Unit 1 Asma Acceleration

Front 1

Describe the XYZ coordinate system used in describing aircraft acceleration

Back 1

x-axis is oriented front to back or perpendicular to a coronal plane, the y-axis is oriented is oriented laterally or perpendicular to a sagittal plane, and the z-axis is oriented vertically or perpendicularly to a horizontal plane. Place your right hand I front of you with the thumb pointed up, index finger pointed directly forward, and middle finger pointed toward toward the left so that each finger is perpendicular to the other two. Now each of the three pointing fingers indicates a “positive” direction (axis) of the centripetal acceleration forces: (a) the thumb points to headward acceleration (+gz); the index finger points forward acceleration (+gx); and the middle finger points leftward acceleration (+gY).One must still remember the sign change associated with eyeballs-in (-x reaction) for +x acceleration. Similarly, +z is eyeballs-down and +y is eyeballs-right.Longitudinal (vertical) is denoted z; lateral (right/left) is y; and horizontal (supine/prone) is x.

Hint 1

Axis
Right hand rule
Eyeballs

Front 2

Define linear centripetal acceleration.

Back 2

When the linear velocity of an object changes over time, the difference in velocity, divided by the time require for the moving object to make the change, gives it a mean linear acceleration. Formula is a=(v2 – v1)/Δt where v1 is the initial velocity and v2 is the final velocity, and Δt is the elapsed time. It is a vector quantity with magnitude and direction. Measured in m/second2. To convert to units of g, simply divide by 9.81.

Hint 2

Definition
Formula
Measurement units
Convert to g

Front 3

Define angular acceleration.

Back 3

Anuglar acceleration, ω, is the rate of change of angular displacement. Formula is ω=(θ2 – θ1)/Δt, where θ1 is the initial angular displacement and θ2 is the final angular displacement. The fact that an object may be undergoing curvilinear motion during a turn in no way effects the calculation of its angular velocity. Because radial or centripetal linear acceleration results when rotation is associated with a radius from the axis of rotation, centripetal acceleration can be calculated with this formula: ac= ω2r. The rate of change of angular velocity is angular acceleration, α. Formula is α=(ω2/ω1)Δt, where ω1 is initial angular velocity and ω2 is the final angular velocity. Measured in degrees/sec or rad/sec. One cannot express angular acceleration in g units.

Hint 3

Definition
Formula
Does an object undergoing curvilinear motion during a turn have an effect?
How calculate centripetal?
Measurment units
Convert to g

Front 4

Define centripetal acceleration.

Back 4

Centripetal acceleration is a type of linear acceleration that results in curvilinear, usually circular motion. This acceleration acts along the line represented by the radius of the curve and is directed toward the center of the curvature. Its effect is a continuous redirection of the linear velocity, in this case called tangential velocity of the object subjected to the acceleration. The value can be calculated if one knows the tangential velocity, vt and the radius, r of the curved path followed. Formula is ac=vt2/r. Measured in m/second2. To convert to g, divide by 9.81.

Hint 4

Definition
Formula
Measurment units
Convert to g

Front 5

Define “G force” as it applies to the aviation environment.

Back 5

Unit of linear and centripetal (radial) acceleration is the "G" which expresses the magnitude of a force (or acceleration) acting on a body. jolt is the rate of change in acceleration (G/sec). It is of particular consequence when discussing short term accelerations such as ejection or crash forces. The effects of acceleration on the body are also classified by duration. Dehart has 2 categories: (1) transitory which is <1 sec and (2) sustained which is >1 sec. Ernsting has 3 categories: (1) short duration which is <1 sec, e.g. crash forces; (2) intermediate duration 0.5-2 sec, e.g. ejection, cat shots, traps; and (3) long duration which is >2 sec, e.g. aircraft maneuvers. Long duration lateral acceleration (+GY) is rare in aviation and won't be discussed

Hint 5

Unit
Jolt
DeHart classification categories
Ernsting classification categories
Which classification category is rare in aviaiton?

Front 6

State the systems that are effected by +Gz on the body.

Back 6

Cardiovascular, pulmonary, central nervous system, renal system, mobility, hormonal response, +Gz tolerance

Front 7

What are the effects of +Gz on the cardiovascular system

Back 7

Cardiovascular response, heart rate changes, and coronary blood flow.

