Do We Still Need Nonvisual Intubating Techniques?

For many decades, tracheal intubation under direct vision using a laryngoscope has been considered the standard technique of intubation. Unfortunately, this approach to intubation has limitations. Difficult and failed intubation employing this technique can be as high as 21%, particularly in emergency situations.¹ Not surprisingly, studies have shown that considerable experience is required before a trainee becomes proficient in laryngoscopic intubation. Konrad and Mulcaster have constructed learning curves showing that a 90% probability of success requires between 47 and 57 laryngoscopic intubations.^2,3

The high incidence of difficulty and failure, coupled with these kinds of learning curves for laryngoscopic intubation have driven the development of many alternative intubation devices and techniques, such as rigid and flexible endoscopes, video-laryngoscopes, and optical intubating stylets. All of these devices have gained a measure of popularity. Unfortunately, these devices are substantially more expensive than the Macintosh laryngoscope. Furthermore, the cleaning and sterilization processes of some of these devices, such as the flexible bronchoscope, require an average of 50 to 60 minutes to complete, hindering their availability and practicality in emergency airway management and in pre-hospital care (i.e., they may be “context” driven).

The challenge of visual techniques employing optical stylets and video scopes is visualization of laryngeal anatomy and the passage of the ETT through the glottic opening in the face of fogging or the presence of blood, secretions, and vomitus in the upper airway. It is precisely these kinds of difficulties that have motivated the search for nonvisual techniques using a variety of devices, such as intubating guides, light-guided intubation using the principle of transillumination, blind nasal intubation, digital intubation, and retrograde intubation, all of which have proven to be effective, safe, and simple techniques.

What Is the Eschmann Tracheal Tube Introducer? How Does It Facilitate the Placement of an Endotracheal Tube?

In 1949, Macintosh⁴ reported the use of an introducer (gum-elastic bougie) to facilitate orotracheal intubation under direct laryngoscopy. Using the concept of the introducer, Venn⁵ designed the Eschmann Introducer (Eschmann Tracheal Tube Introducer, Portex Limited, Hythe, UK), a tube like core woven from polyester threads and covered with a resin layer. The Eschmann Introducer (EI) is 60 cm long, with a J (coudé) tip (a 35-degree angle bend) at the distal end to facilitate advancement anteriorly underneath the epiglottis into the trachea and to provide tactile tracheal confirmation (Figure 12–1A). Centimeter markings designate the distance from the tip. The EI is often referred to as the “gum-elastic bougie” or “bougie.” However, to avoid confusion, historically the “gum-elastic bougie” has been used to refer to a shorter urinary catheter made of different material and without a curved tip.⁶

The EI is particularly useful when the glottic opening cannot be clearly seen using a laryngoscope (e.g., Grade 3 laryngoscopic view as described by Cormack/Lehane [C/L]).⁷ Under these circumstances, the EI can be “hooked” underneath the epiglottis and advanced into the trachea. If it is correctly placed in the trachea, a subtle tactile “clicking” sensation can be felt as the tip of the EI slides over the tracheal rings while advancing it into the trachea. Furthermore, if the EI correctly enters the trachea, as it is gently advanced it will eventually be lodged (or “holdup”) in a distal airway and cannot advance beyond the 30 to 35 cm mark. In contrast, if it is placed in the esophagus, the entire EI can be advanced without encountering resistance. With the EI in place and positioned at 20 to 25 cm at the teeth, the ETT can then be advanced over the EI into the trachea. To facilitate the advancement of the ETT over the EI, the tongue and epiglottis must be elevated by a gentle jaw lift, a jaw thrust, or preferably, by the laryngoscope already in place. If difficulty persists while advancing the ETT, rotating the ETT 90 degrees counterclockwise will turn the ETT bevel facing posteriorly and minimize the risk of catching on glottic structures.⁸ Following intubation, the position of the ETT is confirmed using conventional methods, such as end-tidal CO₂ and auscultation. The EI has also been used to facilitate retrograde intubation in a trauma patient,⁹ and placement of a tracheostomy device during the performance of a difficult or emergency surgical airway (e.g., cricothyrotomy).^10,11

What Other Intubating Guides or Introducers Are Commercially Available?

