Chris, Coming in a bit late on this. The BTPS stated for the flow requirement is a pulmonary physiology term expressing gas conditions within the body. If it is intended to state vent inlet flow requirements it is not an appropriate way to express it.
BTPS means Body Temperature (37°C) and Pressure (760mm Hg [mercury], Saturated (water vapor pressure fully saturated at 37°C [PH20 47 mmHg]) and is an important calculation in Pulmonary Function Testing and other pulmonary work.
If the inlet flow were expressed in physiological terms (inappropriate in this context) it would be ATPD, meaning Ambient Temperature (generally assumed 20°C, if not otherwise indicated), and Pressure (760mmHg), Dry (PH20 0 mmHg [pressure]).
For med gas purposes the difference between the two terms is not significant, and could be better stated that the peak inlet flow requirement is 180 L/M (at ambient pressure or 14.7 psia in our terminology). See here http://mgpho.org/Medical-Gas-Equipment/4313041 for similar vent flow usage previously discussed. End Respiratory Physiology 101 :- )