I think this is server sided, if you find the addies for hp your hp will lock but only on your screen, so when someone is shooting at you your hp bar wont move but when the guy has shot u enough times u will die, the best option is finding the 3 second spawn addy and freeze that but i dont think its possible.
Tip: if u are using cheat engine first search for unknown value then get someone to shoot you and then search for decreased value and keep doing this unti u find your hp and then lock it.