Comparison of the orthonasal and retronasal detection thresholds for @entity544 in XXXX .

@entity1 @entity544 @entity515
Several studies have investigated the orthonasal detection threshold for @entity544 ( @entity515 ) in @entity1 . The aim of current study was to investigate whether 24 healthy young subjects exhibited differences of @entity515 detection thresholds during orthonasal or retronasal stimulation. As nasal mucosa is believed to desensitize to @entity515 concentrations at or below 4% (v/v) during expiration, the second aim of the study was to explore the influence during nasal versus oral breathing on the detection thresholds. @entity515 stimuli of varying concentrations and a duration of 1000 ms were applied with an air-dilution olfactometer in either the anterior nasal cavity or the nasopharynx during nasal respectively oral breathing. In these 4 conditions, the mean @entity515 detection thresholds using the staircase forced-choice procedure were between 3.9% and 5.3% (v/v). Statistical analysis revealed a significant difference between orthonasal and retronasal stimulation. The @entity515 detection threshold was lower in retronasal stimulation. The nasopharyngeal mucosa is more sensitive to perithreshold @entity515 stimuli than the nasal mucosa. The breathing route had no influence on the detection thresholds. The results of this study indicate that the natural contact of the nasal mucosa with approximately 4% (v/v) @entity515 during nasal expiration does not influence @entity515 detection thresholds.
