G-Forces modeling please fix

[JG27*PapaFly]

1 hour ago, Nazgul* said:

neurons do not store oxygen in any meaningful way. Brain cells are therefore exclusively dependent on blood perfusion to function since their energy demands can only be obtained by aerobic metabolism and/or metabolism of ketones

When looking at FBP, oxygen plays a minor role. Stored chemical energy is the key to FBP.

Like all our cells, neurons do have an ATP store, which is the main reason why there is a FBP in the first place. More precisely, the brain, like many other tissues, employs a two-stage ATP store. Most high-energy phosphate groups are stored in phosphocreatine (PCr). This molecule passes these on to ADP molecules to recycle them into ATP, the molecule that serves as THE energy currency of the cell. To my understanding, when intracranial O2 partial pressure reaches a critical threshold of around 35 mm Hg, the PCr levels begin to drop, while ATP levels are maintained for a few seconds. Once the PCr high-energy phosphate store is exhausted, the ATP levels drop very fast, and lights go out.

[Nazgul*]

1 hour ago, Floppy_Sock said:

You clearly understand way more of this than I do - maybe I can ask you a few questions when I come back to this.

 

So where does the metric "brain tissue oxygenation" fall into this discussion? If I understand it correctly, that includes all brain tissue and surrounding fluid. This is the wordage that is used in the papers on this topic that I've read. 

 

On another note, given what you said in your response to Papafly, is length scale for anaerobic respiration an explanation for the 9 second buffer period?

 

Sorry, did not want to come out as rude (english is not my first language). Metric brain oxygenation refers, to my understanding, to the correlation between perfusion (amount of oxygen dissociated and associated with hemoglobin being delivered to the tissue at a given time) and ability of the brain to extract oxygen from blood. Although, oxygen may be found in dissociated form in the CSF, most has to be delivered via arterial blood supply so we can conclude that the "amount" of oxygen being received by the brain is directly proportional to CO and, since the brain cells cannot extract any additional oxygen directly, the only way to obtain additional oxygen supply is by inducing changes in blood flow. As you know, from the paper, inducing the required changes in blood flow to compensate for the effects of gravity (either positive or negative Gs) is difficult depending on the Gs being pulled/pushed and there is only so much the barorreceptor reflex can do to regulate the degree of vasodilation/constriction to compensate them. We know that, in normal individuals (no comorbities or heart associated pathology), the brain obtains about 15% of the CO and uses approximately 20% of the total oxygen being supplied to it, therefore, if we know the CO or the oxygen consumption of the brain, we can calculate blood flow and, indirectly, the oxygen supply/consumption of the brain at a given time using the Fick's principle:

 

CO = rate of O2 consumption/(arterial O2 content - venous O2 content)

 

To conclude, what the paper may consider "storage" of oxygen is nothing more than a measure of blood flow being received at a given time during the high G maneuvers. I hope it is clear. Since blood flow is required to maintain proper oxygenation to the brain and oxygen is needed to support the major mode of energy supply to the brain (aerobic respiration), decreasing blood supply to the brain will directly decrease its ability to produce enough energy to support its own functions.

 

20 minutes ago, JG27_PapaFly said:

When looking at FBP, oxygen plays a minor role. Stored chemical energy is the key to FBP.

Like all our cells, neurons do have an ATP store, which is the main reason why there is a FBP in the first place. More precisely, the brain, like many other tissues, employs a two-stage ATP store. Most high-energy phosphate groups are stored in phosphocreatine (PCr). This molecule passes these on to ADP molecules to recycle them into ATP, the molecule that serves as THE energy currency of the cell. To my understanding, when intracranial O2 partial pressure reaches a critical threshold of around 35 mm Hg, the PCr levels begin to drop, while ATP levels are maintained for a few seconds. Once the PCr high-energy phosphate store is exhausted, the ATP levels drop very fast, and lights go out.

 

Correct and I never said otherwise. I was merely correcting the statement where you indicated that the brain is incapable of utilizing anaerobic respiration to produce ATP, which is false.

