The 6G standard aims to be an integral part of the future economy by providing high-performance communication and sensing services. At terahertz (THz) frequencies, indoor campus networks can offer the highest sensing quality. Health monitoring in hospitals is expected to be an application site for these. This work outlines a monostatic phase-based system for breathing rate monitoring. Our feasibility study observes motion measurement accuracy down to the micrometer level. However, we also find that the patient's pose needs to be considered for generalized applicability. Thus, a solution that leverages multiple propagation paths and beam orientations is proposed.