Steerable access sheath and methods of use

An articulatable access system for accessing a body cavity comprising:

• a shaft having a proximal end, a distal end, and a central lumen therethrough, the central lumen having proximal and distal openings, wherein a portion of the shaft comprises a series of articulating members defining a distal region near the distal end, a proximal region proximal to the distal region, and a middle region therebetween, wherein the distal end is passable through to the body cavity and wherein the central lumen and the distal opening are sized for passage of an interventional device therethrough;
• a first set of pullwires operably coupled with the proximal region at a primary attachment location such that applying tension to the first set of pullwires deflects the articulating members to form a primary curve proximal to the primary attachment location, the primary curve having a first radius;
• a second set of pullwires operably coupled with the middle region at a secondary attachment location such that applying tension to the second set of pullwires deflects the articulating members to form a secondary curve proximal to the secondary attachment location, the secondary curve distal to the primary curve and having a secondary radius different than the first radius;
• a third set of pullwires operably coupled with the distal region at a distal attachment location such that applying tension to the third set of pullwires moves the distal end of the shaft through an angle theta,
• wherein at least some of the pullwires extend through one or more pullwire lumens disposed in one or more of the articulating members, at least some of the pullwire lumens being oblong and adapted to reduce binding of the pullwire passing therethrough, the oblong pullwire lumens having a length in the circumferential direction substantially longer than a width in the radial direction;
• and
• an obturator removably positionable in the central lumen and configured to position the portion of the shaft in a first shape.