 

EDIT: Actually, there is a problem in your previous statement. Oxygen does play a key role here and not a minor one as you stated, since O2 is required for the induction of both Krebs cycles (although this system does not directly need it, the cycle will come to a hault because NADH and FADH2 will accumulate and not be available to the electron transport chain) and the ETC and the brain contains very little PCr overall (Xia et al. 2011. Phosphocreatine Preconditioning Attenuates Apoptosis in Ischemia-Reperfusion Injury of Rat Brain. BioMed Research Internation.). PCr will only be a minor stop gap to prevent sudden LOC and supply some energy in the very initial phase of the hypoxic condition but these levels will most likely be consumed by glycolysis (remember, the initial phases of glycolysis actually requires ATP consumption before the pathway actually induces the required substrate level phosphorylation reactions to produce ATP) and some of it will also be lost by spontaneous dissociation through decreasing pH. Therefore, we can also conclude that the most important factor contributing to the LOC associated with high G maneuvers is not the total storage of ATP in the brain but, instead, the amount of oxygen being supplied to it that will, in turn, induce synthesis of sufficient ATP.

 

@JG27_PapaFly

 

Edited July 14, 2020 by Nazgul*
Correction on final statement (point was missed)

[Nazgul*]

@JG27_PapaFly See above.

[Floppy_Sock]

48 minutes ago, Nazgul* said:

 

Sorry, did not want to come out as rude (english is not my first language). Metric brain oxygenation refers, to my understanding, to the correlation between perfusion (amount of oxygen dissociated and associated with hemoglobin being delivered to the tissue at a given time) and ability of the brain to extract oxygen from blood. Although, oxygen may be found in dissociated form in the CSF, most has to be delivered via arterial blood supply so we can conclude that the "amount" of oxygen being received by the brain is directly proportional to CO and, since the brain cells cannot extract any additional oxygen directly, the only way to obtain additional oxygen supply is by inducing changes in blood flow. As you know, from the paper, inducing the required changes in blood flow to compensate for the effects of gravity (either positive or negative Gs) is difficult depending on the Gs being pulled/pushed and there is only so much the barorreceptor reflex can do to regulate the degree of vasodilation/constriction to compensate them. We know that, in normal individuals (no comorbities or heart associated pathology), the brain obtains about 15% of the CO and uses approximately 20% of the total oxygen being supplied to it, therefore, if we know the CO or the oxygen consumption of the brain, we can calculate blood flow and, indirectly, the oxygen supply/consumption of the brain at a given time using the Fick's principle:

 

CO = rate of O2 consumption/(arterial O2 content - venous O2 content)

 

To conclude, what the paper may consider "storage" of oxygen is nothing more than a measure of blood flow being received at a given time during the high G maneuvers. I hope it is clear. Since blood flow is required to maintain proper oxygenation to the brain and oxygen is needed to support the major mode of energy supply to the brain (aerobic respiration), decreasing blood supply to the brain will directly decrease its ability to produce enough energy to support its own functions.

 

 

Correct and I never said otherwise. I was merely correcting the statement where you indicated that the brain is incapable of utilizing anaerobic respiration to produce ATP, which is false.

 

 

Never thought you sounded rude! I appreciate the information - I know very little biology. 

There is substantial evidence that tissue oxygenation seems to be a good metric for predicting GLOC. See the attached figure. Here rSO2 denotes relative cerebral tissue oxygen saturation values.

Source

It also seems to be a good predictor of consciousness recovery - as you can see the "end of the absolute phase" line correlates with a return of rSO2 values to baseline. 

However, is not a good predictor of performance recovery as you can see rSO2 values shoot back up to baseline quite quickly, yet performance in quantitative tasks is still impaired until some 50 seconds after the GLOC episode. 

 

This paper corroborates claims from other publications that LOC occurs around 85% rSO2 .

