k clipart 1

Occasionally, an end-expired level of 2.5% (17-18 mm Hg, highest observed measurement in swine study was 38-39 mm Hg) or more may be observed in first six breaths during esophageal intubation in the presence of carbonated beverages in the stomach. However, the shape of the capnograms appear abnormal  and should alert to a non tracheal intubation.

Reference:
Sum Ping etal. Reliability of capnography in identifying esophageal intubation with carbonated beverage or antacid in the stomach. Anesth Analg 1991;73:333-7.