Hypoxia, Hyperventilation, the eye and the ear Flashcards
What is the composition of air?
78% Nitrogen, 21% oxygen and 1% other gases
What is Boyle’s law?
At a constant temperature the volume of a gas is inversely proportional to its pressure
What is Charle’s law?
The volume of a fixed mass of gas held at a constant pressure varies directly with the absolute temperature
What is Dalton’s law?
The total pressure of the gas mixture is equal to the sum of its partial pressure
What is Henry’s law?
At equilibrium the amount of gas dissolved in a liquid is proportional to the gas pressure
What is Hypoxia?
A lack of sufficient oxygen to meet the demands of the body
What is an early symptom of Hypoxia?
Common sense tend to be diminished
What are some symptoms of Hypoxia?
Impaired thinking and judgement slow reactions mental and muscular in-coordination diminished vision and hearing impaired memory
Who is affected earlier with Hypoxia?
Smokers
What is the effect of altitude below 6000ft?
No Supplemental oxygen supply
What is the effect of altitude below 10000ft?
Normal activities can be carried out
What is the effect of altitude at 14000ft?
Significant lack of judgement and concentration
What is the effect of altitude at 18000ft?
Total lack of judgement and concentration
What happens to oxygen pressure with increase in altitude?
Oxygen pressure decreases
Does the proportion of the air mixture change with the change in altitude?
No
What is Hyperventilation?
Breathing in excess of the metabolic needs of the body
What are the main symptoms of Hyperventilation?
Dizziness, Increased sensation of body heat Tingling sensation in fingers and toes Increased heart rate Nausea Blurred vision
How many hours is recommended after a controlled ascent dive ( decompression dive)?
24 hours
How many hours is recommended after a controlled ascent before flight to a cabin pressure altitude of up tp 8000ft?
12 hours
What is the recommended waiting time for pressure altitudes above 8000ft for any type of dive?
24 hours
What is the cornea?
the transparent part of the outer covering of the eyeball which overlies the pupil
Where does light enter the eye from?
The cornea
What is a pupil?
Central Aperture of the iris
What is the function of the pupil?
Control the amount of light entering the interior of the eye
What is behind the iris?
The lens
What is a lens?
A transparent biconvex structure which focuses the light rays onto the retina at the back of the eye
What is the function of the retina?
Convert the images made by the received light into electrical signals whicha re then sent to the brain by the optic nerve
What does Ciliary muscles and ligaments do?
Modify lens curvature
What effects vision in flight?
Amount of light
Contrast of an object against its background
Size and contours of an object against its background
The distance an object is from the eye
The relative motion of of a moving object
Atmospheric conditions ( dust smoke mist rain)
What is the blind spot?
Where the optic nevre is, image is not formed here
What kind of illusion might an up sloping runway give?
The aircraft is higher than it is and lead to a lower approach
What kind of illusion might a down sloping runway give?
The aircraft is lower than it is and lead to a higher approach
What makes runway illusions worse?
Lack of visual ground aids
What does the ear flaps do?
Collects sounds and directs them along the ear canal to the ear drum
What causes the drum to vibrate?
Sounds which are small fluctuations in air pressure
What is the eustachian tube?
Equalizes the ear pressure and connect the ear with the back of the throat
What is needed for the drum to be sensitive?
The air in the middle ear must be the same pressure as the air in the outer ear
Where is the organ of balance?
In the ear
What does the organ of balance consist of?
3 inter-connected semi-circular canals which contain fluid
What happens when the head moves?
The relative movements between the fluid and the canal displaces the receptor which sends a signal to the brain via the auditory nerve
How are the semi circular motion sensing systems arranged?
At right angles to each other in the roll ptch and yaw axis
What does the motion sensing system detect?
Angular acceleration , gravity and linear acceleration
What is Aerotitis?
when the ear becomes distended and inflamed as the pressure in the ear is not readily equalized
How can the ventilation of the middle ear be brought?
yawning and swallowing
Why is it not recommended to fly if you have a cold or other respiratory infection?
Because the tissue around the nasal end of the Eustachian tube is likely to be swollen
Why should pilots not fly when suffering from head colds?
Due tp risk of damage to ear drums
