[Mullins]

Can you elaborate on why long-term packing might increase RV? I understand you're only citing somebody else's study, but do you have any more details on what their hypotheses might be?

I may be off-track here, but my understanding is that RV is determined by the limit to which the ribcage/diaphragm can be compressed by ambient pressure before resistance increases to the point where the pressure differential between the space in the lungs and the ambient pressure has to be equalised in another way - by liquid first filling the alveoli forming the walls of the lung cavity and then forcing its way through them (causing damage) into the space itself.

I don't understand RV to be an attribute of the lung tissue itself (please correct me if this is wrong). The term 'RV' as it is commonly used seems to me to mean "lung volume following forceful exhale without other mechanical aid" and as such is reliant on the force supplied by the breathing muscles as well as the flexibility of the diaphragm/ribcage. Given adequate mechanical force (over and above that supplied solely by the breathing muscles) RV for everybody would be zero. Given sufficient bloodshift even in a thoracically inflexible person, RV would also be zero. Obviously this would mean a nasty injury in both cases because nobody is that flexible/nobody's alveolic can take that much engorgement, it's just my way of suggesting RV is not an absolute value unless you add the above condition.

If this is the case I would have thought that long-term packing would decrease RV, as it presumably makes the diaphragm and ribcage (intercostals, other connective tissue, whatever) more flexible. If they can flex further outwards, surely they would also be able to flex further inwards - particularly in the case of the diaphragm?

What in my account is missing/inaccurate? There must be something awry if there is an assumption (prior to actually testing it, granted) amongst medical professionals that packing increases RV...