A hemostasis valve, comprising: a) a longitudinal valve housing defining a conduit and having a proximal end and a distal end; b) a gasket within the housing, the gasket defining an interior conduit and having, i) a distal end portion, the distal end being fixed relative to the longitudinal valve housing, ii) a proximal end portion that is moveable relative to the longitudinal housing, and iii) a collapsible intermediate portion between the distal end and the proximal end; c) a grip assembly at the proximal end of the longitudinal valve housing and linked to the proximal end of the gasket, the grip assembly being rotable relative to the longitudinal valve housing, and including, i) a grip portion at the first end of the longitudinal valve housing, ii) a spindle portion characterized in that the spindle portion fixed to the grip and extending from the grip portion into the conduit of the longitudinal valve housing, the spindle portion fixed to the gasket at the proximal end of the gasket, iii) a ratchet extending about the spindle portion and fixed to the spindle portion, the ratchet defining teeth at an end of the ratchet extending about the spindle, the ratchet being biased in a direction relative to the longitudinal valve housing and along a major longitudinal axis of the longitudinal valve housing; and d) an interference element within the longitudinal valve housing that interferes with the teeth of the ratchet and against which the teeth of the ratchet are biased, whereby rotation of the grip portion relative to the longitudinal valve housing causes rotation of the proximal end of the gasket relative to the distal end of the gasket, thereby changing the internal diameter of the internal conduit, and whereby rotation of the grip relative to the housing causes the teeth of the ratchet to disengage and re-engage the interference element with the ratchet, re-engagement of the ratchet with the interference element locking the diameter of the internal conduit of the gasket in place upon termination of rotation of the grip relative to the longitudinal valve housing. a) a longitudinal valve housing defining a conduit and having a proximal end and a distal end; b) a gasket within the housing, the gasket defining an interior conduit and having, i) a distal end portion, the distal end being fixed relative to the longitudinal valve housing, ii) a proximal end portion that is moveable relative to the longitudinal housing, and iii) a collapsible intermediate portion between the distal end and the proximal end; i) a distal end portion, the distal end being fixed relative to the longitudinal valve housing, ii) a proximal end portion that is moveable relative to the longitudinal housing, and iii) a collapsible intermediate portion between the distal end and the proximal end; c) a grip assembly at the proximal end of the longitudinal valve housing and linked to the proximal end of the gasket, the grip assembly being rotable relative to the longitudinal valve housing, and including, i) a grip portion at the first end of the longitudinal valve housing, ii) a spindle portion characterized in that the spindle portion fixed to the grip and extending from the grip portion into the conduit of the longitudinal valve housing, the spindle portion fixed to the gasket at the proximal end of the gasket, iii) a ratchet extending about the spindle portion and fixed to the spindle portion, the ratchet defining teeth at an end of the ratchet extending about the spindle, the ratchet being biased in a direction relative to the longitudinal valve housing and along a major longitudinal axis of the longitudinal valve housing; and i) a grip portion at the first end of the longitudinal valve housing, ii) a spindle portion characterized in that the spindle portion fixed to the grip and extending from the grip portion into the conduit of the longitudinal valve housing, the spindle portion fixed to the gasket at the proximal end of the gasket, iii) a ratchet extending about the spindle portion and fixed to the spindle portion, the ratchet defining teeth at an end of the ratchet extending about the spindle, the ratchet being biased in a direction relative to the longitudinal valve housing and along a major longitudinal axis of the longitudinal valve housing; and d) an interference element within the longitudinal valve housing that interferes with the teeth of the ratchet and against which the teeth of the ratchet are biased, whereby rotation of the grip portion relative to the longitudinal valve housing causes rotation of the proximal end of the gasket relative to the distal end of the gasket, thereby changing the internal diameter of the internal conduit, and whereby rotation of the grip relative to the housing causes the teeth of the ratchet to disengage and re-engage the interference element with the ratchet, re-engagement of the ratchet with the interference element locking the diameter of the internal conduit of the gasket in place upon termination of rotation of the grip relative to the longitudinal valve housing.