The readings are the on'yomi readings, though 必 (ひつ) gets shortened to ひっ. In your desperate situation just imagine that you're trying to get out of it, and to do so you move the つ only to find a smaller っ blocking your way. It is certain death.
Even if I try desperately, it might still be futile.
I heard that my grandfather went to the war front prepared to die.
"Captain, I really need to return to Mars. I left my iPhone there," he said desperately.