Selective Stiffening Catheter
A controllable stiffness catheter comprises a shaft comprising an inner sheath defining an access lumen, an outer sheath surrounding the inner sheath and defining an annulus therebetween, the annulus having a vacuum connection at which a vacuum is applied to the annulus, and a mechanical stiffener disposed at least at a portion of the annulus and free to move relatively in the annulus with respect to at least one of the inner sheath and the outer sheath.
1 . A controllable stiffness catheter, comprising:
a shaft comprising:
an inner sheath defining an access lumen;
an outer sheath surrounding the inner sheath and defining an annulus therebetween, the annulus having a vacuum connection at which a vacuum is applied to the annulus; and
a mechanical stiffener disposed at least at a portion of the annulus and free to move relatively in the annulus with respect to at least one of the inner sheath and the outer sheath.
2 . The catheter according to claim 1 , wherein:
the outer sheath has an inner surface;
the inner sheath has an outer surface opposing the inner surface of the outer sheath; and
the mechanical stiffener is movably disposed between the inner surface of the outer sheath and the outer surface of the inner sheath.
3 . The catheter according to claim 1 , wherein:
the outer sheath has a smooth inner surface; and
the inner sheath has a smooth outer surface opposing the smooth inner surface of the outer sheath.
4 . The catheter according to claim 1 , wherein the mechanical stiffener is continuous throughout the portion of the annulus.
5 . The catheter according to claim 1 , further comprising a vacuum device fluidically connected to the vacuum connection and configured to apply the vacuum to the annulus.
6 . The catheter according to claim 1 , wherein the mechanical stiffener is at least one of granular aluminum oxide and granular silica.
7 . The catheter according to claim 6 , wherein, when the vacuum is applied to the vacuum connection, pressure is lowered within the annulus and the outer sheath compresses the grains of the mechanical stiffener to stiffen the shaft at least at the portion at which the mechanical stiffener is disposed without straightening the shaft at the portion.
8 . The catheter according to claim 1 , wherein, when the vacuum is applied to the vacuum connection, pressure is lowered within the annulus and the shaft is stiffened at least at the portion at which the mechanical stiffener is disposed without straightening the shaft at the portion.
9 . The catheter according to claim 1 , wherein a magnitude of a pressure change between an outside of the shaft and the interior of the annulus affects stiffness of the shaft such that, as the pressure difference increases, the stiffness at least at the portion increases.
10 . The catheter according to claim 1 , wherein the mechanical stiffener stiffens at least the portion to a relatively stiff state when the vacuum is applied at the vacuum connection and softens the portion to a relatively soft state when the vacuum is released from the vacuum connection.
11 . The catheter according to claim 1 , wherein the inner sheath is one of:
substantially concentric with the outer sheath; and
off-center within the outer sheath.
12 . The catheter according to claim 1 , wherein the outer sheath is of polyurethane and the inner sheath is of PTFE.
13 . The catheter according to claim 1 , wherein an entire length of the shaft is controllable in stiffness.
14 . The catheter according to claim 1 , wherein some of the shaft is controllable in stiffness.
15 . The catheter according to claim 1 , wherein the portion is a distal 20 cm of the shaft.
16 . The catheter according to claim 1 , wherein the mechanical stiffener is subdivided into different stiffening segments.
17 . The catheter according to claim 1 , wherein the shaft has a proximal portion and which further comprises a luer fitting at the proximal portion.
18 . The catheter according to claim 17 , wherein the luer fitting provides access to the access lumen.
19 . The catheter according to claim 17 , wherein the luer fitting provides access to the annulus.
20 . The catheter according to claim 1 , wherein:
the access lumen has a diameter of at least 0.4064 mm; and
the shaft has an outer diameter no greater than 1.651 mm.
21 . A controllable stiffness catheter, comprising:
a shaft comprising:
an inner sheath defining an access lumen;
an outer sheath surrounding the inner sheath and defining an annulus therebetween, the annulus having a vacuum connection at which a vacuum is applied to the annulus; and
a mechanical stiffener disposed at least at a portion of the annulus and fixed to neither the inner sheath nor the outer sheath.
22 . The catheter according to claim 21 , wherein the mechanical stiffener is unattached to both the inner sheath and the outer sheath.
23 . The catheter according to claim 21 , wherein:
the outer sheath has an inner surface;
the inner sheath has an outer surface opposing the inner surface of the outer sheath; and
the mechanical stiffener is movably disposed between the inner surface of the outer sheath and the outer surface of the inner sheath.
24 . A controllable stiffness catheter, comprising:
a shaft comprising:
an inner sheath defining an access lumen;
an outer sheath comprising a smooth inner surface, the outer sheath surrounding the inner sheath and defining an annulus therebetween, the annulus having a vacuum connection at which a vacuum is applied to the annulus; and
a mechanical stiffener disposed at least at a portion of the annulus and movable within the annulus with respect to the smooth inner surface of the outer sheath.
25 . A controllable stiffness catheter, comprising:
a shaft comprising:
an inner sheath defining an access lumen;
an outer sheath comprising a smooth inner surface, the outer sheath surrounding the inner sheath and defining an annulus therebetween, the annulus having a vacuum connection at which a vacuum is applied to the annulus; and
a mechanical stiffener disposed at least at a portion of the annulus and separated from at least one of the inner and the outer sheath.
26 . The catheter according to claim 25 , wherein the mechanical stiffener is separated from both the inner sheath and the outer sheath.