[Hydrogen sulphide stimuli shorten exhalation during sleep as well as in wakefulness].

Background: In the attentive waking state, pleasant odours often prolong inhalation while unpleasant odours often shorten the exhalation. It should be checked whether this induced breathing pattern is maintained even during sleep.
Methodology: 23 healthy normosmic adults were examined by polysomnography for one night and randomized pulsed either with H ₂ S, phenylethyl alcohol (PEA) or CO ₂ via a flow olfactometer. The determination of the sleep stages was based on the standard polysomnography curves. From the breathing curves (respiratory nasal pressure breathing, thoracic or abdominal belt breathing) a low-artefact curve was selected and seven breaths were measured from their breathing signal around the trigger impulse. The duration of inspiration (DIN) and the duration of the expiration (DEX) were determined from the six prestimulatory breaths and from breath with the stimulus onset and thus defined a reaction index (RI) indicating whether there is a significant change in shortening or prolonging DIN and/or DEX. These different RI were corrected by the spontaneous baseline RI and analysed according to the type of stimulus and the sleep stages.
Results: Reaction indices with reductions of DEX were larger than spontaneous RI and RI for PEA and H ₂ S stimulation. In the case of CO ₂ irritation, RI with reductions of DIN and DEX were larger than with olfactory stimulation. All RI were equal in their amount between sleep stages. In REM, the difference between olfactory RI with shortened DEX between H ₂ S and PEA stimulation was greatest.
Conclusion: When stimulated with an unpleasant smell in sleep, the respiratory reaction pattern from the awake state is preserved. RI with shortened DEX can be considered as an imperfect arousal.
Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht.
(© Georg Thieme Verlag KG Stuttgart · New York.)