Aerospace Physiologist

1. G-TOLERANCE IMPROVEMENT PROGRAM Aerospace Physiologist MSC Symposium LT Yniguez MCAS, Cherry PT

2. 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

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

4. G-LOC A DEADLY THREAT • AIRCRAFT NO. G’s • 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

5. Why pull Gs? • it’s fun • it builds character • so you can kill the other guy • so you don’t get killed • actually only pull Gs to change direction

6. Anatomical/Physiological effects of G-Forces • Cardiovascular • Respiratory • Sensory • Cerebral

7. 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

8. 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

9. 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

10. The Cardiovascular Reflex, or“Why 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

11. 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 you’ll be needing the extra help

12. 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 • won’t occur unless -Gs last over 3-4 sec.

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

14. Respiratory Effects • Atelectasis • Hard to inhale

15. 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

16. Hard to inhale • may feel like you can’t get enough air in • due to physical forces compressing your chest • breathing is usually rather easy -- this isn’t • 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!

17. Visual effects of +Gz: • in retinal circulation • in retinal perfusion • grayout or blackout • visual field

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

19. 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!

20. 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 • don’t go by your instruments!

21. Cerebral effects of +Gz: • cerebral perfusion • cerebrospinal fluid pressure

22. 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 today’s quiz question is: 6 sec

23. Stohl curve

24. 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

25. 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

26. fully conscious light loss blackout cognitive impairment = ALOC unconscious = GLOC GLOC -- A Continuum

27. 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

28. 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

29. 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

30. Does Physical Training help G-tolerance? • before we can answer, we must understand the terms: • Relaxed G-tolerance • Endurance G-tolerance • Straining G-tolerance

31. 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

32. 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

33. 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”

34. your relaxed G-tolerance is decreased by: • fatigue • alcohol • dehydration • illness • medication • layoff from G exposure

35. 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

36. 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!

37. 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

38. 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

39. 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

40. Neck Strength • neck pain is #1 cause of down time for high-G aviators • movement under Gs • helmet, mask, NVGs, etc. • Great Benefitscome with neck strength • better control (don’t want to kiss your belly button!) • less likely to be injured • so, include neck strength training in your weight workout!

41. 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 can’t anticipate G onset • head movement under Gs • additional head mounted equipment • good neckstrengthtraining minimizes injury potential

42. The “Det Effect”or, “Where’d my G-tolerance go?” • Training Effect • G-tolerance increases when you fly Gs • Layoff Effect • and drops off again when you don’t

43. Training Effect • relaxed G-tolerance will increase all by itself with frequent exposure to Gs • it’s 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 don’t ever have to strain. • You get used to not having to strain

44. Engineering changes to improve G tolerance • tilt back seat (30 deg tilt) • gives < 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

45. 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....

46. 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)

47. AGSM • M-1 classic grunt • L-1 glottis closed completely • “Hook” maneuver • I say it’s 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!

48. 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 • it’s hard to inhale under high Gs • 5. work only as hard as you have to