Various methods and devices are provided for use of a cannula. For example, provided herein is a flexible cannula having an elongate body with an elongate shaft extending between a proximal hub and a distal dam. A lumen can extend through the cannula. The dam is in the form of a flexible annular member formed on a distal end of the shaft. The dam and the hub have diameters greater than a diameter of the shaft. A flexible, expandable sleeve is removably positioned on the distal end of the shaft of the cannula. The sleeve deformably encapsulates the dam such that the dam is folded against the shaft of the cannula. An obturator is also provided having an elongate shaft configured to be removably positioned within the lumen of the cannula. The shaft can be configured to fit within the lumen in a clearance fit.