Front 8

What Is the effect on Heart rate with +Gz

Back 8

Howard reports that HR increases directly (but not linearly) w/max +GZ level of exposure. Rate will vary between and w/in subjects on individual runs. Burton suggested HR response during high +GZ has 3 separate components: (1) physical work (straining), (2) acceleration, and (3) psychological stress.

Front 9

What is the effect on coronary blood flow from +Gz

Back 9

Controlled by aortic diastolic BP and remains adequate during +GZ exposure and increase w/ increasing +GZ. However, subclinical coronary artery disease could manifest itself during a high +GZ exposure.

Front 10

What is the cardiovascular response to +Gz?

Back 10

The cardiovascular reflexes respond to blood pooling below the heart level due to the hydrostatic column effect. Pooling of blood occurs mainly in lower limbs w/some occurring in abdominal area. BP decreases above the heart and increases below the heart which has an immediate effect on the size of blood vessels which is based on transmural pressure (difference between intra- and extravascular tissue pressure), distensibility of vessel and amt of blood available to fill it. In comparison, BP at rt and lt atria remain unchanged up to +4.5 GZ. Transmural pressure increases in arteries and arterioles below the heart will decreases peripheral resistance and increases local blood flow. Transmural pressure decreases in veins above the heart can produce complete collapse and cease blood flow. The transmural pressure  in the skin capillaries can increase enough that vessels rupture, especially in the lower extremities. This leads to petechial hemorrhages (petechiae or "G-measles") after prolonged or repeated exposure > +4GZ. The decrease in both central BP and apparent blood vol causes stimulation of the high pressure stretch receptors in the carotid sinus and aortic arch causing decrease parasympathetic (vagal) inhibition and increase sympathetic stimulation resulting in increase HR, increase vasoconstriction, increase venoconstriction and increase heart contractile force. Venous return to the rt side of the heart starts to increase 10-15 sec after onset of exposure and CO increase w/in a few beats.

Hint 10

Blood pooling
BP
Blood vessel size
Heart BP
Transmural pressure
Cause of G-measles
Vagal effect

Front 11

What are the effects of +Gz on the pulmonary system

Back 11

Pulmonary ventilation and lung volume, regional plumonary blood flow, Pulmonary Gas Exchange and Arterial Gas Saturation, G-Induced Atelectasis

Front 12

What are the effects on Pulmonary ventilation and lung volume from +Gz

Back 12

As +GZ increase resp. rate and VTHowever, VT starts to increase between +5-7 GZ because of G pushing diaphragm and abdominal contents down and G-suit pushing diaphragm up into thoracic area. W/out G-suit counterpressure FRC would decrease by 500 ml at +3 GZ . At +5-7 GZ the physiologic dead space incresae and in spite of incresae resp. rate the arterial PCO2 changes very little w/ increasing GZ . Normally, ventilation is greater at the base areas of the lungs than the apex because of the incresae plural pressure from apex to base. The pleural pressure gradient results in increase alveolar distention in apex alveoli while the base alveoli are near min vol. Upon inhalation, the base alveolar expansion is > apex alveolar expansion. With high +GZ, the pleural pressure gradient increase by 0.2 cm H2O/cm lung/+GZ which increase differences in expansion between apex and base of lung. At +5GZ the pleural pressure at base is 30 cm H2O > the apex. The increase pleural pressure in the base will cause collapse of base alveoli (airway closure). The anti-G suit abdominal bladder decrease FRC and increase amt of non-ventilated basal due to increase pleural pressure.

Hint 12

VT
Pleural pressure

Front 13

What are the effects on the regional pulmonary blood flow from +Gz

Back 13

The +GZ has great effect on blood flow distribution in lung because of ventilatory (alveolar gas) pressures which remain constant and unaffected by +GZ and the low pulmonary BP. Mean pulmonary arterial (15 mm Hg) and venous (0 mm Hg) BP at junction of middle and lower thirds of lung are unaffected by +GZ.. The arterial BP above and below junction is affected by hydrostatic forces.Blood flow increase descending down the lung and the increase blood flow/cm down the lung increase w/ increasing +GZ.

