How to handle the difficult airway, part 2

July 1, 2005
Vance Vanier, MD
Vance Vanier, MD

,
Barry C. Simon, MD
Barry C. Simon, MD

Volume 5, Issue 7

Abstract: The laryngeal mask airway (LMA) and intubating LMA are valuable alternatives in patients in whom intubation has failed and who need oxygenation and ventilation immediately. The dual-lumen, dual-cuffed airway tube is effective in a variety of settings and can tolerate ventilation at pressures as high as 50 cm H2O; it is contraindicated in awake patients who have intact airway reflexes, caustic ingestions, and upper airway obstruction from a foreign body or pathology. Surgical airways are lifesaving techniques when intubation is unsuccessful or impossible through the mouth or nose. It may be particularly appropriate in patients with laryngeal or facial trauma, upper airway obstruction, or oropharyngeal injury. When patients aged 12 years and older cannot be ventilated by mask or intubated with traditional methods, surgical or needle cricothyrotomy is the procedure of choice. (J Respir Dis. 2005;26(7):298-302)

Many factors should be kept in mind when alternative methods of airway management are being considered, including the patient's risk of aspiration, the reason for the difficult airway, the degree of urgency, and the available equipment. In the June 2005 issue of The Journal of Respiratory Diseases,we reviewed the risk factors for a difficult airway and a variety of airway management techniques, such as direct laryngoscopy.

In this article, we will discuss the laryngeal mask airway (LMA), the dual-lumen airway tube, and surgical approaches.

LARYNGEAL MASK AIRWAY

The LMA is essentially an endotracheal tube (ETT) with an inflatable silicone collar at the distal end. The nose of the collar fits into the patient's upper esophagus and forms a seal around the larynx. When the LMA is properly seated and inflated, oxygen is then directed into the larynx and trachea.

The intubating LMA (ILMA) is a modification of the original LMA. It is designed to direct and facilitate blind endotracheal intubation through the device. LMA sizes range from 1 to 5; sizes 1, 1.5, 2, and 2.5 are used in infants and small children, and size 5 is used in large adults. To apply the LMA and ILMA, the provider must perform the following steps:

• Use water-soluble lubricant on the surfaces of the LMA and ILMA that will slide against the palate.

• Place the patient's head in a neutral position for blind passage of the device.

• Advance the mask back against the palate, then behind the tongue, and position it in the posterior pharynx, rotating it with gentle pressure until it is wedged in the esophagus. Inflate the cuff and begin ventilation.

• If definitive airway protection is desired after adequate oxygenation and ventilation have been established, pass an ETT through the ILMA to complete tracheal intubation. This can be accomplished by blind placement or by using a fiberoptic scope to facilitate placement in the trachea.

Note that the ETT must be well lubricated to facilitate the passage and removal of the ILMA. Significant resistance may be felt as the ETT navigates the sharply curved portion of the ILMA. The ETT must be pushed past this curve to be directed into the trachea. Traditional methods should be used to confirm ETT placement. The cuff of the ILMA may be removed immediately or may be deflated and left in place until the patient has been stabilized.

The LMA is not considered a definitive airway tool because regurgitation and aspiration of gastric contents are not prevented. Nevertheless, the LMA and the ILMA are excellent alternatives in the patient in whom intubation has failed and who needs oxygenation and ventilation immediately.

The record of successful LMA placement is excellent, even in novice hands.1,2 One study demonstrated a first-attempt success rate of 94% when students or paramedics placed the LMA. Experienced practitioners have had a success rate of 98% and a time to placement of less than 20 seconds.3

Some proponents of the LMA cite it as the airway adjunct of choice in patients who have limited cervical spine mobility, such as those with cervical collars, cervical spine fusion, or halos.4 This recommendation stems from the fact that the LMA can be inserted with the patient's head in a neutral position and, thus, neck manipulation is not necessary. Overall, the success of the LMA has made it a recommended adjunct in the American Society of Anesthesiologists' difficult airway algorithm5; the LMA is the first alternative for the patient who cannot be intubated or ventilated.

