If I'm stuck in the same area as someone who is clearly sick (runny nose, coughing etc) is there some combo of short/long breaths or nose/mouth breathing that's a better defense against catching it?
Everyone is answering about wearing a mask, when the poster clearly makes the point that they don't have one. They can't just poof it from the air. The answers are not helpful.
The question is about whether shallow breathing and nose or mouth breathing is better. It's a very particular question. An interesting question.
Does anyone know, with real scientific knowledge, what the answer to this specific question is? Can anyone answer to the specific question?
I know that breathing through your nose is generally better than breathing through your mouth for the simple fact that your nose has special follicles that act as a filter. But honestly the eyes and nose are most sensitive to infection and that's part of the reason people are suggesting masks. It's to lower the number of mucus membrane vectors for infection.
Op is more likely to get sick, especially if the other sick person isn't washing their hands and cleaning surfaces they touch, and limiting the amount of time touching their own mucus membranes.
Masks are suggested not for your own safety but for the safety of others... as you mentioned the eyes are quite sensitive to infection so masks on public transit aren't an effort to keep germs in the air from getting to you - they're an effort to prevent germs from getting in the air.
You didn't hear that talked about much during the pandemic because, if we're honest, most people are assholes... they'll bear a minor inconvenience to keep themselves safe but couldn't be assed to keep anyone else safe.
What a mask does do for you is to keep you from touching your mouth or face in general... that can be quite effective at reducing illness and, post-covid, I think we should all be more aware of doorknobs and other shared surfaces.
No offense but this was explained many a time during the pandemic, especially in relation to immunocompromised people. If op can't mask I doubt there are any breathing techniques they can use to prevent them from getting sick. But cleaning anything they touch and washing their hands is as good a solution as any.
But if you inhale through the mouth as the alternative, you'll directly track the viral load to the lungs which also had mucus and the viral load would multiply there instead. So take your pick. At least the nasal passage has some defences.