Figure 3. Changes in phrenic nerve activity before, during, and after perfusion with hypoxic Krebs-Ringer solution equilibrated with three levels of halothane concentration (protocol 4). Phrenic nerve activity is expressed as the percentage of the value obtained during perfusion with the hyperoxic Krebs-Ringer solution equilibrated with halothane, 0%(control 1). *P < 0.05 compared with halothane, 0%. #P < 0.05 compared with halothane, 0.1%. $P < 0.05 compared with before and after perfusion.