A collapsed vein is a vein where the vessel has collapsed a the blood no longer flows. This most often occurs because the extremities are cold. A blown vein occurs when the wall of the vein has been punctured and blood escapes from the vein to create a hematoma. A collapsed vein can usually be recovered by using techniques such as arm dangling or a warm compressed. A blown vein cannot be recovered for an IV insertion. It must first heal.