The capillaries in the lungs become engorged with blood -- which is caused by the suction -- so the lungs can harden and protect the whole chest cavity from being crushed.
肺の毛細血管が吸引により充血し 肺の毛細血管が吸引により充血し 肺が硬くなり 胸腔全体が潰れてしまうのを防ぎ