Abstract: Needle restraining apparatus is provided which serves to prevent a stylet needle of a venipuncture device which fits telescopically within a catheter of the venipuncture device from longitudinally moving with respect to the catheter during venipuncture. In one embodiment, the needle restraining apparatus provides a collar constructed of heat-shrinkable plastic releasably conforming to a needle hub and the hub of a tube adaptor of the venipuncture device. The collar is shrunk so that the leading and trailing ends of the collar form a non-slip fit over the irregular contour of the hub of the tube adaptor and the hub of the stylet needle. In a second embodiment of the invention, the collar is constructed of rigid plastic and preformed to engage the hub of the tube adaptor of the device and the hub of the stylet needle thereby preventing longitudinal movement of the stylet needle relative to the catheter.

Abstract: A catheter assembly for sampling gases in biological tissue in vivo, including a catheter constructed of a hollow tube sheathed in a gas-permeable membrane, and an impermeable barrier between the tube and membrane to define the boundary of a sampling tip. A catheter hub slideably surmounts the catheter and detachably receives a calibration chamber normally surrounding the sampling tip. The method includes purging the calibration chamber with a calibration gas and thereafter removing the calibration chamber and inserting the catheter into the tissue to be sampled.