Chapter 11. Nonvisual Intubation Techniques

11.1.1 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 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 prehospital care (ie, they may be context driven).

The challenge of visual techniques employing optical stylets and videoscopes is visualization of glottic structures and the passage of the Eschmann Tracheal Tube Introducer 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.

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

In 1949, Macintosh reported the use of an introducer (gum-elastic bougie) to facilitate orotracheal intubation under direct laryngoscopy.4 Using the concept of the introducer, Venn designed the Eschmann introducer (endotracheal tube [ETT], Portex Limited, Hythe, UK), a tubelike core woven from polyester threads and covered with a resin layer.5 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 11-1). 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 (eg, Grade 3 laryngoscopic view as described by Cormack).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 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 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 (eg, cricothyrotomy).10,11

11.2.2 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 ETT introducer (Green Field Medical Sourcing, Inc., Northborough, MA) is a flexible plastic introducer with a distal tip that can be bent by means of a proximal handle.12

2. The Sheridan tube exchanger (Sheridan Catheter Corp., Oregon, NY) is a hollow flexible straight tube designed as a tube exchanger for patients with difficult airways. It can be used to ventilate patients under difficult circumstances through the inner lumen, distal ports, and an adapter at the proximal end.

3. The Cook airway exchange catheter (Cook® Critical Care, Inc., Bloomington, IN) serves a similar function as the Sheridan tube exchanger (Figure 11-1).

4. Frova intubation introducer (Cook® Critical Care Inc., Bloomington, IN) is an intubating catheter with a coudé tip at the distal end (Figures 11-1 and 11-2).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 metal stylet to prevent kinking and damage during shipping and to increase stiffness, facilitating tracheal placement and ETT passage (Figure 11-2). 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.

5. 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 11-3). 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

6. Endotracheal tube introducer (Sun Med, Largo, FL) is similar to the EI in size and shape, but it is 10 cm longer. 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 is a single marking at 20 cm on the device to indicate the depth of insertion. It is a single-use disposable device, though resterilization is possible (Figure 11-1).

7. Portex intubation stylet (SIMS Portex Ltd, Hythe, Kent, UK) is available in outer diameter sizes ranging from 2.2 mm 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.

11.2.3 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 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 prehospital health-care practitioners as a standard airway management adjunct.22-24 A telephonic survey of emergency departments in England revealed that 99% of respondents stocked the EI on their difficult airway carts.25

Following a recent 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.

11.2.4 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 studied the reliability of these signs.27 They found that holdup was observed in 100% of tracheal EI placement, whereas clicks were appreciated in only 90%. Importantly, however, neither were 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 (eg, 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 reported a detachment of the tip of the EI following its withdrawal.31 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.

11.2.5 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 (eg, the Frova intubation introducer, and the 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 recently 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.32 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 Grade 3 laryngoscopic view in a manikin, a recent 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.

11.3.1 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 in 1959 with nasotracheal intubation.33 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 11-4A). 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 11-4B). 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.

11.3.2 Are All Lightwands the Same?

Through the 1970s and 1980s, many versions of a lighted stylet had been introduced, including the Fiberoptic Malleable Lighted Stylette (Metropolitan Medical Inc., Winchester, VA), Fiberoptic Lighted-Intubation Stylette (Anesthesia Medical Specialties, Santa Fe, CA), Lighted Intubation Stylet (Aaron Medical, St. Peterborough, FL), Flexilum™ (Concept Corporation, Clearwater, FL), Tubestat™ (Xomed, Jacksonville, FL) (Figure 11-5), 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 Trachlight™ (Laerdal Medical, Wappingers Falls, NY) device became available.

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

The Trachlight™ (TL) consists of three parts: a reusable handle, a flexible wand, and a stiff retractable wire stylet (Figure 11-6). 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. A recent animal study confirmed an absence of heat-related tissue histopathological changes, suggesting that thermal injury following the use of the TL is unlikely.37

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 11-6). 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 midtrachea.

