Respiratory impact on motion sickness induced by linear motion.

Area of Science:

• Human physiology
• Vestibular system research
• Motion sickness etiology

Background:

• Motion sickness incidence (MSI) is maximal at 0.167 Hz for vertical sinusoidal motion.
• Normal breathing frequency is close to this peak MSI frequency, with some evidence of respiratory-stimulus synchronization.

Purpose of the Study:

• To investigate if enforced breathing over a broader frequency range (0.05–0.8 Hz) contributes to high MSI at 0.167 Hz.
• To determine the relationship between respiratory parameters and nausea during motion exposure.

Main Methods:

• Participants were exposed to vertical sinusoidal motion (0.3 g amplitude) at various frequencies (0.05, 0.1, 0.2, 0.4, 0.8 Hz).
• Nausea was assessed using MISC-scores, and respiratory parameters (tidal volume, respiratory frequency, end-tidal CO2 [PetCO2], respiratory minute volume) were measured.
• Control conditions included rest and a hyperventilation provocation test.

Main Results:

• Nausea scores were highest at 0.2 Hz, not 0.167 Hz.
• Respiratory minute volume increased and PetCO2 decreased with increasing stimulus frequencies.
• The hyperventilation provocation test did not induce nausea.

Conclusions:

• High motion sickness incidence at 0.167 Hz is not caused by enforced breathing.
• Enforced breathing increases with higher stimulus frequencies, but this does not directly correlate with the peak MSI frequency.