Abstract: An airflow perturbation device and system wherein airflow of a subject is alternatingly blocked and unblocked by a mechanism to provide an output of an airflow/differential pressure conversion device based on oscillating differential pressure signals created by the alternating perturbation. The signals are provided by pressure transducers which provide signals to a data acquisition computer which calculates respiratory resistance as an indicator of airway resistance. An airflow perturbation device according to the invention could be a self-contained unit wherein the airflow perturbation mechanism, differential pressure conversion device, transducers, and data acquisition computer are in a single unit. In another embodiment, an airflow perturbation device could include the airflow perturbation mechanism and pressure transducers in a single unit, and provide transducer output to the data acquisition computer for calculation of respiratory resistance.