A tool and method of positioning and delivering medical devices and therapeuticswithin the pericardial space, as well as other body part or space. A needle is insertedinto the chest through a sub-xiphoid puncture, and the pressure within the needleis monitored manometrically or otherwise sensed as the needle is advanced towardsthe pericardial space. By reading the pressure within the needle while it is advanced,the clinician is able to know that he or she is avoiding insertion of it into organsor spaces not intended to be the target location. In addition the retractablesharp edge allows the operator to access the space and cut tissue but do so safelyby retracting the sharp edge.
