Funny you should ask!
I keep one Always like the pic, in my handbag.
'Why'.
Well on the odd times I have been quite sick, and had to be rushed to hospital...drip put in my arm, in a bed....hospital staff (not so quite of course)...in Emergency.I can put the mask on, and also I carry ear plugs...and try to block out all that light and noise.
So if I eliminate, two big factors....I can try to manage the pain, or compliant.
I'm an old hand at this.