A Digital Olfactometer for Smell Threshold Measurements in Neurodegenerative Disease Diagnostics

Ink-jet microdispensing technology was used to develop an instrument for the quantitative determination of the olfactory threshold. An electrical pulse applied to the piezoelectric microdispenser causes a drop of fluid to be ejected through a precise orifice. An electronic console actuates the piezoelectric dispensing elements and controls the number of drops that are dispensed and evaporated to create a fragrance cloud. The number of drops that are generated, evaporated and presented to the patient's nose for detection is adjusted according to a preset algorithm until the patient's smell threshold is discovered. Neurodegenerative disease patients tested with the developed olfactometer showed a significant elevation of their olfactory threshold as compared to normal controls. This result agrees with literature studies that indicate the sense of smell is one of the first affected by neurodegenerative disease. Through its precise control and detection capability, the digital olfactometer described in this paper can be used as an early screening tool for neurodegenerative diseases through olfactory threshold determination.