Front 14

What are the effects on the pulmonary and arterial gas exchanges from +Gz

Back 14

The +GZ increase accentuates the ventilation-perfusion inequalities that normally exist. The area of the lung which is ventilated but non-perfused increases w/increasing +GZ. PO2 in non-ventilated alveoli (closed terminal airways) is absorbed by the blood and reaches equilibrium w/mixed venous blood w/in few sec. Blood flowing in this area constitutes a rt-to-lt shunt and proportion of blood in shunt increases w/increasing +GZ. This shunt markedly increases O2 saturation and arterial PO2. Arterial blood desaturation is evident at +3GZ and oxyHb saturation decrease to 85% at +5GZ. Breathing 100% O2 prior to onset helps delay desaturation. Inflation of G-suit abdominal bladder increase desaturation due to raising of diaphragm and increase alveoli closure

Hint 14

Effects
what can you do to help delay desaturation
Inflation of G-suit abdominal bladder

Front 15

What are the effects on G-induced atelectasis from +Gz

Back 15

Exposure to +GZ causes closure of alveoli in base of lung which prevents their ventilation even though their perfusion continues. The number of closed alveoli increases w/increasing +GZ and w/inflation of abdominal bladder of anti-g suit. Blood absorbs trapped gas at rate limited by rate which least soluble gas (N2) is removed. If little of no N2 present - such as when breathing 100% O2 - gas is absorbed rapidly, the alveoli are rendered free of gas and the alveoli collapses and will remain so until an inspiration provides gas pressures high enough to exceed the alveolar wall surface forces. Atelectasis seen as low as +3GZ w/g-suit and breathing 100% O2. Symptoms usually apparent after exposure include dry cough w/or w/out substernal discomfort. Deep inspirations are used to reinflate the alveoli and can cause reflexive bouts of coughing. PPB and AGSM can increases FRC and decreases the magnitude of alveoli collapse. However, the use of counter-pressure w/PPB will decrease or negate this improvement. Smoking is thought to increase chance for atelectasis

Hint 15

What causes it
N2
Symptoms
Counter-pressure
Smoking

Front 16

The min N2 needed in breathing gas to prevent atelectasis is?

Back 16

40%

Front 17

What are the effects of +Gz on the central nervous system

Back 17

LOC and a progressive decrease of peripheral vision (greyout) and central vision (blackout) are caused by decrease blood flow to cerebral and retinal tissue. Intraocular pressure is 20 mm Hg and the retinal artery BP must be > 20 mm Hg to maintain blood flow to eye. If retinal artery BP is < 20 mm Hg then blackout occurs 4-6 sec later w/delay due to O2 stored in retinal extravascular fluid. After blood returns to eye there is also several sec lag in recovery to restore the retinal O2 store.

Front 18

What is the cause of peripheral light loss due to G forces

Back 18

The early peripheral loss is due to the anatomical arrangement of these vessels which increase sensitivity to +GZ.

Front 19

What are some other visual indications caused by G forces?

Back 19

Other visual indications of decrease retinal blood flow are pupillary dilation, decrease ocular motility, progressive and concentric narrowing of visual field and decrease visual acuity.

Front 20

What defines a person's blackout threshold in regard to G forces

Back 20

A person's blackout threshold is defined as that G exposure (w/onset rate of 1G/sec) where blackout occurs and vision then returns in 2 sec due to the compensatory reflex. Redistribution - through autoregulatory vasodilatation and siphon effect - of blood flow found near upper +GZ tolerance level so that cerebellum and brain stem blood flow is preserved even w/ decreasing cerebral blood flow. At +5GZ this provides a pos pressure increase between the arterial and venous sides of cerebral circulation of 50-60 mm Hg w/a corresponding jugular bulb pressure of -50 mm Hg. This redistribution overcomes what would be expected if predicting BP based on hydrostatic column effect. However, as +GZ increase jugular veins collapse which breaks the siphon and empties cerebral vessels leaving 3-4 sec worth of intratissue O2 and consciousness remaining. At moderate +GZ (5-6GZ) blackout precedes LOC, but increase or rapid onset +GZ LOC may occur w/out any visual symptoms in about 4-6 sec. Consciousness after LOC occurs in about 15 sec w/a similar period of confusion. Amnesia of event is common.

Front 21

Can prolonged exposeure to lower levels of +Gz cause LOC? If so, how?