Since the introduction of the EI, many intubating guides of different sizes, shapes, lengths, and materials have been developed. All of the designs serve a function similar to the EI, but many have some additional features.

1. 
   

   The Flex-Guide ET Tube Introducer (Green Field Medical Sourcing, Inc., Northborough, MA) is a single use 60 cm length of flexible polyethylene tubing (5.0 mm in diameter) with a similar distal coudé tip as the Eschmann Tracheal introducer.¹²

   
   
2. 
   

   The Muallem Stylet (VBM Medizintechnik, Sulz am Neckar, Germany) (Figure 12–1B) is a single-use 65 cm long tracheal introducer with a soft distal coudé tip. Unfortunately, there is no published data comparing this device to other intubating guides.

   
   
3. 
   

   Frova Intubation Introducer (Cook^® Critical Care Inc., Bloomington, IN) is an intubating catheter with a coudé tip at the distal end (Figure 12–1C).¹³ It has a hollow lumen with side ports distally; Rapi-Fit^® adapters (luer lock and standard 15/22 mm) come with the device to permit oxygen insufflation in the event intubation cannot be achieved. It also has a removable internal rigid metal stylet (Figure 12–1D) to prevent kinking and damage during shipping and to increase stiffness, facilitating tracheal placement and ETT passage. The Frova Introducer has two sizes: the adult version for ETT with greater than 5.5 mm internal diameter (ID) and the pediatric version for ETTs 3 to 5 mm ID.

   
   
4. 
   

   Endotracheal Tube Introducer (Sun Med, Largo, FL) is similar to the EI in size and shape, but it is 10 cm longer (Figure 12–1E). This confers some advantage in employing the device as more of the device protrudes from the mouth making it easier to thread a standard 30 cm adult sized ETT and capture the proximal end of the introducer. It is stiffer than the EI, conferring an advantage in guiding the ETT, but at the same time serving to emphasize the importance of gentle maneuvers to prevent airway injury. There markings on the device to indicate the depth of insertion. It is a single-use disposable device, though resterilization is possible.

   
   
5. 
   

   The Aintree Catheter (Cook^® Critical Care, Inc., Bloomington, IN) is also a hollow flexible straight tube designed for tracheal intubation together with a pediatric bronchoscope through an extraglottic device (EGD) such as the LMA-Classic or LMA-Unique. The Aintree Catheter can be advanced over a pediatric tube exchanger to obtain additional stiffness to facilitate advancement of an ETT over the pliable tube changer. Because of the hollow tube, it can also be used to oxygenate patients under difficult circumstances through the inner lumen and the distal ports after fitting the provided adaptor at the proximal end (Figure 12–1F).

   
   
6. 
   

   The Cook Airway Exchange Catheter (Cook^® Critical Care, Inc., Bloomington, IN) is a hollow flexible straight tube (with no coudé tip bend at the distal end) designed as a tube exchanger for patients with difficult airways (Figure 12–1G). It can be used to oxygenate patients under difficult circumstances through the inner lumen, distal ports, and an adapter at the proximal end.

   
   
7. 
   

   The Sheridan Tube Exchanger (Sheridan Catheter Corp., Oregon, NY) serves a similar function as the Cook Airway Exchange Catheter.

   
   
8. 
   

   The Schroeder (Parker Flex-It™ Directional Stylet) Oral/Nasal Directional Stylet (Parker Medical, Englewood, CO) is a disposable articulating stylet that requires no bending prior to intubation (Figure 12–2). Inserting the stylet into an ETT allows the practitioner to elevate the tip of the ETT by wrapping the index and middle fingers around the proximal tracheal tube and using the thumb to depress the proximal end of the stylet. Although the stylet is suitable for both oral and nasal intubation, it has been reported to be somewhat awkward to use and the curvature created is not at the tip, but rather over the distal half of the tube.¹⁴ However, it has been reported to be effective for difficult as well as blind intubations.¹⁵

   
   
9. 
   

