Phrenic nerve and vagal nerve activities during differential lung ventilation in cats

The effect of differential lung ventilation (DLV) on afferent vagal and efferent phrenic nerve activities was studied in urethane anesthetized cats. One endotracheal tube was inserted into the left bronchus to ventilate its side lung. Another tube was inserted until its tip reached about 1 cm above the carina to ventilate the right lung. Using two respirators, each lung was ventilated independently. Using hooked silver electrodes, the vagal and phrenic nerve activities were recorded. The afferent vagal nerve was activated in concurrence with lung inflation at any ventilation rate. The right and left vagal nerves were activated by right and left lung ventilation, respectively. On the other hand, the right and left efferent phrenic nerves were synchronized, whether the ventilation was discussed or ventilation was achieved by right or left one lung ventilation or even by asynchronous DLV. The phrenic nerve activity was surpressed by one-lung, right or left, ventilation independently, so that the rhythm of the phrenic nerve was disturbed by asynchronous DLV. From these results, to reduce the stress of patients during asychronous DLV, it was considered that patients need heavier sedation than a usual mechanical ventilatory support.