 

From this figure, as someone who understands next to zero of the underlying biology, I would venture to guess that the slope between 26 and 36 seconds can be used as an oxygen consumption rate. The duration over which the rSO2 values decrease is about 8 seconds. This corresponds well with the FBP number published in the paper I previously linked. 

 

It seems to me, that there does exist, at least to some degree, some form of stored oxygen in the brain tissue which clearly decreases as acceleration is applied, and furthermore, seems to be a good predictor of LOC.

 

Edit: I should add that the acceleration profiles were as follows: 
 

Quote

a rapid +Gz onset rate (ROR) of +3 Gz/s to a preestablished target level at which the participant was rendered unconscious. That level was set individually for each participant on each testing day. It was reached by adding 1 +Gz to the GORmax. The G levels required to induce GLOC ranged from 5.5 +Gz to 8.5 +Gz with a mean of 6.7 +Gz (SD = 0.91 +Gz).

 

Edited July 14, 2020 by Floppy_Sock

[Nazgul*]

22 minutes ago, Floppy_Sock said:

Never thought you sounded rude! I appreciate the information - I know very little biology. 

There is substantial evidence that tissue oxygenation seems to be a good metric for predicting GLOC. See the attached figure. Here rSO2 denotes relative cerebral tissue oxygen saturation values.

Source

It also seems to be a good predictor of consciousness recovery - as you can see the "end of the absolute phase" line correlates with a return of rSO2 values to baseline. 

However, is not a good predictor of performance recovery as you can see rSO2 values shoot back up to baseline quite quickly, yet performance in quantitative tasks is still impaired until some 50 seconds after the GLOC episode. 

 

This paper corroborates claims from other publications that LOC occurs around 85% rSO2 .

 

From this figure, as someone who understands next to zero of the underlying biology, I would venture to guess that the slope between 26 and 36 seconds can be used as an oxygen consumption rate. The duration over which the rSO2 values decrease is about 8 seconds. This corresponds well with the FBP number published in the paper I previously linked. 

 

It seems to me, that there does exist, at least to some degree, some form of stored oxygen in the brain tissue which clearly decreases as acceleration is applied, and furthermore, seems to be a good predictor of LOC.

 

Your are correct in your assumption regarding the slope between the slope in points 26 and 36 but not regarding storages of oxygen in the brain. From my explanation above, by understanding how oxygenation of the brain is directly associated with blood flow, you can see that what you call "oxygen storage" to  the brain is actually a hemodynamic compensation by the brain vasculature to compensate for the negative hemodynamic effects. For example, assuming we are applying a progressive large G to the pilot that is forcing most of his blood to be trapped in his legs. This trapping of blood will decrease flow and pressure to the aortic arch and carotid sinus where the baroreceptor is located. Afferent nerves (mainly CN X) will relay this information to the medulla which will, in turn, evoke a vascular reflex by inhibiting parasympathetic activity to the blood vessels while stimulating sympathetic activity.The overall result will induce vasoconstriction to the blood vessels in order to shunt blood from the legs into the heart (increasing pre-load) and also by increasing myocardial contractility and heart rate. Both of these effects constitute a quick mechanism (compensation) to attempt to increase blood pressure back to normal. Since, for the brain, we can view blood flow as determinant of oxygenation, preventing larger drops in blood flow can also be viewed as preventing larger drops in oxygenation. The system, however, is not perfect and there is only so much it can compensate for before perfusion declines too much. Hope it is clear.

Edited July 14, 2020 by Nazgul*

[Floppy_Sock]

5 minutes ago, Nazgul* said:

 

