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G Induced Loss of Conciousness Part 3 II
Gjunkie1
#1 Posted : Monday, May 30, 2011 5:25:29 PM(UTC)
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A Plain Pilots Guide to GILOC - part 3 (second half)


10. We can enhance cardiac filling by leg and abdominal muscle contraction, raising the lAP (as when straining to defecate when constipated, but keeping our orifices closed!).
11. Raise cardiac ejection/output pressure. that is our blood pressure, by INTERMITTENTLY raising the pressure in the chest (IAP) as when blowing a trumpet, but providing a resistance to blowing-out, either by closing your throat altogether (the "MI" manoeuvre) or blowing out with your mouth obstructed by tongue against teeth and pursed lips ("L1”).

These AGSMs, Anti-G Straining Manoeuvres, both raise IAP, Cardiac Ejection Pressure and sBP, as our red faces testify when practising on the ground. You can check the actual pressure generated by blowing up a blood pressure machine. Your heart, until it runs out of blood, will then be pumping blood to your head and face at your normal blood pressure + the additional pressure in your chest. Beware doing this if you have got any cerebral aneurysms about to pop! Better to practice under high +Gz in the air at altitude or better get on a centrifuge, but unfortunately most of us do not have access to one.

However, you can easily practice the sequence gently against a Blood Pressure machine (purloined from your long-suffering Doctor) or a column of water in a transparent plastic pipe.
If you keep the pressure up for too long you will eventually keel-over as the high pressure in your chest will stop blood getting into your chest and back to the heart. If you really hammer yourself you could even get "on-the-ground” GILOC. This is not recommended as you might display a convulsive response to the later return of blood to your brain, once unconsciousness and your collapse to the floor had allowed blood to flow back to your head and on to your brain. This is not unusual, but is tiresome as we would then have to rally round and prove that this was not epilepsy.

YOU have to "blow" therefore for a relatively short period to shove the blood up to the brain and then smartly breath-in to get blood back into chest and heart which you then duly blow back up to the brain again. The advantage of the 'L1" manoeuvre is that by blowing out through your teeth most of the air in your lungs has already been blown out and you have only to eject the rest before sucking in both new air to the lungs and fresh blood to the heart. Hence The "Warminster Grunt', which tells you over the RT that you're up against a Navy man. It sounds a bit like "hook" pronounced "uH-oo (3seconds) oo-K" followed immediately by “-uH (and oooooH again)". The "oooo" bit is him straining out through his teeth to perfuse his brain. The explosive "K" is him letting go and expelling the last of his breath from his chest followed by immediate, urgent inspiration (the “uH”) to suck air in down his throat and blood up from his belly. Then back to the “oooo” straining, etc.. Many settle for a 3-second "Thh (straining/blowing) hhhhhhhhthAH (blowing tongue and mouth open and last of intrathoracic air out”, and then “-UuuuH (1-second suck-in and then back to 3-second blow) -Thhh...” and so on, repeated as a 4 - 5 second cycle.

"M1" men (and also girls) sound like: “... (3-4 sec. silence) ..." then an explosive “Pah-aaH” (all in 1 sec), the “Pah” being an explosive ejection of all the air you can blow suddenly out of your lungs; the “aaH” being a gasp to refill them and suck blood into the heart before closing your mouth and throat again for the next blow, all repeated cyclically every 4-5 seconds, so that cerebral perfusion only ceases only for a second every 4-5 seconds and the return of blood to the heart is achieved during that one second interval.

The present “ultimate” alternative is to squeeze the whole man, like a toothpaste tube, and squirt the blood up into the head. This is achieved in PPB, Positive Pressure Breathing (Fig 4). It can be uncomfortable as the blood is also squeezed out into the arms and through the thoracic inlet at the base of the neck, where the venous system is unsupported either by muscles within a tough deep fascia or by one-way valves. Worse is the effect on the cervical nerve roots exiting through their foramina from the high pressure intra-spinal domain to the un-protected low pressure area in the neck. These symptoms are not mortal, but they are uncomfortable and may be distracting - undesirable in a sequence or operational flying.

Needless to say, the Chinese have something different (Fig 5). Their "Qigong” manoeuvre depends on anticipation (or terror, take your pick - have you ever flown a Peking-built MiG-15? Dr. von DIRINGSHOFEN would have approved). Leg followed by abdominal straining (so far so good, the blood's back at the diaphragm) and then "bicycle-pump" rapid breathing, with breathing-out against resistance (no doubt appropriately through your teeth) at 30-60 cycles/min. With high leg and IAP each inspiration, depressing the diaphragm on to an already
pressurised abdomen, squirts blood up into the heart, supercharging it; the following
forced/obstructed expi ration raises the ITP high enough to perfuse the brain.