Contraindications to use of the LMA or ILMA include a foreign body in the upper airway or trachea, pathology or recent local irradiation of the pharynx or upper esophagus, tracheal disruption, and upper airway infection (such as epiglottitis).6 In addition,lungs that are noncompliant may make ventilation with the LMA difficult, because the device frequently leaks significant amounts of the tidal volume when peak inspiratory pressures exceed 30 cm H2O.

DUAL-LUMEN AIRWAY TUBE

The 2 lumens allow ventilation whether this tube is placed in the esophagus or the trachea. The dual-lumen, dual-cuffed airway tube differs from the esophageal obturator airway in that it does not require an adequate mask seal to effect adequate ventilation. A large oral pharyngeal balloon provides a sufficient seal to permit ventilation through the appropriate distal aperture.

The approach with the dual- lumen tube may be blind, or it may be aided with a laryngoscope as follows:

• The tube is placed while the patient is in a supine position, preferably with the tongue and jaw thrust upward by the practitioner's nondominant hand. However, the patient can also be in a neutral position.

• Two black bands are embedded in the tube near the junction of the proximal and middle third of the tube. The device is inserted through the oral pharynx down toward the esophagus and trachea until the 2 bands are at the level of the alveolar ridge.

• The proximal, large, oral pharyngeal balloon is inflated with 100 mL of air. This balloon is labeled with a blue port and is identified as No. 1.

• The distal balloon, which is labeled with a white port and identified as No. 2, is inflated with 5 to 15 mL of air.

• Given the most common scenario, in which the tube is positioned in the esophagus, ventilation should be initiated through the longer blue connecting port. Air is forced through the holes and directed toward the larynx. The presence of air entry into the lungs and the absence of air entry into the stomach indicate that the tube has been placed in the esophagus.

Even if ventilation is successful, placement should be confirmed by using traditional methods. The absence of breath sounds in the chest and the presence of gas entering the stomach indicate that the tube has been placed in the trachea and that ventilation should be performed through the shorter, clear connection tube. If the tube is placed in the esophagus and ventilation is successful through port 1, gastric contents can be aspirated by passing a nasogastric tube through port 2.

• If no breath sounds are heard on auscultation, the tube has probably been inserted too deeply. The balloons should be deflated, and the tube should be repositioned before ventilation is attempted again.

The dual-lumen tube has been shown to be an effective rescue airway device. It has been used effectively in routine and difficult airways in a variety of settings, including the prehospital environment, ICU, emergency department, and operating suite.7-9 As a result of the dual-lumen construction, the tube provides greater protection against gastric aspiration and can tolerate ventilation pressures of 50 cm H2O. Thus, if necessary, it can be used for prolonged intubation (8 hours).10,11

Use of the dual-lumen tube is contraindicated in awake patients who have intact airway reflexes, caustic ingestions, and upper airway obstruction as a result of a foreign body or pathology. Although the tube may provide increased protection against aspiration, unless it is positioned in the trachea, it does not definitively prevent aspiration and should be replaced with a definitive method of airway management as soon as possible.

SURGICAL AIRWAYS

These airways are lifesaving techniques when intubation is unsuccessful or impossible through the mouth or nose. Although the techniques described above usually result in the securing of a definitive airway, there are patients in whom intubation from above the vocal cords is not possible. These include persons with laryngeal or facial trauma, upper airway obstruction, and oropharyngeal injury.12

In such situations, a surgical cricothyrotomy or needle cricothyrotomy is the procedure of choice for adults and children older than 12 years. However, in children younger than 12 years, these approaches are very difficult or impossible. Percutaneous transtracheal ventilation should be considered the surgical airway of choice in this age group.

