Background: Respiratory orienting reactions after olfactory stimulation can be seen as an indicator of an intact olfactory processing. Olfactory stimuli have to be recognized and they have to be important for a subject in order to generate a respiratory orienting reaction.
Methods: Hyposmic patients were stimulated pre-nasally with one sub-threshold and two supra-threshold concentrations of hydrogen sulfide (H(2)S) using a flow olfactometer. Nasal respiration was measured unilaterally using a differential pressure transducer. The data were processed after digitalization with the LabView software package. Duration of inspiration (DIN) and duration of expiration (DEX) were used as test variables for the evaluation of a regular resting respiration or a poststimulation respiration complex (PRC), respectively.
Results: The rate of poststimulatory respiration alterations (47%) in hyposmic subjects was significantly higher than the rate of spontaneous changes after resting respiration (31%). The reaction rate was not stimulus concentration-dependent. In spite of the stimulus recognition poststimulatory respiration alterations were less often in hyposmic subjects compared to normosmic subjects.
Discussion: Maybe this is due to the reduced significance of perceptible odors for hyposmic persons.
Georg Thieme Verlag KG Stuttgart * New York.