Your are correct in your assumption regarding the slope between the slope in points 26 and 36 but not regarding storages of oxygen in the brain. From my explanation above, by understanding oxygenation of the brain is directly associated with blood flow, you can see that what you call "oxygen storage" to  the brain is actually a hemodynamic compensation by the brain vasculature to compensate for the negative hemodynamic effects. For example, assuming we are applying a progressive large G to the pilot that is forcing most of his blood to be trapped in his legs. This trapping of blood will decrease flow and pressure to the aortic arch and carotid sinus where the baroreceptor is located. Afferent nerves (mainly CN X) will relay this information to the medulla which will, in turn, evoke a vascular reflex by inhibiting parasympathetic activity to the blood vessels while stimulating sympathetic activity.The overall result will induce vasoconstriction to the blood vessels in order to shunt blood from the legs into the heart (increasing pre-load) and also by increasing myocardial contractility and heart rate. Both of these effects constitute a quick mechanism (compensation) to attempt to increase blood pressure back to normal. Since, for the brain, we can view blood flow as determinant of oxygenation, preventing larger drops in blood flow can also be viewed as preventing larger drops in oxygenation. Hope it is clear.

 

Understood - from another publication "Cerebral TOI is a measure of cerebral tissue saturation of haemoglobin with oxygen." i.e. it's a metric for oxygen rich blood in the cerebral tissue.

[ACG_Smokejumper]

On 6/10/2020 at 9:34 AM, Floppy_Sock said:

@JG27_PapaFly

 

While the duration of the blackouts is probably somewhat correct, I find that modern models of +Gz tolerance do not match up with what we have in the game.

 

First, the most dangerous maneuver one can do as a pilot is a push pull. It is generally the biggest killer of pilots due to GLOC. Note that this is not simply due to a bunt followed by a pull, but also aircraft with high roll rates can induce substantial negative G forces due to the radial acceleration. Even very short exposures to -Gz can substantially reduce +Gz. This effect is not modeled in the game at all and it contributes to the multiplayer meta of oscillating between bunts and pulls to avoid GLOC. 

 

Second, G onset rate is not as important as the devs make it out to be. That theory is outdated and has been readily disproven in the literature. See the following paper for the full details - I’m just going to pull a few figures and a section of the abstract to illustrate. 

 

Paper url: https://link.springer.com/article/10.1186/2046-7648-2-19

 

First, the most comprehensive collection of GLOC incidents as a function of onset rate:

Notice that after 1g/s onset rate is irrelevant. The physiological explanation is in the paper if you’re interested.

 

Furthermore, a comparison of the model used in IL2 GB was authored by Stoll(depicted below by the red curve), compared to the modern model (depicted by the blue curve)

Note that the biggest reason for this discrepancy is that the red curve is an extrapolation from 14 gloc incidents. The blue curve is an average of over 800 incidents.

 

Two big things can be gleaned from this study:

1. Above 1G/s - onset rate does not matter.

2. For any rapid onset rate pull, mean duration until GLOC is long - slightly above 9 seconds in the average.

 

As a comparison, here’s a fresh pilot in a spit mk9 during a max performing horizontal break turn:

I recorded this using the motion simulator output - this is the same data that is depicted on the in game G-meter. This is pretty steady 2G/s onset rate. A pretty measly 3.7 seconds to gloc. That’s pretty far off form the 9.1g seconds it should be.

 

It should be noted, that this is also the absolute minimum of human tolerance since this is data collected during pilot training. This data did not come from a study conducted to find the true average time to GLOC. From the methods section we know 

But we do now know how many total recruits have passed through these tests. I know for a fact that one of the samples used in these tests showed GLOC for somewhere between 5-30% of the recruits lost consciousness depending on the onset rate. Interestingly, the gradual onset rate test (.1g/s if I remember correctly) actually induced the most GLOC episodes due to the duration of the test. Students performed much better in the rapid onset rate tests. I can dig that data up if you’re interested. Thus, it’s safe to say that this curve is invariably skewed low. 

 

Let me conclude with a excerpt from the abstract of the paper above - please note the final sentence:

 

 

 

 

 

 

 

Great post! This is how one debates ideas. Evidence.

 

Nice one Floppy.

On 6/10/2020 at 1:10 PM, LLv24_Zami said:

Hi Tumu!

 

All pilots have same G tolerance, expect for a few American planes. They have +1G for their G-suits. That is the information we have

 

 

Shouldn't seat angle be accounted for?

