Journal of Applied Physiology, Vol 76, Issue 2 584-588, Copyright © 1994 by American Physiological Society
Tidal volume and alveolar clearance of insoluble particles
J. John, P. Wollmer, M. Dahlback, A. Luts and B. Jonson
Department of Clinical Physiology, University of Lund, Sweden.
We studied the effect of 3 h of large tidal volume ventilation on alveolar
clearance of 0.63-micron fluorescent latex particles in rabbits during
pentobarbital anesthesia. After particle deposition, six animals were
killed as controls, six were subjected to large tidal volume ventilation
with a peak pressure of 27 cmH2O, and six were subjected to conventional
ventilation with a peak pressure of 11 cmH2O. Mean tidal volumes were 30.2
+/- 6.1 and 8.4 +/- 1.6 ml/kg in the large tidal volume and conventional
groups, respectively. End-expiratory pressure was 2 cmH2O in all groups.
Compliance decreased only after large tidal ventilation (P = 0.0036).
Compared with controls the conventional ventilation group showed no
alveolar clearance, but more particles were clustered within macrophages (P
= 0.01). Compared with other groups the large tidal volume group had fewer
alveolar particles (P = 0.0005), most of which were single particles.
Accordingly, large tidal volumes enhance alveolar particle clearance, which
is possibly related to distension-related evacuation of surfactant to
proximal airways. Clearance may be due to accelerated motion of the
particle-loaded macrophage in response to the fast film motion.
Alternatively, single particles embedded in the surfactant film may be
dragged by the fast-moving film toward the airways.
