Flashcards in The Flight Environment Deck (112):
The Push-Pull Effect refers to a potential aircraft maneuver that can set up a pilot for G-induced loss of consciousness. The Push-Pull Effect is characterized by ______________
Decreased + Gz tolerance when preceded by 0 Gz or - Gz exposure. Increased baroreceptor pressure due to increase blood volume in the neck triggers reduced blood pressure during the 0 or - Gz exposure. the subsequent + Gz exposure catches the pilot with (1) reduced eye level blood pressure and (2) dilated blood vessels.
Of the 304 F-16 Class A mishaps in the US Air Force from 1975 to 2003, the three PRIMARY causes were:______________
Engine failure, collision with ground, and midair collision account for the majority of the primary causes of Class A mishaps.
G-induced loss of consciousness is best defined as:
A state of altered perception wherein (one's) awareness of reality is absent as a result of sudden, critical reduction of cerebral blood circulation caused by increased G force.
The pilot of a high performance aircraft turns in his seat to "check six" just prior to pulling + 9 Gz. Which answer best describes what could happen next to the pilot:
The pilot is no more likely to GLOC while checking six than when facing forward and pulling 9 Gz.
The following statements concerning the use of positive pressure breathing for G-protection are true except:
1) PBG can aggravate arm pain in some seat configurations
2) PBG can approximately double the duration of G-exposure that a pilot can tolerate.
3) PBG is effective in preventing G-LOC when used without anti-G trousers.
4) Chest counter pressure increase pilot comfort and allow for the use of higher levels of PPB.
3) the use of PBG without anti-G trousers leads to blood pooling in the extremities and loss of consciousness. It does not prevent G-LOC under these circumstances.
The following statements concerning the physiologic and medical consequences of + Gz acceleration are true except:
a) Ultrasound studies have demonstrated cardiac abnormalities, such as right ventricular enlargement, resulting from chronic exposure.
b) Cervical spine injuries have been reported in high performance pilots.
c) G-induced loss of consciousness can be preceded by loss of vision (greyout or blackout).
d) A pilot can experience G-LOC and not remember it.
e) None of the above.
A. Ultrasound studies have NOT found significant cardiac abnormalities in pilots exposed to + Gz acceleration.
The following factors are associated with increased tolerance to + Gz acceleration EXCEPT:
a) Reclined seat back angle greater than 45 degrees from vertical.
b) Sex (males have a greater tolerance for + Gz).
c) Short stature
d) A properly performed anti-G straining maneuver.
e) A recent exposure (within the past two weeks) to the high-G environment.
b). There is no evidence of a difference in G tolerance between the sexes.
Angular acceleration is defined as:
a) the centripetal acceleration acting along the radius of a circle during curvilinear motion.
b) the rate of change of angular velocity, which in turn is the rate of change of angular position.
c) the rate of change of linear velocity acting tangentially during curvilinear motion.
d) 32.2 ft/sec2 or 980 cm/sec2
e) radians/sec or degrees/sec
b. Angular acceleration is the rate of change of angular velocity, which in turn is the rate of change of angular position. In aviation, angular accelerations occurs as a change of pitch, roll, or yaw velocity.
Systems (or studies) that have been used to improve + Gz tolerance include:
a) water immersion
b) anti-G suit/valve
c) tilt back seat
d) vasoactive drugs
e) all of the above
e. All of the above. Any technique that increases venous return, increases cardiac output, increases arterial blood pressure, or that counters the gravitational effect will increase + Gz tolerance. All of the above systems or studies have been used to try and improve pilot G tolerance.
Studies of miniature swine exposed acutely to G stress up to levels of + 9 Gz for 45 seconds have consistently revealed subendocardial hemorrhage and cardiomyopathy. The cardiomyopathies include myofibrillar degeneration, translocation and clumping of mitochondria and necrosis of cardiac myocytes. It is believed that these same cardiomyopathies occur in humans who are exposed to similar G forces. True or False.
False. Although the swine studies revealed these pathologies at operational G levels, a follow on study in humans using all available clinical monitoring techniques did not reveal similar conditions.
Loss of vision or blackout during + Gz acceleration ensues when the retinal artery pressure falls below the intraocular pressure. The intraocular pressure is approximately:
The arterial pressure drop at eye level is linearly related to the increased G level, ie- it falls about 24 mmHg per G. It was noted that vision was affected as retinal systolic pressure fell below 50 mmHg and a complete loss of vision occurred when retinal systolic pressure fell below 20 mmHg which is intraocular pressure.
During - Gz acceleration the following symptoms may occur EXCEPT:
a) rapid heart rate
b) severe facial congestion, throbbing headache
c) subconjunctival hemorrhage
d) an increase in arrhythmic heart beats
a) Rapid heart rate is incorrect. The increase in preload and vagal stimulation would actually decrease the heart rate. The increase in arrhythmia is due to an increase in vagal tone as a result of increased pressure in the neck, precipitating carotid sinus syndrome. This would cause a decrease rather than an increase in heart rate.
