Count it daily when the cat's at laying down for a few minutes. You want to count a rate that is steady. Cat's breathing rate increases during dreams, when sniffing, when pouncing, looking outside, etc. You want to count the cat when it's not distracted.
Count one up/down chest movement =one count. Number of those in 15 seconds. Times by four for one minute breathe rate. Some vets count in ten seconds and then times by six. Choose your method.
A cat at rest should be 24 breaths per minute; a cat beginning to have CHF will be about 30 or more. Between 30 and 36, to bring it down-as long as the cat's not in distress-give an extra dose of your diuretic and wait an hour. The cat should improve. Give water by mouth if the cat's not drinking enough (again, water is key to help kidneys in the diuresis process.) If the rate increases or if the cat is stumbling/fainting/in distress/hiding-go to the ER a.s.a.p. If you have injectable lasix on hand, inject .2ml into the cat and wait an hour and follow the above. If the rate is above 36, you may need the ER.
Now, if your cat is like Myrna, and the norm (after three years) becomes 32, then your window of CHF becomes smaller. When she's 32+ we give extra diuretic, we've done injections, we've gone to the ER. At the ER, they will give oxygen and inject lasix. Oxygen helps the cat to calm down as oxygen (explained in an earlier post) is what the cat is fighting to intake and circulate. Oxygen helps to put breathing back in balance even as the cat is still in CHF.