Confirming Tube Positioning in the Trachea
In managing the difficult airway, one of the most disastrous possibilities is the failure to recognize misplacement of the ETT, usually in the esophagus. This is not a life-threatening situation unless it is unrecognized. Thus, confirmation of ETT placement in the trachea is essential. Visualizing the tube passing through the glottis into the trachea is the definitive method to assess correct positioning. This may not always be possible as a result of poor visualization and (potentially) the operator's reluctance to accept that the tube is not in the trachea. There are several clinical observations that support the presence of the ETT in the trachea.
Chest wall movements on manual ventilation are usual but may be absent in patients with chronic obstructive pulmonary disease, obesity, or decreased compliance, for example, severe bronchospasm. Although the presence of condensed water vapor in the ETT suggests that expired gas is from the lungs, this may occur with esophageal intubation. The absence of water vapor is more strongly suggestive of esophageal intubation. Auscultation of breath sounds (in both axillae) supports correct tube positioning but is not absolutely confirmatory.
The use of capnography to detect end-tidal carbon dioxide is the most reliable method of confirming ETT placement and is increasingly available in critical care. False-positive results may occur initially when exhaled gases enter the esophagus during mask ventilation or when the patient is generating carbon dioxide in the gastrointestinal tract, for example, recent ingestion of carbonated beverages or bicarbonate-based antacids. A false-negative (ETT in the trachea but no CO2 detected) may occur when pulmonary blood flow is minimal, for example, during cardiac arrest with poor cardiopulmonary resuscitation.
Visualizing the trachea or carina through a fiberoptic bronchoscope, which should be readily available in critical care, will also confirm correct placement of the ETT. Note that after emergency intubation and clinical confirmation of the ETT in the trachea, 15% of ETTs may still be inappropriately close to the carina.
Crit Care Med. 2008;36(7):2163-2173. © 2008 Lippincott Williams & Wilkins
Cite this: The Difficult Airway in Adult Critical Care - Medscape - Jul 01, 2008.