Bumped dilator tip

1. A method for inserting at least a portion of a dilator and sheath assembly into a patient and for removing the dilator from the patient, the method comprising:

receiving the dilator and sheath assembly, the dilator and sheath assembly comprising:

a sheath comprising an elongate tubular sheath body defining a sheath lumen, the elongate tubular sheath body comprising a sheath proximal end and a sheath distal end, the sheath distal end being circumferentially continuous and having an inner distal radius and an outer distal radius, a thickness of the sheath distal end being less than a thickness of the sheath body, an outer surface of the sheath distal end having a portion tapering to terminate in a pointed tip, and the sheath proximal end comprising a sheath hub defining an aperture in fluid communication with the sheath lumen, and

a dilator comprising an elongate dilator shaft comprising a dilator proximal end and a dilator distal tip, and a dilator hub at the dilator proximal end, the dilator distal tip comprising a radially enlarged dilator bump,

wherein the dilator bump comprises a proximal taper that increases in external radius from the proximal to distal direction, and a distal taper that decreases in external radius from the proximal to distal direction,

wherein the dilator bump has a maximal radius at a point between the proximal taper and the distal taper, the maximum radius of the dilator bump being greater than the inner distal radius of the sheath distal end,

wherein the proximal taper of the dilator bump has a point of minimal radius, such that when the sheath hub and the dilator hub are coupled, a longitudinal gap having a gap length is between the point of minimal radius of the dilator bump and the sheath distal end;

inserting at least the dilator distal tip and the sheath distal end in an incision in the patient when the sheath hub and the dilator hub are coupled;

exerting a vector force to the dilator and sheath assembly to push the dilator and sheath assembly further within the patient;

decoupling the dilator hub from the sheath hub; and

removing the dilator from the patient through the sheath, wherein the dilator bump radially stretches at least the circumferentially continuous sheath distal end during removal of the dilator from the patient.

2. The method of claim 1 , wherein the dilator distal tip enters a blood vessel of the patient.

3. The method of claim 1 , wherein receiving the dilator and sheath assembly comprises receiving the dilator and sheath in a non-assembled state.

4. The method of claim 3 , further comprising:

inserting the dilator through the aperture of the sheath hub until the dilator distal tip extends entirely distally from the sheath distal end, wherein the dilator bump radially stretches at least the circumferentially continuous sheath distal end during insertion of the dilator into the sheath; and

coupling the dilator hub to the sheath hub.

5. The method of claim 4 , wherein the sheath hub and the dilator hub are reversibly coupleable with a coupling mechanism.

6. The method of claim 5 , wherein the coupling mechanism is a tongue of the dilator hub and a groove of the sheath hub configured to receive the tongue of the dilator hub.

7. The method of claim 6 , wherein the groove of the sheath hub extends at least partially circumferentially around the sheath hub.

8. The method of claim 1 , wherein receiving the dilator and sheath assembly comprises receiving the dilator and sheath in an assembled state where the dilator hub is coupled to the sheath hub and the dilator distal tip extends entirely distally from the sheath distal end.

9. The method of claim 1 , wherein the sheath distal end is tapered, such that the elongate tubular sheath body has an inner body radius that is greater that the inner distal radius of the sheath distal end.

10. The method of claim 1 , wherein the distal taper of the dilator bump comprises a longitudinal axis and a distal outer surface, a distal angle being defined between the distal outer surface and the longitudinal axis, and the distal angle being between 1 and 2 degrees, 1.5 and 2.5 degrees, or 2 and 3 degrees.

11. The method of claim 1 , wherein a distal longitudinal length of the distal taper of the dilator bump is greater than a proximal longitudinal length of the proximal taper of the dilator bump.

12. The method of claim 1 , wherein the gap length is between 0.1 and 0.5 mm, 0.3 and 0.7 mm, 0.5 and 1.0 mm, 0.7 and 1.2 mm, or 0.9 and 5.0 mm.

13. The method of claim 1 , wherein the maximal radius of the dilator bump is equal to a maximum outer diameter of the elongate tubular sheath body.

14. The method of claim 1 , wherein the maximal radius of the dilator bump is less than a maximum outer diameter of the elongate tubular sheath body.

15. The method of claim 1 , wherein the elongate tubular sheath body comprises a polytetramethylene glycol based polyurethane elastomer.

16. The method of claim 1 , wherein the elongate dilator shaft comprises a high density polyethylene resin.

17. The method of claim 1 , wherein the sheath distal end and the proximal taper of the dilator bump have complementary shapes.

18. The method of claim 1 , wherein the difference between the outer distal radius of the sheath distal end and the radius of the elongate dilator shaft is less than 50% of the difference between the maximal radius of the dilator bump and the radius of the elongate dilator shaft.

19. The method of claim 1 , wherein a sheath distal end outer diameter is smaller than a sheath body outer diameter when measured in a non-assembled state.

20. The method of claim 1 , wherein a sheath distal end inner diameter is smaller than a sheath body inner diameter.