It has surprisingly been found that nasal NO release is greatly increased by the presence of a an oscillating airflow in healthy subjects. Accordingly, a device comprising means for generating and/or maintaining an oscillating airflow is described and suggested for use in the diagnosis of a condition of the upper airways of a human. The invention also encompasses method wherein the concentration and/or flow of at least one gaseous component in nasally exhaled air is determined and recorded in the presence and absence of an oscillating airflow acting on the upper airways or parts thereof.