Common sense tells us that having a smaller airway should make breathing more difficult. A recent report from Kansas State University investigates this point. Dr. Bonnie E. Coyne, who headed the investigation, reported what problems were associated with hypoplastic trachea (HT) in 103 dogs.
HT is a congenital anomaly seen most commonly in Bulldogs, Boston Terriers and other brachycephalic (short-faced) breeds. The term hypoplastic means 'under grown' or below normal size, that is the lumen in narrower than in normal dogs of the same breed. Diagnosis is based on biopsy or measurements from thoracic radiographs.
Symptons included dyspnea (difficult breathing), stridor (noise with inspiration), coughing, gagging, choking, exercise intolerance and syncope (fainting).
However, many dogs with HT also have other obstructive respiratory congential conditions including elongated soft palate, everted laryngeal saccules and stenotic nares. This makes it difficult to distinguish which symptoms, if any, were solely attributable to HT.
Eight percent of the dogs studied had bronchopneumonia, upholding the wide belief that HT dogs commonly have secondary and recurring respiratory infections. Congenital megaesophagus, present in 10 dogs, may have arisen from the same defect causing KT. Congenital heart defects were also expected and were observed in 12 dogs.
Conclusions: In the absence of other significant defects or disease, simple HT does not cause difficult breathing. When HT is coupled with obstructive respiratory conditions, it may exacerbate those conditions. While HT alone may be well tolerated, dogs may limit their own physical activity to avoid increased respiratory work. HT dogs without concurrent disease may go unidentified; diagnosis in many cases may be purely incidental. (Journal of the AVMA, Volume 201, Number 5, September 1, 1992.)