A system for collecting antegrade blood flow from a vessel comprising: a. a collection member having: i. an elongated, flexible tubular portion terminating at a distal end; ii. an expandable, annular sealing member secured to said tubular portion spaced from said distal end; iii. a collection lumen with a fluid inlet distal to said sealing member; iv. a proximal end adapted to be connected to a source of suction for applying a suction to said collection lumen; v. said expandable, annular sealing member sized to be inserted into said vessel; and vi. a sensor capable of providing a pressure measurement, said pressure measurement being utilized at least in part to determine the extent of expansion of the expandable, annular sealing member when no suction is applied to said collection lumen; b. a collection container in proximity to said proximal end of said collection member for collecting blood from said lumen; c. a regulator adapted to be connected to a source of a vacuum and connected to said lumen to apply a regulated vacuum to said lumen with said regulator adjustable to adjust said regulated vacuum to apply a suction to said collection lumen in an amount sufficient to draw blood from said vessel through said fluid inlet and into said collection lumen and further sufficient to urge an opposing surface of said vessel wall to migrate into sealing engagement with said expandable, annular sealing member when said expandable, annular sealing member is in an expanded state so as to occlude antegrade blood flow in a vessel; and d. a non-occlusive support device positionable at a location distal to the distal end of the tubular portion, wherein the support device is configured to support the blood vessel during the application of suction. a. a collection member having: i. an elongated, flexible tubular portion terminating at a distal end; ii. an expandable, annular sealing member secured to said tubular portion spaced from said distal end; iii. a collection lumen with a fluid inlet distal to said sealing member; iv. a proximal end adapted to be connected to a source of suction for applying a suction to said collection lumen; v. said expandable, annular sealing member sized to be inserted into said vessel; and vi. a sensor capable of providing a pressure measurement, said pressure measurement being utilized at least in part to determine the extent of expansion of the expandable, annular sealing member when no suction is applied to said collection lumen; i. an elongated, flexible tubular portion terminating at a distal end; ii. an expandable, annular sealing member secured to said tubular portion spaced from said distal end; iii. a collection lumen with a fluid inlet distal to said sealing member; iv. a proximal end adapted to be connected to a source of suction for applying a suction to said collection lumen; v. said expandable, annular sealing member sized to be inserted into said vessel; and vi. a sensor capable of providing a pressure measurement, said pressure measurement being utilized at least in part to determine the extent of expansion of the expandable, annular sealing member when no suction is applied to said collection lumen; b. a collection container in proximity to said proximal end of said collection member for collecting blood from said lumen; c. a regulator adapted to be connected to a source of a vacuum and connected to said lumen to apply a regulated vacuum to said lumen with said regulator adjustable to adjust said regulated vacuum to apply a suction to said collection lumen in an amount sufficient to draw blood from said vessel through said fluid inlet and into said collection lumen and further sufficient to urge an opposing surface of said vessel wall to migrate into sealing engagement with said expandable, annular sealing member when said expandable, annular sealing member is in an expanded state so as to occlude antegrade blood flow in a vessel; and d. a non-occlusive support device positionable at a location distal to the distal end of the tubular portion, wherein the support device is configured to support the blood vessel during the application of suction.