A rugged, miniature, spectroscopic gas analyzer apparatus for rapid, non-invasive, multi-component breath monitoring and analysis and subsequent determination of Q or other medical diagnostic applications. The system is comprised of one or more IR emitters focussed by optical elements through a low volume sample cell receiving a sample input of a patient's breath for analysis. The patient either at rest or during exercise, inhales C.sub.2 H.sub.2 --SF.sub.6 mixtures (balance of oxygen and nitrogen) which is subsequently monitored upon exhalation for CO.sub.2, H.sub.2 O, C.sub.2 H.sub.2, and SF.sub.6 which can be employed to determine Q directly and accurately. Measurements are performed in real-time or via post-processing of stored original data. Due to its small size, ruggedness, and low power consumption, the monitor can conveniently be employed in the field or data can also be retrieved remotely using telemetry. The miniature analyzer operates on the principle of infrared absorption spectroscopy and allows very precise concentration measurements of the analytes of interest, without any bias or interference from other matrix components.