Airway closure and re-opening assessed by the alveolar capsule
oscillation technique.
Otis, David R., Ferenc Petak, Zoltan Hantos, Jeffrey Fredberg, and
Roger D. Kamm.
Fluid Mechanics Laboratory, Department of Mechanical Engineering,
Massachusetts Institute of Technology, Cambridge, MA 02139,
Departments of Medical Informatics and Experimental Surgery, Albert
Szent-Gyorgyi Medical University, H-6720 Szeged, Hungary, Department
of Environmental Health, Harvard School of Public Health, Boston, MA
02215
APStracts 3:0069A, 1996.
An alveolar capsule oscillation technique was used to determine (i)
the lobe pressure and volume at which airways close and re-open, (ii)
the effect of expiration rate on closing volume and pressure, (iii)
the phase in the breathing cycle at which airway closure occurs and
(iv) the site of airway closure. Experiments were conducted in
excised dog lobes; closure was detected by an abrupt increase in the
input impedance of surface-mounted alveolar capsules. Mean
transpulmonary pressure at closure was slightly less than zero (Ptp
2.5 cm H2O); the corresponding mean re-opening pressure was Ptp 14 cm
H2O. The expiration rate, varied between 1 and 20 %TLC/s, had no
consistent effect on the closing volume and pressure. When lung
volume was cycled up to frequencies of 0.2 Hz, closure generally
occurred on expiration rather than inspiration. These observations
lend support to the conclusion that mechanical collapse rather than
meniscus formation is the most likely mechanism producing airway
closure in normal, excised dog lungs. Analysis of measured acoustic
impedances and re-opening pressures suggests that closure occurs in
the most peripheral airways. Re-opening during inspiration was often
observed to consist of a series of stepwise decreases in capsule
impedance, indicating a sequence of opening events.
Received 24 February 1995; accepted in final form 16 January
1996.
APS Manuscript Number A220-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 February 96