Aerospace Physiology JP101-JP112 Flashcards
Human factors - JP101
study of the physiological, physical, psychological, and pathological limitations and capabilities of people as they interact with their environment
atmosphere
the gaseous envelope surrounding the Earth
Atmospheric Functions
It contains oxygen, essential for animal life and carbon dioxide, essential for plant life. It is a shield that attenuates cosmic and ultraviolet radiation.
Precipitation occurs in the atmosphere, helping maintain the temperature and climate.
Atmospheric Composition
The gaseous envelope surrounding the Earth contains nitrogen, oxygen and argon with traces of carbon dioxide and inert gases (such as helium and neon).
Atmospheric Gas Percentages
The approximate percentages of gases in the atmosphere are 78 percent nitrogen, 21 percent oxygen and 1 percent other gases (including 0.03 percent carbon dioxide).
Pressure
Force/Area
Units of measurement for pressure
psi, mmHg, inHg
Atmospheric or barometric pressure
the combined weight of all the atmospheric gases acting to create a force upon the surface of the Earth.
standard temperature lapse rate
altitudes up to about 35,000 feet reflect a constant decrease in temperature of about 2 deg C (3.6 deg F) per 1,000 feet
physiological zone
extends from sea level to approximately 10,000 feet and is the zone the human body is adapted to
altitude when the use of supplemental oxygen is required
When flying unpressurized above 10,000 feet MSL
Physiological Deficient Zone
This zone extends from approximately 10,000 feet to approximately 50,000 feet. Because of reduced atmospheric pressure, inadequate oxygen is available to sustain normal physiologic functions. Also, decompression sickness (caused by evolved gas) can occur in the body tissues and joints.
Altitude required for pressure suits
FL500
Space Equivalent Zone
exists above 50,000 feet. The physiological problems of flight above 50,000 feet are essentially the same as those for space. The need for protection in a sealed cabin or pressure suit, the problem of ebullism (tissue water vaporization) above 63,000 feet
mmHg in each zone
760 at 0 MSL, 523 at 10,000 MSL, 87 at 50,000 MSL
Partial Pressure
the amount of pressure that a single gas out of a mixture of gases contributes to the sum or total pressure of that mixture, designated with a P in front of the element/compound symbol
Dalton’s Law
explains how exposure to a high ambient altitude can reduce the available oxygen. As ambient altitude increases, the partial pressure of oxygen (PO2) decreases even though the percentage of oxygen remains the same.
Boyle’s Law
When the temperature remains constant, as in the human body, a volume of gas is inversely proportional to the pressure surrounding it.
Henry’s Law
the amount of gas in a solution varies directly with the partial pressure of that gas over the solution.
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.
Charles’ Law
When volume is constant, the pressure of a gas increases or decreases proportionally to an increase or decrease in its temperature.
Respiration - JP102
the process our body uses to exchange gases with our environment. The primary purpose of respiration is to provide oxygen to, and remove excess carbon dioxide from, the body. The respiratory process also helps maintain the acid-base balance (pH) of the blood.
Metabolism
the sum of all the physical and chemical processes used by cells to produce energy and building materials needed to sustain life.
Phases of Respiration
ventilation, diffusion, transportation and utilization
Ventilation
The volume of gas exchanged between the lungs and the ambient environment per unit time.
Diffusion
Oxygen and carbon dioxide pass through the alveolar membrane and capillary walls.
Transportation
Links the transfer of gases from the lungs to their site of production or use in the cells of the body.
Utilization
Cellular metabolism. This phase involves the use of oxygen in energy production and the production of carbon dioxide and water
The Oral-Nasal Cavities (mouth, pharynx, etc.)
Lined with a mucous membrane. Hair like structures (cilia) in the nasal cavity mucous membrane filter inspired air. The oral cavity plays a lesser role in filtering the air, but regardless of the pathway, air is humidified and heated to body temperature before entering the lungs.
