Tissue destruction from energy

[tuoni]

Destruction of tissue, heating and heat transfer

Are there any references available for the energy required to destroy tissue (or different types of tissue)? I have been told that it is related to the energy required to break the bonds of the proteins in the cells, but I have not found any specific values.

I have found values for specific heat capacity, thermal conductivity, heat of vaporisation, and some other things, but in order to do some simple (crude approximated) calculations, I'd also need the energy required to destroy tissue. At first I thought that it was enough to find the energy required to raise tissue to 41 ºC, as I already have specific heat capacity.

But is 41 ºC really a universal point of no return for tissue? Or is it more related to brain functions?

I'm basically trying to approximate injury from heat transfer/heating, nothing fancy, but still to give a little insight.

I think I have all the correct equations for the various forms of heat transfer and heating, but without any data on how tissue behaves it's pretty much useless.

EDIT:

After searching for various terms and looking through sites, I've found bond dissociation energy. As the body is mostly water, would it be too far off from realistic values if you simply needed to break the O-H bonds in order to destroy soft tissue? If so, would it then be the sum of all the bonds in water, i.e. two O-H bonds (460 kJ/mol)?

 

[bobze]

I don't think its as simple as you seem to imply. Tissues "die" long before bonds are broken. Because, proteins maintain their 3d shape through "weaker" types of molecular and atomic interactions (hydrogen bonds, salt-bridges, Van der Waals, hydrophobic forces etc). Proteins becoming denatured then, is the "point of no return" for tissue damage.

Our bodies combat this with special types of chaperon proteins who try and help or repair denatured proteins from heat damage (creatively named "heat shock proteins", though that is only one of their functions).

Some tissues will be more resistant than others to heat damage. Neurons for instance, are very picky and fastidious little things. They need to maintain constant gradients across their membranes and rely on proteins for this (sodium-potassium pumps, calcium-sodium exchangers, membrane pores etc). So when these proteins suffer catastrophic failure from heat damage they cause the death of the neuron, the death of the brain and the death of the organism. This is why that magical dangerous temperature number is at ~42 ºC.

Other types of tissues (or even individuals, because of variation between individuals) may handle these temperatures better or worse, depending largely on the types of proteins that predominate there.

 

[tuoni]

I never exepected it to be that simple, but I was hoping of finding a simple solution for it. I am working on a computer game, and this would be part of the "injury & disease" model. I have already spent 4 years learning ballistics, going from knowing nothing (except the ubiquitous cannon ball trajectory) to having a pretty good model and detailed data on projectiles, and so on. I don't feel like spending another 4 years for every other topic I'm studying (and I haven't)...I would end up dead before I got anything done.

Heat transfer, electromagnetic radiation, particulate radiation, and electricity, they have unique ways of injuring tissue/the body, and have different penetration and secondary effects, etc., but they also share the basics. Given enough energy, they are able to "burn" tissue. At least from what I've read, this is close enough to reality.

The problem is modelling the "burning" of tissue, the energy required to do this. From superficial burns to carbonised tissue (only carbon left), chronic or acute burning.

 

[Mapes]

Thermal damage to tissue is often modeled by an Arrhenius equation of the type

[tex]r=A\exp(-E/RT)[/tex]

where r is the damage rate per second (and a damage of 1 indicates a burn), A and E are tissue-dependent constants, R=8.3 J mol^-1 K^-1 is the gas constant, and T is temperature in kelvins. E is typically 10⁵-10⁶ J mol^-1 (see, for example, Table 4.4.10 in The CRC Handbook of Thermal Engineering).

The problem is that A is usually not well known; various values from 10⁵⁰-10¹⁰⁰ s^-1 have been reported.

The bottom line is that 60 degrees C will burn you in about a second. Lower temperatures will be much slower; higher temperatures will be much faster.

 

[tuoni]

Thermal damage to tissue is often modeled by an Arrhenius equation of the type

[tex]r=A\exp(-E/RT)[/tex]

where r is the damage rate per second (and a damage of 1 indicates a burn), A and E are tissue-dependent constants, R=8.3 J mol^-1 K^-1 is the gas constant, and T is temperature in kelvins. E is typically 10⁵-10⁶ J mol^-1 (see, for example, Table 4.4.10 in The CRC Handbook of Thermal Engineering).

