An embolic protection device or system for use in a lumen of a vessel in a patient’s vascular system. A composite queue size for multiple work queues each having an associated processor is determined. In formula, R3 represents a \u2014p\u2014 group or a phenylene group and p represents an integer from 4 to 8. In various embodiments, the needle-free injector may be configured to inject the fluid injectate according to a combined injection relationship that is both substantially linear between the adjusted pressure and the desired penetration depth and between the nozzle orifice diameter and the desired penetration depth.