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Updated: Jun 25, 2026

Expired CO2 Measurement in Intubated or Spontaneously Breathing Patients from the Emergency Department
Published on: January 29, 2011
False-positive colorimetric capnometry after ingestion of carbonated beverages
William Ryan Keller1, Jefrey Biehler, Marc Yves-Rene Linares
1Department of Pediatrics, University of Oklahoma School of Medicine, Oklahoma City, OK, USA.
Study Objective:
To investigate the potential for false-positive colorimetric capnometric readings during esophageal intubation after ingestion of carbonated beverages.
Methods:
The study was conducted in the human patient simulation laboratory of a tertiary care pediatric hospital. The sole outcome measurement was the capnometric indicator membrane color after expiration for 10 breaths. Readings were recorded for scenarios simulating 8 different models.
Results:
For all carbonated beverage trials with a cuffed endotracheal tube (ETT) and those with 2 and 6 oz of beverage in the gastric sac with an uncuffed ETT, a false-positive result was observed on the capnometer's indicator for breaths 1 through 10. The sensitivity of the capnometer for the detection of CO2 after full exhalation of breath 6 for these trials was 100%. For trials containing 12 oz in the gastric sac and an uncuffed ETT, yellow was observed on the capnometer indicator for breaths 1 through 3, tan for breaths 4 through 6, and purple for breath 7. The sensitivity of the capnometer for the detection of adequate CO2 after full exhalation of breath 6 for these trials was 0%. The overall sensitivity of the capnometer for the carbonated beverage models with a cuffed ETT was 100%, whereas the combined sensitivity for the trials with an uncuffed ETT was 67%.
Conclusions:
Under proper circumstances, a significant potential exists for false-positive colorimetric capnometric results in the presence of even small amounts of carbonated beverages.
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