Back 21

Prolonged exposure to lower levels of +GZ can also cause LOC by vasovagal syncope when there is also pallor, sweating and bradycardia.

Front 22

What % TACAIR aircrews reported LOC due to G-forces?

Back 22

12% of USAF/USN/USMC TACAIR crews report LOC.

Front 23

What % is estimated to be the true number of TACAIR aircrew who have LOC'd?

Back 23

Since 50% of centrifuge LOC's don't remember incident, it is extrapolated that 24% of TACAIR crews have LOC'ed

Front 24

What are the effects of +Gz on the renal system?

Back 24

Data based on non-human studies show that renal blood flow decrease w/+GZ exposure and wearing an anti g-suit.

Front 25

Why is the renal system important in regards to +Gz?

Back 25

Renal system is important as small decrease in Na+and H2O decrease +GZ tolerance

Front 26

Renal system is important as small decrease in Na+and H2O decrease +GZ tolerance

Back 26

The increase wt of soft tissues and limbs makes unassisted emergency egress and raising from a sitting position impossible at +3GZ. If properly supported, fine motor movements are unhindered at +8GZ. Helmeted head movements are severely hindered at +4-6GZ. This is exacerbated w/HMD's as it shifts the CG forward relative to the atlanto-occipital junction and upper thoracic vertebrae. Back, neck and limb injuries are commonly associated w/ high, rapid onset +GZ. The neck in a flexed and rotated position is particularly vulnerable to include ruptured intervertebral discs

Front 27

What are the effects of +Gz on hormonal response?

Back 27

Acceleration stress psychologically induces an epinepherine release. The stress itself increase serum cortisol and catecholamine levels. The cortisol increase is too slow for acute exposure but may be significant for prolonged or repeated exposures. The catecholamine release and ADH may also increase tolerance by increase peripheral resistance, HR and heart contractility

Front 28

What are the effects of +Gz on G tolerance?

Back 28

Difficult to define tolerance because of 3 factors: (1) magnitude of the acceleration stress which varies from LOC w/out preceding blackout at high levels down to vasovagal syncope or fatigue at low levels; (2) G-onset rate as increase onset rates usually elicit G-stress response at decrease G levels; and (3) large individual variations. However, DeHart states that using 100% peripheral light loss and 50% central light loss are reliable reference points for determining tolerance

Front 29

What factors effect G tolerance?

Back 29

Heat, hypoglycemia, alcohol, hyperventilation, hypoxia, and gastric distention

Front 30

What effect does heat have on G tolerance?

Back 30

. For every 1oC increase in core temp the blackout tolerance decrease 30-40% due to cutaneous vasodilatation which shifts blood flow to periphery. The decrease peripheral vascular resistance and increase central blood vol decrease arterial BP

Front 31

What effect does hypoglycemia have on G tolerance?

Back 31

A 50% decrease in blood glucose from base line decrease blackout threshold by 0.6 +GZ. However, if blood glucose decrease is enough to elicit hypoglycemic reaction the blackout threshold increase by 0.5 +GZ due to the arterial hypertension produced by epinepherine secreted in response to reaction

Front 32

What effect does alcohol have on G tolerance?

Back 32

A moderate dose decrease tolerance by +0.1-0.4GZ and will increase severity of symptoms produced by a given +GZ

Front 33

What effect does hyperventilation have on G tolerance?

Back 33

Markedly decrease tolerance as the increase in cerebral vascular resistance produced by hypocapnia accentuates the decrease in blood flow through brain. A decrease of arterial PCO2 by 20-25 mm Hg decrease tolerance by 0.6 G. Moderate hyperventilation can cause LOC at + 3 GZ

Front 34

What effect does hypoxia have on G tolerance?

Back 34

Decrease inspired PO2 to 70 mm Hg decrease blackout threshold by 0.6 G and decrease inspired PO2 to 55 mm Hg decrease threshold by 0.8-1.2G

Front 35

What effect does gastric distention have on G tolerance?

Back 35

Stomach distention increase tolerance due to distended stomach decrease descent of diaphragm and heart during exposure. Ingestion of 1.5 L H2O increase blackout threshold by 0.6-1.3 G

Front 36

That is the most important system in the body that determines the tolerance and response to +Gz in the body.