The RT music changes to “THhhUH (expiration) HuuuH (inspiration) THhhUH-HuuuH... (1 second each)”'. It would be neat to synchronise the inspiratory “HuuuH” with cardiac filling (diastole, cardiac relaxation) and the “THhhUH” expiratory grunt with cardiac ejection (contraction, systole) to maximise the effect. Unfortunately even CONFUCIUS did not have the answer to this one. Even if he did, no doubt the recently-risen wraith of Chairman-destroy-all-that-is-best-in-China, MAO, would not let them read it, let alone include it in the bibliography. Nevertheless the "bicycle pump" works in the skies over Tin-a-min Square and it is well worth more study now that with EchoPlanar imaging we can see exactly what is happening during these manoeuvres. Of course, what we need is a magnet on its side in the Warminster Centrifuge (this lS a commercial on behalf of the Dept. of the Navy. Aerobats in Congress please take note!).

GILOC antidote:
11. Use an AGSIM, Anti-G Straining Manoeuvre: M1, L1, or Qigong (if you must!).
12. Better still follow Dr. WOOD's advice and fly horizontally, in the prone position or supine with visual aids. Bad enough in a two-pilot Meteor, but the hang-gliding merchants do it. What they do not experience is the high Gx (into which the aircraft's Gz is converted for the prone pilot). This means that head stabilization in full head extension becomes mandatory, with all the additional discomfort and restriction of head mobility which this entails.
13. Half-measures, principally the reclining seat, help less than you might expect. You have to recline your seat back 60° to halve the heart-head distance, that is to fly with your seat back only 30° up from the horizontal. Good for the frontal area, but not the neck ache. Often, as in the Su 27, adding a back-pack parachute ends up with most of the theoretical advantage of a reclining seat being lost in practice.
14. After thinking about this you may opt for more conventional sealing and being carefull to keep within the G-free Window. It makes a large stop watch an essential part of one's equipment, especially when learning or developing new manoeuvres. Be careful, note the time span of all high Gz segments of manoeuvres and the times between high –Gz way-gates.
15. Lastly, be careful for or avoid high +Gz after -Gz. Your subsequent +Gz tolerance may be significantly reduced. This can catch you out in any programme. You have to be particularity careful in Unknowns. Check for this in Programme 3 and be sure to object.

V. CEREBRO-VASCULAR MICROCIRCULATORY REGULATION OF CBF, CEREBRAL BLOOD FLOW (“AUTO-REGULATION”).

This is a bit of a mouthful, but it's where the action is within the Brain. Many of the factors contributing to this have been mentioned before (including CO, cardiac output; sBP, systemic blood pressure in the body; SNS, the sympathetic nervous system; paO2 and paCO2, the levels of oxygen and carbon dioxide in the blood which depend on efficient lung ventilation; pH, the blood’s acidity). But Cerebro-vascular "Auto-regulation" has not. This is another of the after-thoughts (mods if you like) introduced by the Almighty on his return on the Second Monday of Creation to get this new-fangled botch-up, Man, to work at all. In essence, if all else fails, the terminal arterioles (the last of the arteries as they turn into the capillaries next to our brain cells) beaver away constantly to convert the constantly fluctuating cerebral blood supply into a steady, orderly flow through the cerebral capillary bed, so that oxygen and glucose can get out to the cells (which are kaput in 5 seconds without them) and at the same time all the debris of cerebral metabolism, principally CO2 and water, can be extracted from the brain and cleared back to blood, lungs and kidneys.

Unfortunately Autoregulation, which should be the toughest physiological mechanism in the body, is very easily abolished and has to be constantly exercised if it is to operate through the range of rapid alterations in CBF posed by high Gz aerobatics. Its quixotic and often apparently capricious variations are one of the major contributors to our slowly acquired and rapidly-lost "G-tolerance". This means, the more flying, or more accurately the more frequent flying, the better.

As the KGB used to say: the day their satellites demonstrated a brace of Pitts on the ramp of every USAF Fighter Base would be the day that they then would know that they had real opposition for the MiG-29 and Su-27 or the mysteriously "big" and "little" versions of Ram-K as they were known in those days. Meanwhile, now that Economics have come home to roost, we in our turn will know that our Air Forces are practising maximal economy whilst extending their operational envelopes not so much when the Su-29 IS the first Russian-built USAF/USN operational type, but when Walter E is shouting "foul" if the Luftwaffe docs not buy 200s and when the DH82a production lines are humming again in England!

GILOC Antidote:
16. Aerobat frequently, even if your budget means that your trips have to be kept short. This is to your advantage. Every aerobatic trip merits meticulous pre-flight preparation, careful observation and criticism from the ground, detailed debriefing and then much cunning thought before the next detail. You can easily keep up progress and probably will do best on three 10-minute trips per day - just SO long as they are accurately observed and criticized, preferably on tape, so that you can re-play and re-fly them a 100 limes before you next take to the air.