Depending on the skill level of the practitioner, success rates for surgical cricothyrotomy are 60% to 98.5%; complication rates are as high as 38%.13-16 Complications can include subcutaneous emphyse-ma, vocal cord injury, laryngeal disruption, subglottic stenosis, and hemorrhage.17

Transection of the trachea is a contraindication to surgical airways, because the cervical fascia may hold together the cut ends of the airway and any incision can cause the distal aspect of the trachea to retract into the mediastinum. The patient's age should be considered.18

Surgical cricothyrotomy

Preparation for this surgery should be undertaken before the decision to perform it has been made.

• The cricothyrotomy tray needs to be made available as early as possible. The patient's neck should be examined, and landmarks properly identified.

Identifying landmarks is generally easier in men, in whom the thyroid cartilage is more prominent. If time permits, the neck should be prepped with appropriate antiseptic solutions and lidocaine.

Palpate the thyroid cartilage prominence and proceed caudad in an attempt to feel the cricothyroid membrane at the base of the thyroid cartilage. This membrane, noted by a small depression, is about 1 finger breadth inferior to the laryngeal prominence, and it is bounded on its inferior aspect by the ridged horizontal cricoid cartilage.

For confirmation or in difficult circumstances, placing 4 fingers over the patient's anterior neck, with the small finger lying on the sternal notch, can approximate the location of the cricothyroid membrane. The area of the neck underneath the provider's index finger approximates the location of the cricothyroid membrane.

• The practitioner should prepare the patient's neck as in basic endotracheal intubation and immobilize the larynx with his or her thumb and long finger. The index finger is placed over the anterior larynx to relocate and identify the cricothyroid membrane.

Make a vertical incision, 2- to 3-cm long, that extends from the superior aspect of the thyroid cartilage caudad toward the sternal notch. It is important not to attempt the procedure through a tiny incision. Enough pressure should be applied to cut through the skin and subcutaneous tissues down to the larynx without any effort to identify individual strap muscles.

The index finger is used to reidentify the cricothyroid membrane, and a horizontal incision is made through the membrane. Immediately, a trachea hook is placed through the membrane. The hook is rotated and positioned at the superior margin of the incision so that traction and stabilization can be applied in a cephalad direction.

It is preferred that the incision through the cricothyroid membrane be made with a No. 11 blade inserted horizontally and as distally as possible to avoid the more superiorly located cricothyroid vessels. The Trousseau dilator is inserted and spread vertically to enlarge the diameter of the cricothyroid space.

The tracheostomy tube, with its inner cannula, is then gently inserted through the incision and between the blades of the dilator. The tube is gently advanced in the direction of its natural curve, and the dilator is rotated to allow the blades to orient longitudinally in the airway. Then, the tube is advanced until it is firmly positioned against the anterior of the neck, and the dilator is removed.

Once the cuff is inflated, tube position can be confirmed with traditional methods. The average adult man can accept a No. 5 or 6 tracheostomy tube, either of which is often too large for the average woman. A No. 4 tracheostomy tube can be used in most adults.

In some emergent situations, a cricothyrotomy tray may not be available. A few simple tools, such as a No. 11 scalpel blade, hemostat, and small ETT (internal diameter, 5.5 or 6.0 mm), may be used to accomplish this procedure.

Needle cricothyrotomy

The devices and kits used to perform this procedure are often referred to as "cricotomes." Several devices are available commercially; most use a modified Seldinger technique to assist with the placement of the tubes. Because this approach is relatively easy and placement is similar to that of central venous catheters, it may facilitate the procedure for most emergency physicians.

• The patient's neck is prepared in a way similar to that for traditional cricothyrotomy, and landmarks are identified in the same manner as they are in the surgical procedure. The introducer needle is inserted through the cricothyroid membrane in a slightly caudal direction.

A syringe with a small amount of water or saline is attached to the needle. As the assembly is advanced into the trachea, negative pressure is maintained on the syringe. The appearance of bubbles in the solution indicates successful placement of the needle into the tracheal lumen.

• The syringe is removed from the needle, and a soft-tip guidewire is inserted through the needle into the trachea in a caudal direction. The needle is removed, leaving the wire in place.

