LECTURE 2: FLIGHT PHYSIOLOGY1

Aviation Human Factors

Learning ObjectivesBy end of this session, you will be able to:• Understand how the body and mind can be

affected in flight as well as why they are affected in flight.

• Be knowledgeable about the physiology of the body in the flight environment.

Why Important?• Flight physiology and human factors both

have an impact on flight.• More than 70 percent of aviation accidents

and incidents are in some way related to human factors.

• An accident is one incident too many. • No accident occurs without a series of

incidents happening beforehand.

What is Physiology?

The study of human systems' integrated functions and the processes by which they

maintain the body functions.

Flight physiology• Flight physiology is how the body and mind work in

the flying environment.• It includes

– How our organs function, – What keeps them from functioning in a abnormal

environment, – What the pilot can do to protect these functions before

and during flight.• Flight physiology, therefore, is an integral part of

human factors and safe flight, and it has a direct effect on human performance.

Remember• Knowing flight physiology, being aware of its

effects on performance, and maintaining a high index of suspicion when performance becomes poor will continue to make everyone a better and safer pilot.

• Suspicion = a feeling that something is possible

SHELL Model• Model developed by ICAO• This model explain why the physiology of flight is

important, since the human element is obviously crucial and central and every aspect of physiology will affect every other interaction as defined in the model.

• Human factors are how these interfaces and interactions ultimately affect performance.

H

LS E

L

SHELL MODEL

S - Software (procedures, documentation) H - Hardware (technology, machine, equipment) E - Environment (weather, temperature, noise L - Liveware (human)

L- L I V E W A R E (Human) • Core of the model

comprised of human operators, most flexible and critical component in the system.

Objectives of Understanding Flight Physiology

• To prevent incapacitation or impairment, whether mental or physical .

• Incapacitation incapable of performing expected normal activity.

• Mental incapacitation is the mind’s inability to use proper judgment, reasoning, and decision making.

Incapacitation• Beyond that, mental incapacitation turns into

“neurological” incapacitation, whereby the signals from the brain fail to use the sensory information and data from the eyes, ears, touch, smell, and the like.

• Physical incapacitation refers to the body’s inability to function in an expected way.

• The end result of both mental (mind) and physical (body) incapacitations is an unsafe and poorly performing pilot.

Human Body System

Human Body System• Respiratory System• Circulatory System• Nervous System (Brain)

Respiratory System • Respiration is the exchange of gases between

the body and its tissues and the outside ambient air.

• The main objective of respiration is to add oxygen and remove carbon dioxide.

Functions of Respiratory System

Intake of Oxygen [O2]

Removal of Carbon Dioxide [CO2]

Maintenance of body heat balance

Maintenance of body acid base balance [pH]

Active Phase INHALATION

Passive Phase EXHALATION

Breathing in Breathing out

Respiration

• air inflates the lungs

diaphragm descends

• air is forced out

diaphragm relax

What is the functions of

Human Lung?

The Lung• Function of Lung: To transport of oxygen to the rest of body.• Exchange oxygen O2 and Carbon Dioxide CO2 .

The Lung• Air enters through

the nose, mouth, trachea to the bronchial tree.

• Distribute to the ALVEOLI (air sacs), where blood brought with OXYGEN molecules.

• Amount of OXYGEN from Alveoli into red blood cells depends on pressure gradient.

The Lung• Within the red blood cell, there is

Hemoglobin, which function as specialized oxygen transport system that allows far more oxygen to be carried by blood

• At high altitude, we need to increase rate and depth of breathing in order to get enough oxygen into our lung.

Effects of reduced Pressure• As the pressure decreases at high altitude the

movement of oxygen into the blood is impaired.

• The result is hypoxia , or oxygen deprivation.

Hypoxia• State of blood when it has an not enough

supply of oxygen for the requirements of the tissues and body cells

• This can cause impairment of body function especially brain.

• Death will follow if oxygen lack continues.

ALTITUDE PRESSURE

FEET mm/HG ATMOSPHERES

0 760 1

18,000 380 1/2

34,000 190 1/4

48,000 95 1/8

63,000 47 1/16

Pressure Decrease With Altitude

Pressure Decrease With Altitude

• The air pressure is 30% lower at the higher altitude due to the fact that the atmosphere is less dense--that is, the air molecules are farther apart.

Circulation SystemFUNCTIONS: • Carries the blood, which in turn transports oxygen,

carbon dioxide, nutrients, and waste products.

• Assists in temperature regulation.REMEMBER• Any change in oxygen levels to the cells immediately

changes the performance of many organs, especially the brain

Low pressure effect to Vascular System

• At high altitudes, the lower air pressure makes it more difficult for oxygen to enter our vascular systems.

