BARRIERS AND METHODS FOR PRESSURE MEASUREMENT CATHETERS
Methods and apparatus of the present invention provide viscoelastic barrier materials for use as barriers in devices such as pressure measurement catheters. Improved barrier materials sometimes include at least one barrier material precursor combined with an amount of a softener. In other embodiments, two barrier material precursor components are combined without a softener to provide a fully cross-linked barrier material having certain softness characteristics. In various embodiments, a softener may be dimethyl silicone oil and may be combined with a barrier material precursor in an amount of between about 25% and about 45% by weight, relative to the final barrier material. Once a viscoelastic barrier material is prepared, it may be placed in a pressure transmission catheter or similar device, for example by injecting the gel into a lumen of the catheter via a syringe. Barrier materials of the present invention have one or more advantageous properties, such as a desired softness, full cross-linking, resistance to washout from a catheter, enhanced stability and/or the like.
1 . A method of making a pressure measurement catheter having an improved barrier, the method comprising:
providing a pressure measurement catheter having a proximal end, a distal end and a lumen;
providing a viscoelastic barrier material formed by at least one barrier material precursor combined with an amount of a softener; and
placing the viscoelastic barrier material in the lumen near the distal end of the catheter.
2 . A method as in claim 1 , wherein the softener comprises dimethyl silicone oil.
3 . A method as in claim 1 , wherein the at least one barrier material precursor is fully cross-linked.
4 . A method as in claim 1 , wherein the at least one barrier material precursor comprises a first component combined with a second component in approximately a 1:1 ratio by weight.
5 . A method as in claim 4 , wherein the first component comprises a liquid polymer including a catalyst, and the second component comprises a liquid polymer having a cross-linker.
6 . A method as in claim 4 , wherein the at least one barrier material precursor, when fully cross-linked, has a penetration range at ten seconds of between about 21 mm and about 37 mm at a temperature of about 25° C., wherein the penetration range is measured in a container of about 100 g of the barrier material precursor, using a penetrometer having a foot and rod, the foot having a 1-inch diameter and the foot and rod weighing about 12 g.
7 . A method as in claim 4 , wherein the at least one barrier material precursor, when fully cross-linked, has a penetration range at ten seconds of between about 30 mm and about 37 mm at a temperature of about 37° C., wherein the penetration range is measured in a container of about 100 g of the barrier material precursor, using a penetrometer having a foot and rod, the foot having a 1-inch diameter and the foot and rod weighing about 12 g.
8 . A method as in claim 1 , wherein the softener is combined with the at least one barrier material precursor at about 25% to 45% by weight, based on the total weight of the viscoelastic barrier material.
9 . A method as in claim 1 , wherein the amount of softener is combined with the at least one barrier material precursor to produce a viscoelastic barrier material having a viscosity of between about 5600 cps and about 7100 cps in an environment having a temperature of about 37° C.
10 . A method as in claim 9 , wherein the viscoelastic barrier material has a viscosity of between about 5200 cps and about 10,100 cps in an environment having a temperature of about 25° C.
11 . A method as in claim 9 , wherein the viscoelastic barrier material has a viscosity that changes by less than about 500 cps during a period of one year in an environment having a temperature of between about 35° and about 40° C.
12 . A method as in claim 9 , wherein the viscoelastic barrier material has a viscosity that changes by less than about 1,000 cps during a period of one year in an environment having a temperature of between about 16° and about 25° C.
13 . A method as in claim 1 , wherein placing the viscoelastic barrier material comprises injecting the material into the lumen using a handheld syringe.
14 . A method as in claim 1 , further comprising providing an amount of the viscoelastic barrier material for refilling a portion of the lumen with the material.
15 . A method of preparing a pressure measurement catheter, the method comprising:
providing a catheter to a user, the catheter having a proximal end, a distal end and a lumen;
providing a viscoelastic barrier material to the user, the viscoelastic barrier material formed by at least one barrier material precursor combined with an amount of a softener; and
placing by the user the viscoelastic barrier material in the lumen near the distal end of the catheter.
16 . A method as in claim 15 , wherein the softener comprises dimethyl silicone oil.
17 . A method as in claim 15 , wherein the at least one barrier material precursor is fully cross-linked.
18 . A method as in claim 15 , wherein placing by the user comprises injecting the viscoelastic barrier material into the lumen at a desired location, using a handheld syringe.
19 . A method as in claim 18 , wherein placing by the user comprises injecting the viscoelastic barrier material into the lumen immediately before implanting the catheter in a patient for use.
20 - 47 . (canceled)