Clinical monitoring and diagnostic systems may require the analysis of multiple physiologic signals to generate a diagnosis. The complexity of these systems is formidable for at least two reasons: clinical physiologic signals are noisy, and systems built around multiple signals may fail when any single signal is absent. In view of these limitations, we have been developing a clinical respiratory CO2 waveform (capnogram) diagnostic system. The purpose of this system is to develop a differential diagnosis from a single signal for subsequent evaluation within the context of multiple single-signals. This paper will review the development issues which we have been confronting, and discuss the tools and methods which have been successful.