D. Linnarsson, PULMONARY-FUNCTION AND CARDIOPULMONARY INTERACTIONS AT MICROGRAVITY, Medicine and science in sports and exercise, 28(10), 1996, pp. 14-17
During short-lasting microgravity the weights of surrounding organs ar
e eliminated, and the lungs attain a slightly reduced volume. Long-ter
m microgravity may lead to deconditioning of respiratory muscles. The
distribution of ventilation becomes more homogeneous but not completel
y so. Indirect estimates of the perfusion distribution point to a redu
ction of gross interregional differences but a maintained intraregiona
l inhomogeneity. The gas/blood interface becomes more effective, as sh
own by an improved diffusion capacity. Thus, data on lung function in
man at microgravity confirm that gravity is an important determinant o
f the distributions of ventilation and perfusion in the lung. However,
both for ventilation and perfusion, significant inhomogeneities of di
stribution persist also in the weightless state, showing that non-grav
ity-related factors also play important roles. It could be speculated
that more homogeneous mechanical properties of the lung tissues surrou
nding the heart contribute to facilitate cardiac diastolic function in
microgravity.