   Portex intubation stylet (SIMS Portex Ltd, Hythe, Kent, UK) is available in outer diameter sizes ranging from 2.2 to 5.0 mm. These stylets can be inserted into a variety of endotracheal tubes. Blind awake orotracheal intubation has been successfully performed utilizing a stylet loaded into an ETT, in a patient with a laryngeal carcinoma and ankylosing spondylitis.¹⁶ Guided tactile probing is used to direct the ETT-stylet unit into the trachea.

Is There Any Clinical Evidence to Support the Widespread Use of These Intubating Introducers?

Over the last several decades, numerous studies have reported the effectiveness and safety of employing an EI to facilitate tracheal intubation in patients with difficult laryngoscopy.^17–20 The EI has been well accepted by most practitioners in the United Kingdom, and it continues to play an important role in the management of the difficult laryngoscopic intubation. According to a recent survey in the United Kingdom, 100% of the respondents reported the use of the EI as their technique of choice when faced with an unanticipated difficult laryngoscopic intubation.²¹ Though primarily a device used by anesthesia practitioners in the past, over the past decade this relatively inexpensive and simple device has found its way to the hands of emergency practitioners and pre-hospital health care practitioners as a standard airway management adjunct.^22–24 A telephone survey of emergency departments in England revealed that 99% of respondents stocked the EI on their difficult airway carts.²⁵

Following a review of the evidence, the Difficult Airway Society Guidelines for Management of the Unanticipated Difficult Intubation in the United Kingdom recommend the use of the EI as the initial device to facilitate a difficult laryngoscopy.²⁶ Many authorities recommend that this device be a standard piece of equipment for every laryngoscopic intubation.

While the EI has been widely accepted as a useful tracheal intubation adjunct, other types of introducers bearing similar features do not share the same popularity. This may be due to a paucity of clinical evidence supporting their use compared to the EI. In addition, most of these new intubating guides and stylets are disposable devices intended for single use and perhaps less cost-effective than the reusable EI.

What Are the Potential Limitations of These Intubating Guides and Introducers?

The popularity of the EI rests on its simplicity, ease of use, high success rates, and relatively few complications. However, it does have limitations.

The much-anticipated “clicks” and the “holdup” as described by many may prove elusive. The appreciation of clicks is particularly subtle in many patients. In 1988, Kidd et al.²⁷ studied the reliability of these signs. They found that “holdup” was observed in 100% of tracheal EI placement, whereas “clicks” were appreciated in only 90%. Importantly however, neither was observed in any of the 22 esophageal placements. It is also possible that “holdup” might occur with esophageal placement of the EI in cases of esophageal stenosis, pharyngeal pouch or diverticulum, or with cricoid pressure, although one would anticipate these occurrences would be rare. Practitioners should be aware of these limitations, particularly where “holdup” can occur without the presence of “clicks.” It is the opinion of the author (ORH) that the probability of feeling the “clicks” with EI placement into the trachea depends largely on the angle of insertion of the EI relative to the trachea. It is unlikely that the tip of the EI will “rub” against the tracheal rings if the EI is advancing into the trachea from a more vertical position. It is also related to the degree to which the EI contacts other soft tissues in the airway (e.g., tongue or lip) insulating against the transmission of the subtle tactile sensation.

Although complications are rare with these devices, they tend to occur when they are used improperly. Soft tissue lacerations, esophageal perforation, and tracheo-bronchial tree injuries have been reported with aggressive insertion of the EI and forceful “railroading” of the ETT over the EI.^28–30 The incidence of these complications can be minimized by employing a gentle advancement technique, and using the laryngoscope to move soft tissues out of the way to improve the angle of insertion of the ETT over the EI. Tip detachment has also been reported. Gardner et al.³¹ reported a detachment of the tip of the EI following its withdrawal. The tip was initially identified just above the bifurcation of the trachea, although it was later documented to have moved into the right middle lobe bronchus. Manually checking the integrity of the tip of the EI prior to use is recommended.

Are There Any Clinical Differences Between the EI and Other Introducers with Identical Features?

