Figure 2. Polygraphic records show changes in phrenic nerve activity during perfusion of the carotid body with hypoxic Krebs-Ringer solution (protocol 4). A, B, and C shows records during the perfusion of solution equilibrated with halothane, 0, 0.1, and 0.8%. BPCCA = blood pressure measured in the left common carotid artery, PNA = phrenic nerve activity.