Respiratory disease can occur anywhere along the respiratory tract (e.g. in the nasopharynx, larynx, trachea, bronchi, or lungs) and can progress to cause life-threatening conditions. Auscultation of the respiratory tract can give clues as to lesion location, since abnormal respiratory sounds can often be categorized according to type and location. For example, stertor is typically caused by lesions in the nasal cavity or pharynx, while stridor is typical of lesions in the larynx or trachea. Lesions of the nares and rhinarium can result from trauma, stricture, infection or inflammation. Fifty percent of internasal lesions are reported to be neoplastic. The remaining cases can have various etiologies, including inflammation, infection, parasitism, or foreign body. Lesions of the pharynx can include pharyngeal collapse, stricture, mass lesion, or inflammation. Diseases of the larynx can be either neurologic, neoplastic, or inflammatory, and laryngeal paralysis is relatively common. Tracheal and bronchial diseases can result from tracheal collapse, trauma, stricture, inflammation, infection, or foreign body. Because severe upper airway, tracheal, and bronchial obstruction can be life-threatening, early diagnosis and treatment are necessary. Diagnostic approach includes auscultation of the airway, palpation, obtaining a detailed medical history, and diagnostic imaging. For definitive diagnosis, visual inspection of the affected area under anesthesia, endoscopic examination, or cytology is necessary. Each condition is treated differently, but the goal of treatment for any airway obstruction is to remove the obstruction and facilitate return of normal ventilation. In this review, diagnosis and treatment of upper respiratory and tracheal diseases are discussed.

Pulmonary hypertension (PH) is a condition in which the pulmonary artery pressure is elevated. With the widespread use of ultrasound devices in small animal clinics, PH has come to be frequently detected in dogs. Elevation of the pulmonary artery pressure is caused by increased pulmonary blood flow, vascular resistance, and venous pressure, and has a complex pathophysiology. Various underlying diseases can cause PH, and the therapy for PH is often based on the underlying disease. In dogs, although degenerative mitral valve disease is the most common cause of PH, left-to-right shunting in congenital cardiac defects, lung disease, and pulmonary thromboembolism can also cause PH. Furthermore, idiopathic pulmonary arterial hypertension has also been reported in dogs. Although underlying diseases should be treated if possible, selective phosphodiesterase type 5 inhibitors, which affect the nitric oxide-cyclic guanosine monophosphate pathway, can be used as a pulmonary artery vasodilator in dogs, with expected improvement in clinical signs.

A thirteen-year-old, unneutered male Shiba with syncope during urination visited our small animal hospital. The dog showed tachypnea and facial edema. A right ventricular dilatation, an increase in diameter of pulmonary arteries and interstitial opacities in precordial area were observed by a chest X-ray. Several findings including tricuspid valve regurgitation, flattened interventricular septum and left ventricular (LV) diastolic dysfunction were observed in an echocardiography. On the basis of these results, the dog was suspected to have a cardiogenic syncope caused by pulmonary hypertension (PH) and subsequent low cardiac output or a neurally mediated syncope. While the LV diameter was increased in response to the treatments, the dog showed abdominal tenderness after fed a nutrient-rich diet. An abdominal ultrasound examination revealed hyperechogenic pancreas. In addition, lipase activity and C-reactive protein levels in blood were increased, suggesting a complication by pancreatitis. Then, a decrease in fractional shortening (FS) and syncope were simultaneously observed. After the dosage of inotropic drug was increased and the food was changed to a low-fat diet, the decrease in FS and the abnormal values in the blood test were ameliorated. Moreover, the syncope was not observed. In this dog, although hemodynamics tended to be improved in response to the treatments for PH and heart failure, the complication by pancreatitis possibly caused a vasovagal reflex and systolic dysfunction, which led to the syncope. It is suggested in an animal with severe circulatory disturbance that the complications which could affect hemodynamics may exacerbate the pathophysiological condition of the cardiovascular diseases.