Methods or techniques other than anti-G suit and straining used to increase + Gz tolerance include all of the following EXCEPT:
a) tilting the pilot back from the vertical, ie- up to 65 degrees.
b) positive pressure breathing
c) pre-breathing 5% CO2
Numerous studies have looked at tilt, decreasing the vertical distance between the heart and eye to increase vision during Gz. From 45 degrees to 75 degrees an improvement in vision, heart rate, and muscular straining decreases. Positive pressure breathing reflexly leads to an increase in systemic arterial blood pressure, hence + Gz tolerance. Prebreathing gaseous mixtures with 5% CO and 95% oxygen causes peripheral vasoconstriction and cerebral vasodilation hence increasing tolerance. Aerobic exercise (running) has not been shown to increase tolerance.
The Acceleration Atelectasis Syndrome requires the combination of three factors acting on the pilot during flight. Which one is NOT a factor?
a) the inflation of the anti-G suit
b) the performance of a vigorous M-1 or L-1 straining maneuver
c) exposure to + Gz acceleration
d) breathing 100% oxygen
B) M-1 or L-1 Straining Maneuver
Several studies have investigated this syndrome. In the USAF, cases were found in a group of fighter pilots, 31 of whom had difficulty in taking a deep breath. The symptoms were attributed to absorption atelectasis but was considered that the creation of edema in the lower lung played an important role. Studies in the RAF showed that pilots with G suit inflation and breathing 100% oxygen while pulling G's were susceptible. M-1 and L-1 straining maneauvers do not appear to be implicated.
Premature ventricular contractions (PVC's) of the heart have been observed in human subjects during high sustained + Gz exposure (+ 6.0 Gz for 15 secs). Possible contributing factors include all of the following EXCEPT:
a) effects of sympathetic nervous system stimulation and increased catecholamine levels.
b) changes in cardiac filling.
c) changes in position and mechanical stresses on the heart.
d) inadequate coronary blood flow.
e) lean body mass of the subject.
e) Lean body mass has not been shown to be a contributing factor. Numerous studies, including Shubrooks (+ 9Gz for 45 seconds) showed impacts due to cardiac filling, catecholamine levels, and coronary blood flow, but lean body mass showed no impact.
What is the current USAF approved Anti-G Straining Maneuver (AGSM)?
The L-1 maneuver. It combines a regular, 3 second strain against a closed glottis, interrupted with a rapid exhalation and inhalation, with tensing of all major muscle groups of the abdomen, arms, and legs.
What is the difference between the M-1 and L-1 and Hook Straining maneuver?
The M-1 is done against a partially open glottis while grunting. However, studies showed that it had a lower intrathoracic pressure when compared to the L-1 (closed glottis) and therefore is no longer recommended. The "Hook" is the Navy version of the L-1 where the pilot says "hook" as they begin to strain to close the glottis.
Factors that determine + Gz tolerance (inertial force acting in a head to foot direction) include all of the following EXCEPT:
a) duration at G
b) magnitude of G
c) restraint system
d) rate of onset of G
e) direction of G
C) Restraint system. The direction of the G, rate of onset of G, magnitude of G and duration of G all have an impact on G tolerance. The restraint system has no impact on G tolerance.
From a cardiovascular standpoint, the M-1, L-1 and Valsalva maneuvers are the same and offer equal + G protection when performed by a fighter pilot during high G maneuvering. True or False?
False. The M-1 maneuver is against a partially closed glottis (audible grunting). This has been shown to be less effective than the L-1. The Valsalva consists of forced exhalation against a closed glottis, but without simultaneously tensing the muscles. Thus it is also inferior to the L-1.
What is the Frenzel maneuver?
The Frenzel maneuver was taught to WWII German fighter pilots to help them clear their ears. It is placing the tongue on the roof of the mouth far forward, moving the closed jaw forward to open the eustacian tubes and allowing air to equalize. It is used by scuba divers as well. It does not have anything to do with G tolerance (like M-1, L-1) but rather pressure equalization in the ears.
Positive Gz forces (ie- the inertial force acting from head to foot) causes cerebral hypoxia by decreasing blood flow to the head. However, arterial hypoxemia occurs because + Gz:___________
a) increase the pulmonary ventilation-perfusion inequalities normally present.
b) increases the distance that arterial blood must travel to the cerebral cortex.
c) decreases the time that mixed venous blood is present in the pulmonary capillaries.
d) decreases the time that arterialized blood remains in the retinal capillaries.
a) increase the pulmonary ventilation perfusion inequalities. With increasing Gz, the amount of blood forced into the lower lung fields increases, which increases the VQ mismatch causing a right to left shunt in the alveoli. At + 5 Gz, the mismatch equals about 50% and oxygen saturation to below 85%.
