SAC vs RMV

[scjoe]

I've beat my head against the wall trying to clarify the differences between these two terms for years. I've finally given up and accepted the fact that many people seem to use them interchangeably.

RMV is a term that exists independent of scuba. It is typically expressed in ml/min and might be measured using a respirometer. SAC is a term use in scuba, is calculated in PSI or CF and is almost always determined off of a scuba tank at depth. I supposed you could breath off of a tank at the surface. RMV doesn't use PSI since PSI has no meaning in terms of a non-scuba diver's respiration. I doubt that pulmonary specialists ever use the term SAC. The conversion of SAC from PSI to CF has created the idea that you are now switching to a RMV measurement. I think it is just an effort at trying to sound more sophisticated. Knowing what your consumption rate in PSI or CF is useful, having separate terms for the measurement and debates about the proper use of each is not. We could have a third term for the measurement using liters and perhaps a 4th since RMV in the non-scuba world is measured in ML.