11.3.4 How Do You Prepare the Trachlight™ Device?

One of the authors (ORH) had significant involvement in the development of the TL, as reflected in the following narrative des-cribing intubation technique using the TL. Although the Trachlight™ device is no longer available, a newer version of the device is currently being developed. In addition, the technique described can be applied to other lightwand device that employs the concept of transillumination-guided tracheal intubation. As with any intubation technique, regular use of a TL improves the clinician'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).38 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 11-6). 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 (>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.39

11.3.5 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 prehospital 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.40 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 (eg, prehospital), 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 11-7). 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 11-8). 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 11-9). 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.41 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 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 Trachlight™, 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 clinician 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 Trachlight™ may minimize the tendency of the ETT tip to bend anteriorly while retracting the internal stiff stylet of the Trachlight™. The combination of softening and reverse loading of the ETT has been shown to overcome the problem of hang up during intubation with the Trachlight™.42

11.3.6 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 lighted stylets, 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 11-10). 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, 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 11-11). 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.

11.3.7 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 20 mL of air will help to elevate the ETT tip and align it with the glottis during intubation.40,43,44 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.45 In certain circumstances (eg, tube tip impingement in the posterior nasopharynx), nasotracheal intubation using the TL can be performed safely with the stiff, internal stylet in place.46 This technique may be associated with fewer head-neck manipulations and deliver better control of the tip of the ETT.

11.3.8 What Are the Limitations of the Trachlight™ Intubating Technique?

The TL intubating technique requires transillumination of the soft tissues of the anterior neck without visualization of the laryngeal structures. Therefore, TL should not be used in patients with known abnormalities of the upper airway, such as tumors, polyps, infection (eg, epiglottitis, retropharyngeal abscess), and trauma to the upper airway, or if there is a foreign body in the upper airway. In these cases, alternative intubating techniques using direct or indirect vision should be considered. TL 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.47 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.40

Intubation using a lightwand device has other potential risks. Stone et al reported disconnection of the light bulb from a lightwand requiring retrieval from a major bronchus.48 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™).49 However, with the retractable wire stylet, the risk of damaging the arytenoid cartilage during TL intubation should be low.

11.3.9 Is There Any Clinical Evidence to Suggest that the Trachlight™ 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 laryngoscope36,40 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 reported similar findings in a study with 511 patients.50 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 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).51 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,52 cervical spine abnormality,53 Pierre-Robin syndrome,54 and cardiac patients with a difficult airway.55

11.3.10 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.40 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 styletted 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.56 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.

The TL has been combined successfully with other intubating techniques including intubation through the LMA Classic™,57,58 use in conjunction with the intubating LMA (Fastrach™),59 with the Bullard laryngoscope,60,61 and with a retrograde intubating technique.62

Recently, the TL has been shown to be useful in identifying the intratracheal position of the ETT tip during percutaneous dilational tracheotomy.63 The TL wand without the stiff wire stylet is passed through the in situ ETT matching the length numbers on the ETT to position the TL tip at the ETT tip. This simple technique may help to prevent inadvertent punctures of the ETT and/or its cuff, ensuring that adequate ventilation and oxygenation can be reinstituted during the percutaneous procedure if required. This technique is inexpensive and minimizes the risk of damaging expensive equipment ordinarily used during procedures such as the flexible bronchoscope. Used properly, it is possible that this simple light-guided technique can also be used to accurately determine when the tip of the ETT is above the surgical tracheotomy site as the tube is pulled back during surgical tracheotomy.

11.4.1 What Is Digital Intubation? When Was It Introduced?

Airway management has been revolutionized by the abundance of extraglottic devices that not only facilitate effective ventilation but also aid tracheal intubation. Despite these advances, certain situations may make the blind insertion of an ETT into the trachea using the digits of the hand (digital intubation or tactile orotracheal intubation) as a suitable alternative method of securing an airway.

It is believed that this technique was first described by Herholt and Rafn in 1796 in drowning victims. It surfaced as a viable method of intubation in the emergency medicine literature in the mid 1980s.64,65 Blind digital intubation has also been used to establish an airway during neonatal resuscitation66 and as an adjunct in blind nasotracheal intubation.67

11.4.2 What Are the Indications for Digital Intubation?

The skill levels of the practitioner, coupled with previous experience in using the technique of blind digital intubation are important prerequisites for success. The importance of practicing this technique in nonemergency situations cannot be overemphasized. The risk of infectious disease transmission must always be borne in mind. Awake patients with an intact gag reflex are not suitable for this technique. Muscle paralysis may be helpful in certain situations. The following list briefly describes the clinical situations where blind digital intubation may be used to establish a patent airway:

