You raised a good question.
I've tried to imitate and duplicate such scenario.
I would try this in order to breathe properly while reading longer sentenses:
1. using more of one's vocal instrument; the nasal and mouth cavity for sound generation;
2. hold as much lung air as possible while reading, release as little as possible during sounding;
3. make a short and quick breathe between thought groups in a long sentence, or at the end of a longer sentence.
Just my two cents.