Acceleration tolerance is an important factor in the design of new aircraft. What type of acceleration is best tolerated by the human body?
a) positive acceleration
b) negative acceleration
c) alternating positive and negative acceleration
d) transverse acceleration
d) Transverse acceleration. Human studies have shown that the body can tolerate up to + 20 Gx acceleration (think space capsules).
Which of the following statements concerning the Valsalva maneuver is INCORRECT?
a) it is safer than the Frenzel maneuver for use in the flying population.
b) Use may cause a temporary reduction in blood pressure.
c) Cardiac arrhythmias may accomany its use.
d) the technique may be difficult for some people to learn.
a) The Frenzel maneuver is safer. It does not cause a change in blood pressure or arrhythmia. The valsalva maneuver may cause a temporary reduction in blood pressure due to pressure in the neck causing vasovagal tone and a decrease in heart rate. The Frenzel maneuver is simply moving the jaw and tongue forward to open the eustacian tube for equalizing ear pressure. It has no vagal or cardiac components.
The mean time of incapacitation resulting from + Gz-induced loss of consciousness on a human centrifuge is:
a) 2 sec
b) 5 sec
c) 10 sec
d) 15 sec
e) 30 sec
d) 15 seconds
All catapult launches typically expose the pilot to 2 to 4 seconds of inertial force that peaks at +3 to + 5 Gx. What is the appropriate velocity of an aircraft immediately after having been catapulted at a constant 4-G acceleration for 2 seconds? (1 nm= 6080 ft).
a) 130 knots
b) 140 knots
c) 150 knots
d) 160 knots
e) 170 knots
C. 150 knots.
Velocity = acceleration x time
= 4 g (32 ft sec2)/g x 2 sec
= 256 ft sec2
= 256 ft sec (1nm/6080 ft) (3600 sec)/hour
= 152 nm/hr or knots
All catapult launches typically expose the pilot to 2 to 4 seconds of inertial force that peaks at +3 to + 5Gx. What is the appropriate velocity of an aircraft immediately after having been catapulted at a constant 4-G acceleration for 2 seconds? (1 nm= 6080 ft).
a) 130 knots
b) 140 knots
c) 150 knots
d) 160 knots
e) 170 knots
c) 150 knots
Velocity = acceleration x time
= 4 g (32 ft sec2)/g x 2 sec
= 256 ft sec2
= 256 ft sec (1nm/6080 ft) (3600 sec)/hour
= 152 nm/hr or knots
Relaxed G tolerance is most closely correlated positively with which of the following parameters?
a) The component of the aorta-to-eye distance that is in line with the net G forces (they hydrostatic column, h).
b) The reciprocal of h (1/h)
c) The size of the angle between the seat back and the vertical.
d) The size of the angle between the seat back and the net G force.
e) The cosine of the angle between the seatback and the net G force.
b) Relaxed G tolerance is the reciprocal of h (1/h).
A pilot notices during sustained high + Gz stress, which has been applied rapidly, that there is a certain delay before the onset of tunnel vision, greyout and/or blackout. How long after the necessary hemodynamic compromise (reverse flow or cessation of flow at the eye level) do the visual symptoms appear?
a) Within 0.5 seconds
b) 0.5 to 2 seconds
c) 2 to 10 seconds
d) 10 to 20 seconds
2 to 10 seconds.
Which factor is the least likely consideration to avoid G-LOC during maneuvering aircraft?
a) magnitude, direction, duration and onset rate of G's
b) Low visibility (IMC- Instrument Meteorological Conditions)
c) Anti-G Straining Maneuver (AGSM)
d) Push-Pull Maneuvers
B Low Visibility and Meteorological conditions may increase susceptibility to spatial disorientation, but it not a causal factor in G-LOC.
The purpose of the anti-G straining maneuver (AGSM) such as the M-1 or the L-1 is to:
a) Keep the venous blood in the extremities
b) Keep the venous blood in vital organs like the brain
c) Increase the pulse rate, thus raising cardiac output
d) Increase intra-thoracic pressure to maintain blood flow to the brain
d) AGMS increases intrathoracic pressure and this increased pressure forces blood flow in the heart to the brain.
G-LOC is a contributing factor in fatal aviation accidents involving:
a) Single-pilot, high performance aircraft operations
b) Flight Training operations
c) Commercial carrier aircraft operations
d) All the above
A) Single-pilot, high performance aircraft operations
The utricle, senses ___________ acceleration, and the saccule, provides sensations of ____________ acceleration.
Ultricle = Horizontal acceleration
Saccule = Vertical acceleration
Head up Illusion: During forward acceleration in the absence of visual cues, the otolith organs in the vestibular system interpret the change in velocity as a pitching-up motion as when the aircraft enters a climb. The is particularly hazardous during take-off and in low level flight. The tendency is for the pilot to push the nose down, which can, and has, resulted in the aircraft impacting the surface. Because this often happens during the acceleration associated with take-off, this illusion is sometimes called the ____________________ illusion.
