Aerospace Physiology Flashcards
AP101: What is the approximate percentage of oxygen, nitrogen and other gases at 18,000 feet MSL?
21% oxygen, 78% nitrogen, and 1% other gases
AP101: Which of the following is the best description of atmospheric pressure and its cause?
The combined weight of all the atmospheric gases which is caused by gravity pulling the gas molecules earthward and thermal and solar radiation expanding the gases outward toward space
AP101: What are the common units used to measure atmospheric pressure?
Inches of mercury (inHg), Millimeters of mercury (mmHg), and Pounds per square inch (psi) - All the above are correct.
AP101: Which of the following represents the notation for the partial pressure of gases?
PO2 partial pressure of oxygen, PCO2 partial pressure of carbon dioxide, PN2 partial pressure of nitrogen.
AP101: PO2 increases and the percentage of oxygen decreases as the altitude increases. (True/Flase)
False
AP101: What is the temperature lapse rate up to approximately 35,000 feet?
About 2 ºC per 1,000 feet
AP101: The human body is adapted to which physiological division of the atmosphere?
Physiological zone
AP101: Explain Boyle’s Law
Explains why a balloon expands as it ascends and also why a volume of air expands when trapped in a body cavity when the pressure is reduced around it
(Pressure v. volume)
AP101: Explain Henry’s Law
Explains why a soda pop bubbles after it is opened
(Gases dissolved in liquids)
AP101: Explain Dalton’s Law
Explains how exposure to a high altitude can reduce the available oxygen
(addition of all the partial pressures)
AP101: Explain Ideal Gas Law
Explains why the temperature increases in a cylinder that is being pressurized
AP101: Explain Law of Gaseous Diffusion
Explains how oxygen moves out of the lungs into the bloodstream
Human factors is concerned with?
optimizing the relationship between people and their activities, by the systematic application of human sciences, integrated within the framework of systems engineering
What is the SHELL model?
S: Software
H: Hardware
E: Environment
L: Liveware
L: Liveware-Liveware
In modern aviation, human factors have accounted for roughly how many aircraft accidents?
the majority of accidents (60-80%)
The atmosphere is defined as
the gaseous envelope surrounding the Earth
Almost all flying takes place in what layer of the atmosphere?
Troposphere
What are some characteristics of the troposphere?
-captures the most solar energy
-has water vapor (humidity)
-decrease in temperature with the increase of altitude
-weather phenomena
What changes about gases with increased altitude?
Pressure (NOT percent)
What is pressure defined as?
force that acts on a unit area
Density and pressure (increase/decrease) exponentially as one ascends from the earth’s surface
decrease
What is the standard temperature and pressure at sea level?
+15 ºC and 760 mmHg (29.92 inHg)
Where does the greatest pressure change occur?
The greatest pressure change occurs at lower atmospheric levels between sea level and 18,000 feet.
What is the standard temperature lapse?
Altitudes up to about 35,000 feet reflect a constant decrease in temperature of about 2 °C (3.6 °F) per 1,000 feet
What is the physiological zone and how far does it extend up to?
The physiological zone extends from sea level to approximately 10,000 feet and is the zone the human body is adapted to
What are the divisions of the atmosphere?
Physiological Zone: Sea level - 10,000’
Physiological Deficient Zone: 10,000’ - 50,000’
Space Equivalent Zone: above 50,000’
What is Dalton’s Law of Partial Pressure?
Dalton’s Law of Partial Pressure states the total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas in the mixture
How does Dalton’s Law explain how exposure to a high ambient altitude can reduce the available oxygen?
As ambient altitude increases, the total atmospheric pressure decreases causing, specifically partial pressure of oxygen (PO2) to decrease even though the percentage of oxygen remains the same.
What is Boyle’s Law?
Boyle’s Law states when the temperature remains constant, as in the human body, a volume of gas is inversely proportional to the pressure surrounding it.
What is the application of Boyle’s Law?
Boyle’s Law explains for the effects of pressure changes in the ears, sinuses, teeth, and gastrointestinal tract
What is Henry’s Law?
if pressure is reduced above the solution, some gas
will come out of the solution.
