Flight Physiology

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Commercial

Commercial Ground School AVF 221

FLIGHT PHYSIOLOGY

THE OXYGEN SYSTEM
Alveoli
Hemoglobin
Carbon dioxide
Hypoxia is a lack of oxygen to the body
Different for different people
5000 feet at night
12,000 during daytime
91.211
12,500 to 14,000 30 min crew
above 14,000 full time crew
Above 15,000 everybody
Cabin pressure altitudes

HYPOXIA
Hypoxia means “reduced oxygen” or “not enough oxygen”
Caused by several factors
insufficient supply of oxygen
inadequate transportation of oxygen
inability of the body tissues to use oxygen
Forms of hypoxia based on their causes include
Hypoxic hypoxia
Hypemic hypoxia
Stagnant hypoxia
Histotoxic hypoxia

HYPOXIC HYPOXIA
Insufficient oxygen to the body as a whole
Blocked airway, drowning and conditions at high altitudes are examples of hypoxic hypoxia
Reduction of oxygen partial pressure at altitude
What is partial pressure?
78% nitrogen, 21% oxygen
At higher altitudes, the % is the same but there is less pressure and fewer molecules
This makes it harder to get adequate oxygen through the alveoli in the lungs
The decrease in the number of molecules at sufficient pressure leads to hypoxic hypoxia

HYPEMIC HYPOXIA
The blood is not able to transport oxygen to the cells
Not caused by a lack of inhaled oxygen
Severe bleeding reducing blood volume, anemia or problems with the hemoglobin’s ability to bond with oxygen
CO blocks the ability of hemoglobin to bond with oxygen
CO bonds 200 times more easily to hemoglobin
Can require several days to work it out of the body

STAGNANT HYPOXIA
This a problem with circulation
Heart attack, shock, cold temperatures and GLOC are all causes

HYSTOTOXIC HYPOXIA
This is the cells inability to use oxygen
Alcohol or other drugs may interfere with the cells natural ability to process oxygen

HYPOXIA
Symptoms:
peripheral vision starts to grey out
cyanosis
Feeling of euphoria
Tingling in the extremities
Headache, dizziness, lightheaded
Drowsiness
numbness
Effects:
Loss of judgment
Unconsciousness
Corrective Actions:
Go on Oxygen
Descend to a lower altitude

HYPOXIA
Time of Useful Consciousness
18,000 20 – 30 Minutes
22,000 10 Minutes
25,000 3 – 5 Minutes
28,000 2 – 3 Minutes
30,000 1 – 2 Minutes
35,000 30 Seconds
40,000 9 – 12 Seconds
43,000 9 – 12 Seconds
50,000 9 – 12 Seconds

HYPERVENTILATION
Abnormal increase in the volume of air breathed in and out of the lungs which causes the body to blow off excessive carbon dioxide
Symptoms:
Similar to hypoxia, in addition the person may feel like they are suffocating
Effects:
Similar to hypoxia
Corrective Actions:
Set O2 system to deliver 100% O2 just in case it is hypoxia
Slow the breathing rate
Do the checklist out loud
Sing the Star Spangle Banner

CARBON MONOXIDE POISONING
CO attaches to the hemoglobin more readily than O2
Takes a Hyperbolic chamber to force the O2 back into the blood
Symptoms:
Similar to hypoxia except finger nail beds and lips will turn red
Effects:
Similar to hypoxia except add death to that list
Corrective Actions:
Close all heat valves
Set O2 system to deliver 100% O2 just in case it is hypoxia
Open window try to ventilate the cabin
Descend to a lower altitude

SCUBA DIVING
The Bends
12 hours for flights below 8,000 and no dives requiring a controlled ascent
24 hours for flights above 8,000 or dives requiring a controlled ascent

MIDDLE EAR AND SINUS
Any gas trapped in the body will expand as altitude is increased
That includes that beef and bean burrito you had for lunch
The same thing that happens to the aneroid in the altimeter happens when the Eustachian tube is blocked
This exerts pressure and cause pain and rupture of the eardrum
Valsalva maneuver
The same situation may exist in the sinus cavities

EAR AND SINUS BLOCK
This happens when the Eustachian tube gets blocked and the pressure will not equalize
Symptoms:
Very painful in ears or behind the eyes
Plugged ears or sinuses
Effects:
incapacitation in some circumstances
Eardrum can rupture
Corrective Actions:
Use the Valsalva Maneuver
Descend very slowly or climb
Menthol inhaler
Menthol cough drops will sometimes work

3 MAIN SENSORY ORGANS
Visual
The eye
Vestibular
Ears including motion sensing and balance
Postural or Somatogravic
Nervous system in the skin, joints, muscles

VISUAL
Your eye is made up of Rods and Cones
Rods are light receptive nerves that sense peripheral vision and shades of grey
Cones are light receptive nerves that sense color and clear visual acuity
It takes 30 minutes for a chemical called Rhodopsin (visual purple) to build
Iodopsin is used by the cones and is present all the time
After 10 minutes of darkness your eyes are 10,000 times more sensitive
After 30 minutes they are 100,000 time more sensitive
The attachment point of the optic nerve creates a blind spot

VESTIBULAR
VESTIBULAR
There are 2 major parts concerned with orientation:
Semicircular canals
Otolith organs
Semicircular Canals
Each of the canals is filled with endolymph fluid
Sensory hairs connected to vestibular nerves sense the movement of the fluid

SOMATOSENSORY SYSTEM
The body’s skin, muscles and joints sense your relationship to gravity
Seat of the pants flying is dependent on postural inputs
Centrifugal force can feel like gravity
Slips and skids can fool the brain and create illusions

