A PRACTICAL APPROACH TO THE COUGHING DOGS

Cough is a defensive reflex originating from the respiratory tract and, together with sneezing, expiratory reflex, and secretion of mucus, it contributes to maintaining a healthy respiratory system. Indeed, the cough reflex is evoked in order to expel harmful substances, such as foreign bodies, excessive mucus or debris, from the airways and preserve the normal function of the respiratory tract. The typical “textbook-defined” coughing reflex is characterised by an initial deep inspiration, followed by a rapid and powerful expiratory act against the closed glottis and finally opening of the glottis, closing of the nasopharynx and forceful single expiration through the mouth, accompanied by a typical sound caused by the vibration of the vocal cords. Conversely, the “expiratory reflex” consists of multiple forced expiratory efforts against a closed glottis not preceded by a deep inspiration. Cough is triggered by stimulation of coughing receptors localised in the larynx, trachea, and large bronchi, whereas the expiratory effort is induced by mechanical or chemical stimulation of the vocal cords and is often observed in dogs as a “huff” sound, frequently described by the owners as “a bone stuck in the throat” or “clearing the throat”. Interestingly, irritation of smaller bronchi, bronchioles, and alveoli does not elicit any form of coughing.