Heart disease in dogs and cats can be difficult to diagnose (at least early in the course of disease) and difficult to treat. One of the most sensitive indicators of fluid accumulation in the lungs is breathing rate. Getting familiar with resting breathing rate (how many breaths your pet takes in one minute while sleeping) can help identify changes in breathing rate later on in life. Take time once a month to count your pets breathing rate while sleeping. Rates for dogs and cats are typically less than 30 breaths per minute.