What is the Ideal Gas Law?
describes gas behavior using three interrelated variables: pressure (P), volume (V), and temperature (T).
What is the Law of Gaseous diffusion?
A gas will diffuse from an area of higher
concentration or pressure to an area of lower
concentration or pressure until equilibrium is reached.
The speed of this movement depends on the relative
concentrations of the gases
What is the physiological significance of the Law of Gaseous Diffusion?
the transfer of gases between the blood or other
body fluids and the tissues they contact (also explains hypoxic hypoxia when coupled with Dalton’s Law)
What is the overall goal of Aerospace Physiology?
to train crewmembers to increase safety and mission effectiveness by identifying and eliminating physical, physiological, and psychological limitations of the flying environment.
AP102: The purpose of respiration is to get ____ into the body and to remove excess _____.
Oxygen into the body and remove excess Carbon Dioxide
AP102: What is/are the site(s) of gas exchange in the lung between the atmosphere and the blood?
Alveoli
AP102: What is the normal breathing rate of an average adult?
12-16 breaths per minute
AP102: What is the most important factor in the control of ventilation under normal conditions?
PCO2
AP102: What is the main function of red blood cells?
Carry oxygen
What are the functions of respiration?
-Intake, filtering, and conditioning of air (warm and humidify)
-Gas exchange
-Temperature regulation
-Metabolic function
-Maintain acid-base balance (pH) of blood
Why are the Oral-Nasal Cavities (mouth, nose, and pharynx) lined with a mucous membrane and why is it important?
the nasal cavity mucous membrane filter inspired air
Humidifying and warming the air protects the lungs from being cooled or dried out
What is the primary function of the lungs?
allow oxygen to move from the air to the microscopic blood vessels (capillaries) and carbon dioxide to move from the capillaries into the lungs
What are alveoli?
tiny air sacs in the lungs at the end of the bronchioles
Where does gas exchange for the respiratory and circulatory systems occur at in the lung?
Why do oxygen and carbon dioxide move between air and blood there?
Gas exchange occurs at the alveolar-capillary interface.
Oxygen and carbon dioxide move between air and blood by simple diffusion, (Law of Gaseous Diffusion) from an area of high to low partial pressure.
What does the rate and depth of breathing change in response to?
the concentrations of carbon dioxide (CO2), oxygen (O2), and hydrogen ions (H+) in arterial blood
What are the three ways the body regulates arterial blood pH?
- Chemical acid/base buffer system
- Respiratory system
- Kidneys
The most important factor in the control of ventilation under normal conditions is?
the PCO2 of the arterial blood
On ascent to high altitude, a large increase in ventilation can occur in response to a lack of sufficient PO2. What can this cause?
An increase in ventilation that can cause an increased loss of CO2 resulting in an increased arterial blood pH (hypocapnia)
What are the five distinct phases of respiration?
Ventilation
Diffusion (1)
Transportation
Diffusion (2)
Utilization
What is ventilation?
the inhalation and exhalation of gas
What is diffusion (1)?
when the oxygen and carbon dioxide pass through the alveolar membrane and capillary walls into the red blood cells
What is transportation?
when oxygen is carried by the blood to the cell and tissues for utilization
What is diffusion (2)?
the movement of gases between the blood, the interstitial fluid, and the cells
What is utilization?
when the oxygen is used to produce energy which results in carbon dioxide and water as byproducts
What is the tidal volume of gas in adults? About how many breaths is that per minute?
about 500 milliliters
12-16 breaths per minute
What are the active and passive components of respiration? Why are they referred to this way?
The active component of respiration is inspiration. This is because it is accomplished by the contraction (downward movement) of the diaphragm and external intercostal muscles.
The passive component of respiration is exaltation. Muscular effort is not required during exhalation.
What does the circulatory system do?
transports and distributes nutrients and oxygen to the tissues and removes waste products of metabolism
What is the circulatory system comprised of?
A pump (heart), a series of distributing and collecting tubes (arteries and veins), and an extensive system of thin vessels that allow the rapid exchange between the tissues and the vascular channels (the capillaries)
Blood circulates through the cardiovascular system in a mixture of cells within a liquid called?
Plasma
How much of the blood is plasma? What is plasma comprised of?
