Open mouth breathing is one of the cut off points I use to classify dyspnoea as severe.An even worse sign for me is when the animals have a glazed look to their eyes and seem unaware of their surroundings.I am also really concerned when a dyspnoeic animal is in any body position that is NOT sternal recumbency. If they are past the point of being able to maintain the best position for themselves, then things are getting critical. If they spontaneously start moving around a lot (using up vital oxygen) then respiratory arrest may be imminent. Lateral recumbency is a bad sign in a dog but it is critical in a dyspnoeic cat. If you see the animal’s pupils begin to dilate then they are respiratory arresting in front of your eyes (eg this cat!).