What's wrong with my dog's breathing?

Sugar is a Dachshund... We think she is about 8 years old. She breathes... how should I put this... like a pig, she snorts and sometimes heaves. I think it's Bronchitis but, my parents say it's just old age. If it also helps, we have another Dachshund name Gypsy she's 3... Could it be stress? Please tell me what it could be! Thanks!