Inspired by the simplicity and effectiveness of the EI, many newer introducers (e.g., the Frova Intubation Introducer and the Sun Med Endotracheal Tube Introducer) share similar characteristics such as the J (coudé) tip at the distal end. By and large, these newer devices are made of different materials and are designed for single use. The Frova Intubation Introducer and the Cook Airway Exchange Catheter are hollow intubating introducers that permit urgent oxygenation and ventilation should the tracheal tube fail to advance into the trachea over the introducer. In addition to the “tracheal clicks” and “holdup” of the introducers during the insertion into the trachea, an aspiration test using a self-inflating bulb (SIB; also known as an Esophageal Detection Device [EDD]) can also be used with the hollow intubating introducers to further confirm tracheal placement. Tuzzo et al.³² reported that a prompt and complete reinflation of the SIB failed to occur when the hollow intubating introducer was placed accidentally into the esophagus with 100% sensitivity and at a 3.5% false positive rate. While these newer devices appear to function similarly to the EI in facilitating tracheal intubation, they may not have comparable success rates. Using a simulated C/L Grade 3 laryngoscopic view in a manikin, a comparative study showed that successful placement of the Frova Introducer (65%) and the EI (60%) was significantly higher than with the Portex Introducer (8%).¹² A separate experiment also revealed that the peak force exerted by the Frova and Portex introducers was two to three times greater than that which could be exerted by the EI, suggesting that placement of the single-use introducers may be more traumatic.

What Is a Lightwand? How Does It Help with the Placement of an Endotracheal Tube?

The technique of transillumination using a lightwand (lighted-stylet) was first described by Yamamura et al.³³ in 1959 with nasotracheal intubation. The lightwand employs the principle of transillumination of the soft tissues of the anterior neck to guide the tip of the lightwand, and the mounted ETT, into the trachea. It also takes advantage of the anterior (superficial) location of the trachea relative to the esophagus.

When the tip of the ETT/lightwand (ETT/LW) combination enters the glottic opening, a well-defined circumscribed glow can be readily seen slightly below the thyroid prominence (Figure 12–3A). However, if the tip of the ETT/LW is in the esophagus, the transmitted glow is diffuse and cannot be readily detected under ambient lighting conditions (Figure 12–3B). If the tip of the ETT/LW is placed in the vallecula, the light glow is diffuse and appears slightly above the thyroid prominence. Using these landmarks and principles, the practitioner can guide the tip of the ETT easily and safely into the trachea without the use of a laryngoscope.

Are All Lightwands the Same?

Through the 1970s and 1980s, many versions of a lighted stylet had been introduced, including the Fiberoptic Malleable Lighted Stylet (Metropolitan Medical Inc., Winchester, VA), Fiberoptic Lighted-Intubation Stylet (Anesthesia Medical Specialties, Santa Fe, CA), Lighted Intubation Stylet (Aaron Medical, St. Peterborough, FL), Flexilum™ (Concept Corporation, Clearwater, FL), Tubestat™ (Xomed, Jacksonville, FL) (Figure 12–4), and Imagica Fiberoptic Lighted Stylet (Fiberoptic Medical Products, Inc., Allentown, PA). Some of these devices have proven to be effective and safe in placing an ETT both orally and nasally.^34–36 Even though favorable results have been reported with these devices, substantial limitations have been identified: (1) poor light intensity; (2) short length, limiting the use of the lightwand device to a short or cut ETT; (3) absence of a connector to secure the ETT to the lightwand device; (4) rigidity of the lightwand, hampering use of the devices with other techniques, such as light-guided nasal intubation; and (5) most lightwands were designed for single use, increasing the cost per intubation. For these reasons and others, intubation using a lightwand did not receive widespread popularity until the introduction of the Trachlight™ (TL) (Laerdal Medical, Wappingers Falls, NY) device in 1995.

What Are Some of the Unique Characteristics of the Trachlight™ Compared to Other Lightwand Devices?

