GTIP

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G-TOLERANCE IMPROVEMENT PROGRAM
Aerospace Physiologist
MSC Symposium LT Yniguez MCAS, Cherry PT
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GTIP Goals andEnabling Objectives

• understand your personal type of light loss
• learn when to utilize the anti-G hook
• understand daily variations in relaxed
  G-tolerance
• respect the 6 sec buffer period
• appreciate the potential GLOC trap
• understand the one-sided light loss that may
  occur in the check-six position

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Terminal ObjectiveG-TIP

• Be familiar with Gz acceleration forces, the
  causes and symptoms of
• (G-LOC), and the methods to improve G-tolerance.

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G-LOC A DEADLY THREAT

• AIRCRAFT NO. Gs
• FA-18 8 5.5-8.0
• F-14 1 4.0
• AV-8B 1 5.5
• EA-6B 3 3.0-4.0
• S-3 1 3.0
• T-2 3 3.5
• T-34 35 1.5-9.0

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Why pull Gs?

• its fun
• it builds character
• so you can kill the other guy
• so you dont get killed
• actually only pull Gs to change direction

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Anatomical/Physiological effects of G-Forces

• Cardiovascular
• Respiratory
• Sensory
• Cerebral

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Cardiovascular Effects of Gz

• BP above the heart
• BP below the heart
• blood pooling lower extremities
• CO and BV
• 10 sec delay in reflex
• Petechial hemorrhages

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Cardiovascular system

• your BP forces blood up to your brain
• high Gs force the blood down away from your head
• Hook maneuver is designed to raise the BP and
  keep blood flowing up to your brain
• the muscle strain keeps blood from pooling in
  your legs or arms, trapping it in your chest
• the hook closes your glottis so you can strain
  against it
• the deep breath and strain raises pressure in the
  chest to squeeze blood up to your head

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G-warm up maneuver, orG-awareness turn

• 1. press-to-test G-suit
• 2. pull about _ Gs for at least 10 sec
• no strain
• 3. OPTIONAL gradually increase Gs without
  straining until you see some light loss
• determines your relaxed G-tolerance
• consider it might be a low-G day

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The Cardiovascular Reflex, orWhy do I do the
G-warm up maneuver?

• the carotid bodies in your neck sense a change in
  BP and initiate the cardiovascular reflex to
  maintain blood flow to your head
• with increased Gs you see lower BP in your neck,
  and
• your pulse increases
• blood vessels throughout your body tighten up
• this raises your BP and increases your relaxed
  G-tolerance

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G-warm-up maneuver ...

• gives you about 3/4 G additional relaxed G-
  tolerance protection
• but it takes 10-15 seconds to occur
• might notice more light loss on first pull of the
  day
• and lasts only about 10-15 minutes
• so might consider doing G-warm-up close to the
  time that youll be needing the extra help

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Push-Pull Effect

• with sustained negative Gs
• push over, or level inverted flight
• BP rises in your head and your carotid bodies
  compensate by
• slowing your pulse, and
• dilating your blood vessels
• this lowers your BP in about 10-15 sec
• but normally Gs come on just as your BP is
  falling and you can GLOC at 3Gs!
• So avoid Gs after sustained -Gs
• wont occur unless -Gs last over 3-4 sec.

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Petechia

• polka-dot bruises in dependent areas where there
  is no counter-pressure
• caused by high, sustained Gs
• worse when you havent flown for awhile
• like a bruise, looks worse the next day, but
  fades out in 3 - 5 days
• are not contagious!

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Respiratory Effects

• Atelectasis
• Hard to inhale

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Atelectasis

• chest tightness and feel short of breath after
  breathing 100 oxygen
• release one side of oxygen mask
• makes you cough
• but is not because the oxygen is dry
• oxygen, unlike air, is absorbed from your lungs
  so quickly that the air cells actually collapse
  and stick closed
• worse after sustained Gs
• the cough is the cure -- this re-inflates the air
  cells and relieves the unpleasant feeling

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Hard to inhale

• may feel like you cant get enough air in
• due to physical forces compressing your chest
• breathing is usually rather easy -- this isnt
• you just have to work at it
• hypoxia may contribute to decrease in
  performance, or increased likelihood of GLOC or
  ALOC
• be efficient -- another reason not to work any
  harder than you have to!

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Visual effects of Gz

• in retinal circulation
• in retinal perfusion
• grayout or blackout
• visual field

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Vision Loss

• 1. tunnel vision gt in-from-the-sides
• 2. dimmer switch effect
• 3. splotches
• 4. curtain
• 5. combination/variations over time.
• Vision loss may be asymmetric.

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One sided light loss

• when check-6, normally inadvertently tilt our
  head a little, so one eye becomes higher than
  other
• top eye loses light before lower eye
• but we tend to use the good eye and ignore the
  light loss
• the light loss in the top eye is the GLOC warning!

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G-Excess Illusion

• head tilt during a turn is misunderstood by the
  body, which thinks your head has tilted more than
  it really has
• but since you know where your head is, you think
  that the plane experienced an uncommanded
  pitch-up
• watch out during a sustained turn
• dont go by your instruments!

