Under the effects of the earth's gravity, blood and other body fluids are pulled towards the lower body. The body's ability to send enough oxygen to the brain without the astronaut's fainting or becoming giddy.

I think your DLCO improves and RV goes down, is it ?

@ Rawat- yes you are right- The DLCO improves as the blood flow also happens to the upper parts of lungs and RV goes down as alveoli are not so distended.

s. Sharma But bizarrely, the range of V/Q ratio does not improve markedly in micro-gravity.

Article Invited Review: Microgravity and the lung

and there's a persistent inhomogeneity in perfusion which is not explicable through the 'gravity' model that we are so familiar with.

https://academic.oup.com/bja/article/98/4/420/298118