Pulmonary perfusion in supine and prone positions: an electron-beam computed
tomography study.
Jones, Andrew T., David M. Hansell, and Timothy W. Evans.
1Unit of Critical Care and 2Department of Imaging, National Heart and Lung
Institute, Imperial College School of Medicine, Royal Brompton Hospital, London,
United Kingdom SW3 6NP
APStracts 8:0038A, 2001.
Acute respiratory distress syndrome is characterized by alterations in the ventilation-
perfusion ratio. Present techniques for studying regional pulmonary perfusion are
difficult to apply in the critically ill. Electron-beam computed tomography was used to
study the effects of prone positioning on regional pulmonary perfusion in six healthy
subjects. Contrast-enhanced sections were obtained sequentially in the supine, prone, and
(original) supine positions at full inspiration. Regions of interest were placed along the
nondependent to dependent axis and relative perfusion calculated. When corrected for the
redistribution of lung parenchyma, a gravitational gradient of pulmonary perfusion
existed in both supine and prone positions. The distribution of perfusion between the
supine or prone positions did not differ, but data analysis using smaller regions of interest
demonstrated marked heterogeneity of perfusion between anatomically adjacent regions
of lung. The distribution of lung parenchyma was more uniform in the prone position.
Gravity was estimated to be responsible for 22-34% of perfusion heterogeneity in the
supine and 27-41% in the prone positions, respectively. These data support the hypothesis
that factors other than gravity may be at least as important in determining the distribution
of pulmonary perfusion in humans. The influence of nongravitational factors may not be
detectable if techniques that sample large tissue volumes are employed.
Received 28 December 1999; accepted in final form 21 November 2000
APS Manuscript Number A1083-9.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 January 2001