Instrument Delivery Device with Nested Housing

Provided herein is an instrument delivery device for advancing an instrument into a vascular access device. The instrument delivery device includes an outer housing, a connector coupled to the outer housing and including a projection member that mates with the vascular access device, and an inner housing having a distal end positioned within the outer housing and engaged with a proximal end of the instrument. The inner housing moves relative to the outer housing so that a distal movement thereof moves the instrument from a first position to a second position, with a distal end of the instrument moving from within the outer housing to out beyond the distal end of the outer housing and the projection member. A fluid flow preventing seal provided in or adjacent the connector prevents a transfer of fluid between the vascular access device and the inner volume of the outer housing.