Akushianakue, apu nipa tshi pushiti. If I had been sick, I would not have been able to leave on a trip.

The conjunct irrealis (#16)  is used to express actions or events for which we cannot assert that they have taken place or will take place in the real world, henceforth the term irrealis. They serve as conditions for other events to happen, so they often get translated by if + verb in English .

Link to the conjugation guide.