That's a good question. Is your breathing worse?
You can't compare "bads" and your normal is not the same as someone else's.
Have you seen a pulmonologist and had breathing tests done? Do you have a peak flow meter at home so you can gauge your normal and know when it gets worse? I have a peak flow meter and an incentive spirometer.
Technically, both the breathing in and/or breathing out muscles can get worse. If you "feel" like you are having trouble doing either of those things, you should call a pulmonologist to have tests.
When breathing gets worse, you can get short of breath more quickly. You might wake up from sleeping short of breath. Sometimes it feels like your lungs can't expand when you breathe in. When you breathe out, it can feel like you are "shallow" breathing. And if you try, you can't take a deep breath in and forcefully blow it out.
When MG breathing gets worse, oxygenation often goes down. I have an oximeter at home which really helps me to know how much worse I'm getting. For example, if you know what your normal O2 is, you can see how much it goes down after an activity. It might not.
If MG breathing does get worse and oxygenation decreases because of weak muscles, then the heart works harder to get you oxygen thereby increasing your pulse. So if your pulse while sitting is higher than it normally is, that can be a sign of your breathing getting worse. You'd have to know what your normal pulse is too.
This issue is best discussed with a pulmonologist, in tandem with your neurologist. It's so different for each person. Some people can do fine at, say, a lower O2 rate. Some can't. Or it can be the relative change or drop in how you breathe that is the issue.
I think the best thing is to talk to your doctors. If you are generally more weak and can't take a breath in or out, you should go to urgent care at the very least. But then you could catch the flu and get worse!
I don't want to recommend anything, though, because having trouble breathing for an MGer is really all about a 911 call!
Annie
http://www.medscape.com/viewarticle/439041