I feel sure I know exactly what the people in the film are doing.
My orthostatic intolerance has many characteristics listed on this thread, and I've reached the point, at my advanced age, where I no longer apologize for lying down and elevating my feet. It is more polite than passing out or becoming incoherent. When I stand, I tend to pace. This keeps my leg muscles pumping blood back to my heart. (Veins have check valves, but need muscle contractions to pump.)
I've had a tendency toward cold hands ever since my teens, and after years of bad advice I finally connected this with time spent upright. When my fingers turn cold and white, I know it is time to change position, though sometimes even lying flat is not enough. This year I've noticed that when I get into a hot bath with cold fingers my fingers and toes remain white while my arms and legs turn pink. After a few minutes the color returns to my fingers and toes.
This might sound like congestive heart failure except that there is no pooling of blood at my ankles. I strongly suspect the kind of
low cardiac fill pressure discovered by Systrom's group in Boston, but have trouble navigating the local healthcare system, where doctors dismiss this.
Doctors waiting rooms are a serious trial for me.