[Breath changes induced by short chemosensory stimuli cannot be intentionally suppressed]

Breathing changes induced by repeated short olfactory stimuli are used as an objective indicator of the integrity of the olfactory system. Until now, it has not been investigated whether chemosensorically induced changes in inspiratory and expiratory time parameters can be suppressed intentionally. The same applies to breathing changes due to weak CO₂ stimuli.

34 healthy adult normosmics were stimulated during relaxed regular nasal breathing using a flow olfactometer with nine differently concentrated H₂S and three weak CO₂ stimulation pulses. They were instructed to intentionally maintain regular nasal breathing during the stimulation. A significant breathing change was present if the duration of the inspiration (DIN) or the expiration (DEX) of the first stimulatory breath was outside the double standard deviation of the mean of five prestimulatory regular breaths. These could be shortened or extended the DIN or DEX.

Despite high motivation, the chemosensorically induced breathing changes could not be suppressed intentionally. Rest breathing reacted to both stimulants by changes in both the inspiratory and the expiratory time parameters. However, it outweighed the expiratory reactions. CO₂ evoked more breathing changes than H₂S. The frequency of reaction rate of H₂S stimuli was not concentration-dependent. Strong H₂S stimuli induced more frequent shortening than prolongation of DEX.

Chemosensorically triggered breathing changes cannot be suppressed intentionally. They therefore provide an additional objective tool to check the functionality of nasal chemosensory afferents.