Aspiration is : the nurse jabs the needle into your arm but does not depress the plunger. Instead she pulls the plunger back out and sees if she sees blood. If she sees blood she knows she is in a vein and discards the needle and injects again.
If she does not see blood, she knows she is in a muscle. So now she injects the vaccine/clotshot
Aspiration is different to air bubbles -
Aspiration is : the nurse jabs the needle into your arm but does not depress the plunger. Instead she pulls the plunger back out and sees if she sees blood. If she sees blood she knows she is in a vein and discards the needle and injects again.
If she does not see blood, she knows she is in a muscle. So now she injects the vaccine/clotshot