VI. THE BBB, BlOOD-BRAIN BARRIER.

This is between the blood in the capillaries and the inside of the Brain cells (which do the flying and allow you to enjoy aerobating). This is effected by many factors which include:
i. The oxygen carrying capacity, oxygen-loosing ability and oxygen content of your blood. These are compromised if you are anaemic (Girls, beware), poisoned by carbon monoxide from the engine or hypoxaemic because half your lungs are piled in a useless heap at the bottom of your chest by prolonged high +Gz.
ii. Blood Glucose. Little essential sugar will get to your brain if there is no glucose in your blood, due either to simple starvation, or to post-alcoholic hypo-glycaemia (watch your drinking, it's also good for sparking a seizure and loosing your licence on the grounds of "Epilepsy"), or just because you arc burning-up glucose (with all this high-G grunting and snorting) faster than your liver can chum it out.
iii. Plasma Osmolarity, the thickness of your blood. This can be thick indeed after you have been steaming for an age down at the holding point before you get on with the serious stuff of loosing the >1 lb/min body water loss often experienced during Unlimited sequences. It's even worse in Nevada or in a nice above-the-weather high-performance jet especially if you do not have a snazzy new super-cooled G-suit and you have to flog all the way up from and back to Miramar, rather than just spin down to ground effect and the Coke truck at Nellis or Benjie and the Bar for tea at Redhill.
iv. A witch's brew of endothelins, calcium ions, vaso-active peptides and The-Lord-knows-what other metabolites which operate at and across the cerebral capillary endothelium.
v. Ambient Tissue Pressure, that is Intra-Cranial Pressure (ICP), which in aerobatic conditions is acutely and continuously changing with Gz-induced CSF (cerebro-spinal fluid) flow up and down through the Foramen Magnum, in and out of your head, from the fixed-volume intra-cranial space above to the expansile, elastic intra-spinal thecal (or dural) sac in your spine below. High +Gz has the same effect on CSF as it has on blood. Your CSF drains down out of the head under +Gz, lowering ICP and to a degree offsetting the progressively greater difficulty the heart has pumping blood up to the head against +Gz. Unfortunately unlike under high –Gz, when the pressure gradients within the head merely operate at greater absolute, but little changed relative pressures, under +Gz the arteries carrying blood from chest to rigid head are themselves collapsible and so the same rigid conditions do not obtain and the high +Gz weight of your blood eventually overcomes your Cardiac Output. (Though some septuagenarian and octogenarian aces in the United States' Team attribute their G-tolerance to their calcified, concrete carotids, others say they have no brains left, which need to be perfused!).

VII. INTRACELLULAR MECHANISMS.

These include "second messengers" and other joys. Prof. LURIA, Moscow, promised the Earth in this field, that is cerebral protection against ischaemia (no blood In the brain) at high +Gz for >5 seconds. That he did not succeed is indicated by the aerodynamic pitch-down of MiG-29 and Su-27 from high Alpha well within the G-free window (the basis of the "Cobra" manoeuvre). However the Air Force that extends its G-Free Window by a second will enjoy an immense tactical advantage (Fig 7). This, together with V and VI above is where we're at in Nottingham, as they hold the keys to many other areas, including Stroke (which gets us all in the end, if something else has not got us first). GILOC is mini-Stroke, which is why an ex-aerobat Neurosurgeon is writing this piece (and why if you are still with me you deserve a PhD, at least!).

GILOC antidote:
17. This should be shrouded in Neuro-physiological obscurities. But it is not. It's really rather simple. As in competition swimming, where you can only swim so far without breathing, so in aerobatics we have now come up against one of Man's physical limitations. Rather than getting all hot and bothered about it, The Message is loud and clear: grinding-on, generating ever-higher +Gz levels for their own sake is a waste of time and effort. Competition aerobatics, all aerobatics, are not stultified 3-dimensional exercises in which the prizes go to the biggest brutes and only to "stupidos".


John Firth, Queens Medical Centre, Nottingham

Steve Johnson
MX2
Nashville, TN
Gjunkie1
#2 Posted : Monday, May 30, 2011 5:29:08 PM(UTC)
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Hi everyone, I didn't realize that part 3 of the GLOC series had a second half. It is posted now.

Steve Johnson
IAC Safety Chair
Steve Johnson
MX2
Nashville, TN
Mv031161
#3 Posted : Tuesday, May 31, 2011 8:24:24 AM(UTC)
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Location: Charlotte,nc

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Gjunkie1 wrote:
Hi everyone, I didn't realize that part 3 of the GLOC series had a second half. It is posted now.

Steve Johnson
IAC Safety Chair



thanks...great reading!
Mitch V
1998 Giles 202 "Primal Fear" s/n G202-0011 N202MK
Former Caretaker/Owner Pitts S2B s/n 5046 N324U Now Down Under
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