The TL has a long and flexible wand with a retractable metal wire stylet and an improved light source. These features add flexibility, broaden the utility of the device for both oral and nasal intubation, make intubation easier, and permit the evaluation of the position of the tip of the ETT after intubation. To date, the TL has been the most popular and well-studied of the lightwands. Although the TL is no longer manufactured, a new version of the lightwand similar to the TL is being developed.^37,38 One of the authors (ORH) of this chapter was involved in the original design and development of the TL. For these reasons, much of the following discussion reflects this experience and bias toward the TL. Nevertheless, the concept and principles of intubation using transillumination is applicable to all other lightwands.

The (TL) consists of three parts: a reusable handle, a flexible wand, and a stiff retractable wire stylet (Figure 12–5). The power control circuitry and three triple “A” alkaline batteries are encased in the handle. A locking clamp located on the handle accepts and secures a standard 15-mm ETT connector. The stylet or “wand” consists of a durable, flexible plastic shaft with a bright light bulb affixed at the distal end, permitting intubation under ambient lighting conditions. After 30 seconds of illumination, the light bulb blinks to minimize heat production and provide a convenient reminder of elapsed time. Ensuring that the tip of the stylet is inside the distal tip of ETT enhances its heat safety profile. An animal study conducted in 1998 confirmed an absence of heat-related tissue histopathological changes suggesting that thermal injury following the use of the TL is unlikely.³⁹

A rigid plastic connector with a release arm at the proximal end of the TL handle allows adjustment of the wand along the handle and into the ETT when the release arm is depressed. Enclosed within the wand is a stiff but malleable, retractable wire stylet. When the stiff wire stylet is retracted, the wand becomes pliable, permitting the ETT to advance easily into the trachea. This may well be the most important feature of this lightwand device, since it significantly improves its ease of use and intubation success rate.

The retractable wire stylet stiffens the wand sufficiently so that it can be shaped in the form of a “field hockey stick” (Figure 12–5). This configuration directs the bright light of the bulb against the anterior wall of the larynx and trachea. In addition, the “hockey stick” configuration enhances maneuverability during intubation and facilitates the placement of the ETT through the glottic opening. However, once through the glottis, the “field hockey stick” configuration can impede further advancement of the tube into the trachea. Retraction of the stiff wire stylet produces a pliable ETT-TL unit, permitting its advancement into the trachea until the transilluminated glow reaches the sternal notch, a point known to be at the level of the mid-trachea.

How Do You Prepare the Trachlight™ Device?

As with any intubation technique, regular use of a lightwand improves the practitioner’s performance and intubation success rates, and reduces the risk of complications.

Lubrication of the internal wire stylet of the wand using silicone fluid (Endoscopic Instrument Fluid, ACMI, Southborough, MA) ensures its easy retraction during intubation. The wand should also be lubricated with the same silicone fluid to facilitate retraction of the wand following the ETT placement. The rail gear of the TL handle should always be inspected for missing fragments (prior to loading of the stylet, after retraction of the stylet).⁴⁰ Cutting the ETT to a length of 26 cm is recommended to facilitate maneuverability of the ETT-TL during oral tracheal intubation. The wand is then inserted into the ETT and the tube attached to the handle. The length of the wand is adjusted by sliding the wand along the handle to position the light bulb close to, but not protruding beyond, the tip of the ETT. With the TL in place, the ETT-TL unit is bent to a 90-degree angle just proximal to the cuff of the tube in the shape of a “field hockey stick” (Figure 12–5). Even though the degree of bend should be individualized to the patient, a 90-degree angle generally makes the intubation considerably easier and projects the maximum light intensity toward the surface of the skin as the device traverses the glottis and trachea, producing a well-defined exterior circumscribed glow. If the TL is bent to 45 degrees, the maximum light intensity will be directed down the trachea. For obese patients or patients with short necks, a more acute bend (greater than 90 degrees) provides better transillumination. Although it is the author’s experience that the recommended length of the TL from bend to tip of 6.5 to 8.5 cm is suitable for most patients, some investigators have suggested that the length from bend to tip is best established by matching it to the patient’s thyroid prominence-to-mandibular angle distance.⁴¹

How Do You Use the Trachlight™ to Perform Tracheal Intubation?

