Journal of Applied Physiology, Vol 59, Issue 3 774-783, Copyright © 1985 by American Physiological Society
Obesity alters regional ventilation in lateral decubitus position
A. N. Hurewitz, H. Susskind and W. H. Harold
Alterations of regional ventilation were determined as a function of body
position in five morbidly obese subjects using 81mKr to assess ventilation
(V) and 127Xe at equilibrium to determine lung volume (V). With subjects in
seated and supine positions, the left lung contributed an average of 43% of
the total V/V. When the apical-basal gradient within each lung was examined
in subjects in the seated position, V/V was greatest in the dependent
(basal) regions in half of the subjects, whereas the others showed greater
V/V near the upper lung regions. All obese subjects preferentially
ventilated the nondependent lung in both the left and right lateral
decubitus positions. In a control group of three nonobese subjects, V/V was
found to be equally distributed between left and right lungs in both the
seated and supine positions. In contrast with the results in the obese
group, V/V was slightly greater in the dependent lung in both lateral
decubitus positions. Although the combination of 127Xe images and
He-dilution measurement of functional residual capacity in the lateral
decubitus positions indicated a reduction in the volume of the dependent
lung of the obese when compared with values in the seated position, other
factors affecting the mechanical function of either the diaphragm or the
intercostal muscles could also have produced these positional alterations
of ventilation.
