I'm sure this one is easy, but I'm only in my second semester and it was my first day in the OR and we haven't learned about capnography yet (that lesson is next week). I was asked:

How long will it take for the EtCO2 to rise from 45 to 50 in an apneic pt? My initial answer was "not that long" and the CRNA said that wasn't good enough...

so I thought about it a little more and came up with this, but I don't know if I'm on the right track..

the pt was pulling tidal volumes of 800ml
45mmHg/760 mmHg = 0.059

0.059 x 800 = 47.2 ml of exhaled tidal volume is CO2

50mmHg/760 mmHg = 0.066

0.066 x 800 = 52.8 ml of exhaled tidal volume is CO2

52.8-47.2 = 5.6 ml CO2 that needs to be produced to raise the EtCO2 to 50mmHg

so I guess I would have to know the pts average production rate of CO2 during surgery to figure out the answer right? So can someone finish this off for me...or am I totally off track???

FYI: I don't know why but I cannot post this in the pimp section...