The problem is that A is usually not well known; various values from 10⁵⁰-10¹⁰⁰ s^-1 have been reported.

The bottom line is that 60 degrees C will burn you in about a second. Lower temperatures will be much slower; higher temperatures will be much faster.

Thank you!

I was looking into these chaperon, or helper, proteins to see if I could make some progress there. I think this simple model will work very well! It will take some experimentation, additional research, and with a little work I might be able to fit it into a unified model...but as a basic starting point it is exactly what I needed!

Thanks again!

 

[Borek]

I am working on a computer game, and this would be part of the "injury & disease" model.

(...)

I don't feel like spending another 4 years for every other topic I'm studying (and I haven't)...

Are you sure you are not wasting time building too detailed models? Games are about playability, not about too detailed realism.

 

[tuoni]

Are you sure you are not wasting time building too detailed models? Games are about playability, not about too detailed realism.

Very off-topic

In an era of gaming where Call Of Duty -- and similar, arcady games -- seems to be the height of gaming, my models and focus on "ultrarealism" would indeed seem wasteful and redundant.

I have two projects that I'm working on, very different, but both sharing the same idea of "educational" gaming. The first one is an RPG that was inspired by the Vendigrothians from Arcanum, and the Dwemer from Morrowind. I found the premise in both games very interesting and I was really eager to find out what happened to them. To my great dismay, the actualy story behind it and the exploration was very shallow, and not much fun. I loved to look for and explore Dwemer ruins in Morrowind, hoping to finally find the large ones that would start explaining the history and disappearance of the Dwemer. All I found was shallow and pretty much empty dungeons with a few monsters.

The basis for the RPG, is the constructed language and the culture of the people that disappeared, and the physical model of "magic." You begin at the foot of a mountain, ready to explore what is believed to be ancient ruins of a lost civilisation. As you venture deeper into the ruins, and further down into the structures carved out of the mountain, the story begins to unravel, and what first appeared to be just a small outpost, becomes a great city and you get more and more immersed in the secrets of the ruins.

One of the fundamentals of the game, is the constructed language. Now, in a typical game the walls would be filled with inscriptions and mysterious looking drawings and stuff...but that's pretty much as far as it would go, there would be no real meaning to it, it just looks cool. I don't like that. So there will be inscriptions all over the place, but it actually means something. There is a real and functional writing system and language. The inscription at the entrance won't mean diddly squat when you first begin the game, but as you progress you'll slowly decode the language and you actually learn something.

You're venturing further down into the mountain, learning the physics of "magic" and how to use it to solve puzzles and manipulate your surroundings, you slowly discover the history of the people that lived there, you learn the writing system, the language. It could very well be a Rosetta Stone learning software, implemented as a game and with an immersive story.

That I like.

Similarly the second project is also based on learning. Originally I began designing it because I wanted more realism in a multiplayer FPS (True Combat and True Combat: Elite that I was palying at the time), thus primarily focused on ballistics, firearms, and wounding. The arcady rush and spray just becomes too tedious after a while. Some years later I played STALKER and fell in love with the idea of freely adventuring in the dangerous Zone, so besides ballistics, I began working on realism in other fields, radiation, various form of physical injury, physiology, a lot more about realistic movement, etc.

Taking place in the Zone, but not scary because of zombies, spooky lighting and music, scary monsters and mutated beasts. No. Scary as hell because it's realistic. You literarly get to learn about ionising radiation, electromagnetic radiation, heat, dangerous particulates, liquids, and gases, how to protect yourself, emergency procedures. Take in-game courses, get the esential equipment, meters and detectors, radiation tags, maps of irradiated areas and hotspots, protective gear, equipment required to do quick in-field repairs, aluminium foil, polymer plates, adhesives, (sic) duck tape, LOTS of duck tape, and other necessities. Then venture into the Zone and see how you fare.

You don't just go running into the most irradiated area of the Zone with your minigun and take a few antirad to get rid of the radiation, then mow down 100+ mercs guarding a run-down ****..er...outhouse, and quickly heal your wounds with a few medkits.

Realistic, educational, engaging -- even difficult -- tactial, fun, FUN.

The second game is kind of ambitious, so for the moment it's just a multiplayer shooter taking place in various dangerous locations, with two teams fighting each other, but still with all the dangers and realism.

*sigh* I get so riled up over my games ^^;

Then again, maybe I'm a nutter.