Dual flow cannula set

Claim 2

A cannula for insertion into a blood vessel comprising a first tube having a piercing tip on the forward end thereof and a second tube adjoining said first tube along a region of tangency and having a non-piercing tip on the forward end thereof, said non-piercing tip cooperating with the external wall of said first tube to form aperture means, said first tube having a longitudinal recess along said region of tangency adapted to receive said second tube, said non-piercing tip being turned down and secured to said first tube at one end of and within said longitudinal recess, the cross-section of each of said tubes along said region of tangency being mutually congruent and mutually cooperating to form a cylindrical periphery, the internal cross-sectional area of each of said tubes being a minimum along said region of tangency, whereby said second tube can follow said first tube as the cannula is inserted into a blood vessel of a human or animal body, said aperture means being shielded against blood vessel collapse while still permitting effective withdrawal of blood therethrough, said first and second tubes together forming a substantially continuous, smooth external surface to said blood vessel.

Claim 3

The cannula according to claim 1 wherein said first tube and said second tube are held firmly together by nontoxic and nonpyrogenic sealing means along said region of tangency.

Claim 4

The cannula according to claim 2 wherein said first and second tubes are additionally held together by a cylindrical sleeve circumscribing both of said tubes along at least a portion of said region of tangency.

Claim 5

A cannula comprising a first tube and a second tube forming a forked tubular structure comprising a stem portion, a discharge branch portion and an intake branch portion, said stem portion terminating in a needle with a cannula aperture which is one end of a discharge tubular passageway bounded at least in part by a discharge tube wall and leading to said discharge branch portion but not to said intake branch portion, said stem portion having a substantially unform periphery along its length so as to be adapted for insertion into a blood vessel, said stem portion having a lateral aperture spaced intermediate said needle and said branch portions, said lateral aperture being one end of an intake tubular passageway bounded by an intake tube wall, said intake tubular passageway leading to said intake branch portion but not to said discharge branch portion, wherein said first tube forms said intake tube wall and said intake tubular passageway but also extends beyond said lateral aperture so as to form a forward portion terminating in said apertured needle, and wherein said second tube forms said discharge tube wall and extends in snug fitting arrangement inside said forward portion of said first tube, the portion of said intake tube wall which is laterally remote from said discharge tube wall extending beyond the portion of said intake tube wall which is closest to said discharge tube wall and forming with said discharge tube wall a structure which preserves a substantially continuous, smooth external surface to said blood vessel, said extension being so shaped and dimensioned as to shield said lateral aperture against blood vessel collapse while still permitting effective withdrawal of blood through said lateral aperture.

Claim 6

A cannula comprising a first tube and a second tube forming a forked tubular structure comprising a stem portion, a discharge branch portion and an intake branch portion, said stem portion terminating in a needle with a cannula aperture which is one end of a discharge tubular passageway bounded at least in part by a discharge tube wall and leading to said discharge branch portion but not to said intake branch portion, said stem portion having a substantially unform periphery along its length so as to be adapted for insertion into a blood vessel, said stem portion having a lateral aperture spaced intermediate said needle and said branch portions, said lateral aperture being one end of an intake tubular passageway bounded by an intake tube wall, said intake tubular passageway leading to said intake branch portion but not to said discharge branch portion, wherein said first tube forms said intake tube wall and said intake tubular passageway but also extends beyond said lateral aperture so as to form a forward portion terminating in said apertured needle, and wherein said second tube forms said discharge tube wall and extends in snug fitting arrangement inside said forward portion of said first tube, the portion of said intake tube wall which is laterally remote from said discharge tube wall extending beyond the portion of said intake tube wall which is closest to said discharge tube wall and forming with said discharge tube wall a structure which preserves a substantially continuous, smooth external surface to said blood vessel, said extension being so shaped and dimensioned as to shield said lateral aperture against blood vessel collapse while still permitting effective withdrawal of blood through said lateral aperture.

Claim 7

A system for the treatment of blood, comprising, in combination with the cannula according to claim 1, pumping means for withdrawal and return of blood through said cannula; blood treatment means; and conduit means for transporting blood from the intake tubular passageway of said cannula to the pumping means, to the blood treatment means, and to the discharge tubular passageway of said cannula.