Human Responses to Propionic Acid. II. Quantification of Breathing Responses and their Relationship to Perception

Abstract

In 20 normal and four anosmic participants, instantaneous inhalation and exhalation flow rates were recorded in response to 15 s stimulations with clean air or propionic acid concentrations (0.16, 1.14, 8.22 and 59.15 p.p.m., v/v) that ranged from peri-threshold for normals to clearly supra-threshold for anosmics. Each odorant/irritant delivery to the face-mask began with an exhalation. This allowed concentration to reach full value before stimulus onset, defined as the point where the participant began to bring the stimulus into the nose by inhalation. Two seconds after this stimulus onset, normals exhibited cumulative inhaled volume (CIV) declines of 39 and 14%, and latencies of 500 and 710 ms, with presentations of 59.15 and 8.22 p.p.m., respectively. With anosmics, 59.15 p.p.m. caused a 19% decline in CIV that began at 730 ms. Examination of the first inhalation after stimulus onset shows that the CIV declines in normals were achieved by a progressive decline in volume (InVol), beginning with a slight drop at 1.14 p.p.m., and a marked decline in duration (InDur) with only the highest concentration. Anosmics exhibited declines in InDur and InVol with only the 59.15 p.p.m. stimulus, and these declines were much more modest than the changes seen in normals. Comparison of these breathing results with perceptual responses from this same experiment demonstrates that: (i) in normals, odor perception rises slightly, but breathing does not change, with the lowest concentration; (ii) the higher breathing sensitivity (declines in InVol) of normals is paralleled by both the higher nasal irritation of these individuals and the presence of odor sensation; (iii) InDur declines in normals only with a stimulus concentration sufficient to cause marked nasal irritation in anosmics; and iv) in anosmics, modest but reliable declines in both InDur and InVol mirror the marked elevation in nasal irritation magnitude seen with only the highest concentration. In view of the failure of prior work to provide evidence that olfactory activation alone can cause any of the breathing changes we observed, we conclude that some breathing parameters are quite useful as rapid and sensitive measures of nasal irritation that arises from activation of nasal trigeminal afferents alone or in combination with the olfactory nerve.

Olfactory Impairments in Patients with Unilateral Cerebellar Lesions Are Selective to Inputs from the Contralesional Nostril

“…We chose these odorants because PA stimulates both the olfactory and trigeminal nerves whereas PEA stimulates only the olfactory nerve (Doty, 1995). Furthermore, PA has been the odorant of choice in experiments measuring odordependent sniffing (Kendal-Reed et al, 1998, 2001Sobel et al, 2001;Walker et al, 2001;Johnson et al, 2003). Threshold tests were administered using two binary-dilution 20-step staircases, with the highest concentration set at 10% v/v phenylethyl alcohol in mineral oil and 0.1% propionic acid, respectively.…”

Spared and Impaired Olfactory Abilities after Thalamic Lesions

“…This held despite altered olfactomotor function in the left patients during this task. In young healthy subjects, higher odorant concentrations are sniffed with reduced vigor compared with lower concentrations (Laing, 1983;Sobel et al, 2001;Walker et al, 2001;Johnson et al, 2003). Such an olfactomotor response was evident here in healthy age-matched controls and to some extent in right hemisphere thalamic patients but not in left hemisphere patients.…”

Propionsäure [MAK Value Documentation in German language, 2010]

“…Dieser Unterschied zwischen Phenylethylalkohol und Propionsäure verdeutlicht, dass die trigeminal vermittelte Reizwirkung von Propionsäure stärker zur Reduktion des Inhalationsvolumens beiträgt als die reine Geruchswahrnehmung einer Substanz (Johnson et al 2003). In weiteren Studien, in denen ebenfalls eine olfaktometrische Applikationstechnik verwendet wurde, um akute Wirkungen von Propionsäure zu untersuchen, ergaben sich ebenfalls Hinweise auf chemosensorisch vermittelte Effekte (Kendal-Reed et al 1998;Walker et al 2001). Es wurden subjektive Angaben zu Geruchsintensität und intranasalen Reizungen bei Propionsäurekonzentrationen von 0,16; 1,14; 8,22 und 59,15 ml/m 3 sowie einer Kontrollbedingung mit reiner Luft beschrieben.…”