Once again, I have to question the validity of cone-beam computed tomography (CBCT) airway studies (Hart PS, McIntyre BP, Kadioglu O, Currier GF, Sullivan SM, Li J, et al. Postsurgical volumetric airway changes in 2-jaw orthognathic surgery patients. Am J Orthod Dentofacial Orthop 2015;147:536-46). Although there is research, as cited by the authors, that looks at reliability and accuracy of volumetric measurements with CBCT using phantoms, for example, despite my best efforts I have yet to find any significant research that demonstrates clearly the reproducibility (or lack thereof) of these measurements in individual patients at different time points. My clinical observation is that the same patient can have very wide variations in airway volume at different times. Without reproducibility, one must call into question the conclusions derived before and after surgery. Not that I think the conclusions are fundamentally invalid, but I fear that they would not stand up to deep scrutiny if challenged.
Airway volume is not comparable with a fixed volume such as a balloon; you have openings at either end, so change with muscular function would seem logical.
I hope that if my observations are incorrect, someone can point me in the right direction.