Although the practitioner usually stands at the head of the table or bed during lightwand intubation, it is possible to employ this technique from the front or side of the patient, in the pre-hospital environment for instance. When the head is in the sniffing position, the epiglottis is in close contact with the posterior pharyngeal wall making it more difficult for the TL to advance behind the epiglottis. It is preferable that the patient’s head and neck be positioned in a neutral or slightly extended position.

In most cases, patients can be intubated easily under ambient lighting conditions.⁴² In very thin patients, the light intensity is so bright that it is possible to mistakenly interpret an esophageal intubation as an intratracheal placement. It is therefore recommended that intubations using the TL in otherwise normal individuals be carried out under ambient light. Dimming room lights may be advantageous in obese patients, patients with thick necks or dark skin, or when the technique is being learned. In settings where controlling the ambient lighting is not possible (e.g., pre-hospital), it may be helpful to shade the neck with a towel or a hand.

Denitrogenation of the patient should precede all light-guided intubations. In an unconscious patient lying supine, the tongue falls posteriorly, pushing the epiglottis against the posterior pharyngeal wall (Figure 12–6). In order to have clear access to the glottic opening during intubation, it is necessary for the practitioner to grasp the jaw and lift it upward using the thumb and index finger of the nondominant hand. This lifts the tongue and epiglottis away from the posterior pharyngeal wall to facilitate placement of the tip of the ETT posterior to the epiglottis and into the glottic opening (Figure 12–7). The ETT-TL unit is then inserted into the midline of the oropharynx. The midline position of the ETT-TL is maintained while the device is advanced gently in a rocking motion along an imaginary anterior–posterior arc. When resistance to cephalad rocking of the handle is felt, the ETT-TL handle should be “rocked” forward (toward the feet) and the tip redirected toward the laryngeal prominence using the glow of the light as a guide. A faint glow seen above the laryngeal prominence indicates that the tip of the ETT-TL is located in the vallecula. When the tip of ETT-TL enters the glottic opening, a well-defined circumscribed glow can be seen in the anterior neck slightly below the laryngeal prominence (Figure 12–8). Retracting the inner stiff wire stylet approximately 10 cm makes the ETT-TL tip more pliable, permitting advancement into the trachea with reduced risk of trauma. The ETT-TL is then advanced until the glow begins to disappear at the sternal notch indicating that the tip of the ETT is approximately 5 cm above the carina in the average adult.⁴³ Following release of the locking clamp, the TL wand can be removed from the ETT.

Occasionally, the circumscribed glow cannot be readily seen in the anterior neck due to anatomical features such as morbid obesity or a short neck. Neck extension as described above may be helpful. Retraction of the breast or chest wall tissues together with “spreading” of the tissues around the trachea by an assistant enhances transillumination of the soft tissues in the anterior neck. Dimming the ambient light is seldom required.

Occasionally, following retraction of the stiff wire stylet, the tip of the tube and lightwand can “hang up” on laryngeal structures, the cricoid ring, or a tracheal ring and cannot be advanced into the trachea readily. This is likely due to the fact that when an ETT is loaded along its natural curvature onto the TL, the tip of the ETT has a tendency to bend anteriorly upon retraction of the stiff internal stylet. While maintaining tube tip contact with the anterior airway, the practitioner should rotate the ETT-TL 90 degrees or more to the right or the left side permitting the tip of the ETT to alter the orientation of the tube tip perhaps enhancing the chance that the ETT will enter the trachea. Alternatively, immersing the ETT in warm saline solution prior to tracheal intubation will reduce its stiffness and the memory of its natural curvature. In addition, reverse loading of the ETT onto the TL. may minimize the tendency of the ETT tip to bend anteriorly while retracting the internal stiff stylet of the TL. The combination of softening and reverse loading of the ETT has been shown to overcome the problem of “hang up” during intubation with the TL.⁴⁴

Can the Trachlight^™ be Used for Nasotracheal Intubation? How Do You Use the TL to Perform a Nasotracheal Intubation?

