Tracheal Collapse. Supposedly doesn't usually manifest in puppies, but a toy dog forum might have some additional information for you.
Tracheal collapse is a commonly recognized disease of toy and miniature-breed dogs (e.g., Toy Poodles, Yorkshire Terriers, Pomeranians, Maltese, Chihuahuas) associated with tracheal cartilage flaccidity and flattening. Either sex may be affected and most animals are middle-aged when clinical signs are noted; however, animals as young as one year of age may be diagnosed with this condition. The etiology of tracheal collapse is unknown and probably multifactorial, but may include genetic and nutritional factors, neurologic abnormalities, and cartilage matrix degeneration. In affected animals, the cartilages usually collapse in a dorsoventral direction, with the cervical trachea collapsing during inspiration and the thoracic trachea collapsing during expiration.
With tracheal collapse, clinical signs often progress with age and include abnormal respiratory noise, dyspnea, exercise intolerance, cyanosis, and syncope. Clinical signs are more severe in obese animals. Respiratory noises include wheezing, hacking, coughing, and stridulous breathing, although some dogs do not make abnormal respiratory noises. The cough may be productive or nonproductive but is classically a \"goose honk\" cough. Coughing often becomes cyclic and paroxysmal and gagging is common. Signs may be elicited or exacerbated by tracheal infections or tracheal compression. Second-hand smoke may also precipitate clinical sign