Black Hole take-off illusion
The ____________ illusion is closely related to the head up illusion and is caused by deceleration. When decelerating, the vestibular system provides a sensation of pitching down or entering a descent. Decelerations in aircraft occur not only in adjustments to the throttle but with flap and landing gear extension. The reaction of the pilot is to raise the nose of the aircraft in an attempt to arrest the erroneously perceived descent. This can result in an aerodynamic stall which is particularly hazardous in low visibility operations and while close to the ground.
Head Down Illusion
When an aircraft abruptly transitions from a climb to straight and level flight, the pilot can experience the sensation of tumbling backwards. the reflexive reaction is to push the nose over, which can exacerbate the illusion and lead to additional erroneous control inputs. This is call the ________ illusion.
In the ______________, typically a pilot will have intentionally or unintentionally begun a prolonged turn with a moderate bank. After the vestibular sense fatigues, and the pilot no longer perceives the angular acceleration of the turn. The cupula-endolymph system within the semicircular canals stabilizes to a constant angular velocity. At this point, a continuing constant turn is perceived as no motion whatsoever.
After a long crew duty day, a pilot is performing a difficult approach in marginal weather conditions. While in a right standard rate turn, he turns his head to check his wingman's position. He subsequently feels his control stick thrust to the right. He is unable to center the stick after repeated effort. When he releases his grip on the stick, it returns to a centered position. The most likely cause of this pilot's difficulty is:
a) a control malfuction
b) the somatogravic illusion
c) the Giant Hand phenomenon
d) severe turbulence
c) the Giant Hand phenomenon.
The National Council on Radiation Protection and Measurements (NCRP) was asked to provide guidelines for crew radiation exposure durings spaceflight. They focused on the risk of four late effects. Which was NOT included among these four risks?
a) serious genetic disorders
b) fatal cancer
d) gonadal infertility
e) CNS effects
e. CNS effects. The NCRP focused on the late effects of a-d. (e) is considered an acute effect. For low-Earth orbit flights (space shuttle, space station) the NCRP proposed an acceptable risk level comparable to other less safe occupations (those with lifetime risk of acceptable death of 3%).
Several hours post exposure of the eyes to a laser source, a clinician observes corneal transparency loss, surface exfoliation, tearing and conjunctival discharge in a patient who is unaware of the laser parameters of exposure. The clinician concludes that the possible wavelength of exposure must have been from:
a) approximately 180 nm (ultraviolet) to 350 nm (violet).
b) approximately 400 nm (violet) to 1400 nm (near-infrared).
c) approximately 1450 nm (near-infrared) to 10,600 nm (far infrared).
d) the entire electromagnetic spectrum.
e) a and b.
e) A and B. ANSI standard Z136.31996
Loudness is a psychoacoustic phenomenon. When a listener judges a sound to be twice (or half) as loud when compared to another sound, the difference in sound pressure level between the two sounds is approximately:
Nicotine and caffeine may make one more alert and attentive due to the resultant elevation of noradrenalin. They are also associated with an increase in coronary heart disease rates and can lead to dependence. It takes approximately the following amount of caffeine to develop dependence (approximately 100 mg caffeine per 8 ounce cup of coffee):
a) one cup of coffee per day
b) 2 to 3 cups of coffee per day
c) 5 to 7 cups of coffee per day
d) 8 or more cups of coffee per day
c) The amount of caffeine in coffee varies, as does the size of the cup. The average 8 ounce cup contains 100mg and, as a generalization, since 10mg/kg of caffeine leads to dependence, one should take less than this per day, ie- for a standard 70 kilo pilot that is less than seven cups per day, and preferabley less than 5 to six cups (sizes of cups varying).
The time required for cabin depressurization is determined by all of the following EXCEPT:
a) volume of the pressurized cabin
b) size of the opening
c) pressure differential
d) speed of the aircraft
e) flight pressure altitude
d) Speed of the aircraft
Which of the following is an effect of altitude exposure?
a) vasodilation of extremities
b) decrease in arterial oxygen tension
c) decrease in respiratory frequency and tidal volume
e) all of the above
b) Exposure to altitude causes a reduction in alveolar oxygen tension. This in turn causes a decrease in arterial oxygen tension. The carotid and aortic bodies, when stimulated, actually increase respiratory frequency and tidal volume as well as causing vasoconstriction of the extremities. As a result, blood pressure increases causing tachycardia, not bradycardia.
The primary factor limiting routine Hyperbaric Oxygen treatment of decompression sickness at 60 feet is:
a) oxygen toxicity
b) increased expense if treatment is prolonged
c) nitrogen narcosis
d) patient tolerance to confinement in a small space
e) prolonged exposure to high pressure on body tissues
A. pulmonary oxygen toxicity will occur on 100% oxygen if treatment is prolonged. Nitrogen narcosis is not a problem when 100% oxygen is used. Pressure on the tissues is not a problem. Expense and confinement tolerance are considerations, but necessity of treatment overrides their importance and should not be allowed to limit treatment.