1. Inadequate access to a patient that prevents standard laryngoscopic techniques from being used.

2. Lack or failure of other airway management devices.

3. Inability to secure an airway with laryngoscopic techniques or extraglottic devices.

4. In the setting of cervical spine instability in an unconscious patient.

5. When blood, secretions, vomitus, or pus make adequate visualization of the glottis impossible.

11.4.3 How Do You Perform Digital Intubation?

The skilled practitioner ensures that an oxygen source, rescue airway devices, suction, and emergency drugs are immediately at hand. In-line immobilization should be performed in the setting of cervical spine instability. Cricoid pressure should be applied where clinically indicated. Although digital intubation can usually be performed without other adjuncts (Figure 11-12), the classic description of blind digital intubation requires a malleable stylet to be inserted into the ETT.68 The ETT is then bent into a shape such that it can elevate the epiglottis and enter the trachea. Alternatively, as the authors believe, an intubating guide (eg, the EI) together with an appropriately sized ETT is a simpler technique. The advantage of this latter technique is that it is easier to guide an EI through the glottic opening, and then railroad the ETT into the trachea than it is to place a stylet-ETT combination in the trachea. The intubating guide has a small external diameter and is easily manipulated with the fingers to enable passage through the vocal cords. In addition, the clicks felt as the intubating guide (eg, EI) advances over the tracheal rings combined with holdup will assist in confirmation that the EI has entered the trachea. The ETT with the malleable stylet is rigid and perhaps more likely to cause blunt trauma to the airway structures, especially if repeated manipulation is necessary for successful entry into the trachea.

To perform the procedure:

1. The patient's head should be placed in the sniffing position as for standard laryngoscopic intubation except in situations where cervical instability exists.

2. The practitioner stands or kneels adjacent to the patient (facing the patient's head) so that the nondominant side of the intubator is closest to the patient (Figure 11-13).

3. If available, an assistant can grasp and pull the tongue forward using gauze. This maneuver helps to lift the epiglottis anteriorly and makes palpation of the structures of the upper airway easier.

4. The practitioner then places the index and middle fingers of the nondominant hand into the patient's mouth. Once the epiglottis is palpated by the middle finger, it is lifted in an anterior direction.

5. The intubating guide is then guided into the mouth along the palmar surface of the index finger of the nondominant hand.

6. The index finger of the nondominant hand is then flexed to steer the intubating guide under the epiglottis and into the trachea (Figure 11-13). Occasionally, the middle finger of the nondominant hand lifting the epiglottis has to be moved slightly laterally to allow successful passage of the intubating guide.

7. The clicks on the tracheal rings and holdup of the intubating guide on the lower bronchial tree serve as indicators of correct tracheal placement.

8. The ETT is then railroaded over the intubating guide into the trachea. Maintaining anterior displacement of the epiglottis facilitates ETT passage.

9. Confirmation of successful tracheal intubation should be determined by end-tidal CO2 detection.

11.4.4 Can Digital Intubation Be Performed on a Child?

Although the principles and techniques of digital intubation are similar, digital intubation can readily be performed without the use of a stylet or the EI in children. Hancock et al have employed this technique during neonatal resuscitation and accidental extubation scenarios.66 Digital intubation of neonates and infants can be considered in situations where direct laryngoscopic techniques have failed, airway equipment failure has occurred, for meconium aspiration in the neonate, or during transport when inadequate access may preclude conventional techniques.

11.4.5 What Are the Limitations of Digital Intubation?

Although digital intubation is a simple and easy to learn technique, it is difficult to perform when the epiglottis cannot be identified or felt during intubation. This is particularly true for the patients who are excessively tall or with a full set of maxillary incisors and a small mouth opening. The procedure can also be difficult to perform if the practitioner has short or large fingers in relation to the patient's anatomy.

To minimize the risk of injury to the practitioner's fingers, digital intubation is generally contraindicated for patients who are awake and uncooperative. However, in emergency situations when limited equipment is available, a digital intubation may be an option with a bite block in place.

