A friend is taking her father to a PFT lab (2500 miles away from where I am the moment so I couldn’t go along with them) because he has been short of breath for a couple of years, but oddly enough, only when lying on his side. I expect that despite these rather specific symptoms he will only get routine spirometry. I don’t necessarily fault the PFT Lab he’s going to for this, partly because physician orders often don’t include specifics, partly because they may not have the facilities to perform supine or lateral spirometry, and partly because its not clear lateral spirometry would show anything.
I don’t think that my lab is necessarily any better. We have only one room with an exam table that allows us to perform positional spirometry and that is largely because of the ALS patients we regularly see. Even so, unless we received specific orders to perform supine or lateral spirometry it’s unlikely that one of our technicians would think it was necessary and then take it on themselves to perform it. That itself is part of the problem not only for my lab but for the field of Pulmonary Function testing in general (but that’s another story).
The real problem however, is that the way in which spirometry is performed around the world is focused almost exclusively on detecting expiratory airway obstruction. It may be true that airway obstruction is primarily expiratory, but this ignores that fraction of individuals who have some degree of inspiratory obstruction. It also overlooks those individuals whose FVC is underestimated and FEV1/FVC ratio overestimated due to some degree of gas trapping. It also overlooks individuals that have positional airway obstruction that is not evident in the upright position.
We’ve fallen into the trap of thinking that there’s only one way to perform spirometry, and this is a mistake.