Ultrasound as a tool to confirm tracheal intubation

In the present review, ultrasound was performed by emergency medicine residents, physicians, or anesthesiologists after briefings for a couple of hours in a workshop, during a didactic lesson, or by a radiologist. Therefore, it is imperative to gain adequate experience in transtracheal ultrasound to verify ETT placement with a greater degree of accuracy. Another issue is availability of an ultrasound machine to confirm ETT placement. Availability varies significantly by location and by the characteristics of the individual emergency department.

A smaller rural emergency department has significantly less access to bedside ultrasound. In our study, use of ultrasound failed to diagnose four esophageal intubations and 12 ETT intubations. This deserves close examination and explanation. Since the trachea is a superficial structure, visualization with a low-frequency probe would be difficult.

This problem can be overcome by positioning the probe just above the suprasternal notch or exerting cricoid pressure. The primary method for ETT verification is visualization of the ETT passing through the vocal cords, which is accomplished by direct laryngoscopy or with a video laryngoscope. In view of various technical limitations, confirmation with direct laryngoscopy remains the standard and ultrasound is secondary even in the absence of pulmonary flow during cardiac arrest.

This review has some methodological limitations. The total sample size of emergency intubations was small, i. The number of esophageal intubations was less than the number of ETT intubations due to a lower incidence rate. We understand from this review that transtracheal ultrasound is a novel technique with an acceptable degree of accuracy to confirm tracheal placement of the ETT in reasonably less time and without ventilation.

This method can be used along with capnography as a preliminary test before final confirmation by capnography. Both transtracheal ultrasound and capnography cannot differentiate between tracheal and bronchial intubation; therefore, transthoracic or diaphragmatic ultrasound should also be performed to avoid endobronchial placement of the ETT.

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Crit Ultrasound J ; 4 Suppl 1 : A6. Principal findings: Eleven studies and intubations were included in the final analysis. Eight studies and intubations were performed in emergency situations and the others were carried out in elective situations.

In emergency scenarios, transtracheal ultrasonography showed an aggregate sensitivity and specificity of 0. Conclusion: Transtracheal ultrasound is a useful tool to confirm endotracheal intubation with an acceptable degree of sensitivity and specificity.

A video laryngoscope was requested and while it was being prepared, we decided to intubate the trachea using real-time surface ultrasound guidance. The probe was moved caudally until a view of the vocal cords and surrounding hypopharyngeal tissue was obtained. The tube was withdrawn slightly and its trajectory modified to direct it into the glottis; hypoechoic shadowing and widening of the vocal cords was noted as the tube entered the trachea, a characteristic of successful glottic placement of the tube.

The intubation was performed in less than 10 s. The patient underwent an uncomplicated clinical course and was extubated uneventfully at the end of the procedure. This is the first report of using real-time dynamic surface ultrasound to successfully guide tracheal intubation. We refer to this technique as ultrasound-guided tracheal intubation UGTI.

UGTI represents a novel approach to intubation and may serve as an alternative technique in patients with difficult direct or video laryngoscopy. It is quickly performed and may have particular utility in patients in whom secretions or blood obscures visualization of the airway, or patients with limitations in mouth opening precluding the use of a laryngoscope. The idea to use ultrasound to guide intubation stemmed from a collaborative effort between intensivists and anesthesiologists at our institution.

Our intensive care team desired a rapid and reliable method to confirm successful tracheal intubation when the detection of carbon dioxide was not reliable such as during cardiopulmonary resuscitation, or when the immediate confirmation was warranted without ventilating to detect carbon dioxide. A review of the published literature revealed that ultrasonography could reliably be used to confirm the tracheal tube location immediately after intubation.

We began to examine the airway in anesthetized children using ultrasound and quickly realized that the critical structures of the airway could be visualized readily on ultrasound.

As lighted stylet intubation is a commonly performed technique at our institution, we considered whether the kinesthetic movements of the lighted stylet technique could be combined with ultrasound to direct the placement of the breathing tube.

We performed this technique in anesthetized patients with normal airways and realized that although the tracheal tube and stylet were not hyperechoic they could be immediately identified in the pharynx by their characteristic hypoechoic shadow and could be guided into the trachea using ultrasonography.

The required ultrasonographic skill can be obtained by first reviewing images of the ultrasonographic appearance of the airway. Clinical practice using ultrasound to visualize the airway structures and to understand sonographic features of successful tracheal intubation is essential before attempting UGTI.

A basic working knowledge of the typical controls and adjustments of the ultrasound machine is also necessary. Marciniak et al. They described ultrasound criteria to confirm tracheal intubation.

Unlike their use of ultrasonography to simply confirm tracheal intubation we used ultrasonography to direct the placement of the breathing tube in real time. We identified the posterior hypopharynx at the level of the thyrohyoid membrane by its hypoechoic appearance. We identified the vocal ligaments as linear hyperechoic structures that abducted with mask ventilation.

We located the tube in the pharynx by means of the ultrasound image and assessed its relationship to the glottic opening. We observed widening of the cords and enhanced posterior shadowing of the trachea as the styletted tube was placed between the cords. Although we performed UGTI without performing laryngoscopy, the technique can be performed in combination with laryngoscopy.

We plan on evaluating this combination approach in patients who fail direct laryngoscopy. If direct line of sight visualization fails, the ultrasound image can be used to guide the insertion of the tube beyond the direct line of sight visual range as the ultrasound view would not be affected by the lack of a direct view.

Some video laryngoscope guided intubations require hyperacute angulation of the styletted breathing tube. This may sometimes result in hang up of the breathing tube on the anterior tracheal wall or glottis during intubation.

UGTI is performed with a standard hockey-stick stylet configuration, which has not been associated with hang up of the tube. Once the stylet is withdrawn, the tube is readily advanced down the trachea. The gold standard for the management of patients with difficult direct laryngoscopy is the fiberoptic bronchoscope. Use of the fiberoptic bronchoscope requires good hand—eye coordination and significant practice.

The fiberoptic bronchoscope is expensive, not easily portable, and requires special cleaning between uses. Portable ultrasound machines are now ubiquitous in many hospitals, they are quickly readied between uses and have a fixed cost. A stylet is all that is additionally needed for UGTI, making this a relatively inexpensive, quick approach to intubation. A disadvantage of fiberoptic bronchoscopes and similar devices such as optical stylets is that visualization is performed through an optical channel within the device; this means that any encroachment of airway soft tissue on the device will result in a loss of the view.