Back 36

The cardiovascular system is by far the most important system that determines the tolerance and response to +GZ

Front 37

State the general effects of -Gz on the body.

Back 37

Feeling of heaviness and interference w/limb movement similar to +GZ. The specific effects of -GZ occur primarily in the head and neck. At -1GZ there is a sense of fullness in head and head pressure which becomes very disagreeable at -2GZ and causes post-exposure headaches. At -2.5GZ there is congestion of air passage mucosal lining that can cause breathing difficulties, eyelids swell, and petechiae appear on the face and neck. Between -2.5 and -3.0GZ the eyes feel like they're popping out of head and vision is blurred by subconjunctival hemorrhages. Exposure to >-4GZ can cause mental confusion and unconsciousness

Front 38

What effect on the cardiovascular system does-Gz have?

Back 38

The initial hydrostatic effect is increase in regional arterial BP above the heart and decrease below the heart. Eye level arterial BP increase by 20-25 mm Hg/-GZ. It takes several sec to level off venous BP as blood has to flow thru the capillaries to fill them to capacity. Eye level venous BP = 100 mm Hg at -3GZ. The increase arterial BP stimulates the carotid sinus baroreceptors which causes bradycardia, cardiac arrhythmias and generalized arteriolar vasodilatation. Arrythmias usually occur at -1GZ and asystole can occur w/a 5-7 sec -2.5GZ exposure. The decrease CO and vasodilatation decrease arterial BP. The increase in cerebral venous BP is countered by increase in CSF which decrease risk of vessel rupture. The decrease CO and increase venous BP combine to decrease arteriovenous BP changes across the cerebral vascular bed causing decrease cerebral blood flow which leads to mental confusion and LOC. LOC can also be caused immediately by cardiac asystole or ectopic rhythm

Front 39

What effect on the pulmonary system does -Gz have?

Back 39

-GZ causes headward displacement of diaphragm which decrease VC, FRC, and pulmonary ventilation. Changes in pulmonary regional blood flow are opposite to those produced by +GZ. With -GZ the apical region is better ventilated and perfused than the basilar region, but most of the lungs remains perfused. Airway closure and atelectasis can occur in the apical region and a rt-to-lt shunt occurs because of decrease FRC

Front 40

How does -Gz affect G tolerance?

Back 40

-GZ isn't well tolerated, max are 5 sec at -5GZ; 10-15 sec at -3GZ; and 60 sec at -2GZ. There is some adaptation as some aerobatic pilots can tolerate -6GZ

Front 41

Describe the “push/pull” effect and the resultant reduction in G tolerance.

Back 41

This is a negative synergy between –Gz and +Gz. This can occur when –Gz maneuvering, accomplished by “pushing” the stick, is immediately followed by +Gz “pulling”. Cardiovascular adaptation decreases, and the incidence of G-LOC increases, in proportion to the level and duration of preceding –Gz acceleration.

Front 42

What mechanisms have been proposed to explain push-pull effect?

Back 42

1. Increased cephalad blood flow during

2. Prior –Gz induces upper body vasoconstriction and lower body vasodilation

3. To prevent cerebral overperfusion during –Gz, vasoconstriction occurs

Front 43

Why would increased cephalad blood flow affect push-pull effect?

Back 43

Increased cephalad blood flow during –Gz stimulates carotid sinus baroreceptors, leading to bradycardia and peripheral vasodilation, thus lowering systemic blood pressure. When the aviator then induces +Gz by pulling, there is a delay in the onset of the compensatory sympathetically mediated increase in heart rate, cardiac output, and peripheral vascular resistance because of the hypotensice effect of the previous –Gz

Front 44

Why would prior -Gz inducing upper body vasoconstriction and lower body basodialation affect push pull effect

Back 44

Prior –Gz induces upper body vasoconstriction and lower body vasodilation. Greater net vasodilation. Greater net vasodilation than vasoconstriction during –Gz leads to lowered systemic blood pressure, predisposing to G-LOC under +Gz stress.

Front 45

Why would vasoconstriction to prevent cerbral overperfusion during -Gz affect push-pull effect?

Back 45

To prevent cerebral overperfusion during –Gz, vasoconstriction occurs. This is increased cerebral vessel resistance seems to persist for about 20 seconds after cessation of –Gz and onset of +Gz, thus predisposing to cerebral hypoperfusion and G-LOC.

