When a healthcare provider shakes a victim ("hey, hey, are you ok?"), they should also be checking for breathing. Essentially, there are 3 types of breathing for this scenario.
1) Breathing like you are doing now,
2) No breathing at all (apnea), or
3) Agonal gasps. Agonal essentially means 'associated with death.'
Agonal gasping should not be confused with normal breathing, and in fact, is a signal that the patient may not have a pulse. It should be treated the same as if the patient is not breathing at all. This gasping is due to residual nervous system activity only, and is very shallow. No air is actually entering the lungs proper, and no true gas exchange is taking place within the lungs.
Agonal gaspers have a greater likelihood of recovery than patients who present with apnea (no respiratory effort at all.) Agonal gaspers are more likely to be in ventricular fibrillation, and their arrest time is generally not as long. For a good synopsis of factors affecting survival, you can read more on this topic here- http://depts.washington.edu/survive/event-factors.php