When an animal presents in respiratory distress it is important not to cause even more stress by trying to administer oxygen. Oxygen delivery should be given by the most effective and least stressful route. Most dyspneic animals will not tolerate an anesthesia face mask held over their nose or an oxygen tube line less than one inch from their noses. Instead you can try an oxygen hood.
Make an Elizabethan collar and cover 1/2 of it with plastic wrap. Place it on the patient and then place oxygen tubing into the collar. The pet can now pant, stand and move around while receiving oxygen. The oxygen hood is able to get up to 60% oxygen in about 10 minutes! Most animals tolerate these better than face masks. You are also able to continue to work with your patient without having to discontinue oxygen administration.