Effect of CO₂ on hyperventilation produced by vibration

¹ The Cardio-Respiratory Service, McGill University, Royal Victoria Hospital, Montreal, Quebec, Canada

Twenty-five normal subjects were exposed to low-frequency high-amplitude passive vibratory movements of the body. Hyperventilation and hypocapnia resulted in most cases. Restoration of the alveolar Pco₂ to its resting value by the addition of CO₂ to the inspired air while vibration continued gave rise to no further increase in ventilation. It is concluded that the hyperventilation produced by vibration is not moderated by the resulting fall in arterial Pco₂. Thus, observed differences between the ventilatory response of different individuals to vibration are unlikely to be due to differences in sensitivity to CO₂. Several other studies have demonstrated a threshold level of alveolar CO₂ below which respiration is not stimulated by CO₂. The lack of response to CO₂ in the present experiments may be due to the fact that they have been carried out at levels of alveolar CO₂ below this threshold.