The present research focuses on analyzing the feasibility of manufacturing complex turbomachinery geometries in a pre-assembled manner through an uninterrupted additive manufacturing process, absent of internal support structures, or postprocessing. In the context of the present COVID-19 pandemic, the concept is illustrated by a three-dimensional (3D)-printable turbine-driven blower-type medical ventilator, which solely relies on availability of high-pressure oxygen supply and a conventional plastic-printer. Forming a fully pre-assembled turbomachine in its final form, the architecture consists of two concentric parts, a static casing with an embedded hydrostatic bearing surrounding a rotating monolithic shell structure that includes a radial turbine mechanically driving a centrifugal blower, which in turn supplies the oxygen enriched air to the lungs of the patient. Although the component level turbomachinery design of the described architecture relies on well-established guidelines and computational fluid dynamics methods, this approach has the capability to shift the focus of additive manufacturing methods to design for pre-assembled turbomachinery systems. Upon finalizing the topology, the geometry is manufactured from polyethylene terephthalate (PETG) plastic using a simple tabletop extrusion-based machine and its performance is evaluated in a test facility. The findings of the experimental campaign are reported in terms of flow and loading coefficients and are compared with simulation results. A good agreement is observed between the two data sets, thereby fully corroborating the applied design approach and the viability of additively manufactured pre-assembled turbomachines. Eliminating long and costly processes due to presence of numerous parts, different manufacturing methods, logistics of various subcontractors, and complex assembly procedures, the proposed concept has the potential to reduce the cost of a turbomachine to capital equipment depreciation and raw material.