Ultrasound Imaging for Endotracheal Tube Repositioning During Percutaneous Tracheostomy in a Cadaver Model: A Potential Teaching Modality

INTRODUCTION

Nearly 25% of intensive care unit (ICU) patients with prolonged mechanical ventilation require a tracheostomy.¹ Historically, placement of the tracheostomy was achieved with an open surgical approach involving dissection through the anterior neck tissues to the level of the trachea where a stoma was created. In 1985, Ciaglia et al published a landmark paper describing a new minimally invasive technique for percutaneous tracheostomy (PCT).² This technique has been increasingly accepted as an alternative to open surgery, and further improvements, such as the use of fiber-optic bronchoscopy, have been adopted over time.³

Among the described advantages of PCT is the ability to perform the procedure safely in the ICU rather than in the operating room.^4,5 In the ICU setting, the procedure may be performed by critical care providers without advanced surgery training (eg, anesthesiologists or pulmonary intensivists). Successive studies have found the complication rates of PCT to be comparable to, if not lower than, traditional surgical methods.^4,6,7 Investigations of resource utilization and cost effectiveness have also favored PCT compared to surgical methods.^4,8

A crucial step in PCT involves bronchoscopic visualization of the needle entering the anterior trachea. Prior to this step, the endotracheal tube (ETT) is withdrawn to the proximal trachea to guard against needle damage to either the ETT or the bronchoscope. The distance the ETT must be withdrawn varies considerably depending on the patient's size and anatomy. Premature loss of airway may occur during the process. In ventilated and critically ill patients, the consequences can be dire, including possible oropharyngeal trauma during reintubation, hypoxic cardiac arrest, or anoxic brain injury.

Ultrasonography is being increasingly used in the ICU environment, with recognized application in the placement of central venous catheters, insertion of chest tubes, and pericardiocentesis.⁹ Ultrasonography's use in tracheostomy for improved anatomical identification was first described in 1995, and subsequent publications described preoperative and real-time ultrasonography use with PCT placement.^10-13 None of the previous studies has specifically discussed sonographic visualization of the ETT cuff for the purposes of repositioning the ETT. We describe a novel approach for decreasing the risk of inadvertent extubation using ultrasound guidance to aid in the repositioning of a patient's ETT and suggest a plausible training modality for learners.

RESULTS

Inflation of the ETT pilot balloon with agitated water permitted ultrasound-guided repositioning of the ETT tip to the proximal trachea. On sonographic imaging, microbubbles from the agitation were detectible and the cuff was visualized. Visualization of the echo-dense fluid-filled cuff within the trachea facilitated ETT withdrawal to the proximal trachea, as is desired during PCT. Concurrent ultrasound screening of pretracheal structures and anatomical soft tissue landmarks in the anterior neck allowed for accurate placement of the ETT. Needle cannulation of the anterior tracheal wall was then performed, with needle entry occurring within the bronchoscopic field of view and distal to the ETT tip.

DISCUSSION

PCT continues to gain popularity and is supplanting open tracheostomy as the method of choice for tracheostomy tube insertion in many ICUs.^14-16 Utilizing bronchoscopy, we were able to intubate a cadaver and inflate the ETT pilot balloon with manually agitated water. The microbubbles in the water enhanced the sonographic visualization of the ETT cuff and helped facilitate ETT withdrawal to the proximal trachea. This technique could potentially decrease the rate of premature loss of airway control via sonographic visualization of an echo-dense fluid-filled ETT pilot balloon during the PCT procedure.

An inherent technical difficulty with employing a cadaveric model was the inability to identify important vascular structures of the neck, mainly the carotid artery, jugular vein, and any vascular anomalies. The postmortem rigidity of the cadaver's neck and mandible presented additional procedural difficulty. Performing the procedure on a cadaver model, however, permitted the less experienced members of the study team to familiarize themselves with neck anatomy and with key steps of PCT. If the procedure is halted after passage of the guidewire into the distal airway and prior to sequential dilation, the procedure could conceivably be performed by a series of medical trainees.

Limitations of the study included the use of a single cadaver, which may pose difficulty in extrapolating procedural results. Additionally, introducing fluid into the trachea and lungs could be harmful if the ETT cuff leaks during an actual procedure. This risk is likely to be acceptably low, as comparable volumes of lavage fluid (eg, saline) are frequently lost to the distal airways with no observable adverse effects during bronchoalveolar lavage. Alternative liquids, such as saline, would potentially function well in the procedure. Specially designed microbubble contrast agents are also commercially available that may be safe for use in this setting. Fluid inflation of ETT cuffs also already occurs in hyperbaric medicine, where increasing hyperbaric chamber pressures would be expected to cause progressive collapse of an air-filled ETT cuff. Fluid is also used to inflate ETT cuffs in operating rooms where nitrous oxide is administered for general anesthesia.¹⁷

Two alternative methods for repositioning the ETT to the proximal trachea exist. The first method uses an external handheld laser light to illuminate the tissues overlying the proximal trachea.¹⁸ The focused light of the laser is assumed to be visible using the PCT bronchoscope when inspecting the anterior tracheal wall. However, in practice, the light may be difficult to see in patients with excess adiposity or who may require significant anterior neck tissue dissection. The second method would be to attempt direct visualization of the ETT cuff from above the vocal cords as the ETT is pulled back. Visualization of the vocal cords through the patient's mouth is achieved either by bronchoscope or intubating laryngoscope. This approach may have varied success based on the amount of secretions in the oropharynx, the presence of other orogastric and nasogastric tubes, and the size of the patient's mouth and tongue.

CONCLUSION

In this study, we were able to successfully reposition an ETT with a fluid-filled cuff to the proximal trachea under sonographic guidance in a cadaver model. This approach to ETT repositioning may provide an incremental improvement to the PCT technique by decreasing the risk of accidental extubation. The cadaver-based model could be applied in physician training and to further improve the safety of the procedure.