Intubating a patient in the ED is stressful enough, but when the patient is really sick, a roomful of people is often watching you go through the process and they are all waiting for signs that the tube is in the trachea. Sometimes you even hear an audible sigh of relief when the end-tidal CO2 detector turns yellow.
But what about when it doesn't? The tools to which we so frequently turn for confirmation (direct visualization, end-tidal CO2 detector, breath sounds) can let us down, especially in our sickest patients.
Ultrasound has a role in detecting correct placement of the endotracheal tube (ETT). A recent meta-analysis of 17 papers with more than 1500 patients found an overall positive predictive value of 34.4 for ultrasound, with a negative predictive value of 0.01. (Ann Emerg Med 2018;72:627.) It can be helpful as a routine method of confirmation, along with our other standard modalities, but ultrasound's real power lies in cases that are unclear. Many times, direct visualization may not be possible because of distorted anatomy or blood. Patients with severe respiratory distress may not have clear, equal breath sounds, and those in the midst of a cardiac arrest may not have detectable color change on their end-tidal device.
Ultrasound allows for another direct look by visualizing the ETT in the trachea and confirming that it does not lie in the esophagus. A high-frequency transducer is used to evaluate the trachea in the midline of the neck. This can be placed over the trachea at any point from the thyroid cartilage to the suprasternal notch. If you are unable to palpate the thyroid cartilage, place the transducer superior to the suprasternal notch, with the indicator dot pointing toward the patient's right side.
The normal anatomy of the trachea is noted in the image. The air-filled trachea is easy to see as a curved hyperechoic line with reverberation artifact. (Image 1.) The esophagus can often be seen as an oval structure deep and to the patient's left of the trachea. When an ETT is placed within the trachea, a second hyperechoic line is typically seen with shadowing extending behind it. (Image 2.)
The ETT can also be gently jiggled at the mouth, with attention paid to movement within the tracheal view on the ultrasound. When the ETT is placed incorrectly within the esophagus, a hyperechoic line, with or without shadowing, will be seen deep and to the left of the trachea.
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