Trachea (or windpipe)
Divides into two branches, one each to the left and right lung. These branches (bronchi) form part of the root structures of the lungs’ air passages.
Lungs
Occupy the greatest part of the chest or thoracic cavity and connect to the bronchi. The lungs’ prime function is to allow oxygen to move from the air to the microscopic blood vessels (capillaries) and carbon dioxide to move from the capillaries into the lungs.
Alveoli
Tiny air sacs in the lungs. Their walls have an excellent blood supply provided by capillaries. In the lung, gas exchange between the respiratory and circulatory systems occurs at the alveolar-capillary interface.
Composition of Inspired Air
Excluding trace amounts of other gases, air is composed of nitrogen and oxygen.
The Dynamic Nature of the Lungs
In adults, the tidal volume (the amount of gas inspired or expired with each normal breath) is about 500 milliliters. This air is normally exchanged an average of 12 to 16 times per minute.
Active/Passive component of respiration
inspiration/exhalation
PCO2, PO2, and pH
Normal ventilation is controlled subconsciously and adapts to changes in ________.
Response to PCO2
The most important factor in the control of ventilation under normal conditions is the PCO2 of the arterial blood.
Response to PO2
Arterial PO2 can normally be reduced from the normal 100 mm Hg to 50–60 mm Hg without evoking a ventilatory response, showing that the role of this hypoxic (low oxygen) stimulus in the day by day control of ventilation is small.
Response to pH
A reduction in arterial blood pH increases ventilation. It is difficult to separate the ventilatory response caused by a fall in pH from that caused by an accompanying increase in PCO2
circulatory system
transports and distributes nutrients and oxygen to the tissues and removes waste products of metabolism
The Heart
Consists of four chambers, but functions as two pumps in series — one to propel blood through the lungs, exchanging O2 and CO2 (the pulmonary circulation) and one to drive blood to all other tissues of the body (systemic circulation)
The Blood
Circulating through the cardiovascular system is a mixture of cells within a liquid called plasma. The cells of the blood serve multiple functions essential for metabolism and defense of the body.
Red Blood Cells
The primary purpose of the red blood cell (RBC) is to transport O2 and CO2
Hemoglobin
Main function is to transport oxygen
hypoxia
A lack of oxygen in body tissues that is sufficient to cause an impairment of function
hypoxic hypoxia
An increase in altitude will reduce the PO2 of inspired air causing ________.
stagnant hypoxia
Blood pooling in the lower extremities during increased-g maneuvering can cause _______, another factor that can reduce oxygen delivery to tissues.
hypemic hypoxia
Various types of toxic gases can cause the blood to carry less oxygen
histotoxic hypoxia
Various types of toxic gases can cause the tissues to be unable to take up or use oxygen
Hypoxia JP103
is an oxygen (O2) deficiency sufficient to cause impairment of function. It occurs most frequently when protection against the fall in O2 partial pressure at altitude fails.
altitude hypoxia
Threshold usually around 10,000 ft MSL, Hypoxic hypoxia is usually caused by exposure to low barometric pressure and is frequently referred to as _____.
Stagnant Hypoxia
Occurs when reduction in cardiac output, pooling of the blood, or restriction of blood flow reduces O2 delivery frequently caused by either hyperventilation or acceleration (G forces)
Histotoxic Hypoxia (2)
Results when the O2 delivered to the cells cannot be used for energy production. Adequate O2 is available to the lungs and the blood is capable of carrying it to the tissues. However, the tissues and cells are unable to use the available O2. Caused by presence of cyanide.
