Most asthma attacks are not sudden onset. Not in my experience, anyways. There's no warning siren that goes off in your head.
WOOOOO!!!!WEEEEEE!!!! OXYGEN LEVELS LOW! WOOOOO!!!WEEEEE!!!!
What you see on tv and movies, that very rarely happens. And the wheezing thing... that's pretty rare, too. Most asthmatics don't wheeze at all, the most common symptom of asthma is coughing. Think about it, locked up lungs, what good is wheezing? Now coughing, coughing has quite a force behind it. Good way to force air out so you can get more in. The real issue with asthma isn't not being able to breathe in, it's not being able to breathe all the air out. Can't get rid of old air means you can't get new, oxygen rich air in. And the whole, I'm fine one second and the next you're collapsed on the floor that you see on shows, that is very unusual.
In fact, outside of exercise induced sudden onset I've only once had an attack hit me that way. I still have no idea what triggered it. We were grocery shopping one day a few months after Trace was born. I had been thinking my breathing was better (it was, but in hindsight we know it only felt that way because my lungs had more room without baby pushing on them). I stepped out of the store and my lungs almost instantaneously locked down. Craziest thing I've ever felt, one moment I could breath and the next it felt like I'd ran at breakneck speed with no treatment first and no inhaler. Most attacks are not like that. They are just as dangerous, though... because the attack can go unnoticed for so long that by the time you notice you have been dealing with some oxygen deprivation for a bit already.
Any parent of an asthmatic child can tell you that the kids rarely seem to notice attacks. Tristian could literally be displaying cyanosis (blue lips and skin around the mouth) and still be trying to run around the play ground. We'd have to physically stop him and get him to take his inhaler. There he is so oxygen deprived he's literally turning blue and all he wants to do is go play.
But that's the way it works. Most attacks you don't even notice them sneaking up on you. In fact, just like parents of asthmatic children notice long before the child will- it's normally those around me that notice before I do. They'll tell me that I'm taking faster breathes, or stopping to inhale more often, that I seem short of breathe. Most attacks sneak up on you and you don't notice the gradual decrease of oxygen, the gradual increase in breathing. You'll be doing something and suddenly realize you are dizzy and have been for a bit. Or you notice that twinging feeling in your chest that means there's not enough oxygen getting through. If it's taken you a really long time that feeling is in your shoulders and down your arms, not really sure how to describe it exactly, but it means there's not enough oxygen. A restless feeling in the muscles and cells themselves. You test a breath breathing in and realize that you can't breathe in nearly as far as you should be able to. You'll realize that fatigued feeling you've been shrugging off isn't really from being tired, but because you need air. I've had attacks sneak up so slowly that I didn't notice until things started feeling numb. Literally only noticed because when you touch things the feeling isn't right. I'm sure for some that seems extreme, but I'm not the only asthmatic to have that happen to. I know it's happened to my older brother a few times and at least two asthmatic friends. BTW, that is the time the pulmonologist is talking about taking 10 puffs in rapid succession on the way to the ER.
Oh well, such are the lessons of life. Don't assume that just because it seems obvious to you that someone is short of breath that the person has even noticed yet... tell them- just in case. If you see a child turning blue on the playground... find their parents... cause they probably won't.