A common problem that occurs when a cockpit instrument is not placed directly in front of the pilot because of the distance between a pointer on a display and the surface of the scale is a visual factor known as:
a) an illusion
d) poor acuity
b. Parallax. A common problem that occurs when a cockpit instrument is not directly in front of the pilot because of the distance between the pointer on a display and the surface of the scale is a visual factor known as parallax.
The Wind-Chill Index was developed by Siple in the 1940's and is widely used to assess cold weather in both military and civilian settings. Which of the following statements correctly describe the Index?
a) It is based on subjective judgements of cold discomfort.
b) It is based on measured cooling power of the atmosphere.
c) It has been empirically correlated with "time to freezing" for exposed flesh
d) It is the most accurate under conditions of extreme cold and high winds
e) A, B, and C
e) A, B, and C. The Index was developed from measurements of the cooling rate of water in a cylinder exposed to ambient conditions in Antarctica. Findings were then correlated with time to frost "nip" of the face and subjective judgments of unpleasantness. The concept of "Equivalent Chill Temperature" was a combination of wind and air temperature. The Index is less accurate under extreme conditions due to instrumentation problems and a paucity of data in the original series of experiments.
Participating in typical flight operations has been recognized by the Aerospace Medical Association as one of the most effective methods to develop knowledge of the mission and equipment. Why is this important for the flight surgeon?
a) To assist him/her in developing appropriate flying safety material.
b) To get flying time and to learn how to fly in case of an emergency.
c) To help in the evaluation of a crew member who has developed a medical problem as a result of flying.
d) As a fring benefit- trips to interesting places.
e) A and C.
e) A and C. It is appropriate to emphasize that flight activities benefit the flight surgeon not only in his flying safety activities, but also in his clinical work. Whether he is evaluating a crewmember who has developed a medical condition as a result of flight duties or determining if a flyer's condition could jeopardize safe flight, the flight surgeon must be well versed in typical flight operations.
Sleep follows biological rhythms. Which of the following is true in "good sleepers" (those not bothered by insomnia)?
a) Minimum body temperature occurs at sleep onset.
b) Minimum body temperature occurs about 2 hours after falling asleep.
c) Minimum body temperature occurs about 4 hours after falling asleep.
d) Minimum body temperature occurs about 6 hours after falling asleep.
e) Minimum body temperature occurs upon awakening.
C. Sleep comes most easily when body temperature is falling and is hardest to sustain when temperature is rising. In good sleepers, body temperature rhythms are appropriately aligned and occur approximately 4 hours after sleep onset.
In regard to potential disasters, tornadoes are an ever present threat and occur, not infrequently, in the US. The predilection of this phenomena for open, flat areas of our country results in an increased potential for a disaster involving airdromes and the associated population. In your preventive medicine program involving disaster medicine, in what location listed below would you point out to be the most dangerous during a tornado?
a) house or public building
b) open area
c) automobile or similar vehicle
d) all of the above are probably equally dangerous
c) Automobile or similar vehicle. A review by the CDC following the tornado disaster at Wichita Falls, TX in April of 1979 revealed of the 44 traumatic deaths, 25 were associated with passenger vehicles, 8 occurred in the open, and 4 each occured in public buildings and houses. The least risk of fatal injury appeared to be those taking shelter in cellars, closets, hallways, and basements, even when the buildings were completely destroyed. Covering with mattresses or heavy blankets provides considerable protection from flying debris. It is advised that automobile passengers should abandon their vehicle and seek shelter in ditches, culverts, or nearby buildings.
Without pressure protection, the most imminent danger following a rapid decompression to altitudes above 50,000 feet is:
a) decompression sickness
b) lung rupture
c) oxygen deprivation/hypoxia
d) boiling of body fluids
c) oxygen deprivation/hypoxia- At these altitudes, even when breathing oxygen, the anoxic onset of unconsciousness is inevitable and overwhelming within a few seconds. The other factors, although critical in themselves, become of essentially secondary importance. Decompression sickness usually has a delay time. Ebullism or boiling of body fluids is at 62,000 feet. Lung rupture only occurs in a rapid decompression when the airway is blocked.
Human impact tolerance is related to which of the following factors?
a) Direction, magnitude, and time history of the imposed acceleration
b) Restraint harness materials
c) Restraint harness geometry
d) Condition of restraint harness occupant
e) All of the above
e) All the above- See Brinkley model and chapter.
An applicant visited his AME and a color perception abnormality was detected. What action should be taken by the AME or the applicant?
a) Disqualify the applicant
b) The AME may issue a medical certificate bearing the limitation "Not valid for night flying or by signal control".
c) An applicant who holds a medical certificate bearing color vision limitations may request a reevaluation and ask for the issuance of a SODA (statement of demonstrated ability). If passed, the FAA will issue a medical certificate without limitation.
d) both b and c.
d) Both b and c. Previous standards required "normal color vision" for first class certification, and the ability to distinguish aviation signal colors for second and third class tickets. However, since September of 1996, the FAA has required all applicants to have the ability to perceive those colors necessary for the safe performance of airman duties.
