Fig. 4

Posterior–anterior X-ray of the pig chest and neck during the trial. The locations of the stimulation electrodes are marked in green. A) Parasternal insertion site of the needle electrode used to puncture the left phrenic nerve at level rib 1 / C7. B) Esophageal electrodes #5 and #6 with the shortest expected distance to the phrenic nerve aligned at the same level, i.e., rib 1 / C7