If the Eustachian tube is blocked, you cannot close the open eardrum.With ET function, you mean the eustachian tube function? What's the reason that influences tympanic membrane healing after tympanoplasty?
The medium ear must be vented in some way. You cannot leave it entirely airtight.
There is a possibility that 25 years ago the ENT decided to leave the open hole in your eardrum because the Eustachian tube was blocked.
So, before closing it now, it is necessary to check if your tube can allow air to pass.
This is easy to check: just perform a Valsalva manouver and see if air blows outside your ear.
This is actually what was invented by dr. Valsalva: he did practice an hole in the eardrum, ask the patient to turn the ear downwards tilting the head, and blow out all the putrid liquid trapped inside.
But, again, @doctormike can explain this better.
I just heard this story of the born of the Valsalva manouvre told by dr. Odaglia, during a seminar when I was being trained for my first instructor degree, in September 1978, in Nervi (near Genoa).
He did also explain in detail the anatomy and physiology of human ears, and the various equalization techniques known at the time, starting from Valsalva and going through Toynbee, Frenzel and his own modification of Frenzel, known as Marcante-Odaglia.