Factors Influencing Hypoxia
Altitude, rate of pressure change, duration of exposure, individual tolerance, physical activity, self-imposed stress,
Signs of hypoxia
increase in rate and or depth of breathing, cyanosis (blueness of the skin, because of insufficient oxygenation of the blood), mental confusion, poor judgment, loss of muscle coordination, and unconsciousness. Behavioral changes, such as euphoria (an exceptional feeling of well-being) or belligerence
Symptoms of hypoxia
dizziness, fatigue, hot and cold flashes, blurred vision, tunnel vision, tingling and numbness. Euphoria and belligerence may also be experienced. headache, nausea, a feeling of apprehension and air hunger
Time of Useful Consciousness (TUC)
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. You are no longer capable of taking proper corrective and protective action, but are still conscious. It is not the time to total unconsciousness.
Ways to treat Hypoxia
- Maximum Oxygen Under Pressure (all 3 switches in on position for O2), 2. Connections - Check Security, 3. Breathe at a Rate and Depth Slightly Less Than Normal Until Symptoms Disappear, 4. Descend Below 10,000 Feet and Land as Soon as Possible,
Pressure Breathing
Delivers oxygen, under pressure, through the crewmember’s oxygen mask. It is a method of maintaining adequate PO2 in the lungs at cabin altitudes above 40,000 ft.
Hyperventilation
a condition in which the rate and or depth of breathing is abnormally increased. This increase causes an excessive loss of carbon dioxide (CO2) from the blood. The excessive loss of CO2 changes the acid-base balance of the blood making it more alkaline.
Causes of Hyperventilation - Voluntary
can be voluntarily induced or corrected by consciously increasing or decreasing the rate and depth of breathing.
Causes of Hyperventilation - Involuntary
Fear, apprehension, tension or stress will sometimes cause an individual to subconsciously increase their rate and or depth of breathing. These stress factors are the most frequent causes of hyperventilation. However, positive pressure breathing can also contribute to hyperventilation.
Recognition of Hyperventilation - Signs
Most often observed in hyperventilation are increased rate and depth of breathing, muscle tightness and twitching, paleness, cold clammy skin, muscle spasms, rigidity and unconsciousness.
Recognition of Hyperventilation - Symptoms
Most often noted are dizziness, faintness, slight nausea, numbness, tingling or coolness and muscle tremors.
Prevention of Hyperventilation
control your rate and depth of breathing
Treatment of Hyperventilation
voluntary reduction in your rate and depth of breathing
Treatment of Hyperventilation (steps)
- Maximum oxygen under pressure, 2. Connections-Check Security, 3. Breathe at a Rate and Depth Slightly Less Than Normal Until Symptoms Disappear, 4. Descend Below 10,000 Feet MSL and Land as Soon as Possible
Trapped Gas disorder
When expanding gas cannot escape places such as the teeth, sinuses, middle ear, gastrointestinal (GI) tract
Ear Anatomy
external ear canal, ear drum, middle ear, inner ear, eustacian tubes, opening to thoat
Valsalva Manuever
Yawning, swallowing, tensing throat muscles, to relieve air pressure in the throat
Ear Block
if the pressure differential of the atmosphere over the middle ear exceeds 80 mmHg, it may be impossible to open the Eustachian tube with equalization pressure methods.
If you are suffering from upper respiratory infections or apparent allergic reactions…
you should not fly or participate in an altitude chamber flight
Delayed Ear Block (Post-Flight ear block)
Can occur up to 2 to 6 hours after landing. It results from breathing high percent oxygen for an extended period of time.
Sinuses
Sinuses are cavities in the bone of the skull and are lined with moist mucous membranes, consists of frontal sinuses, located above and behind each eye, and the maxillary sinuses, located in the bones of the cheeks beneath the eyes.
Sinus Block
When pressure changes occur during ascent or descent, the gases in the sinuses increase or decrease in volume, if the sinus ducts are swollen because of an upper respiratory infection, there may be a blockage of the ducts.
Expansion of Trapped GI Gas
A problem that may be experienced with a decrease in atmospheric pressure is discomfort from expansion of gases in the GI tract
decompression sickness
the disorder produced by the evolution of gas from tissues and fluids of the body (nitrogen bubble formation)
DCS - The Bends
The evolution of nitrogen bubbles into the joints of the body, causing pain. Once bends have developed, breathing 100 percent oxygen while at altitude will not normally resolve the pain. Descent is the only cure and is mandatory for any DCS.
