Nerve-wracking, absolutely. Here is a typical case I would describe as such:
I had a patient the other day who was somewhat stridorous, looked like a grownup with croup. No pulmonary history, no ACE inhibitors, and gradual onset over 4 days.
But... a CT showed a 7mm airway. (Yes, he was more stable that his CT let on, and I'd already tried steroids.) But still, I'm intubating that. Having exhausted all my airway toys, I still needed to call for help from anesthesia, who still gave me the credit after somehow maneuvering the 6-0 tube past the edema "since I already had the glidescope view." The surgeon was poised to trach at a second's notice. And this sphincter-tightening moment was brought to you thanks to the foresight of not using sux. Had I gone with sux, it would have certainly ended with me cricing him.
I think that airway issues are probably the number-one sphincter-tightening events we deal with.
The phrase "pucker-factor" is similar in meaning.