11.5.1 What Are the Indications for Blind Nasal Intubation?

The technique of blind nasal intubation was first popularized by Sir Ivan Magill and Stanley Rowbotham in the 1920s. This method of tracheal intubation has proved life saving in many difficult airway situations. Maintenance of spontaneous ventilation facilitates blind nasal intubation. The experience and skill of the practitioner are key determinants for success with this technique. The following is a list of indications for blind nasal intubation:

1. Elective oral, pharyngeal, and dental surgery

2. When the oral route is difficult or impossible (eg, limited mouth opening or severe masseter spasm)

3. Difficult airway—elective or unanticipated

11.5.2 What Are the Contraindications of Blind Nasal Intubation?

The following may contraindicate blind nasal intubation, although all are relative:

1. Inadequate experience or skill of the practitioner

2. Base of the skull cranial fractures

3. Severe maxillofacial fractures with distorted nasal or midface anatomy

4. Known or suspected nasal obstruction secondary to pathology (eg, massive nasal polyps or tumors)

5. Bleeding diathesis secondary to hematological disease or anticoagulant medication

11.5.3 Which Nostril Should Be Used for Blind Nasal Intubation?

As most practitioners are right handed, naturally, most would favor the use of the right hand to advance the ETT through the right nostril while using the left hand to feel the anterior neck to assess the position of the tip of the ETT during blind nasal intubation. In the absence of a septal abnormality (eg, a septal deviation), traditional teaching also suggests the right nostril over the left for nasal intubation.69 It is generally felt that the left-facing bevel of the tracheal tube is the main cause of nasal trauma. The mucosa over the turbinates is highly vascular and can be easily traumatized. It is likely that the mucosa over the left turbinate is particularly at risk during left-sided intubation since the bevel tends to impact directly against it. So, to minimize trauma, most practitioners would insert the ETT with the bevel facing the flat nasal septum rather than facing the irregularly shaped turbinates along the lateral wall of the nasal cavity. However, others consider that the tip of the tracheal tube is more likely to cause nasal trauma than the bevel and therefore it is more reasonable to have the tip of the ETT to advance alongside the septal mucosa during intubation. Hence, some practitioners choose to advance the ETT through the left nostril during nasal intubation. Unfortunately, no scientific evidence currently exists to suggest that one nostril is safer than the other for nasal intubation in patients with a normal nasal anatomy.70 Instead of debating which is the preferred nostril to minimize the risk of injury, it is perhaps more important to properly prepare the ETT (eg, selecting an appropriate size ETT and softening the ETT in warm saline or water) and the patient (eg, apply vasoconstrictor to the nostrils prior to performing the nasal intubation), resist excessive force during intubation, and change to a different nostril or use a smaller ETT when it becomes necessary.

11.5.4 How Do You Perform a Blind Nasal Tracheal Intubation?

The answer to this question is largely determined by the indication for tracheal intubation. In elective situations, the nares are best prepared with a vasoconstrictor (though there is little evidence that this maneuver reduces bleeding or enhances success rates) and a local anesthetic of choice. In emergency situations with life-threatening hypoxemia, this may not be possible. The potential for severe epistaxis with airway hemorrhage must always be borne in mind. Rescue airway equipment including extraglottic devices and surgical airway kits should be available. Vital sign monitors are attached and the patient is fully denitrogenated if practical prior to the procedure being undertaken. Cervical spine precautions and cricoid pressure should be instituted as indicated. Maintenance of spontaneous ventilation is preferred to assist with successful tracheal intubation. Confirmation of tracheal tube placement is obtained by the usual clinical criteria as well as CO2 detection methods. Some practitioners fully insert their little finger to gently dilate the nostril, minimize bleeding on tube insertion, and identify mid nares or posterior nares anatomical abnormalities that would preclude use of that nostril.

To perform the procedure:

1. Insert the appropriate size ETT into the naris.

2. Gently advance the ETT. If resistance is met, do not use excessive force. This may mean that the tip of the ETT has entered the depression in the nasopharynx where the eustachian tube enters (see Chapter 3). Consider switching to the alternative nostril.

3. Listen for breath sounds as you advance the ETT. The author has successfully used a stethoscope attached to the ETT adaptor to auscultate for breath sounds during the procedure. The BAAM whistle (Beck Airway Airflow Monitor, Great Plains Ballistics, Inc., Lubbock, TX) to provide an auditory cue in the form of a to and fro whistle to facilitate nasotracheal intubation coupled with an Endotrol™ ETT (Mallinckrodt Medical Inc. Argyle, NY) has been reported.71 Careful inspection of the neck can also provide useful clues to the location of the tip of the ETT.

