Nestor participates in several breathing experiments in the book. Does his participation in these experiments add to or detract from the credibility of his research?

Why does Nestor claim that nasal breathing is superior to mouth breathing? How convincing is his argument?

Nestor begins Breath with a description of his first experience trying a breathing technique called Sudarshan Kriya. He concludes the book by returning to the same class ten years later. What changes for Nestor from the beginning of the book to the end of the book?