~55% of the blood
Plasma is made of red blood cells, white blood cells, and platelets
What is the primary function of red blood cells?
Transport O2 and CO2
(Hemoglobin is responsible within the cell for transporting O2)
What is the function of metabolism?
To convert chemical energy into mechanical and thermal energy to sustain life
What factors affect oxygen delivery to the tissues?
- Altitude
- G-forces
- Toxic Gases or substances
A lack of oxygen in body tissues that is sufficient to cause an impairment of function is called?
Hypoxia
AP103: During ascent (as ambient pressure decreases), gases trapped within body cavities will _____.
expand
AP103: The four areas of the body influenced by the mechanical effects of trapped gases are:
Ears
Sinuses
G.I Tract
Teeth
AP103: What is the best method of preventing problems with the ears and sinuses in-flight?
Do not fly with a cold
AP103: Match each symptom with the appropriate decompression sickness type
CNS (neurological manifestations)
Partial paralysis, loss of speech or hearing
Severe, persistent headache
Vertigo, loss of orientation
Tingling of one arm, leg, or side of the body
AP103: DCS is caused by _____ coming out of the solution in the tissues and blood
nitrogen
AP103: List, in order, the corrective actions for any suspected or observed DCS.
______ oxygen
______ the affected area
______ as soon as practical
Obtain ______ (flight surgeon)
______ therapy (if required)
100% or maximum
Immobilize
Land
Medical Assistance
Hyperbaric
AP103: Adequate protection against DCS can be established by _____ and/or _____
cabin pressure; denitrogenation
AP103: The USAF forbids flight within ______ hours of a compressed air exposure for all normal flying operations
24
AP103: ______ is a state of oxygen deficiency in the blood, cells, or tissues sufficient to cause an impairment of function
Hypoxia
AP103: ______ _______ is usually caused by exposure to low barometric pressure
Hypoxic hypoxia
AP103: Match each type of hypoxia with the appropriate cause
Hypoxic hypoxia
Loss of cabin pressurization
Oxygen equipment malfunctions
Improper use of oxygen equipment
AP103: Match each type of hypoxia with the appropriate cause
Stagnant hypoxia
Cold temperatures
Shock
Hyperventilation
“G” forces
AP103: Match each type of hypoxia with the appropriate cause
Hypemic hypoxia
Drugs
Carbon monoxide
Blood donation
AP103: Match each type of hypoxia with the appropriate cause
Histotoxic hypoxic
Alcohol
Cyanide
AP103: The most dangerous characteristic of hypoxia is its _____ _____
insidious onset
AP103: What signs/symptoms are normally associated with hypoxia
Bluing (cyanosis)
Impaired vision
Hot or cold flashes
Dizziness
Light headedness
Loss of muscle coordination
Apprehension
Feeling of well being
Tingling
Impaired judgment/confusion
AP103: The time of onset of hypoxia and the severity of symptoms are identical with all crewmembers from one day to the next. (True/False )
False
AP103: __________ of __________ is the period of time from the interruption of the oxygen supply or exposure to an oxygen poor environment, to the time when useful function is lost.
Time of useful consciousness
AP103: What factors decreases TUC (Time of Useful Consciousness)?
Increased physical activity
Stress
Hypoxia (histotoxic, hypemic, stagnant)
Rapid decompression
Anxiety
Increased altitude
AP103: A _____ can reduce your TUC by as much as _____ %
rapid decompression can reduce TUC by as much as 50%
AP103: Hyperventilation is a condition in which the _____ and/or _____ of breathing is abnormally increased
rate and/or depth
AP103: Hypocapnia causes an excessive loss of ______ from the lungs and blood
carbon dioxide
AP103: List five signs and symptoms of hypocapnia
Signs: muscle tightness/spasms, increased rate/depth of breathing, paleness, cold, clammy skin, unconsciousness
Symptoms: dizziness, faintness, slight nausea, numbness, tingling, coolness, muscle tremors
AP103: The most frequent cause of hypocapnia in flying training is?