SPATIAL DISORIENTATION
This happens when your kinesthetic inputs disagree with what is really happening with the plane
The fluid in your semi-circular canals gets to sloshing around
Pay attention and believe your flight instruments

VESTIBULAR/POSTURAL ILLUSIONS
The leans
Abrupt correction of a roll feels like a roll in the opposite direction
Coriolis Illusion
Fluid in the ear stabilizes in a turn, abrupt head movement creates the sensation of movement around a different axis
Graveyard Spiral
Prolonged coordinated turn causes the pilot to feel like a turn in the opposite direction after rollout, causing the pilot to re-enter the turn
Loss of lift in the turn results in increase back pressure which tightens the turn resulting in a spiral
Somatogravic Illusion
Rapid acceleration results in the sensation of a nose up attitude, a pitch down is the result
Inversion Illusion
Change from climb to straight and level creates the sensation of tumbling backwards
Elevator Illusion
An updraft creates the illusion of being in a climb, a pitch down is the result

VISUAL ILLUSIONS
False Horizon
Sloping cloud formations
Obscured horizon
Northern lights
Autokinesis
Stationary light jumps about when stared at
Runway Width Illusion
Narrower than usual looks high
Wider than normal looks low
Runway and Terrain Slopes Illusion
Upsloping runway or terrain looks high causing a low approach
Downsloping runway is opposite
Featureless Terrain Illusion
Over water approach, dark areas, snow creates a black hole app
roach
Causes a lower than normal approach

VISUAL ILLUSIONS
Water Refraction
Rain on the windscreen looks high causing a low approach
Haze
Looks like you’re farther away than you actually are
Causes a low approach
Clear bright conditions have the opposite effect
Fog
Flying into fog or clouds can create the illusion of pitching up
This causes the pilot to pitch down

MOTION SICKNESS
When the brain receives conflicting messages from the visual, vestibular and somatogravic systems
Corrective actions
Fly in less turbulent conditions
Have plenty of ventilation
Keep cool
Don’t puke

STRESS
This is the body’s response to physical and psychological demands
Increased from adrenaline and other hormones include
Metabolism
Blood sugar
Heart rate
Respiration
Blood pressure
Perspiration
Stress falls into 2 categories
Acute
Chronic

STRESS
Acute stress is short term
Usually comes from the perception of danger
Fight or flight mechanism engages
Chronic accumulates over the long term
Usually comes from an intolerable burden
Exceeds the coping mechanisms of the individual
Unrelenting psychological pressures like loneliness, financial, relationship problems
Performance falls off rapidly
Pilots who have this are not safe to fly
Needs a doctor to remedy

FATIGUE
Fatigue also falls into 2 categories
Acute
Short term from physical exertion or lack of sleep
Cured by getting a good nights sleep
Skill fatigue
Special subcategory of acute fatigue
Timing disruption
Appearing to perform a task as usual but the timing is off
Disruption of the perceptual field
Concentrating attention on movement or objects in the center of vision and ignoring those in the periphery

FATIGUE
Chronic fatigue extends over a long period of time
Usually has psychological roots
Continuously high stress levels
Not relieved by a good nights sleep
Symptoms include
Weakness
Tiredness
Palpitations
Breathlessness
Headaches
Irritability
Can cause stomach and intestinal problems and emotional illness

DEHYDRATION AND HEATSTROKE
Dehydration is a critical loss of water from the body
Causes
Hot cockpit
Wind
Low humidity
Diuretic drinks
Symptoms
Headache
Fatigue
Cramps
Sleepiness
Dizziness
The first effect is usually fatigue
Drink 2-4 quarts of water every 24 hours
Most people become thirsty with a loss of 2% of body weight
Carry a container to measure daily intake
Stay ahead of the thirst sensation
Limit daily intake of caffeine and alcohol
Heatstroke is a problem with the body’s ability to control its temperature
May lead to complete collapse
The body absorbs water at the rate of 1.2 to 1.5 quarts per hour
Wear light porous clothing and a hat
Keep the flight deck well ventilated

ALCOHOL
Impairs the efficiency of the body
Impairs judgment
Decrease sense of responsibility
Affect coordination
Constrict visual field
Diminish memory
Reduce reasoning power
Lower attention span
Takes about 3 hours to rid 1 beer
Altitude amplifies the effect
Interferes with the brain’s ability to use oxygen

DRUGS
Painkillers are divided into 2 groups
Analgesics
Anesthetics
Aspirin, Tylenol, Advil are analgesics
Have few side effects in proper dosage
Propoxyphene (Darvon), oxycodone (Percodan), Demerol
Cause mental confusion, dizziness, headaches, nausea, vision problems
Anesthetics are used for surgeries and usually wear off quickly

NIGHT FLYING
After a 30 minutes adaptation the rods are 10,000 time more sensitive to light than the cones
Off center viewing 5-10°
Fatigue and hypoxia have major effects on night vision
Visual acuity may not be rectified for over an hour after a descent from a high altitude
Avoid bright lights
Use red light
When VFR at night watch for a gradual disappearance of ground lighting
Diet and general physical fitness
Vitamin A and C enhance night vision

OXYGEN SYSTEMS
DEP-C is your acronym
Diluter Demand
Supplies oxygen only when the user inhales
May mix cabin air with oxygen or go 100% O
Tight seal on the face
Used up to 40,000 feet
Electrical Pulse Demand
Detects inhalation and delivers oxygen
O is only delivered during inhalation so very little waste
May have an internal barometer that increases O at higher altitudes

OXYGEN SYSTEMS
Pressure Demand
O is supplied under pressure
Tight seal on the face
Provide positive pressure application with a regulator
Used above 40,000 feet
Continuous Flow
Usually for passengers
Has a reservoir bag that collects oxygen from the flow tube
The bag has a higher aspiratory flow rate during inhalation

 

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