Caution When Using Colorimetry to Confirm Endotracheal Intubation : Anesthesia & Analgesia

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Letters to the Editor: Letters & Announcements

Caution When Using Colorimetry to Confirm Endotracheal Intubation

Srinivasa, Venkatesh MD; Kodali, Bhavani-Shankar MD

Editor(s): Saidman, Lawrence

Author Information
doi: 10.1213/01.ane.0000253918.18547.13
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To the Editor:

Devices which detect exhaled carbon dioxide by changing color are used to confirm the correct (tracheal) placement of endotracheal tubes (ETT). The following case emphasizes a limitation of these devices in emergent circumstances.

A 71-year-old male, 168 cm, 83 kg, was admitted to the intensive care unit (ICU) with a history of acute abdominal distension due to partial small bowel obstruction, chronic renal failure, and altered mental status. While in the ICU, he became unresponsive and developed respiratory arrest. An 8.0-mm ETT was inserted and bilious secretions were seen and suctioned from the ETT. A “colorimetric” device (Easy Cap II, Tyco Health Care, CA) was attached and positive pressure ventilation begun. The color of the device changed from purple to yellow indicating 2%–5% (15–38 mm Hg) carbon dioxide. However, the ETT again filled with gastric contents and laryngoscopy revealed the ETT to be in the esophagus, after which the trachea was intubated with a second ETT. Examination of the first Easy Cap II revealed a permanent color change to yellow (or representing 2%–5% CO2) (Fig. 1).

Figure 1.:
Left: Easy Cap II, which has changed color permanently to yellow (representing 2%–5% CO2) due to gastric secretion. A false positive result. Right: Easy Cap II, which has come back to its original color after it was used to confirm endotracheal tube placement. It is imperative that the change in color be observed with each breath to avoid a false positive result.

These devices have been recommended by the American Heart Association (AHA) (1), American College of Surgeons (ACS) (2), and other societies.

Easy Cap II is a device which changes color in the presence of carbon dioxide (3). Although the package insert for Easy Cap II does alert the user to permanent color change with gastric contents or drugs, this point is not included on the packaging of each individual device, nor is it emphasized in the courses conducted by both the AHA (Advanced Cardiac Life Support) (1) and the ACS (Advanced Trauma Life Support) (2). Given that the incidence of esophageal intubation in areas out of the operating room is as high as 16% (4), it is imperative that the users are aware of the limitations of all colorimetric devices.

Venkatesh Srinivasa, MD

Department of Anesthesiology

Harvard Medical School

VA-Boston Healthcare System

West Roxbury, MA

[email protected]

Bhavani-Shankar Kodali, MD

Department of Anesthesiology

Harvard medical School

Brigham and Women’s Hospital

Boston, MA


1. The advanced ACLS skills. In: Cummins RO, ed. ACLS provider manual. Dallas, TX: American Heart Association, 2001:19–40.
2. Airway and ventilatory management, skills station II. In: Advanced trauma life support for doctors-student course manual. 6th ed. Chicago, IL: American College of Surgeons Committee on Trauma, 1997:73–82.
3. CO2 detection: intubation and cardio pulmonary resuscitation. Available online at: Accessed July 31, 2006.
4. Katz SH, Falk JL. Misplaced endotracheal tube by paramedics in an urban emergency medical services system. Ann Emerg Med 2001;37:32–7.
© 2007 International Anesthesia Research Society