Why should instruments with lumens be soaked in a horizontal position?

Instruments with lumens shouldalways besoaked in a verticalposition and shouldnot besoakedin ahorizontal position.

True - Soaking agent must come in contact with all parts of the lumen

They shouldn't! This is because the item can then grow microorganisms, which will defer the purpose of any cleaning, decontamination and sterilization processes.

I don't think they should. Vertical soaking cylinders are used to soak instruments with lumens so all surfaces will be contacted by the cleaning solution.