esophagus manometry.
A tube through your nose down into the food-pipe.
I had it in 1999, it was difficult to go behind
the throat-resistance in multiple attempts while swallowing water.
I remember they had a C64 to store the data .
That test was why they decided to do fundoplication.

[keyword search for esophagus manometry ...]

Mayo calls it Scleroderma - I never heard that word