I´m Mexican and since we use this idiom as an ironic or mocking way we are calling other person a king or something almighty , because he refuse or dispraises our opinion or our behavior or conduct, we as a manner of counteracting we say "perdóname la vida" that literally means spare my life (that one sentenced to death would say meaning please don´t kill me), sometimes is used in a sort of kindly or friendly way.
As I said in the beginning since I'm Spanish speaker I was looking up a translation or a similar to say "perdonar la vida" (to spare the life) in the case of the fish that begged Bart Simpson not to be killed, in this case I think the most accurate is "spare my life ".
But in the case of the phrase we are commenting, this phrase is used as idiom meaning just "spare my life" but if you the English native speaker use the idiom "just please don't kill me" that would be the closest equivalent in order to signify "Pardon me for breathing!"(or living).
We also have other expression that is "perdóname por vivir" where the literal translation would be "Excuse me for living!", and believe me, some people don´t distinguish between both expressions and use one instead of another when this second one is used just when someone don´t want your presence or allude you are not welcome e.g. a couple of spouses about to divorce when he or she arrive back form the work to the house and one find the slacks on the floor and then say don't you know where is the bin for laundry or one say to the other why do you always leave the tooth paste uncapped; the other would say Perdóname por vivir ! this could be used even when you are not divorcing."