Click on the picture below if you want to read more:
Astronauts get POTS!
Astronauts Get Tilt Table Tests
Here is an image of Chris Hadfield undergoing a Tilt Table Test. A Tilt Table Test of some form is how doctors diagnose POTS.
So next time you start to faint, just pretend you're an astronaut returning from orbit! Or not...
http://www.medscape.com/viewarticle/745090
http://www.nasa.gov/mission_pages/station/research/experiments/1024.html
http://www.vice.com/read/nasa-patient-8179-200