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Department of Anesthesiology, Lahey Clinic, Burlington, Massachusetts
Address correspondence and reprint requests to Michael Stix, MD, PhD, Department of Anesthesiology, Lahey Clinic, 41 Mall Rd., Burlington, MA 01805. Address e-mail to michael.s.stix{at}lahey.org
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Abstract |
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Implications: It is often necessary to change a patient’s breathing tube (endotracheal tube). This can be a risky procedure. This report describes a technique for changing an endotracheal tube by using a modified "intubating laryngeal mask" (a commonly used airway and breathing device) and a fiberoptic bronchoscope.
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Introduction |
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Recently, Asai (9) described the use of a laryngeal mask airway (LMA) for endotracheal tube exchange. He inserted a "classic" LMA into a patient with a defective oroendotracheal tube (OETT). The LMA was placed in the hypopharynx (as usual), resting behind the larynx and OETT. He then guided a fiberscope via the LMA and through the glottis (alongside the existing OETT) into the trachea. The defective OETT was removed and the trachea reintubated by advancing a new ETT over the fiberscope.
We believe that the use of LMAs for OETT exchange offers many advantages. The use of a "classic" LMA is not optimal for tracheal intubation, however. Instead, we modified an "intubating" LMA (ILMA) by cutting off the epiglottic elevating bar (Fig. 1) and report an interesting case of tube exchange using this device.
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Case Report |
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On examination, the patient was sitting upright and was visibly dyspneic. Arterial blood pressure was 150/90 mm Hg, heart rate 120 bpm, respiratory rate 30 breaths/min, and oxygen saturation 87% with oxygen via nasal cannula. Lung examination revealed bilateral, diffuse, wet crackles. The patient’s airway exam was remarkable only in that he was bearded. After discussion with the surgeon, it was agreed that the patient should remain tracheally intubated and mechanically ventilated postoperatively.
An arterial line was placed preoperatively pH 7.45, PaCO2 37 mm Hg, and PaO2 45 mm Hg. In the operating room, monitors were placed and the patient breathed oxygen. The plan was to first tracheally intubate with a single-lumen ETT, ventilate optimally, and then place the double lumen tube (DLT). Despite a rapid sequence induction of anesthesia, pulse oximetry decreased from 96% to 81% during endotracheal intubation. After mechanical ventilation with a fraction of inspired oxygen of 1.0, the trachea was extubated, and a 39F left-sided DLT was placed. Fiberoptic positioning was then undertaken without the use of simultaneous ventilation, but the patient quickly desaturated to 80%. Thereafter, the patient’s lungs were mechanically ventilated with the DLT and the fiberscope used for positioning via the tracheal-lumen port.
The patient was positioned left lateral decubitus and single-lung ventilation successfully established without desaturation less than 94%. A right video-assisted thoracoscopy for lung biopsy was unsuccessful (access to a specific pulmonary lesion was not possible), so a small thoracotomy incision was made. The remainder of the surgery proceeded without problems.
At the conclusion of surgery, the patient was placed in the supine position, and the oropharynx was suctioned. The modified ILMA (size 4) (Fig. 1) was placed while the DLT remained in situ. Fiberoptic examination via the ILMA tube revealed lingual tissue. A second insertion of the modified ILMA was performed, and with the device fully advanced, the fiberoptic view from the ILMA airway tube showed the DLT passing anterior to the ILMA bowl through the larynx. After insertion, the cuff was inflated with 20 mL, and the ILMA was secured with tape.
The 5-mm fiberscope was loaded with an 8.0-mm inner diameter ETT and readvanced via the modified ILMA. A 14F jet-ventilation exchange catheter was passed via the tracheal lumen of the left-sided DLT, as seen in Fig. 2A. The exchange catheter is seen in this figure in the right (tracheal) lumen of the DLT. The DLT was then slowly withdrawn. As soon as the tip of the DLT emerged from the glottic opening, the fiberscope was advanced into the trachea, alongside the exchange catheter. This is seen in Figure 2B. The new ETT was passed uneventfully over the fiberscope.
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Discussion |
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Tube exchange is particularly difficult with supraglottic swelling or in an anatomically difficult airway that does not permit direct laryngoscopic exposure of the larynx. The most common exchange technique, in our experience, involves the use of a jet ventilation exchange catheter (4–8). In this situation, we use rigid laryngoscopy, as well, to displace soft tissues. The LMA offers an alternative technique for fiberoptic-assisted tube exchange (9). Insertion of an LMA in an orally intubated patient quickly establishes a protected conduit that emerges within centimeters of the glottic opening (10,11). Placement of the ILMA does not require head extension (12). The ILMA also has a "V-shaped ramp" where the airway tube fuses with bowl (12,13). This ramp centralizes the ETT toward the glottic opening and, it is reasonable to speculate, enhances the success of advancing an ETT over a fiberscope.
Before the exchange, it is possible to optimize preoxygenation (1). The ETT is withdrawn under direct visualization until the cuff is at the vocal cords. The cuff is then inflated, if possible, and the patient mechanically ventilated and oxygenated before proceeding with the final steps of the exchange.
We consider use of the jet-ventilation exchange catheter to be an integral part of this procedure. This catheter provides yet another degree of safety to the procedure. Both the fiberscope and the exchange catheter enter the trachea and can be used for railroading a new ETT. In addition, jet ventilation for oxygenation is possible with this device. Finally, the LMA itself can be used to provide rescue ventilation and oxygenation. The anesthesiologist, therefore, has two fall-back options for delivering oxygen.
Although the tube exchange in the above case report went smoothly, the initial fiberoptic view did not include the arytenoids or vocal cords; it is possible that soft tissue collapse could have occurred in the immediate supraglottic region once the DLT was withdrawn. This could have made the short fiberoptic navigation to the glottis problematic and/or could have caused difficulty with advancing the new ETT. Without direct visualization of the arytenoids or vocal cords, the exact proximity to the glottis cannot be determined.
Because the ILMA has a curved metal airway tube, a size 4 device cannot always be inserted fully into the hypopharynx of large adults (14). The fiberoptic bronchoscope can therefore emerge quite a distance from the vocal cords in large patients [in excess of 5 cm (see Fig. 3 of Ref. 12)]. (The size 5 ILMA has an identically shaped metal airway tube and will not necessarily allow the fiberscope to emerge closer to the glottis.) Also, the metal airway tube and silicone tracheal tube guiding ramp, designed to enhance intubation by directing the ETT anteriorly, eliminate the bottom-most portion of the field of view from the ILMA bowl. There are several reasons, therefore, why the posterior glottis and arytenoids may not be viewed. Again, determining the precise fiberscope location in the upper airway is difficult without a view of the arytenoids.
The number of techniques for ETT exchange is limited (1–9,15–17). The use of a LMA (9) is an option that, depending on patient selection, might be the most appropriate. The ILMA, in particular, can be used without the need for head and neck manipulation. The LMA rests in the hypopharynx, behind the larynx and (original) ETT. It offers a route for tracheal intubation and a means for rescue ventilation and oxygenation. Asai (9) used a classic LMA in his case report. It is our experience that the airway tube of a classic LMA brings the fiberscope closer to the glottis (and provides a more reliable view of the laryngeal inlet and ETT) than the airway tube of an intubating LMA. This is particularly important in a fiberoptic technique such as the one just described. The classic LMA design, unfortunately, is not optimal for intubation. The ILMA, however, has a sophisticated design to enhance the ease and practicality of intubation. Both types of LMAs have distinct advantages; the optimal use of an LMA to facilitate ETT exchange has yet to be determined.
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