Influence of Oxygen Inhalation on the Chemo‐receptor Activity of the Sinus Region

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Abstract
Summary.: When oxygen was substituted for air in anesthetized cats or dogs, an almost instantaneous, sometimes very considerable, reduction of respiratory rate and amplitude occurred. This effect was abolished by denervation of both sinuses and was due to the disappearance of a slight oxygen want which stimulated the chemoreceptors of the carotid body. After some minutes of oxygen breathing the ventilation again closely approximated to the value from air breathing. This compensation is partly explained by an increased carbon dioxide tension, but a greater excitability of the center may also occur.Oxygen inhalation under the same conditions usually caused a fall in arterial blood pressure, amounting on an average to 2.2 per cent in the cat. After denervation of both sinuses and section of the vagodepressor nerves, oxygen inhalation led to an increased blood pressure. It is assumed that the first effect is due to the abolition by oxygen of the normal stimulation of the chemoreceptors, whereas the second effect is caused by the relief of a central depression, caused by hypoxia.The pulse rate also decreased, on an average 3.3 per cent in the cat, during oxygen inhalation. Most of the effect was abolished by section of the vagodepressor nerves and denervation of the sinuses.The expenses of this investigation have been defrayed by a grant from the Therese and Johan Andersson Memorial Foundation.