ABSTRACT
The normal respiratory system is exquisitely sensitive to gravity, which causes regional differences in intrapleural pressure, alveolar size, ventilation and perfusion, gas exchange, and parenchymal stresses within the lungs (West, 1977, 1991; Engel, 1991) and determines the configuration of the relaxed chest wall (Agostoni and Mead, 1964 ). Despite this susceptibility, there have been relatively few experimental observations on the respiratory function under conditions of microgravity. In part this is due to the difficulty in creating gravity-free environments. Also, weightlessness affects many organs in the body and the resultant functional disturbances are generally more important than in the case of the lung. In fact, ventilatory function during space flights has appeared to be adequately maintained, and no major respiratory problems have been identified so far.
