First, I am glad to see that his respiratory rate is within the normal rate (since we want to see it <30 bpm) and that his gums are pink (a sign of good oxygenation). This tells us that despite sounding congested, these flu signs are not compromising his breathing such that he is having to breathe faster or cannot take up enough oxygen.
As well, while its not nice for Oscar, it is good to hear that both sides are affected. The reason I asked is because sometimes we can see fungal infections or even cancer appear like flu. Usually when these are present they do only appear in one nostril, but if his signs have always affected both, this would be a wee bit less likely for Oscar. Of course, if we don't see any improvement with treatment and the supportive care I will now outline, then those further tests I asked about may be the next point of call to make sure there is nothing underlying that Oscar isn't telling us about.
Now with those aside, I would note that a lot of these upper respiratory tract infections that bother our older cats are actually viral in nature. Therefore, while antibiotics can help prevent secondary bacterial infection, we need to use supportive care to help the immune system fight off those viruses.
In regards ***** ***** care, there are a few home treatments that can be of benefit to reduce this congestion for him. To start, since he is so congested, you can take him in the bathroom while you run a hot shower. The steam will help loosen and clear some of the snot congesting him. You can also use a baby nebulizer/humidifier, but often cats don’t like things held up to their faces (but you can often make little ‘steam tents’ with the kitty in their carrier with these and a sheet).
If he is building up mucus that the steam isn't shifting, you can use a cotton ball moistened with warm water to wipe away crust and mucus. Furthermore, you can use saline nasal drops like Ocean Mist (but not anything medicated) to further reduce discharge build up. To do so, just tilt his head back and drop 2-3 drops in one nostril. Cats hate this, but it helps. After the drops go down, you can let the head up and wipe away any discharge that gets loosened. Then repeat with the other nostril.
As well, just in case allergies are suspect for him, we can potentially trial him on an antihistamine. Most commonly we use Benadryl/Diphenhydramine for these cases (More Info/Dose @ http://www.petplace.com/drug-library/diphenhydramine-benadryl/page1.aspx). A low dose (ie. 0.25mg per pound of his body weight twice daily) can just be enough to reduce any allergic irritation for him. We like to keep the dose low in cats, as they can have drowsiness with this medication (just like people). And of course, this medication shouldn't be used if your lad has any pre-existing conditions or is on any other medication without speaking to your vet.
As well I am glad to hear that he is eating, especially as congested cats who can’t smell their food
often won’t eat as well as they should. Still if you were to see any decline in his normal appetite, then we'd want to consider tempting him with smelly wet foods (since they are high in water). It may help to warm it up a bit in the microwave to help him be able to smell it.
Finally, since feline herpes virus is a common lifetime infection that can cause flu flare ups in older cats, you can consider trying him with L-lysine. This is a nutritional supplement that can help them recover quicker if this virus is present. This is available over the counter at pet stores, vets, online, and heath food stores. They tend to come as powders, gels, or crushable tablets that can be mixed into food. An average cat dose is 500mg a day.
Overall, we do have a few concerns for your lad's signs. If he is not improving with treatment, we do need to tread with care. Therefore, since his breathing rate is actually normal and he is getting adequate oxygen despite being so congested, I would advise the above supportive care. Of course, if you use this and he doesn't settle over the next few days, then we may want to consider those other tests to make sure there are no other factors that need to be addressed to help him make a full recovery.
I hope this information is helpful.
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All the best,
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