Front 46

Describe the principal central nervous system factors that limit short-duration, high +Gz exposure tolerance.

Back 46

Positive Gz is a downward force that attempts to force blood into the lower extremities. Physiological reflexes that attempt to counteract the positive Gz forces are an increased heart rate, vasoconstriction of the blood vessels in the lower body and vasodilatation of blood vessels in the brain.

Front 47

What are the physiological reflexes to G forces designed to do?

Back 47

All of these reflexes are designed to increase blood return to the heart and blood delivery to the brain.

Front 48

What happens when the physiological reflexes can't compensate enough against G-forces?

Back 48

When these physiological reflexes cannot compensate enough to maintain blood flow to the brain, brain hypoxia ensues. Brain hypoxia can result in a loss of consciousness episode (G-LOC). G-measles (cutaneous petechiae) occur in the unsupported areas of the body during +Gz exposure.

Front 49

Where are the most common areas for G-measles to occur?

Back 49

Most common areas are the feet and ankles, followed in decreasing frequency in the legs and arms.

Front 50

What is the probable cause of G-measles

Back 50

The probable cause of these G-measles is either rupturing of capillaries or diapedesis in response to high intravascular pressure.

Front 51

Given a G-time Tolerance curve, describe the regions of the curve and how they relate to human performance while experiencing Gs

Back 51

This curve shows tolerance to +Gz acceleration and effect of onset rate. A brief rapid onset run (10G/s) can be tolerated to 12 G without visual loss, but if prolonged for more than 4-5 seconds loss of conscious may occur without visual warning. Even a moderately fast onset rate exceeds the cardiovascular reflexes, though loss of consciousness will be preceded by visual symptoms of greyout, tunnel vision, and blackout. A slow onset rate allows cardiovascular reflexes to develop during the G stress and development of visual signs at a higher G level. Also allows time for the cardiac reflex to kick in increasing resting G tolerance as a result of vasoconstriction mediated by the sympathetic nervous system via the baroreceptors that increase arterial tension at head level. Gs lower than resting G tolerance will not result in light loss or GLOC.

Hint 51

Rapid onset
Slow onset

Front 52

List the symptoms of grayout as they apply to the +Gz environment.

Back 52

100% peripheral light loss (PLL), and 50% central light loss (CLL), consciousness and hearing remains undisturbed.

Front 53

List the symptoms of blackout as they apply to the +Gz environment.

Back 53

100% PLL, 100% CLL, consciousness and hearing remains undisturbed

Front 54

List the symptoms of G-induced loss consciousness (GLOC), as they apply to the +Gz environment.

Back 54

Consciousness and hearing functions are interrupted

Front 55

Once actual loss of consciousness results due to G forces, what is the total average incapacitation time

Back 55

24 seconds

Front 56

Describe the differences between absolute and relative incapacitation as they relate to GLOC

Back 56

Absolute incapacitation signifies complete loss of brain blood flow. It is during this phase that the flyer is unconscious. Usually the G’s are unloaded and slowly blood flow to the brain resumes. Relative incapacitation represents the period of time when the brain is being “rebooted”. This is a period of confusion and disorientation. Some basic senses like vision, hearing, and speech come back on line as well as some reflex capabilities, but cognitive thought and higher processing is unlikely to occur. A pilot is unable to maintain aircraft control during either of these periods.

Front 57

What are the two distinct phases that incapacitation from G-LOC can be divided into?

Back 57

Absolute and relative incapacitation.

Front 58

What is the time range for absolute incapacitation in GLOC?

Back 58

This period has ranged from 2 - 38 seconds, the average time is 12 seconds.

Front 59

What is the time range for relative incapacitation in GLOC?

Back 59

The relative incapacitation time averages also 15 seconds but ranges from 2 - 97 seconds.

Front 60

What is the total incapcitation time for GLOC?

Back 60

Averaging 28 seconds with a range of 9 to 110 seconds.

Front 61

Differentiate between Almost Loss of Consciousness (ALOC) and GLOC.

