Aerobic exercises during mouth breathing do not change the detection threshold of H2S

Background In a previous study, the detection threshold for H2S during aerobic exercise worsened with forced nasal breathing. The cause remained unclear. It is to be examined how the detection threshold changes with exclusive mouth breathing. Material and methods During a resting phase, an aerobic physical load and subsequent recovery phase, different H2S concentrations were applied inspiratory-synchronously intranasal using a flow-olfactometer in a staircase procedure. The missing nasal breathing was objectified online and offline. The reaction times were determined. In parallel, various vital parameters have been measured. Results The passive detection thresholds for H2S between the load and recovery phases did not differ. In the resting phase, the threshold was highest. The reaction times were not different in the three experimental phases. Conclusion An increased sympathetic tone, resulting from an approximately half-hour aerobic exercise, did not change the passive olfactory threshold for during oral respiration compared to the subsequent recovery period. The high olfactory threshold in the resting phase might be explained by initial adaptation difficulties to the experimental conditions.