The most commonly held theory regarding this breed’s origin is that Russian Blues were brought to Great Britain in 1860 by British sailors from the White Sea port town of Archangel (Arkhangelsk) in northern Russia. Whether this story is true—and if true, whether the cats really originated in that area—is anyone’s guess. Their thick coats give credence to the theory that they developed in a cold climate, and, according to accounts, blue shorthairs still exist in Russia.
I'm afraid that I can't offer much more assistance for Bella than what you have already done, without being able to see or examine her. If she has not had a trans-tracheal wash, that may be one test that can help determine the type of cells that are present in her lungs, and if the x-rays have not been evaluated by a specialist, that is another possibility, as your veterinarian should be able to send those x-rays to be evaluated further.
If Chester’s respiratory rate is over 100 breaths per minute you should visit your Veterinarian immediate for an examination since this is well over physiological range; infections, anaemia, allergies, congenital anomalies, foreign objects, fluid, parasites among other causes may be the underlying cause. I cannot give you any at home advice in a case this severe except to visit a Veterinarian for a thorough examination. Regards Dr Callum Turner DVM
Characteristics: You will first be struck by the beautiful silvery-blue coat of the Russian Blue. Their coat gives them an elegant appearance that is distinctly their own. The Russian Blue is a medium size cat that is muscular, with long legs and a long body. They are fine boned but often appear larger because of their thick double coat. They have large ears that are set far apart and are somewhat pointed. They have a medium, wedge-shaped head and, in addition to their uniquely beautiful coat, they have striking green eyes. They are wide-set and their vivid green color stands out because of the surrounding blue coat. They are truly a lovely and very beautiful cat.
Lethargy and increased respiratory rate are not specific symptoms as they are shared with many conditions; however I’m concerned that they are a common sign that an animal is in pain, but without examining Marilyn I cannot say whether she is in pain or there is another cause for the symptoms. You should visit your Veterinarian for an examination to be on the safe side especially if this has been going on for a day or more. Regards Dr Callum Turner DVM