Long term risk of post traumatic epilepsy is determined by:
a) prolonged period of loss of consciousness (LOC) and/or post traumatic amnesia (PTA).
b) dural penetration
c) neurologic deficits
d) evidence of hematoma (epidural, subdural, intracerebral)
e) all of the above
e) Post traumatic epilepsy (PTE) may be seen in the early (
You are seeing a 41 year old Black male loadmaster for his periodic short physical examination. He tells you that his father (70 y/o) recently died of cancer of the prostate and his older brother is undergoing an evaluation for prostate disease. He denies any voiding difficulties. His rectal exam reveals a small, normal prostate without any nodules. His PSA is returned with a value of 3.8 mg/ml. Your next step is:
a) Repeat the same evaluation at his next annual physical examination.
b) disregard the PSA results because the digital rectal exam was normal and he is young.
c) refer him to your local urologist as an urgent consultation for probable prostate cancer.
d) Repeat PSA at 3 and 6 months. If PSA is increasing, refer to urologist.
d) Repeat PSA in 3 and 6 months, if increasing, refer to urology.
One important reason why functional hypoglycemia is of aeromedical significance is:
a) it can cause loss of consciousness
b) it can cause a decreased G tolerance
c) it can cause convulsions
d) it can result from skipped meals
e) it may indicate early diabetes mellitus
b) There is evidence that acceleration and hypoglycemia are additive and will cause loss of consciousness, however "functional hypoglycemia" will not. It was reported tht the brain is abile to regulate its blood flow until the arterial pressure falls below 60 mmHg, which can occur with + Gz. Beyond that point, the brain can sustain its metabolism only by extracting greater amounts of glucose and oxygen from the blood. Therefore, if either of these substances were reduced, there would be a correspondingly reduced tolerance to +Gz acceleration. Hence, if a pilot developed functional hypoglycemia when flying a mission requiring accelerative maneuvers, his G tolerance could be compromised causing a loss of consciousness.
Most weather occurs here. There is a constant rate of temperature decrease with altitude.
At this leve of the atmosphere, there is almost a complete absence of moisture and nearly uniform temperature of -55 degrees Celsius, most ozone exists at this level.
This is the portion of the atmosphere where most meteors disappear.
At this level of the atmosphere there is a gradual increase in temperature; this is the area where most auroras are found.
What is the altitude of physiologic pressure zones?
Sea level to 10,000 feet
What is the altitude for the physiologic deficient zone?
10,000 to 50,000 ft
What is the altitude for the space equivalent zone?
50,000 feet to 120 miles
From an atmospheric perspective, where does space begin?
Above 120 miles
In this gas law, volume varies inversely with pressure.
At what altitude is a gas bubble twice its sea level size?
True or false; wet gas occupies more volume than dry; gases in the body are saturated.
Which gas law states that the pressure of mixed gases are equal to the sum of each of the gas pressures. This explains why the partial pressure of oxygen drops at altitude per volume.
This gas law states that the partial pressure of a gas dissolved in a liquid is equal to the pressure of the gas in contact with the liquid. It is responsible for decompression sickness and also why your coke bottle fizzes.
This gas law states that with constant pressure, volume is proportional to temperature.
_______________ determined by barometic pressure, ventilation, and inspired gas oxygen content, is by far the most important determinant of arterial oxygen tension and resulting hemoglobin saturation.
Alveolar oxygen tension
On the typical oxygen hemoglobin dissociation curve, 40mmHg is where oxygen saturation is typically ____________.
On the typical oxygen hemoglobin dissociation curve, 60mmHg of oxygen tension translates to a saturation of _________.
Hyperventilation will ensure at alveolar PO2 of ______________, resulting in a decrease in the partial pressure of carbon dioxide and respiratory alkalosis, which in turn decreases P50 resulting in decreased tissue oxygenation and increased nerve irritability.
55 to 60 mmHg
_____________ is the most hazardous type of hypoxia to flight crew at increasing altitude; is caused by decreased partial pressure of oxygen in the ambient atmosphere.
______________ hypoxia is caused by decreased tissue profusion or circulation of blood flow to the tissues. It can occur with sustained acceleration (G forces) and , in case of circulatory failure, with the heart being unable to successfully pump blood.
___________ hypoxia is the inability of the body to use oxygen at the cell and tissue level because of toxins that impair those functions. A classic mechanism for this is cyanide poisoning.
_____________ hypoxia is due to a decreased ability of the blood to carry oxygen to the blood tissues. This can be due to a lack of red blood cells, or a contamination of the blood cells making them less effective (methemoglobinemia or carbon monoxide).
Anemic or hypemic hypoxia.
"The amount of time in which a person is able to effectively or adequately perform flight duties with an insufficent supply of oxygen" is the definition of ___________.
Effective performance time or time of useful consciousness.
What is the effective performance time at 18,000 feet?
20 to 30 minutes
What is the effective performance time at 35,000 feet?
