Respiratory distress, often called “dyspnea”, difficult breathing, or shortness of breath can occur during inspiration (breathing in) or expiration (breathing out).
Dyspnea may be caused by the following: heart disease or heart failure; lung disease; tumors or cancer in the lung or that press on the airway; infections (e.g. pneumonia); obstructions (something that occludes the airway); abnormal fluid accumulation in or around the lungs (from various causes including heart and lung disease); trauma; or bleeding into the lungs or chest.
The potential causes of rapid breathing (tachypnea), dyspnea (difficulty breathing) or respiratory distress are numerous. Some of these can also cause a cough, but many conditions cause breathing difficulty without causing a cough.
When your pet has trouble breathing they may not be able to get enough oxygen to their tissues. Additionally, if they have heart failure they may not be able to pump sufficient blood to their muscles and other tissues. Dyspnea is often associated with accumulation of fluid (edema) in the lungs or the chest cavity (pleural effusion). This fluid can lead to shortness of breath and coughing.
Certain breeds are predisposed to some of the conditions that cause dyspnea. For example: Brachycephalic
breeds (short faced breeds such as Bulldogs and Boston Terriers) are predisposed to upper airway problems (e.g., stenotic nares, laryngeal paralysis, elongated soft palate) where they have trouble getting air into their airways. Of course, brachycephalic breeds often have noisy breathing because of the shape of their face and neck but respiratory difficulty may be exacerbated and become serious (“pathologic”) when the animal is exposed to the stress of hot or humid weather, undergoes anesthesia, has a fever and/or is excessively excited.