossed (complete
attention) in flight duties, the pilot might not even notice the
impairment.
Stage of Hypoxia
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INDIFFERENT STAGE – earliest symptoms-effect on the eye. (Decrease in night
vision)
COMPENSATORY STAGE –
– Physiological compensations provide some defense against hypoxia so that the
effects are reduced unless the exposure is prolonged or unless exercise is
undertaken. Respiration may increase in depth or slightly in rate, and the
pulse rate, the systolic blood pressure, the rate of circulation, and the cardiac
output increases.
– Symptoms: poor judgement, drowsiness(sleepy state), impaired coordination,
impaired efficiency.
DISTURBANCE STAGE
– In this stage the physiological compensations do not provide adequate oxygen
for the tissues.
– Chance of recovery greatly diminished.
– Symptoms: impaired in flight control, handwriting, speech, coordination
CRITICAL STAGE –
– Unconsciousness (e.g: blackout, faint)
– In the critical stage consciousness is lost. Death follows shortly.
Sign and Symptoms of Hypoxia
• Sign- can detected by observer/ crew
members
• Symptoms-perceived by crew members
Sign of Hypoxia
• Increase in depth and rate of breathing
• Cyanosis (A blurry effect of the skin, most
noticeable on the lips and the fingernail)
• Delayed in reaction time
• Poor Judgment
Symptoms of hypoxia
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Air Hunger ( a feeling not enough breathable air)
Feeling of fearful or anxiety (nervousness)
Mental confusion
Fatigue
Nausea (just before vomit)
Headache
Dizziness
Hot and cold flashes
Tingling (Prickle)
Visual Impairment (colour vision, night vision, blurred)
How to prevent??
• Reduce tolerance to altitude (descends)
– Don’t fly to high altitude
• By enriching the inspired air with oxygen from
an appropriate oxygen system (Oxygen Tank &
Mask)
• By maintaining a comfortable, safe cabin
pressure altitude (Cabin Pressurization)
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Avoid alcohol and smoking
Healthy Diet
Good physical condition
Lower altitudes
Avoid temperature extremes
Slower Climb rates
Corrective action
• Once the symptoms/sign are identified, the
corrective action must be taken (based on
FAR):
– Wear oxygen mask
– Turn on Oxygen
– Make sure all connection secure
– Slow down your breath rate
– Descend to altitude where supplementary oxygen
no longer required.
Supplemental Oxygen
Effective Performance Time (EPT)
• 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 EPT, 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).
• EPT decrease as altitude increases.
Conclusion
• The danger of hypoxia is that the pilot is probably
unsuspecting that he/she is hypoxic.
• The key to flying safe at high altitude is to recognize:
– The conditions under which you could be hypoxic.
– The physical and mental symptoms that indicate you are
hypoxic.
– When a crewmate is susceptible to hypoxia in those
conditions.
Presented by Mohd Amirul for AMC
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Key Points
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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
Presented by Mohd Amirul for AMC
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End of Presentation #2
5 Minutes for Q/A session
Presented by Mohd Amirul for AMC
49