30 to 60 seconds
What is the effective performance time at 43,000 feet?
Less than 10 seconds
What happens to the TUC or EPT if there is a rapid decompression?
The times are divided by half. So for example, the TUC/EPT at 35,000 feet is typically 30-60 seconds. In a rapid decompression it would be 15-30 seconds.
At altitudes greater than __________ a full pressure suit or a closed cabin is needed because pressure breathing along will not be sufficient to combat the hypoxia.
At sea leve, the volume of a given unit of gas will double at what altitude? Triple at what altitude? Quintuple at what altitude?
What is the definition of explosive decompression?
Any decompression that occurs in less than 0.5 seconds.
In a rapid decompression, TUC is cut by what percentage?
50%, in half.
Haldane noted that DCS could be prevented by avoiding pressure ratios exceeding a _____________ in pressure changes.
How long must someone wait to fly after a non-decompression stop dive?
How long must they wait after doing decompression stop diving?
What are the five factors that influence passenger survival rates in crashes, known by the acronum CREEP.
Crashworthiness (aircraft structure and design)
Environment (surrounding area the body may strike)
Postcrash Factors (Fire, EMS, Fumes)
The primary source of information we use to orient ourselves in the 3 dimensional environment is _________.
Roughly ________ of all civilian fatal aircraft accidents are attributed to _________.
Of crashes where spatial disorientation was the main factor, what is the mortality rate?
Notes- Weather and most air operations occur in the tropopause and troposphere (pause is the outer margin of a sphere).
The States Make The Exceptions. TSMTE. Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere.
The tropopause is lower at the poles and higher at the equator.
Water vapor is most prevalent in troposphere at 5%.
Ozone found between 40,000 and 140,000 feet. It shields the surface from ultraviolet rays. Broken down by compression of the jet engine.
Notes- Surface pressure is 14.7 or 760 mmHg or Torr.
At 18,000 feet the pressure is halved.
Von Karman Line (62 miles or 262,000 feet) aerodynamic forces and negligible and reaction control surfaces needed for propulsion.
The lapse rate is 2 degrees C for every 1,000 feet until you get to the top of the tropopause and beginning of stratosphere then things begin to heat up.
Cosmic radiation: 90% proton, 9% helium, 1% heavier atoms
At sea level the ionizing power is 1/70th of that encountered at 70,000 feet.
NOTES: Sea level temperature calculated at 15 degrees C.
Water vapor pressure in the body is 47 mmHg at body temperature (37 C or 98 F). Must subtract this contribution to the total pressure prior to using the gas laws if dealing with gases in living tissue.
The four forces acting in equilibrium in flight: weight, drag, thrust, and lift.
Helicopter blades rotate in counterclockwise direction when looking from above. The pilot normally sits on the right in a helicopter and left in an airplane. Cyclic is the stick, collective is up and down.
The boundary between the atmosphere and space is about 655,000 feet or 120 miles where air resistance is insignificant.
Von Karman line is 262,000 feet.
About 200 Kg of meteroid mass is within the 2,000 km of Earth. Makes shielding a requirement. 3 million Kg of orbital debris is manmade mass within 2,000 Km of Earth.
Anatomic dead space: volume is 150 ml. Runs from nose to brochilioles. Adding a mask or other device adds to the deadspace.
Notes: Which of the lungs volumes can't be measure by spirometry? Residual volume.
Ventilation with 100% oxygen can compensate for hypoxia but can give rise to "acceleration" atelectasis. If someone comes back from air combat maneuvering and is short of breath, think of this one.
The mean pulmonary arterial pressure is 15 mmHg. Under + Gz there is a loss of perfusion to the upper lungs. At + 3 Gz, the entire upper half of the lungs are not perfused.
For a PaO2 of 30 mmHg, SaO2 is = 60%
For a PaO2 of 60 mmHg, SaO2 is 90%
Notes- The primary driver of ventilation is carbon dioxide, sensed centrally.
The secondary driver is oxygen level, sense peripherally in the carotid and aortic bodies, usually when the oxygen partial pressure drops below 60 mmHg.
The response is first to increase the depth and then the rate of ventilation.
The cause of high CO2 in the aviation enviroment is that the sealed cabin CO2 is rising or the dry ice from the storage of frozen foods might increase CO2.
Types of Spatial Disorientation
Type 1: Unrecognized. Most SD mishaps are Type 1. Pilot does not recognize there is a problem.
Type 2: Recognized. Pilot knows there is a problem, but can't correct it or know exactly what is happening.
Type 3: Incapacitating. Pilot unable to regain orientation.
NOTES: The threshold for the semicircular canal is 2 degrees per second per second.
If you stop or turn upright, you will perceive you are turning the other direction. This causes the Graveyard spiral.
Somatogravic illusions deal with the OTOLITHS. Usually caused by acceleration in the linear direction. The reaction is a pitch down into the water or ground.
Notes- Tilting head while in a bank, can give G- excess illusion.