Back 61

ALOC is a transient incapacitation, without loss of consciousness which occurs during and after short duration, rapid onset +G2 pulses. ALOC is considered to be part of the G-LOC syndrome. Therefore, it has many of the same symptoms of G-LOC including a similar psychological impact, dreamlets, confusion, and sensory and motor symptoms. The duration of incapacitation is much shorter than with G-LOC, reflecting a more transient degree of ischemia.The GLOC syndrome is the transition from normal consciousness to a neurological state of unconsciousness that results when blood flow to the nervous system is reduced below the critical level necessary to support conscious function.

Front 62

What is ALOC characterized by?

Back 62

ALOC is characterized by unresponsiveness to voice communication and loss of numerical skills, with various degrees of memory compromise and may include transient paralysis and convulsive motor activities.

Front 63

List physical and physiological factors that may reduce an individual’s tolerance and/or endurance to G forces.

Back 63

Age, Reduced height, High diastolic and systolic arterial tension, Increase in ambient (cockpit) temperature, Cold stress, Dehydration, Inhaled gas mixtures that are hypoxic or hyperoxic, Nutrition, Experience, Recent Illness, Conditioning, Fatigue, Alcohol & Self Meds

Front 64

How does hydration affect G tolerance?

Back 64

Hydration is critical to G-tolerance. At 3% dehydration (2 qts low, 170lb man), 50% of G-tolerance is lost. As blood volume drops due to fluid loss, the cardiovascular system is unable to maintain or generate adequate blood pressure needed to counter the effects of G-forces.

Front 65

How does repeated exposure to the G environment affect G tolerance?

Back 65

It is important to emphasize the increase in G-tolerance attained through repeated exposure to the high G environment, specifically it is important to note the benefit of recency of experience. Not only does the body become more tolerant of G-forces, the pilot becomes better trained at countering the effects through greater anticipation and practice. When significant lay-off periods happen, it is prudent to re-enter the high G environment with anticipation of a lower than normal G-tolerance.

Front 66

How does illness affect G-tolerance?

Back 66

Any recent illness, especially if the aircrew member is still recovering, can reduce G-tolerance. The body is expending a lot of energy fighting off disease and leaves little energy available to “fight off the Gs”. The great aspect of the human body is its adaptability and improvement in performance while exposed to stress.

Front 67

How does exercise affect G-tolerance?

Back 67

Aircrew can specifically train to perform better under G. Several studies have indicated that aircrew who exercise have a higher G-tolerance than those who don’t, specifically those who engaged in weight training and moderate aerobic exercise.

Front 68

List the methods available to increase a crewmember’s tolerance to +Gz forces.

Back 68

Anti G Straining Manuever, anti G-suits, positive pressure breathing, centrifuge training, physical training, posture, breathing CO2, drugs, inducement of positive cardiac reflex and G-warm up.

Front 69

State the benefits of wearing an anti-G suit

Back 69

The anti-g suit increases tolerance by: (1) increasing peripheral resistance and decreasing blood pooling by providing counter pressure in the lower limbs and abdomen; (2) raises the diaphragm which decreases the heart-to-eye distance; (3) prevents loss of plasma into tissue; and (4) plays minor role in venous return. The inflation must be rapid (2-3 sec) to ensure effectiveness. The anti-G suit is also effective in reducing the physiologic stress response of the G exposure by reducing the amount of fluid shift below the heart and increasing blood flow to all organs of the body.

Hint 69

4 benefits

Front 70

How much G protection does a G suit give?

Back 70

1-1.5 G protection

Front 71

The G-suit is a combinat ion of what and how does it work?

Back 71

Is a combination of the garment and the aircraft mounted anti-g valve. The anti-g valve controls the pressure in the garment in proportion to the applied acceleration, usually 1.25lb/in2/G,

Front 72

When does the G-suit begin to inflate?

Back 72

Doesn't begin to inflate until > 1.75-2 G's to avoid unnecessary and distracting inflations during routine maneuvering.

Front 73

What are some improvements that have been made to the G-suit?

Back 73

Improvements to anti-g suit include more responsive valves, pre-inflated suits, and use of multiple bladders that inflate sequentially to aid venous return.

Front 74

Why is the G-suit effective in reducing the physiologic stress response of G exposure?

Back 74

Because it reduces the amount of fluid shift below the heart and increases blood flow to all organs of the body.