In contrast to other commercially available lightwands, once the stiff internal wire stylet is removed, the wand of the TL becomes pliable and able to facilitate a light-guided nasotracheal intubation. When used with a nasal RAE (Ring, Aldair, and Elwyn) ETT, the inner wire stylet should be inserted halfway (about 15 cm) to allow unbending of the proximal curvature of the nasal RAE tube (Figure 12–9). Application of a vasoconstricting nasal spray to the nasal mucosa prior to intubation may help to minimize bleeding. The ETT-TL should be immersed in a bottle of warm sterile water or saline to soften the ETT and reduce the risk of mucosal damage during nasal intubation. Water-soluble lubricant is applied to the nostril to facilitate entry of the ETT-TL through the nose. As with oral intubation, a jaw lift during intubation will elevate the tongue and epiglottis away from the posterior wall of the pharynx (see Figure 12–7), facilitating the placement of the tip of the ETT behind the epiglottis and into the glottic opening. The TL is switched on once the tip of the ETT-TL has advanced into the oropharynx, positioned in the midline, and advanced gently using the light glow as a guide. A faint glow seen above the laryngeal prominence indicates that the tip of the ETT-TL is located in the vallecula. A jaw lift and slight withdrawal of the ETT-TL will help to elevate the epiglottis and enhance the passage of the ETT-TL under it. When the ETT-TL enters the glottic opening, a well-defined circumscribed glow is seen in the anterior neck just below the thyroid prominence (Figure 12–10). Following the release of the locking clamp, the TL is withdrawn from the ETT. Correct tube placement should be confirmed using end-tidal CO₂ and auscultation.

What Are the Common Problems with a Blind or Light-Guided Nasotracheal Intubation? How Do You Overcome These Problems?

Due to the natural curvature of the ETT, the tip of the tube often goes posteriorly into the esophagus during a “blind” or light-guided nasal intubation, despite external posterior pressure on the thyroid cartilage. To elevate the tip of the ETT anteriorly during intubation, it is sometimes necessary to flex the neck of the patient while advancing the ETT-TL slowly. In the event that flexing the neck of the patient is contraindicated, inflating the ETT cuff with 15 to 20 mL of air will help to elevate the ETT tip and align it with the glottis during intubation.^45,46 Alternatively, the use of a directional-tip tube, such as an Endotrol™ tube (Mallinckrodt Critical Care, Inc., St. Louis, MO), flexes the tube tip anteriorly and into the glottis.⁴⁷ In certain circumstances (e.g., tube tip impingement in the posterior nasopharynx), nasotracheal intubation using the TL can be performed safely with the stiff, internal stylet in place.⁴⁸ This technique may be associated with fewer head–neck manipulations and deliver better control of the tip of the ETT.

What Are the Limitations of the Lightwand Intubating Technique?

The lightwand intubating technique requires transillumination of the soft tissues of the anterior neck without visualization of the laryngeal structures. Therefore, lightwand should not be used in patients with known abnormalities of the upper airway, such as tumors, polyps, infection (e.g., epiglottitis, retropharyngeal abscess), and trauma to the upper airway, or if there is a foreign body in the upper airway. In these cases, alternate intubating techniques using direct or indirect vision, such as bronchoscopic intubation, should be considered. Lightwand should also be used with caution in patients in whom transillumination of the anterior neck may not be adequate, such as patients who are grossly obese or with a limited neck extension. However, these contraindications and precautions must be weighed in the light of the urgency of achieving a patent airway in any patient whose ventilation may be compromised and urgent intubation is required. Clearly, this light-guided technique should not be attempted with an awake uncooperative patient unless a bite block is used to prevent damage to the device or injury to the practitioner.

Since its introduction in 1995, the TL has been used extensively in many countries. While the potential risks of damage to the glottic opening during tracheal intubation using a “nonvisual” intubating technique is real, there have been no serious complications reported. Aoyama et al. used a nasally placed bronchoscope to visualize the airway during TL intubation. They reported that the epiglottis may be pushed into the laryngeal inlet by the ETT-TL during a TL intubation.⁴⁹ Fortunately, the epiglottis usually spontaneously returned to its correct position. They also reported that structures around the glottic opening, including the epiglottis and the arytenoids, were transiently displaced during the placement of the ETT using the TL. The investigators concluded that there are potential risks of laryngeal damage in addition to the down folding of the epiglottis during the ETT placement using the TL, but such occurrences do not appear to cause permanent damage. Other investigators have identified a reduced incidence of sore throat in patients intubated using the TL compared to laryngoscopic intubation.⁴²