Stress
AP103: Complete the crewmember’s emergency procedures for the treatment of hypocapnia and/or hypoxia
a. _____ oxygen under _____
b. Connections - _______
c. Breathe at a ______ and depth slightly less than normal until symptoms ______
d. Descend below _______ feet MSL and land as soon as ______
a. Max; pressure
b. Check security
c. rate; disappear
d. 10,000; practical
What is aircraft pressurization via isobaric system?
Constant cabin pressure
With this type of system, the pressure difference between cabin pressure and ambient pressure increases with altitude.
What is aircraft pressurization via an isobaric differential system?
With this system, the aircraft is unpressurized until a preset cabin pressure is reached. Once reached, the isobaric function of the system maintains a constant pressure within the cabin until a selected pressure differential (cabin pressure versus ambient pressure) is attained. Thereafter, as the aircraft climbs, the system maintains the designated pressure differential between cabin pressure and ambient pressure.
How does the T-6 pressurization system work? What kind of system is it?
The T-6 is equipped with an isobaric differential pressurization system. As the aircraft approaches 8,000 feet pressure altitude, the control valve regulator will open and close the control valve to maintain cockpit pressure. An 8,000-foot cockpit altitude is maintained until a pressure differential pressure of 3.6 ±0.2 psi is reached at 18,069 feet. This differential is maintained from 18,069 feet to 31,000 feet, where maximum cockpit pressure altitude is 16,600 feet.
Why are fighter/attack aircraft pressurization systems typically set at a lower pressure differential?
This safeguard is provided because of the smaller cabin volume and the increased danger of decompression during combat operations
What is the primary purpose for aircraft pressurization?
reduce the possibility of DCS and hypoxia
What are the advantages of aircraft pressurization?
- Reduced risk of hypoxia
- Reduced risk of decompression
- Reduced GI expansion
- Allow more room to move around with less oxygen equipment
- Protects sinus and inner ear with controlled descent
- Controls cabin temperature, humidity, and ventilation
- Minimizes fatigue and discomfort
- Reduce need for supplemental oxygen below 10,000 feet
What are the disadvantages of aircraft pressurization?
***1. Decompression
2. Increased weight
3. Additional design
4. Decreased performance
5. Increased cost
6. Requires control of cabin air contamination from smoke, fumes, etc.
What are the three types of decompression (and associated times)?
Explosive (0.5 sec)
Rapid (0.5 to 15 secs)
Slow (15 secs+)
What is the difference between explosive and rapid decompression?
Explosive decompression decompresses the lungs, which could damage them.
What is perhaps the most dangerous type of decompression?
A slow decompression is potentially the most dangerous type of decompression because it can be so slow that you may not even notice. If unaware of the decompression, hypoxia may occur, and you could be incapacitated
A pressurization loss requires descent to what altitude?
Below 10,000 feet
What determines the rate and severity of the decompression?
the pressure differential
The initial difference between the cabin pressure and the ambient pressure
What determines the time required for decompression?
The pressure ratio, defined as the ratio between cabin pressure and ambient pressure
The larger the ratio, the longer it takes for the two pressures to equalize.
The most severe physiological effects are produced by a decompression involving?
a large pressure change over a short period of time
What are physical indications of a rapid decompression?
Explosive noise
Pressure
Temperature
Fogging
Flying debris
AP104: The primary purpose for aircraft pressurization is to
reduce/prevent decompression sickness and hypoxia
AP104: List additional advantages of aircraft pressurization
a. Reduced need for supplemental oxygen
b. Reduced expansion of G.I. gas
c. Control temperature and humidity
d. Move without the encumbrance of oxygen equipment
e. Minimize fatigue
f. Protect ears/sinuses from rapid pressure change
AP104: The primary, and most critical, disadvantage of aircraft pressurization is the potential for a _____
decompression
Rods and cones are distributed over the entire retina except for?
where the optic nerves and blood vessels exit the eyeball
What is the optic disk known as?
The anatomical blind spot
Why can we not normally recognize the anatomical blind spot?
the optic disks are in different locations in each eye, therefore, when the eyes are being used simultaneously, called binocular vision, the nerve impulses from the retinas provide the brain with an image negating the effects of the blind spots. The blind spot will only be noticed when an object is being viewed with one eye, monocular vision
Why do you not notice a blank spot even with monocular vision?
the blind spots is “active.” The brain “fills in” the missing visual information caused by the blind spot with surrounding visual information
What is the fovea?
a tiny pit containing only cones and the natural point on the retina where the lens focuses an image. Your best color vision and maximum visual acuity are in the fovea
What are cones?
