Use of a cross-circulation technique in studying respiratory responses to CO₂

¹ Department of Physiology, State University of New York Downstate Medical Center, Brooklyn, New York

The effect of hypercapnia and hypocapnia on ventilation was investigated in cross-circulated dogs in which the recipient dog's head and neck regions were perfused by blood from a donor dog. Hypercapnia of the donor dog was produced by administering CO₂-O₂-N₂ gas mixtures in the inspired air. Hypocapnia was produced by hyperventilating the donor dog with the aid of a respiratory pump. When the donor dog was hyperventilated, the ventilation of the recipient was maintained at or just below its resting level and it was independent of the arterial Pco₂ of the donor. The donor dog was apneic when the artificial hyperventilation was suspended and this response was not abolished by vagotomy. Bilateral vagotomy caused an increase in ventilation in the recipient when its head was perfused by hypocapnic blood. Bilateral removal of the carotid receptors did not influence the response to CO₂ qualitatively although there was some reduction in the ventilation of the recipient to cephalic hypercapnia. The ventilation of the recipient dog was best correlated to the pH and Pco₂ of its cerebrospinal fluid in both hypercapnic and hypocapnic states.

Note:
(With the Technical Assistance of S. S. Mei)

Submitted on February 19, 1964