By far the most important pattern to be able to recognise is the inspiratory dyspnoea that is associated with upper airway obstruction. When you watch an animal with an upper airway obstruction you will see that they spend much longer trying to breathe in compared to breathing out. Because of the obstruction they can only manage a very small inspiratory tidal volume so expiration is usually short. In all but the most severe cases you will hear a noise associated with inspiration that is either stertorous (snoring) or stridorous (wheezing). Rule of thumb: if you can hear the dog breathing on the other side of the room it has an upper airway obstruction til proven otherwise.Much less commonly, inspiratory dyspnoea can be due to large volume pleural space disease, usually a severe, chronic, pleural effusion. In this case your clue is that there will be no upper airway noise.Many upper airway obstructions are dynamic ie they can move in response to the pressure changes in the airways. Laryngeal paralysis is the classic one. With dynamic obstructions the dyspnoea only occurs on inspiration because there is no obstruction to expiration. Fixed upper airway obstructions are thankfully rare but when they do occur you will also see the animal struggle to exhale against the obstruction as well.In the most severe cases of fixed obstruction there may actually be little or no noise (because of the very small amount of air getting past the obstruction) but there will be a lot of chest movement as the animal struggles to get air in. These cases will always have paradoxical abdominal movement.One last word of caution for severe, upper airway obstructions that have come on gradually (like slow growing tumours): the animals will have learned not to move around much to compensate for their chronic hypoxia. These animals are sometimes NOT DYSPNOEIC at rest but on minimal stimulation they can go into respiratory arrest and die if you can’t perform an immediate tracheostomy. Learn from my mistakes: an emergency tracheostomy in a 16 year old cat is no fun at all. And especially not after 3 cups of coffee!!!!