• A small (0.5 cm) skin incision is made directly adjacent to the wire to facilitate passage of the airway through the skin.

• The airway catheter with an internal dilator in place is threaded over the wire and passed toward the trachea. A firm twisting motion is applied as the device passes through the skin and cricothyroid membrane. When the catheter is firmly seated in the trachea, the wire and dilator are both removed.

• Tube position is confirmed with traditional methods.

Percutaneous transtracheal ventilation

This rescue form of ventilation can be used successfully as a temporizing measure to provide oxygenation and ventilation until definitive methods of airway management can be performed. Although rarely used, percutaneous transtracheal ventilation is simple, relatively safe, and effective. In children younger than 12 years, this approach is considered the preferred surgical method of airway management when intubation through the mouth or nose is unsuccessful or impossible. The only absolute contraindication is complete airway obstruction above the vocal cords.

As with the other surgical procedures, preparation for percutaneous transtracheal ventilation should be undertaken as soon as the practitioner suspects that alternative airway methods may be needed.

• The tools needed for this procedure include a 12- to 16-gauge catheter (the larger, the better). A catheter with an interlocking connector is preferred to secure the catheter to the tubing. A high-pressure source of oxygen, 50 psi, is required for ventilation and is commonly obtained from any standard oxygen cylinder or hospital wall outlet.

The flow regulator interposed between the oxygen source and traditional tubing reduces the flow to a maximum of about 17 L/min. Except in small children and infants, this flow rate is not sufficient to provide adequate ventilation. An adapter has to be placed on the wall-outlet connector or the oxygen tank to deliver a flow of 50 psi to the patient.

The tubing that carries oxygen from the wall outlet to the patient must have a valve or interrupter placed between the oxygen source and the cannula. This is essential to allow the patient to exhale in the same way as with conventional positive pressure ventilation. The valve can consist of a hole cut in the tubing over which the provider places his or her thumb to regulate flow into or out of the patient's airway. Commercial valves are also available.

• Once the tools are arranged, the trachea is prepared in a manner similar to that for needle cricothyrotomy: landmarks should be identified, and the neck should be prepared. Lidocaine should be administered if time allows.

The larynx should be immobilized with an approach similar to that used for cricothyrotomy. The large-bore needle catheter is attached to a 20-mL syringe and is partially filled with a clear liquid. This assembly is then passed in a caudal direction into the trachea until bubbles are aspirated into the syringe.

The catheter is passed farther into the trachea, the needle is removed, and the catheter is secured to the neck. Air should be aspirated again to confirm that the catheter is in the trachea. The catheter is connected to the polyvinyl chloride tubing and is then physically held in place until it can be firmly secured or until a definitive airway is established.

Once the catheter is connected to the tubing system, the cycle of ventilation should allow air inflow for about 1 second, followed by 2 to 3 seconds of exhalation. A 1:3 ratio should be continued in all patients. Commercially produced devices have control valves to regulate the degree of pressure and flow.

Large adults can handle the 50 psi of oxygen that is delivered unimpeded from the wall outlet. Smaller adults and children should be regulated to 20 to 30 psi. Children younger than 5 years should be ventilated with a bag device attached to the catheter. A No. 3 pediatric ETT adapter is perfectly sized to have the small, tapered end fit snugly into the catheter hub and the larger, round end into the ventilation bag.

It is not possible to monitor exhalation of end-tidal carbon dioxide to confirm ventilation of the patient with these devices. Therefore, the chest should be inspected for evidence of expansion with each high-pressure "breath." To avoid barotrauma, inspiration should be stopped when chest expansion is noted. Inspiratory pressures should only be as high as are necessary to provide adequate chest expansion.

SUMMARY

Recognition of the potential for a challenging airway is of paramount importance when assessing the patient. This allows the practitioner to have adjunct equipment and anesthesia ready. We suggest becoming comfortable with 2 or 3 of the techniques discussed above and in part 1 of this article. After traditional orotracheal intubation, we recommend the techniques that are summarized in the Table.

References:

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