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These disorders are characterized by inspiratory dyspnea. The increased resistance to airflow caused by upper airway obstructions often creates audible inspiratory noise and results in referred airway sounds through the tracheobronchial apparatus. If the respiratory sounds can be heard without a stethoscope, they are most likely originating from the upper respiratory tract.
The upper airway examination should include detection of airflow from both nostrils, close examination of soft tissues of the head, and oral examination if necessary. Severe upper airway obstruction can cause open-mouth breathing and head extension as the affected cow tries to decrease the resistance to airflow Fig.
Open-mouth breathing and neck extension in adult Holstein with retropharyngeal abscessation, upper airway obstruction and pain associated with iatrogenic trauma. Congenital disorders, including pharyngeal cysts of respiratory epithelial origin, nasal cysts, cystic nasal conchae, skull anomalies, laryngeal malformations, and branchial cysts, have been observed in calves and adult cows. Inspiratory dyspnea with audible snoring sounds or stertorous breathing is a sign common to most of these problems.
The condition may be present at birth or is most often observed within the first few months of life. The degree of dyspnea associated with these abnormalities tends to be progressive as a result of either enlargement of the lesion cyst or worsening upper airway edema and swelling from the mechanical overwork associated with respiratory efforts to move air through an airway narrowed by a malformation.