DCS - Neurological Manifestations
In rare incidents of high altitude exposure, the brain and or spinal cord may be affected by nitrogen bubbles, common symptoms are very similar to those of a stroke: disturbances in vision, varying from blind spots in the visual field to flashing and or flickering lights. Other symptoms include severe persistent headache, partial paralysis, loss of speech or hearing, vertigo, distinct sudden personality changes or loss of orientation. Immediate descent is necessary after any evidence of Central Nervous System involvement.
DCS - Chokes
symptoms are very similar to those of a heart attack, and may be misdiagnosed if they are presented to a civilian physician. Immediate decent is necessary
DCS - Skin Manifestations
a mottled, reddish or purplish rash develops on the skin. The rash may be localized in a small area or may be diffused over the body. A slight swelling of the skin may be noted and a slight increase of temperature may exist.
Delayed Reactions (DCS)
Occasionally, the onset of DCS symptoms may appear after the flight. This condition is known as a delayed DCS and may occur within 12 hours.
Factors Affecting DCS Incidence and Severity
increased altitude, rate of ascent, Physical Activity, Previous Injury, age, body composition, repeated exposure, dehydration, diving prior to flying,
USAF and USN regulations forbid flight within _____ after SCUBA diving
24 hours of a compressed air exposure
Prevention of DCS
Aircraft Pressurization, denitrogenation
Treatment of DCS
- 100 percent oxygen 2. descend ASAP 3. consult flight surgeon or aeromedical examiner
Pressurization (JP104)
mechanical means of maintaining greater than ambient pressure within an aircraft cabin.
isobaric system
constant cabin pressure
isobaric-differential 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.
Advantages of Pressurization Systems
- Reduced probability of DCS, 2. Reduced possibility of hypoxia (primary purpose of aircraft pressurization is 1 and 2), 3. Reduced need for supplemental oxygen equipment below 10,000 feet cabin altitude. 4. Reduced expansion of gastrointestinal trapped gas, 5. Controls cabin temperature, humidity, and ventilation within a desired comfort range, 6. Allows the crew and passengers to move freely within large cabins unencumbered by oxygen equipment, 7. Minimizes fatigue and discomfort of crew and passengers during long flights (air evacuation, troop transport, etc.), 8. Protects the sinuses and middle ears from sudden pressure increases during descents by slowly scheduling the
cabin descent
Disadvantages of Pressurization Systems
- Decompression. The primary, and most critical, disadvantage of aircraft pressurization is the potential for decompression. 2. Increased aircraft weight because of the additional fuselage strength required. 3. Requires additional design engineering, mechanical systems, and engine power. 4. Decreased performance and payload. 5. Increased maintenance requirements and costs. 6. Requires control of cabin air contamination from smoke, fumes, carbon monoxide, carbon dioxide, water vapor
and odors
Types of Decompression
- Slow Decompression—Can occur when a leak develops from a failing pressure seal. 2. Rapid Decompression — Easily recognized and you must consider its physiological effects. 3.
Factors Affecting Decompression
speed - size of cabin or size of opening, initial difference determines rate and severity. Larger pressure differential leads to a more severe decompression. The pressure ratio, defined as the ratio between cabin pressure and ambient pressure, determines the time required for decompression.
Physical Indications of a Rapid Decompression
Explosive Noise, Windblast/Flying Debris, Fogging, Temperature, rapid pressure drop
Anatomy of the Eye (JP105)
Cornea, pupil, Lense, rods, Cones, Retina, optic disk, Fovea, optic nerve (anatomy from front to back)
The Retina
The retina is the innermost layer of tissue of the eye, containing millions of photoreceptors (rods and cones) allowing you to “see” an image.