Front 75

Describe the elements of the anti-G straining maneuver (AGSM) and how they interrelate.

Back 75

The AGSM is a forced exhalation effort against a closed (L-1 maneuver) or partially closed (M-1 maneuver) glottis while tensing leg, arm, and abdominal muscles which increases intrathoracic pressure that is directly transferred to the arterial pressure at heart level. The breathing rate is 3- to 4- second intervals. This brief-rapid effort allows adequate venous return because of a low intrathoracic pressure. Although the head level arterial tension (Pa) falls to nearly zero in conjunction with a lowered thoracic pressure, the period is so brief (less than 1 second) that the brain and retinal tissue maintain unaltered function (vision and consciousness). It is a two phase act - phase one is isometric tensing of the leg muscles, the abdomen and upper body. The leg tensing is of critical importance and the G-suit will assist this muscular work in preventing the pooling of blood in the lower extremities. This muscle tensing must be maintained while at G. Phase two is the cycle of breath holding. Take a big breath prior to the pull, bear down against a closed glottis, hold breath until at max G, and then exchange the air in quick, small amounts in three second cycles. Any longer breath holding can result in “starving the pump” and imminent G-LOC.

Front 76

The AGSM can prodive how much G protection?

Back 76

The AGSM can provide 3.5 - 4 +Gz of protection provided it is performed correctly.

Front 77

What is the purpose of the breath holding cycle during the anti-G straining maneuver?

Back 77

The purpose of the breath-holding cycle is to generate and maintain pressure in the thoracic cavity which will assist in getting blood flow to the brain. The air exchange (quick release of pressure) is needed to allow for adequate venous return (helped by the G-suit).

Front 78

The respiratory aspect of the anti-G straining maneuver is an adaptation of what?

Back 78

The respiratory aspect of the AGSM is an adaptation of the Valsalva maneuver that produces a high intrathoracic pressure (125mm Hg). However, unlike the Valsalva maneuver test that challenges the circulatory system to cope with a reduced VR, the AGSM interrupts the effort at 3- to 4- second intervals with a rapid expiration and inspiration effort (less than 1 second).

Front 79

Describe common errors in performing the AGSM.

Back 79

•  Too little time tensing and straining and too much time breathing can result in little venous return to the heart, thus starving the pump.

•  Holding the breath longer than needed also starves the pump from venous return.

•  Exhaling and/or grunting without muscle tensing and straining will cause early fatigue and possible hyperventilation.

•  Delaying the start of AGSM until onset.

•  Over or under-tensing and straining.

Front 80

Describe exercises (physical training) that can be performed in order to improve an individual’s G-tolerance.

Back 80

A combination of whole-body strength (wt training) and aerobic conditioning will increase performance of AGSM, especially for repeated or prolonged exposure.

Front 81

What are the two types of physical training that can impact anti-G straining maneuver ability?

Back 81

Aerobic and anaerobic

Front 82

Describe aerobic training in terms of G tolerance affect

Back 82

Aerobic training helps you avoid the fatigue associated with flying against high G forces. As you increase your aerobic capacity, your body increases its ability to move oxygen and utilize that oxygen to a maximum efficiency. It has been documented that excessive aerobic training can lead to decreased G tolerance. This is due to the resting blood pressure decreasing as an individual becomes more aerobically conditioned.

Front 83

Describe anaerobic training in terms of G tolerance effect

Back 83

Otherwise known as weight training. As you weight train, your skeletal muscles increase in muscular tone which allows you to more efficiently perform the AGSM. Weight training also improves the muscles’ endurance so they don’t fatigue as quickly after repeated isometric contraction in response to repeated G exposure.

Front 84

Research has shown that a 10- to 12- week weight lifting program can increase G-duration tolerance approximately by what % with an individual correlation between what?

Back 84

50% with a direct individual correlation between muscular strength and D-duration tolerance.

Front 85

According to Dehart does aerobic conditioning have an effect on G-tolerance?

Back 85

Aerobic conditioning has no effect on G tolerance.

Front 86

Excessive aerobic conditioning in some individuals can have what effects on G related issues?

Back 86

1) cause serious cardiac dysrhythmias associated with reduced G tolerance

2) increase susceptibility to motion sickness on the centrifuge

3) increase the length of time of incapacitation of GLOC.