4. In the event that esophageal entry occurs repeatedly, the ETT can be withdrawn to the hypopharynx and the cuff of the ETT inflated to produce anterior displacement of the ETT tip toward the glottic opening.44 Neck flexion is a commonly used maneuver to aid in passage of the ETT into the trachea if the ETT repeatedly impinges anterior to the epiglottis. Neck extension is employed if the ETT repeatedly passes posterior to the glottis into the esophagus. An Endotrol™ ETT as described above may also be used in this situation.71 Clearly, this maneuver should not be performed in patients with known or suspected cervical pathology.

5. Confirm ETT placement once tracheal entry is suspected.

11.6.1 What Is Retrograde Intubation and When Was It Introduced?

In 1960, two surgeons, Butler and Cirillo, reported the first retrograde intubation in surgical patients through an existing tracheotomy opening.72 The technique was subsequently modified by Waters who performed a cricothyroid membrane puncture using a Touhy needle.73 Waters inserted an epidural catheter through the Touhy needle and advanced it cephalad so that the catheter was brought out through the mouth. An ETT was then advanced over the epidural catheter into the trachea while pulling both ends of the catheter taut. After the ETT entered the trachea, the catheter was pulled out through the oral cavity.

11.6.2 How Do You Perform a Retrograde Intubation?

To improve success rates for this technique, many modifications have been suggested since its introduction. For instance, the use of a guide wire rather than an epidural catheter, even though the authors continue to prefer an epidural catheter because it is substantially cheaper, more pliable, and perhaps less traumatic.

11.6.2.1 Equipment

Although a preassembled kit is commercially available, the list of equipment necessary for the retrograde intubation is summarized in Table 11-1.

11.6.2.2 Patient Preparation

In contrast to the sniffing position advocated for laryngoscopic intubation, the patient's head and neck should be in a neutral or relatively extended position to favor an epiglottic position that is off the posterior pharyngeal wall. The epiglottis is almost in contact with the posterior pharyngeal wall when the head is in the sniffing position, making it difficult for the ETT to go underneath the epiglottis. In obese patients or patients with an extremely short neck, placing a pillow under the shoulders and neck may be useful.

11.6.2.3 the "Classic" Technique

This technique can be used in patients who are awake under topical anesthesia with sedation or under general anesthesia.62,74 Although a cricothyroid membrane puncture can be performed using a blunt tip Touhy needle, the Angiocath is less traumatic and substantially easier to use. The cricothyroid membrane is punctured at an angle 90 degree to the skin using the 18-gauge Angiocath (or needle) in the midline position. Correct tracheal placement can be confirmed by aspirating a free stream of air bubbles in a fluid-filled syringe. Once the tracheal lumen is entered, the Angiocath needle is removed, leaving the catheter behind. The Angiocath catheter is then angled at 45 degree in a cephalad direction through which a 21-gauge epidural catheter (or a guide wire) can be inserted and advanced cephalad into the oropharynx. The epidural catheter can be readily retrieved from the mouth using the Magill forceps. After the removal of the Angiocath catheter from the anterior neck, and to avoid accidentally pulling the epidural catheter (or the guide wire) through, a hemostat is attached to the distal end of the epidural catheter or guide wire at the skin entry point. Similarly, a hemostat is attached to the epidural catheter or wire where it emerges from the mouth. The epidural catheter or guide wire is then inserted into the ETT. Lubrication of the tip of the ETT will facilitate its entry into the glottic opening. To elevate the tongue and epiglottis away from the posterior pharyngeal wall, the tongue of the patient is then gently pulled forward by an assistant if the procedure is performed under general anesthesia. While pulling the epidural catheter or the guide wire taut from both ends by an assistant, the ETT is inserted into the oropharynx in the midline position. When the tip of the ETT enters the glottic opening, the tension of the epidural catheter at the distal end should be relaxed and the ETT can be advanced gently into the trachea. (For the guide wire technique, the guide wire should be removed before advancing the ETT into the trachea.) While leaving the epidural catheter in place, correct placement of ETT is confirmed using end-tidal CO2. The epidural catheter is then removed through the mouth end of the ETT.