Intubation using a lightwand device has other potential risks. Stone et al.⁵⁰ reported disconnection of the light bulb from a lightwand requiring retrieval from a major bronchus. However, the lightwand device employed in this instance (Flexilum™) was not designed or recommended for tracheal intubation. A later version of the same device solved the problem of bulb loss into the trachea by encasing stylet and bulb in a tough plastic sheath (Tubestat™). In contrast to the older lightwand devices, it is extremely unlikely that the light bulb will be detached from the TL, since the light bulb is firmly attached to the durable plastic sheath of TL. In fact, since its introduction in 1995, there have been no reported cases of detached light bulb from the TL. Although rare, subluxation of the cricoarytenoid cartilage has been reported in a study using an older version of a lightwand (Tubestat™).⁵¹ However, with the retractable wire stylet, the risk of damaging the arytenoid cartilage during TL intubation should be low.

Is There Any Clinical Evidence to Suggest That the Lightwand Is an Effective and Safe Intubating Device?

A large clinical study involving 950 elective surgical patients conducted to determine the effectiveness and safety of orotracheal intubation using either the TL or direct-vision intubation using a laryngoscope,⁴² showed a statistically significant difference in the total intubation time between the groups (15.7±10.8 vs. 19.6±23.7 seconds for TL and laryngoscopy, respectively). However, such a small difference is probably of little clinical importance. There was a 1% failure rate with the TL and 92% success rate on the first attempt, compared with a 3% failure rate and an 89% success rate on the first attempt using the laryngoscope. There were significantly fewer traumatic events and sore throats in the TL group compared to laryngoscopy patients. Tsutsui et al.⁵² reported similar findings in a study with 511 patients. TL intubation was highly successful (99%) with the majority of the successful intubations (93%) being accomplished after one attempt. Unsuccessful intubation even at the third attempt occurred in only three patients (1%).

In 1995, Hung et al.⁵³ reported the effectiveness of TL intubation in 265 patients with a “difficult” airway (206 patients with a documented history of difficult intubation or anticipated difficult airways and 59 anesthetized patients with an unanticipated failed laryngoscopic intubation). Tracheal intubation was successful in all patients except two in the anticipated difficult laryngoscopic intubation group. Apart from minor mucosal bleeding (mostly from nasal intubation), no serious complications were observed in any of the study patients. The results of this study indicate that TL is an effective technique for placement of ETTs (nasally and orally) for patients with both anticipated or unanticipated difficult airways. Other investigators have reported successful use of the TL in patients with a difficult airway. These include patients with a history of limited mouth opening,⁵⁴ cervical spine abnormality,⁵⁵ Pierre-Robin syndrome,⁵⁶ and cardiac patients with a difficult airway.⁵⁷

What Are Some of the Potential Uses of the Trachlight™?

Tracheal intubation can fail with TL as well as with the laryngoscope. However, one study of 950 patients showed that all TL failures were resolved with direct laryngoscopy.⁴² Similarly, all failures of direct laryngoscopy were resolved with TL. These results suggest that a tracheal intubation success rate approaching 100% can be achieved by combining the techniques. This combined approach may be particularly useful when an unanticipated Cormack/Lehane (C/L) Grade 3 laryngoscopic view is encountered.⁷ Instead of using a styleted ETT with a 90-degree bend, one might employ an ETT-TL with the same bend. Under direct laryngoscopy, the tip of the ETT-TL can be “hooked” under the epiglottis. A well-defined circumscribed glow seen in the anterior neck slightly below the laryngeal prominence indicates that the tip of the ETT is placed at the glottic opening. In the event that such a glow is not seen, the ETT-TL can be repositioned until it can be seen. The effectiveness of this combined technique has been reported by Agro et al.⁵⁸ In this study, the investigators successfully performed tracheal intubation in all 350 surgical patients studied with a simulated difficult airway using a combined laryngoscope/TL approach.