Colorimetric Capnometry


Colorimetric Capnometry, Nellcor Easy Cap CO2 Detector

  • See Also
  • Indications
  1. Confirmation of Endotracheal Tube placement (successful intubation)
  • Mechanism
  1. Exhaled CO2 passes through device deposits in a liquid layer over a pH Sensitive filter paper
  2. Results in a change in color based on the pH of the exhaled gas (i.e. CO2)
    1. Paper within the detector starts as purple color
    2. Exhaled carbon dioxide turns the paper tan or yellow
    3. Paper returns to purple color after exhalation
  1. Color change
    1. Nearly confirms endotracheal placement (with 1% False Positive Rate)
    2. Confirmation of tube placement requires a second method (e.g. auscultation)
  2. No color change
    1. Confirms esophageal intubation (100% of cases)
    2. Extubate immediately and oxygenate and ventilate and then reattempt intubation
  1. Color change
    1. Color change confirms endotracheal placement (100% of cases)
  2. No color change
    1. Unreliable - does not accurately predict esophageal intubation (in trachea 77% of the time despite no color change in Cardiac Arrest)
  • References
  1. Marino (2014) ICU Book, 4th ed, Wolters-Kluwer, p. 417-8
  2. Ornato (1992) Ann Emerg Med 21:518-23 [PubMed]