Journal of Applied Physiology, Vol 55, Issue 6 1784-1789, Copyright © 1983 by American Physiological Society
Airway closure in humans does not result in overestimation of plethysmographic lung volume
D. O. Rodenstein, C. Francis and D. C. Stanescu
Exercise Physiol. 52: 638-641, 1982) have shown in dogs that airway closure
may induce rib cage deformation and nonhomogeneous alveolar pressure
swings, and they have suggested that this could lead to thoracic gas volume
(TGV) overestimation by body plethysmography. However, in humans the rib
cage is less easy to distort than in dogs. In four healthy volunteers we
measured TGV by plethysmography before (B) and during (D) the occlusion of
the middle and lower right lobes by a balloon (attached to a double-lumen
catheter) positioned in the intermediate right bronchus. Subjects were
trained to perform panting maneuvers preferentially with intercostals and
accessory muscles or the diaphragm. Five to eleven TGV measurements were
made in each subject with each panting pattern B and D occlusion. Balloon
inflation resulted in no change in TGV whether low [13.3 +/- 3.4 (SD)
cmH2O] or high (46.8 +/- 8.4 cmH2O) transdiaphragmatic pressures (Pdi) were
used: TGV 4.0 +/- 0.4 (B) vs. 4.0 +/- 0.4 liters (D) and 4.3 +/- 0.4 (B)
vs. 4.3 +/- 0.4 liters (D) for low and high Pdi, respectively. Thus, in
trained subjects performing maneuvers aimed to distort the rib cage, no
pressure difference was observed between the occluded and the nonoccluded
lung during panting against the closed shutter. We conclude that it is
unlikely that the mechanism proposed by Brown et al. might explain errors
in lung volume measurements by body plethysmography in humans.