11.6.3 What Other Techniques Can Be Used to Improve the Success Rate of the Retrograde Intubation?

While retrograde intubation is simple technique, the success rate of tracheal intubation is unacceptably low. In a study involving 35 cadavers, Lenfant et al75 reported a success rate of 69% using the conventional guide wire technique. The investigators suggested that failures were likely due to incorrect positioning of the endotracheal tube. In addition, because of the short distance between the cricothyroid membrane and the vocal cords, the depth of insertion of the ETT is not much (<10 mm in adults74), and accidental extubation can easily occur during the removal of the guide wire with this technique.

A number of technique modifications have been suggested to improve the success rate of the retrograde intubation. These include the insertion of the epidural catheter (or guide wire) through the Murphy eye of the endotracheal tube76 from outside to inside to increase the length of ETT actually in the trachea, the use of a subcricoid puncture77 for the same reason, pulling rather than guided technique,78 and employing a multilumen catheter guide.79 To increase the stiffness and allow easier negotiation of the ETT through the oropharynx into the trachea, a tapered tip anterograde guide catheter (eg, pediatric tube changer) placed over the guide wire has been suggested to improve the effectiveness of retrograde intubation.74,80 Although these modifications are useful, they do not overcome the difficulty of determining the location of the tip of the ETT during intubation. Simultaneous visualization of the ETT passage can be achieved if a flexible endoscope is placed through the nose beforehand.

Retrograde intubation using a guide wire passed retrograde through the working channel of a flexible bronchoscope has also been shown to be effective as the tip of the ETT can be guided into the glottis under indirect vision.81-83 However, the bronchoscope is expensive and the retrograde passage of the guide wire through the working channel of the bronchoscope can potentially damage the internal lining of the channel.84 In addition, visualization of the laryngeal structures through a bronchoscope can also be difficult in the presence of blood and secretions.

The tip of the ETT can also be guided into the trachea using transillumination. The placement of the bulb of a lightwand at the tip of the ETT during retrograde intubation may assist ETT advancement. A bright circumscribed glow can be readily seen in the anterior neck when the tip of the ETT enters the glottic opening and advances to the cricothyroid membrane puncture site, potentially improving the success rate of the technique. The light- guided retrograde intubating technique using the flexible Trachlight™ (without the stiff internal stylet) has been shown to be effective and safe in patients with cervical spine instability.62

11.6.5 What Is the Clinical Utility of the Retrograde Intubation?

While retrograde intubation is not often considered to be a technique of choice, it remains a useful and effective technique. The technique can be performed either under general anesthesia or awake with skin infiltration and topical anesthesia.62,74 In both the original and revised American Society of Anesthesiologists Difficult Airway Algorithms,85,86 retrograde intubation is recommended as an alternative method of intubation when encountering a difficult tracheal intubation if the patient's lungs can still be ventilated. In other words, retrograde intubation can play an important role in the management of a "cannot intubate, but can ventilate" failed airway. It can also be used in patients with a predicted difficult laryngoscopic intubation but no anticipated difficulties in BMV, such as patients with cervical spine instability.62

11.6.6 What Are the Complications of the Retrograde Intubation?

While the retrograde intubation is an effective intubating technique, it has some potential complications. Although rare, complications, such as sore throat, hoarseness, bleeding (puncture site and peritracheal hematomas), subcutaneous emphysema, upper airway obstruction (secondary to subcutaneous emphysema), pneumothorax, pneumomediastinum, pretracheal abscess, and trigeminal nerve trauma have been reported with retrograde intubation.74 Fortunately, most of these complications are minor and self-limiting. It should be emphasized that, compared to the Touhy needle, the use of an 18-gauge Angiocath or needle has made the cricothyroid membrane puncture substantially easier to perform and less traumatic compared to the Touhy needle. In addition, to avoid wound contamination by the oral bacterial flora, the epidural catheter or guide wire should be removed from the cephalad end wherever possible following intubation.

Although tracheal intubation under direct vision using a laryngoscope remains the conventional method of tracheal intubation, it is challenging in a small percentage of patients. Many alternative techniques have been developed over the last several decades to improve the success rate. However, these techniques often require expensive equipment, specialized skills, and are sometimes not particularly useful for patients in an emergency situation with limited resources.

Nonvisual intubating techniques occupy an important role in airway management. Over the last several decades, these nonvisual techniques have been shown to be effective and safe in securing an airway. However, as with all technical skills, one has to recognize that there is a learning curve and a skills maintenance requirement for all of these techniques to be of clinical utility.