Tubular flixible instruments

Claim 1

**WARNING** start of CLMS field may overlap end of DESC **. whole tube still on the metal rod is heated to around 2500--2600C and expanded to form unsintered porous portions between sintered solid portions. 5) The resulting tubing is then restrained by clamping the ends on the rod and placed in a constant temperatiure oven and raised to a temperature above the crystalline melt point of PTFE to produce a catheter tube as shown in Fig. 1. Example II The material from step 2 of Example I is expanded producing a completely porous tube. This tube is placed on a metal rod and then wrapped with intermittent metal foils with spaces therebetween and heated, unrestrained, above the crystalline melt point of PTFE. The metal foil is removed, the tubing is then restrained as in Example I and heated again above the crystalline melt point of PTFE. This is an alternate method of producing the tube shown in Fig. 1. Example III The porous tube from Example II, after placing on a metal rod, was spirally wrapped with a heat conductive tape and the tape raised, unrestrained, to a temperature above the crystalline melt point of PTFE providing a spirally sintered solid portion. The resulting tube was restrained and heated above the crystalline melt point to produce a tube as shown in Fig. 2 with solid and porous portions in a spiral mode. In the above examples, the tip portion of the tubes can be rendered porous as described and then the open end closed by suturing or heat sealing. Also, in order that the position of the catheter in the body can be followed, x-ray detectable fillers such as metal powder or BaSO4 may be incorporated at paste formation state. Example IV The expanded porous tube made according to Example II is cut to a length of about 13-16 cm. The tube is placed on a metal rod, both ends are exposed and the center portion is enclosed in an insulator. The tube Is raised, unrestrained, to above the crystal line melt point of PTFE. The end portions shrink back lengthwise to form a solid sintered portion, the middle portion remains porous. The center portion insulator is removed and the tube again raised above the crystalline melt point of PTFE, this time restrained by damping at the ends to prevent shrinkage. A tube as shown in Fig. 4 is suitable for use as an infusion cannula tubing, after the attach anent of adapter, is produced. Example V The porous center portion of tubing made as in Example IV is placed on a metal rod and wrapped with ring heaters with spaces between adjacent heaters. The heaters are raised above the crystalline melt point of PTFE, the tube being unrestrained lengthwise. Thus, the portions beneath the heaters are sintered and rendered solid by shrinkage. The heaters are then removed, the tube restrained by clamping at the ends, and again raised above the crystalline melt point of PTFE. A tube, as shown in Fig. 5, is thereby produced. Example VI The porous center portion of tubing made as in Example IV is placed on a metal rod and spirally wrapped with a heating tape and the tape raised to a temperature above the crystalline melt point of PTFE, the tube being unrestrained lengthwise. The heater tape is removed, the tube restrained as before, and again, raised above the crystalline melt point of PTFE. A tube, as shown in Fig. 6, is thereby produced. While the invention herein has been dis closed, using specific embodiments and examples, these are intended to be illustrative only and not limitative, and changes, modifi cations or equivalents can be used by those skilled in the art. Such changes within the principles of the invention are intended to be within the scope of the claims below. WHAT WE CLAIM IS: 1. A tubular flexible instrument for inSertiOn into a body cavity comprising a sintered polytetrafluoroethylene tube comprising solid and porous wall portions, said solid and porous portions alternating along the length of said tube.