Journal of Applied Physiology, Vol 60, Issue 2 427-432, Copyright © 1986 by American Physiological Society
Scintigraphic evaluation of shape of lung and chest in upright and head-down posture
M. Demedts, I. Clarysse and M. De Roo
We determined the configuration of lungs and chest in six healthy young
subjects using anteroposterior and lateral technetium-99m-labeled
scintigraphic images obtained in upright and in 90 degree head-down posture
at 0, 25, 50, 75, and 100% vital capacity (VC). The lung shape was
evaluated from curves relating vertical height vs. cumulative volume of 20
apicodiaphragmatic lung zones of equal height. S-shaped curves were
obtained, which, after size normalization, were largely independent of
volume or posture (P greater than 0.1). However, the apical zones tended to
become relatively wider and the diaphragmatic zones relatively smaller with
increasing volume, especially between 0 and 25% VC in upright posture and
0-50% VC in head-down posture. Changing posture from upright to head-down
also tended to slightly widen the apical zones and to narrow the
diaphragmatic zones, which is in line with a greater intrathoracic
penetration of the diaphragm/abdomen. The shape of the chest was evaluated
from the ratio of the transverse-thoracic and anteroposterior distances
over height. These ratios did not clearly change with posture (P greater
than or equal to 0.05) but increased by approximately 30% with decreasing
volume (P less than 0.01). The fact that these shape changes of the chest
were not accompanied by similar changes in lung shape can be explained
mainly by widening of the mediastinum when volume decreases. In conclusion,
the shape of the lung and chest are similar in head-down and upright
humans, in contrast to the reversal of the apicodiaphragmatic differences
in alveolar expansion and in transpulmonary pressure.
