Escalating tension and stakes for the main character(s). Worry they can't get through it.

Gregg Hurwitz, in one of his Orphan X novels, has a multi-chapter action scene which starts in a hotel room and spills out into a busy city street, as our hero tries to clear a path for a mother to reach and rescue her child. It just keeps tightening the screws because you care about all 3 characters and the odds are brutal.

Absolutely virtuoso action and suspense writing.