Ok, so you hear more often than we would like about "perfectly healthy" braceaphalic dogs collapsing and dying during baths or nail trims.
The photo above explains clearly what has happened. The soft palate is too long and it swells and falls back to block the throat and closes the airway. It is a birth defect that is common in bulldogs of all shapes and sizes. Pugs, Frenchies, Bostons and even Shih-Tzu have this condition. So do PEOPLE. It is what causes obstructive sleep apnea and snoring.
There is literally a very easy way to open that airway once it has happened and the video below will show you how.
So. Now you are armed with information to save a dog's (or human's) life.