 

109 pilots sit more reclined than Spits, Hurris and Tempests.... I think. If I'mm wrong pls feel free to correct me. I'm basing this off Cliffs of Dover not anything real.

[Nazgul*]

1 hour ago, Floppy_Sock said:

 

Understood - from another publication "Cerebral TOI is a measure of cerebral tissue saturation of haemoglobin with oxygen." i.e. it's a metric for oxygen rich blood in the cerebral tissue.

 

Perfect! In a steady state situation and without considering disease such as anemia, polycythemia, etc. The amount of Hb is steady across a population with little variation among the same sex so, again, we can derive the oxygenation by taking into consideration blood flow. Also, note that hemoglobin functions as a method of transportation of oxygen (as well as other gases like CO2) and is not a storage of oxygen like the similar protein myoglobin. The saturation of Hb is expected to decrease in this scenario due to several factors but most importantly:

1 - Decrease in paO2;

2 - Decrease in pH (development of acidosis due to glycolysis respiration);

3 - Accumulation of CO2 and H+ (Bohr effect).

[JG7_X-Man]

On 7/12/2020 at 9:23 PM, LukeFF said:

 

I'm a vet, and I can tell you there was severe punishment for those who didn't want to wear their body armor in Iraq. It really wasn't a choice. 

 

@LukeFFThank you for your service!

I am also a vet - 3rd Marine Division Combat Engineer and in Desert Shield and Desert Storm (and two MEF deployments) This was before I got an MBA! The bugabo was staying hydrated and then there was the MOP gear drills in training (Sateside) that were never used in country. I guess it comes down to the sliver bar as my flack jacket was on my bunk most of the time. Then again the AR500s are more comfortable then the old school Woodlands we had. 

[JG27*Kornezov]

On 6/22/2020 at 12:44 PM, taffy2jeffmorgan said:

, does give us some idea of what the pilots actually experienced during combat, but this effect has decreased my combat victories dramatically, I am finding it frustrating.  I work hard to get into position for a deflection shot [ which took me some time master ] and just about to pull the trigger and the scre

 

The G limitations force you to maneuver into a position that requires lower delflection and lower G. Most of the pilots just put hard G towards the ennemy as soon as they see them, then put their pipper into a lead no matter what is their or their opponent relative position.

 

That reminds me a story about the old il2. One Russian guy asked his grandfather, who was an ex ww2 pilot to fly the sim. He was curious to see some real ww2 tactics. After the duel started his opponent started to turn like a madman, while he just climbed in a lazy spiral. Then the grandson sked:
-"What are you waiting for, are you going to fight or not?

Then the grandfather answered:
-"Well I saw him turning like a maniak, he has to use   high Gs, he would get tired very soon, and when he is tired I am going to fight him".

Of course that was not the case in the old game, only 15 years later we get into those scenarios. 

Edited July 22, 2020 by JG27_Kornezov

[JG27*PapaFly]

On 7/22/2020 at 11:56 AM, JG27_Kornezov said:

The G limitations force you to maneuver into a position that requires lower delflection and lower G. Most of the pilots just put hard G towards the ennemy as soon as they see them, then put their pipper into a lead no matter what is their or their opponent relative position.

+1

@Gate

Anticipation of upcoming turning requirements and speed management are now extremely important.

 

Many pilots must unlearn stuff that worked well before the physiology model was implemented, but gets them killed now. If you prepare to attack an opponent, especially if he is below you, you must maneuver yourself into a good position in terms of geometry, AND you must control your speed and g load during the attack. That often means throttling back, opening radiators, deploying flaps, side slipping, in order to be at the right speed and conscious the moment you press the trigger.

[MigSu]

On 7/23/2020 at 12:56 PM, JG27_PapaFly said:

+1

@Gate

Anticipation of upcoming turning requirements and speed management are now extremely important.

