Direct Laryngoscopy

Trachea vs. Esophagus

Following laryngoscope intubation, tracheal placement should be immediately confirmed through clinical signs and carbon dioxide monitoring. Clinical signs of proper endotracheal tube placement include bilateral axillary breath sounds, absence of gurgling over the stomach, and chest rise. Unfortunately clinical signs alone do not reliably exclude esophageal intubation, regardless of the laryngoscopist training or expertise in airway management. It should become routine for the clinician performing the intubation, especially difficult tracheal intubations, to develop a check list to ensure that as many of these clinical signs of proper placement are identified.

Esophageal intubation can occur through improper recognition of critical structures, restricted visualization, mis-shaping of the stylet obscuring the target, or from lack of concentrated focus on where the tip of the tracheal tube is being placed.

Esophageal intubation is caused by the visual restrictions inherent to laryngoscopy, misunderstanding laryngeal anatomy, and failure to pay attention to and visualize where the tip of the tracheal tube is directed.

1) The esophagus and trachea lie in close proximity.

2) Upward force on a laryngoscope blade inserted in the esophagus may create a rounded, poorly defined hole that can be mistaken for the larynx.

3) An epiglottis-first approach prevents misinterpretation of structures; plunging the blade in and out easily causes the tip to enter the esophagus and create landmark confusion.

4) Straight-to-cuff stylet shape and visualization of the tube tip, combined with proper recognition of posterior landmarks, are fundamental to ensuring proper placement.

5) During placement, always keep the tube tip below the line of sight and watch it travel upward to the larynx, making certain that the tip passes anterior to the interarytenoid notch.

6) An optical stylet permits immediate visual verification of tube position. End-tidal CO2 detection has the potential risk of insufflating the stomach if the tube entered the esophagus.

End-tidal CO2 detection, colorimetric or capnography, should be used on all patients. In cardiac arrest, end-tidal CO2 may be non-existent; an esophageal intubation detector is useful in these cases. Breath sounds, repeat laryngoscopy, and other clinical signs alone are inadequate.

1) Colorimetric end-tidal devices can be inactivated by liquids or falsely turn yellow if exposed to air. Make sure the device is unopened prior to use and appears purple when first opened. Color change should be assessed at six ventilations, however, insufflating the stomach risks regurgitation if tube is in the esophagus.

2) Esophageal intubation detectors (EID), such as the self-inflating bulb, create negative pressure when compressed and connected to a tracheal tube.

3) The trachea and esophagus are structurally different–the tracheal is a rigid open tube (because of the tracheal rings) and the esophagus is flat. The EID does not self-inflate when connected to a tube in the esophagus. The device must be securely attached to tube to prevent false results; secretions, obesity, and high negative pressure may cause slow self-inflation.