Cones are the photoreceptors allowing you to see the details of the world in color under bright light conditions. They are densest in the center of the retina and decrease in number toward the periphery.
What are rods?
Rods are the photoreceptors densest at the periphery of the retina and decreasing in number as the center of the retina is approached. They allow you to see in gray tones under conditions of dim light and provide for our peripheral vision. Anything interfering with rod function interferes with your ability to see at night.
What are the three types of vision?
Photopic: daytime vision
(Colors are easily discerned, and images are sharp)
Scotopic: nighttime vision
(Cone cells are ineffective, resulting in poor resolution of detail. Color vision is lost)
Mesopic: dawn and dusk
(both rods and cones are active, although not at peak efficiency)
The total visual field is roughly how many degrees?
150º
What is considered “central vision”?
The center 30º of the visual field
How much of central vision is used for focal vision or high acuity?
The very center 3º
(The rest of the visual field is considered peripheral)
What kind of vision is processed at a higher level of consciousness?
Focal vision is processed at a higher level of consciousness and peripheral vision is processed at a more subconscious level.
Why does focal vision require high illumination levels?
Focal vision also requires high illumination levels because the fovea consists solely of cone cells. As a result, you don’t have the same visual acuity during night or low-light operations as during the day.
What is peripheral vision primarily used for? What photoreceptors make up most of the peripheral vision?
Peripheral vision is used primarily to orient oneself relative to the environment
Most of the photoreceptors used in peripheral vision are rods (poor visual acuity)
What is the mechanism for judging distances of objects within about 200 meters?
Stereopsis
Binocular cues refer to?
the mechanisms by which aircrew assess depth and distance
What are the 4 Common Physiological Limitations and Threats?
Visual Contrast
Shapes of Targets
Movement of a Target
Environment
Visual Contrast helps the eye acquire the target. Objects are sensed by the differences between light and dark. Therefore, the greater the contrast of a target against its background, the ____ it is to detect.
easier
Shapes of Targets also affect the eyes’ ability to acquire them. The larger, more angular the shape of the target, the _____ it is to see
easier it is to see and is sometimes referred to as its “visual cross section.”
The movement of a target is easier to detect than a stationary target. What kind of background is easier to detect movement in?
An aircraft flying against a broken, irregular background, like a partly cloudy sky, requires less apparent movement to be detected than when it is flying against a featureless background, like a clear sky
Name one environmental influence on vision
Hypoxia (starving the eyes of oxygen)
Terrain around airfields can contribute to miscues and false perceptions of altitude during approach to landing. An airfield situated at an end of a valley with slowly rising terrain at the approach end of the runway can cause you to land your aircraft ______. Conversely, flying an approach over terrain sloping away from the approach end of the runway may cause you to ______.
land long with rising terrain
descend early with sloping away terrain
How can differently shaped runways change your perception during landing?
Longer/skinnier runways will make you feel too high on the approach, whereas shorter/fatter runways make you feel too low on the approach
Reaction time is a measure of how quickly an organism can respond to a particular stimulus. How long does it take an average aviator to make a decision with a resultant motor input?
6.1 seconds
What is the proper scanning techniques?
During the day, a “Z” pattern
At night, an off-centered diamond
Most near mid-air collisions in the United States occur
below 12,500 feet MSL
A majority of bird strikes occur
Below 2,000 feet AGL
What does the subtle limitation (tending to increase perception time/reaction time) of expectancy mean?
Once you are notified of conflicting traffic, and especially if you are given the type of conflicting aircraft, you form a mental picture of your target. Unfortunately, your mental picture may not accurately reflect what you should really be seeing
What is the physiological blind spot?
At night, there may not be enough light emanating or being reflected from a target to stimulate the cones in the fovea. Therefore, the central area of vision (cone vision) becomes a central area of no-vision
How long do rods take in absolute darkness to obtain maximum sensitivity?
20-30 minutes or longer