Chances are that RS-232 will be the protocol used. If you have the time, patience, and a few bits of test kit (which you can make up yourself if you're
really keen), plus a bunch of leads (as Robert mentions), you can establish what's going on by experimentation. The difficulty could lie in getting the device (NIBP monitor
etc.) to give up, that is
send, its data.
As an aside, this sort of playing around is where good old kit like the BBC Micro can come in very handy (for those of you who remember them). That and "old" PC's ... typically of the so-called "Pentium 1" 100 MHz classic PC running MS-DOS. Either way, and obviously, the computer used needs to have a serial port.
