kiristäen
Kiristäen is a Finnish verb form. It is the present active participle of the verb "kiristää," which means to tighten or to constrict. As a participle, "kiristäen" describes an action that is happening concurrently with another action or as a manner in which something is done.
For instance, "lanka kiristäen" would describe a situation where a thread is tightening. Similarly, "hengitys kiristäen"
The grammatical function of "kiristäen" is to add descriptive detail about the ongoing process of tightening