Regional ventilation in statically and dynamically hyperinflated
dogs.
Hubmayr, Rolf D., and Susan S. Margulies.
Division of Pulmonary & Critical Care Medicine, Mayo Clinic,
Rochester, MN 55905, Bioengineering Department, University of
Pennsylvania, Philadelphia, PA 19104-6392
APStracts 3:0288A, 1996.
Using the parenchymal marker technique in normal anesthetized dogs, we
compared the dynamics of regional lung expansion between two
ventilation strategies designed to increase mean thoracic volume.
Dynamic hyperinflation (DH) was produced by ventilating the lungs at
a rate of 50/min and with a duty cycle of 0.5. Static hyperinflation
(SH) was produced through the application of extrinsic positive end
-expiratory pressure (PEEP) while the lungs were ventilated at a rate
of 15/min and with a duty cycle of 0.15. Regional tidal volumes
(Vtr), end-expiratory volume (FRCr), and the time delay between
regional expansion and the flow signal at the common airway (TDr)
were computed for up to 100 regions per lobe in 5 animals.
Ventilation strategy had no effect on the overall variance of Vtr
within lobes. While Vtr measured during SH correlated with Vtr
measured during DH, the average correlation coefficient was only
0.69. Ventilation rate related differences in Vtr and FRCr varied
with TDr in ways qualitatively consistent with in parallel
inhomogeneity of unit time constants. However, a large component of
frequency-dependent behavior remains unexplained by established
mechanisms. We conclude that DH and SH should not be considered
equivalent lung unit recruitment strategies.
Received 7 December 1995; accepted in final form 24 May 1996.
APS Manuscript Number A1268-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96