Distribution of ventilation and perfusion, and correlation to
atelectasis in anesthetized-paralyzed man.
Tokics, Leif, G[diaeresis]oran Hedenstierna, Leif Svensson, Bo
Brismar, Torsten Cederlund, Hans Lundquist, and [angstrom]ake
Strandberg.
Departments of Anesthesiology, Hospital Physics, Surgery and
Roentgenology, Huddinge University Hospital, S-141 86 Huddinge Sweden
and Department of Clinical Physiology, University Hospital of
Uppsala, S-751 85 Uppsala, Sweden
APStracts 3:0219A, 1996.
Regional ventilation and perfusion were studied in 10 anesthetized,
paralyzed, supine subjects by single photon emission computerized
tomography (SPECT). Atelectasis was estimated from 2 transaxial CT
scans. The ventilation/ perfusion distribution (V/Q) was also
evaluated by multiple inert gas elimination. Awake, inert gas V/Q was
normal and shunt did not exceed 1 % in any patient. CT showed no
atelectasis. During anesthesia, shunt ranged from 0.4 to 12.2%. Nine
patients displayed atelectasis (0.6 to 7.2% of the intrathoracic
area), and shunt correlated to the atelectasis (r=0.91;
P<0.001). Shunt was located in dependent lung regions,
corresponding to the atelectatic area. There was considerable V/Q
mismatch with ventilation mainly of ventral lung regions and
perfusion of dorsal regions. Hardly any perfusion was seen in the
most ventral parts (zone I) of caudal (diaphragmatic) lung regions.
In summary, shunt during anesthesia is due to atelectasis in
dependent lung regions. The distributions of ventilation and blood
flow differ from what has been shown earlier in awake subjects.
Received 5 December 1995; accepted in final form 2 April 1996.
APS Manuscript Number A1258-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 May 96