 

Many pilots must unlearn stuff that worked well before the physiology model was implemented, but gets them killed now. If you prepare to attack an opponent, especially if he is below you, you must maneuver yourself into a good position in terms of geometry, AND you must control your speed and g load during the attack. That often means throttling back, opening radiators, deploying flaps, side slipping, in order to be at the right speed and conscious the moment you press the trigger.

 

Yes Papa, but, what do you think when you managed your plane in order not to go sleep you are braking and maintaining mm some 400 km/h in a soft vertical recovery movement around some seconds, ok and your enemy in that time run fast from you at one km away, turn back and came in a front encounter against you one and again and again, so in the time that you are slowly turning like a delicate flower uy uy  the other f.. guy runs away 1km from you, turn come and pass away IN THE SAME TIME? and you loosing energy all those moment like , o baby take care omg the G force is so strong.

 Do you think is that normal? 

 

 Now soviet planes are USELESS.

[JG27*PapaFly]

21 hours ago, MigSu said:

 

Yes Papa, but, what do you think when you managed your plane in order not to go sleep you are braking and maintaining mm some 400 km/h in a soft vertical recovery movement around some seconds, ok and your enemy in that time run fast from you at one km away, turn back and came in a front encounter against you one and again and again, so in the time that you are slowly turning like a delicate flower uy uy  the other f.. guy runs away 1km from you, turn come and pass away IN THE SAME TIME? and you loosing energy all those moment like , o baby take care omg the G force is so strong.

 Do you think is that normal? 

 

 Now soviet planes are USELESS.

I'd say if that happens to you all the time your positioning was poor most of the time. If the tectonically situation permits it, you should first position right above your opponent, and then start the attack. A lot of folks get that wrong by immediately diving towards an opponent irrespective of geometry. If you now dive towards an opponent in an attempt to get him in a high speed head on situation with very low kill probability, you invite the guy to do an energy-conserving guns defense jink at the merge and extend away from you in the opposite direction from yours. Now you find yourself in a bad position, screaming along at very high speed, in need of a 180 degree reversal in order to give chase. By the time you've finished your reversal the opponent will be several km away.

For me, the fight is a constant loop:

1) anticipate

2) decide

3) act

4) check current status against the desired/anticipated status and go back to 1)

 

If you find that your opponents trick you all the time, perhaps you are too predictable. You are then playing their game. Try to break out of your pattern by doing something unexpected. Then your opponent will have to adjust his pattern.

[MigSu]

6 hours ago, JG27_PapaFly said:

I'd say if that happens to you all the time your positioning was poor most of the time. If the tectonically situation permits it, you should first position right above your opponent, and then start the attack. A lot of folks get that wrong by immediately diving towards an opponent irrespective of geometry. If you now dive towards an opponent in an attempt to get him in a high speed head on situation with very low kill probability, you invite the guy to do an energy-conserving guns defense jink at the merge and extend away from you in the opposite direction from yours. Now you find yourself in a bad position, screaming along at very high speed, in need of a 180 degree reversal in order to give chase. By the time you've finished your reversal the opponent will be several km away.

For me, the fight is a constant loop:

1) anticipate

2) decide

3) act

4) check current status against the desired/anticipated status and go back to 1)

 

If you find that your opponents trick you all the time, perhaps you are too predictable. You are then playing their game. Try to break out of your pattern by doing something unexpected. Then your opponent will have to adjust his pattern.

 

 Thanks Papa for that interesting explanation, i appreciate it. But what i say is not a rare case, no man, i just realized this problem i have flying with red planes for ever so immediately noticed something is changed now so i came the the forum and see several post about it.

 That is not only against human piloting also IA planes, so i feel now (not before) fighting those german planes with my FN and Yak1,7Bs something simply ridiculous. 

[JG7_X-Man]

On 1/13/2019 at 12:22 AM, bzc3lk said:

?

I agree DetCord12B, looking at the photo below you can clearly see the weathered appearance along the lines of what you are trying to achieve. This skin is the Ducks guts.

 

 

 

 

 

 

Hey! Where is this guys G-Suit?