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Cerebral effects of Gz

• cerebral perfusion
• cerebrospinal fluid pressure

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Buffer Period

• your brain functions normally without any blood
  flow for about 6 seconds, then simply shuts down!
• probably a self-protective mechanism
• answer to todays quiz question is

6 sec
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Stohl curve
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GLOC Trap

• get in habit of waiting for light loss before we
  start to strain
• but may have no light loss warning before GLOC
  above 6 Gs

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Neurological Effects

• Cognitive changes -- error making
• some fatigue related, some ALOC
• ALOC -- Almost GLOC
• impairment but not LOC
• typical almost lost it scenario
• GLOC -- G induced loss of consciousness
• LOC is all-or-none, but
• G effects are a continuum

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GLOC -- A Continuum
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More about GLOC

• G-induced loss of consciousness
• 1. Absolute Incapacitation Period
• classic LOC -- out cold
• varies 1-18 sec, mean 12 sec
• typical in-flight GLOC is short 1-6 sec
• as pilot lets go of the stick, plane goes to 1G
• flailing is common
• blood flow returns in watershed pattern

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• 2. Relative Incapacitation Period
• 1-24 sec additional
• lights are on, but no one is home
• subject is upright, looks OK, but
• incapable of thinking or responding
• terminates abruptly with reintegration of mental
  functions and return to near normal capabilities
• may lose SA

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If you GLOC you may ...

• have some tingling or numbness
• have some twitching or jerking
• have a pleasant dream
• not realize that you GLOCed!
• be a little confused or disoriented
• be aware that you have lost your hearing
• feel a little off the rest of the day

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Does Physical Training help G-tolerance?

• before we can answer, we must understand the
  terms
• Relaxed G-tolerance
• Endurance G-tolerance
• Straining G-tolerance

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Relaxed G-Tolerance

• the G level at which you have significant light
  loss without doing a straining maneuver.
• relates to heart-to-eye distance
• body shape
• seat-back angle

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Relaxed G-Tolerance

• varies
• from person to person
• from day to day
• same for women and men
• 4 to 6 Gs for most people
• obviously different with or without an anti-G
  suit
• does not relate to physical training

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your relaxed G tolerance is increased by

• tilt-back seat
• lowers shortens heart-to-eye distance
• less than 1G improvement seen in F-16
• anti-G suit
• onset delayed until after the Gs come on
• recent G exposure -- the training effect

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your relaxed G-tolerance is decreased by

• fatigue
• alcohol
• dehydration
• illness
• medication
• layoff from G exposure

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Straining G-tolerance

• the highest G-level you can stand when doing your
  best straining maneuver
• but is hard to measure and study
• does relate to physical strength, and is improved
  by working out
• physical training improves your ability to
  repeatedly strain without wearing out

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Endurance G-tolerance

• the time you can keep straining against varying G
  levels until you are exhausted
• hard to measure, hence hard to use reliably in
  research
• improved by both aerobic and anaerobic training!

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Aerobic Training

• was once thought to decrease your relaxed
  G-tolerance probably not true
• aerobic training actually improves your staying
  power by allowing rapid recovery from the
  straining
• avoid extreme training -- keep your resting heart
  rate above 45

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So, Physical Training ...

• does not affect your relaxed G-tolerance
• does improve your strength and endurance
  G-tolerance
• pays off on long, difficult engagements, and on
  frequent flights

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Physical Training

• So, train the muscles you strain
• your goal is sustained, repeated straining with
  rapid recovery
• include aerobic training
• my personal view is that you are better served by
  understanding Gs, and doing what you have to
  effectively and efficiently

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Neck Strength

• neck pain is 1 cause of down time for high-G
  aviators
• movement under Gs
• helmet, mask, NVGs, etc.
• Great Benefits come with neck strength
• better control (dont want to kiss your belly
  button!)
• less likely to be injured
• so, include neck strength training in your weight
  workout!

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Neck Pain/Injury

• leading cause of down time for high-G aviators
• associated with high rate of G onset (snatching
  on the Gs)
• non-pilot cant anticipate G onset
• head movement under Gs
• additional head mounted equipment
• good neck strength training minimizes injury
  potential

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The Det Effector, Whered my G-tolerance go?

• Training Effect
• G-tolerance increases when you fly Gs
• Layoff Effect
• and drops off again when you dont

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Training Effect

• relaxed G-tolerance will increase all by itself
  with frequent exposure to Gs
• its not flight time, but G-time
• can increase up to 2 Gs within a week
• say usual relaxed G-tolerance is 5 G-suit makes
  it 6. So training effect can push it up to 8!
  You dont ever have to strain.
• You get used to not having to strain

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Engineering changes to improve G tolerance

• tilt back seat (30 deg tilt)
• gives lt 1 G additional relaxed tolerance
• standard seat is 13 deg this raises your head
  and lets you see out better
• anti-G suit
• always lags the G onset
• start your muscle strain before the Gs come on --
  esp before high Gs
• gives a 1G increase in relaxed G-tolerance

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Navy Combat Edge

• positive pressure breathing with chest jerkin and
  Eagle anti-G suit
• can sustain 8 Gs without straining!
• can keep talking and breathing throughout high Gs
• so increases your endurance too
• less straining
• better breathing
• high Gs still suck, though....

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Proper G suit fit ...

• G-suit helps you by doing some of the work
• strain first, then slack off after the G-suit
  fills
• fit should be snug, not tight
• too loose just takes longer to fill up
• while standing, should easily slip
• two fingers down by the thigh and calf, and
• open hand down the front
• release G-suit when you need to (spring, fall)

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AGSM

• M-1 classic grunt
• L-1 glottis closed completely
• Hook maneuver
• I say its OK to use your own combination of leg
  strain/abdominal strain/hook maneuver as you need
  to.
• Do what you have to do, but no more
• understand what to do and why
• know and respect the traps!

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Hook maneuver

• 1. tighten all muscles before G onset
• Get a Jump on the Gs! above 6
• 2. deep breath, close glottis (say hook)
• 3. bear down and strain for 3 seconds
• strain harder for higher Gs slack off at lower
  Gs
• 4. while maintaining continuous muscle strain,
  rapidly exchange full lung of air
• its hard to inhale under high Gs
• 5. work only as hard as you have to