Abstract: Apparatus and associated methods relate to a coaxial stream delivery device having an inlet section and outlet section in fluid communication via a plenum chamber. In an illustrative example, an inner radius of the plenum chamber may monotonically decrease distally along a longitudinal axis. The inlet section may include an inner tubular wall extending along the longitudinal axis. At least one bridge may extend radially inward from the inner tubular wall to coaxially align an inner conduit therewithin relative to the longitudinal axis. The at least one bridge may define a corresponding number of annular sector apertures bounded by the inner tubular wall and an outer wall of the inner conduit. Various embodiments may advantageously be disposed in a fluid path to coaxially align a therapeutic fluid stream entering the inner conduit within a sheath fluid stream entering the annular sector apertures.