Vascular System

• The link between the heart, lungs, brain, and other parts (blood vessels)

• Function: To maintain blood supply to all tissues of the body

The HeartThe heart is an organ

that pumps the blood through the circulatory system by contraction and dilation.

The Heart at high Altitude• At higher altitudes, our bodies initially develop

inefficient physiological responses.• There is an increase in breathing and heart

rate to as much as double even while resting.• Pulse rate and blood pressure go up sharply as

our hearts pump harder to get more oxygen to the cells.

• These are stressful changes, especially for people with weak hearts.

The Heart at high Altitude• The heart muscle requires oxygen for energy• The heart can fail or become less effective if

oxygen does not reach the heart muscle.• Total blockage of blood to the heart muscle

leads to death of some of the tissues • Dead heart tissue lead to heart attack.

The Brain 1st Part of Brain (4 lobes)-Frontal lobes: thoughts, decisions,

and judgments-Parietal lobes: senses and send

information for processing. -Temporal lobes: Speech center

location and where the brain computes information (for written and spoken communications).

-Occipital lobes: are where information from the eyes is processed.

The Brain• 2nd part of brain (Midbrain): Hypothalamus,

which produces hormones that affect temperature, growth, and other physiological activities.

• 3rd part of brain (Hindbrain): The center of regulation of many of the body’s basic functions, including breathing, blood pressure, heart rate, and many others.

Effect of lack oxygen to Brain

Lack of oxygen to the brain, lead to the failure of the brain function such as

• Inability to do normal physical activities, • Distorted vision • Difficulty with memorizing • Difficulty in judgment and decision making• Loss of thinking ability • Fail to communicate and write well

TYPES OF HYPOXIA

Reduced pO2

in the lungs(high

altitude)

Body tissue

Red blood cells

Hypoxic HypoxiaA deficiency in Alveolar

oxygen exchange

Hypoxic Hypoxia• 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.

An oxygen deficiency due to reduction in

the oxygen carrying

capacity of the blood

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Hypemic Hypoxia

Low- Haemoglobin

Hypemic Hypoxia• Hypemic hypoxia is caused by a reduction in the

oxygen-carrying capacity of the blood.

• Can cause anaemia, a condition in which there is a deficiency of red cells or haemoglobin in the blood.

• Means less capacity for blood to carry oxygen.

• Hemoglobin (Hgb) physically carries 75 times more oxygen molecule.

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Reduced bloodflow

Blood movingslowly

Adequateoxygen

Red blood cells not replenishing

tissue needs fast enough

Stagnant Hypoxia

G-Forces

Stagnant hypoxia• In stagnant hypoxia, the oxygen-carrying capacity of the

blood is adequate but, circulation is inadequate.

• Such decrease in blood flow results from the heart failing to pump effectively.

• Such conditions as heart failure, arterial problem, and blockage of a blood vessel predispose the individual to stagnant hypoxia.

• More often, when a crew member experiences extreme gravitational forces, disrupting blood flow and causing the blood to stagnate.

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Red blood cells retain oxygen

Inability of the cell to accept or use oxygen

Poisoned tissuePoisoned tissue

Adequateoxygen

Histotoxic Hypoxia

Alcohol

• Histotoxic means the target cell expecting and needing oxygen is abnormal and unable to take up the oxygen that is present.

• This abnormality has been created as a result of a toxins present/absorbed by the cell (ex: Alcohol becomes a toxin to the cell)

• Alcohol, narcotics, and certain poisons interfere the use of Oxygen by body tissues.

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Histotoxic Hypoxia

Importance to know hypoxia• No matter what the reason for oxygen not getting to the cell

the lack of oxygen (hypoxia) results in a variety symptoms.• 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.

Why important to recognize?

• Because the nervous system tissues have a heavy requirement for oxygen, especially the brain (and eyes), most hypoxic symptoms are directly or indirectly related to the nervous system (brain).

• 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 in flight duties, the pilot might not even notice the impairment.

Symptoms of hypoxia• Apparent personality change – change in

outlook and behavior• Impaired judgment – loss of thinking ability

with the individual unaware of reduced performance.

• Memory impairment -short term memory is lost early.

Symptoms of hypoxia• Sensory loss- vision, especially for color, is affected

early, and then touch, orientation, and hearing are impairment.

• Impairment of consciousness- as hypoxia progresses the individual’s level of consciousness drops until he becomes confused, then semiconscious, and unconscious. Unless he is rescued he will die and at high altitude death can occur within a few minutes.

How to prevent• Reduce tolerance to altitude (descends)

• 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)