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Where is the ET tube? - Answer

Diagnostic Challenge

Bruce Cload, PhD, MD;* Daniel W. Howes, MD;* Marco L. A. Sivilotti, MD, MSc;*† Jay J. Ross, MD;‡ John A.C. Murdoch, MB ChB‡

From the Departments of *Emergency Medicine, †Pharmacology and Toxicology, and ‡Anesthesia, Queen's University, Kingston, Ont.

CJEM 2006;8(6):446-447

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Answer

The most appropriate next step in the management of this patient is to attempt video laryngoscopy again (i.e., answer D).

Despite what the end-tidal CO2 detector indicated, the endotracheal (ET) tube was above the vocal cords. When the GlideScope® video laryngoscope (Saturn Biomedical Systems Inc., Burnaby, BC) was reinserted, it was apparent that the tip of the ET tube was lodged in the hypopharynx and had bent into the shape of a U (Fig. 1). End-tidal CO2 was detected because oropharyngeal edema created a seal around the ET tube.

Figure 1: One possible representation of flexed ET tubing causing a partial seal in the glottis sufficient to detect end-tidal CO2 synchronous with respiration

The cuff was deflated, the tube was removed, and the patient was effectively ventilated with a bag–valve–mask unit, during which oxygen saturation did not fall below 92%. Orotracheal intubation was then again attempted using the GlideScope, and this time the tip of the tube was seen to pass through the vocal cords.

Although a portable chest x-ray would definitely help in confirmation of ET tube placement, the management delay would be inappropriate. Changing the end-tidal CO2 monitor and aggressive ventilation would be futile, since the ET tube was not in the trachea.

Proceeding directly to tracheostomy is a reasonable option after failed difficult intubation. Given the fact that oxygen saturations were maintained and considering the anticipated early resolution of airway angioedema, however, we opted for one more try at orotracheal intubation.

Commentary

Colorimetric end-tidal CO2 detectors provide continuous semiquantitative measurement of end-tidal CO2 using a pH-sensitive chemical strip that changes colour upon exposure to the gas. The colour ranges for the Portex® device (Smiths Medical ASD, Keene, NH) are blue, green, green-yellow, and yellow, which correspond to levels of 0–1, 1–2, 2–5, and >5% CO2, respectively. Normally, end-tidal CO2 is > 4%.1,2

In hemodynamically stable patients, colorimetric capnometry can discriminate between tracheal and esophageal intubation with almost 100% sensitivity and 100% specificity provided that the ET tube cuff is inflated.1 Colorimetric detectors can also detect inadvertent tracheal placement of feeing tubes.3 Falsely positive CO2 levels can occur with esophageal intubation during cardiac arrest,1 contamination of the detector with lidocaine or gastric acid, and when there are carbonated beverages in the stomach.4,5 To our knowledge, falsely positive colorimetric CO2 detection due to ET tube distortion has not been reported.

In this patient the end-tidal CO2 detector was accurately indicating abundant carbon dioxide from cellular respiration, yet clinical signs indicated that the tube had not passed through the vocal cords. In retrospect, supraglottic airway distortion had prevented passage of the ET tube, and it bent during advancement; consequently, passage of the fibreoptic bronchoscope was impossible. Tongue and palatal edema provided a partial seal, so that expired CO2 flowed out through the proximal connection of the ET tube leading to an appropriate colorimetric change in the detector.

This case should remind emergency physicians that no one method to confirm proper ET tube placement is bulletproof. Clinical signs can still help us make the right choice in emergency airway management.

References

  1. Ornato JP, Shipley JB, Racht EM, et al. Multicenter study of a portable, hand-size, colorimetric end-tidal carbon dioxide detection device. Ann Emerg Med 1992;21:518-23.
  2. Goldberg JS, Rawle PR, Zehnder JL, et al. Colorimetric end-tidal carbon dioxide monitoring for tracheal intubation. Anesth Analg 1990;70:191-4.
  3. Howes DW, Shelley ES, Pickett W. Colorimetric carbon dioxide detector to determine accidental tracheal feeing tube placement. Can J Anesth 2005;52:4.
  4. Qureshi S, Park K, Sturmann K, et al. The effect of carbonated beverages on colorimetric end-tidal CO2 determination. Acad Emerg Med 2000;7:1169.
  5. Garnett AR, Germin CA, Germin AS. Capnographic wavefoms in esophageal intubations: effect of carbonated beverages. Ann Emerg Med 1989;18:387-90.

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Competing Interests: 
None declared.
Correspondence to: 

Dr. Bruce Cload, Department of Emergency Medicine, Empire 3, Kingston General Hospital, 76 Stuart St., Kingston ON K7L 2V7

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