Elevator illusion is caused by the utricle. The increased Gz acceleration on pull out from a descent causes a sensation of pitching up and climbing, which can cause the pilot to pitch back down.
The leans are the most common vestibular illusion. Seems to be closest to a somatogyral illusion.
Again, the threshold acceleration for the semi-circular canals is about 2 degrees/sec per sec.
NOTES- Opportunism. If information is missing, pilot may substitute faulty information to satisfy their illusion.
Giant Hand- Thinks aircraft controls are improperly responding. Solution is to activate the autopilot. Use thumb and forefinger on controls. Feels like a giant hand is fighting you on the controls.
Notes- The major resonance peak for the human body is 4-8 Hz.
The vestibuloocular reflex will usually allow for normal vision performance up to about 20 Hz.
Tympanic rupture causes a 20-40 dB hearing loss across all frequencies.
Hearing aid indications: losses of greater than 35-40 dB in the speech range.
Pain occurs at 130-140 dB SPL.
NOTES_ The NIOSH standard is 85 dB with a 3 dB doubling exchange rate for 8 hours.
The normal eye has + 60D of refractive power. (+45 cornea and +15 lens).
Visible light range is 380nm -760nm.
Cones perceive colors
Rods perceive levels of gray or sharpness. More sensitive.
Cones are concentrated in fovea. Highly dense and have dedicated individual nerve cells. Not as sensitive as rods.
Rods- Not concentrated in fovea, low acuity due to less density and sharing of nerve cells. More sensitive than cones.
Scotopic vision: Rod threshold reached, very dim light. Cones not working.
Mesopic Vision: Cone threshold reached, colors discernable.
Photopic vision: cones fully functional, normal lighting.
Notes- Purkinje shift: Photopic vision (cones) has a peak sensitivity at a lower frequency (yellow-green) than scotopic (rod) which has a peak sensitivity at higher frequencies.
This allows us to use Red Filters in the cockpit that allow low freq light to allow for photopic vision, while at the same time keeping scoptopic vision with the rods ready for dark adaptation and dark use.
Hypoxia degrades color vision.
Dark adaptation of cones takes 6-8 minutes (well innervated) while the rods take 20-30 mins. In darkness or faint light, you have to look "off center" to activate the rods.
Night vision goggles, they provide little steropsis (using both eyes).
Color vision deficiencies:
Congenital is almost always red-green and usually males.
Acquired: usually blue-yellow and affect both sexes (from toxicity or disease).
Young Helmholtz theory- three classes of cones in the macula: red, green and blue.
Monochromats- Complete lack of color vision
Dichromats- two of the three cones are present.
Protans: Red missing
Deuterans: Green missing, 5% of males
Tritans: Blue missing
Notes: Acclimatization to a new climate takes roughly 10 days, but is largely complete at 2-3 days.
Effective acclimatization takes at least 2 hours of heat exposure per day.
The Wet Bulb Globe Temperature is used to predict human performance and is a combined reading using wet, dry, and globe temperature readings.
Solar cosmic radiation consists of proton-electron plasma ejected from the sun. Varies on an eleven year cycle. These particles get trapped in the geomagnetic belts. Van Allen belts formed by magnetic poles. Trap high energy particles. One part of the belt dips closer to the Earth is the South Atlantic Anomaly. There is higher radiation in this area.
Notes: The lens of the eye is the most vulnerable to microwave radiation.
Toxicology: Alveoli can get 5 micron particles.
Carbon monoxide binds 200 times more strongly to hemoglobin than oxygen.
Methylene chloride (paint stripping agent) is metabolized to CO and can also cause coronary vascular spasm (MI).
Half life of elimination of CO:
Room air: 4 hours
100% oxygen 1 hour
Hyperbaric oxygen at 2.5 ATA: 30 minutes
Notes- The pulse ox measures carboxyhemoglobin as 90% saturation.
Hydrogen cyanide: produced in high temperature fires, plastics.
Interferes with cellular respiration (histotoxic hypoxia)
100 ppm HCN fatal after 1 hour, 280 ppm immediately fatal.
CO2 from dry ice. Limit on an aircraft is 0.5%
Organophosphates: crop duster, remove from insecticide. Treatments if toxic are atropine and 2PAM.
Notes: Fuel dumping. Above 5,000 feet in above freezing temperatures, 98% of jet fuel will evaporate before reaching the ground.
The three hand altimeter is most commonly misread type of instrument.
It is easier to travel Westward. Allow one day for each time zone travelled.
One liter of LOX will expand to 862 liters of gaseous oxygen.
Perchlorate candles (was on MIR, backup on ISS, some airlines) produce oxygen.
Molecular sieve (OBOGS on F-16, etc) used in tactical aircraft uses zeolite crystals to produce oxygen.
US Spacesuits operate at 4.3 psi, Russian at 5.6 psi and 100% oxygen. LiOH cans are used to scrub the CO2 from the suit.
Space station uses exercise prebreath or 4 hour prebreath.