Abstract: Methods and systems related to sealing punctures in blood vessels (such as following an angio or PTCA procedure) are disclosed. The position of a distal end of an introducer assembly in tissue is determined using a pressure sensor. The pressure sensor is connected to the proximal end of the introducer assembly. The introducer assembly has a fluid path between its distal end and its proximal end. Measured blood pressure is outputted as an indication of the position of the distal end of the introducer assembly in the tissue. Proper positioning of a seal is confirmed by placing the introducer assembly such that its distal end is in tissue outside a puncture in a blood vessel wall and observing a characteristic of blood at the proximal end of the introducer assembly.