Digital Intubation
Digital intubation is a technique that uses the index and middle finger to blindly direct the endotracheal tube into the larynx. It is particularly well adapted to the out-of-hospital situation in which a trapped victim cannot be positioned for intubation. An out-of-hospital series of 66 digitally intubated patients demonstrated an 89% success rate.
Indications and Contraindications
Digital intubation is indicated in the deeply comatose patient whose larynx cannot be visualized and who has a contraindication to nasotracheal intubation. Advantages include speed and ease of placement, immunity to anatomic constraints and other difficulties visualizing the larynx, and little neck movement. Contraindications are primarily precautions to protect the operator: digital intubation should not be attempted on any patient who presents a significant risk of biting. This includes the calm and awake patient as well as the agitated patient.
Procedure
The patient's head and neck are placed in neutral position. The operator stands at the patient's right side, facing the patient. The operator's left index and middle fingers are introduced into the right angle of the patient's mouth and are slid along the surface of the tongue until the epiglottis is palpated. The tip of epiglottis is palpated at 8 to 10 cm from the corner of the mouth in the average adult. The use of a stylet in the tube is optional; the largest reported series had good success without a stylet. For the operator with short fingers or a patient with an anterior larynx, a stylet is advantageous. If a stylet is used, it is placed in the tube and bent into the form of an open "J" with the distal end terminating in a gentle hook. A lubricated tube is introduced from the patient's left between the tongue and the rescuer's 2 fingers . The tube is cradled between 2 fingers and the tip is guided beneath the epiglottis. Gentle anterior pressure directs the tube into the larynx. If the operator has sufficiently long fingers, they can be placed posterior to the arytenoids, acting as a "backstop" for the tube to both avoid esophageal passage and to assist in laryngeal placement. If a stylet has been used, it is withdrawn at this time while simultaneously advancing the tube. An alternative to using a stylet for directing the tube anteriorly is to select an endotracheal tube with a controllable tip (Endotrol, Mallinckrodt Medical Inc, St Louis).
A variation on the technique of digital intubation has been described for intubating the newborn. Only the index finger is used to guide the tube intraorally into the larynx. The end of the tube is bent and both the tube and the finger are moistened with sterile water. The index finger of the nondominant hand follows the tongue posteriorly to easily palpate the epiglottis and paired arytenoid. The thumb of the same hand may be used to apply cricoid pressure to steady the larynx. The endotracheal tube is held in the dominant hand and advanced using the nondominant index finger as a guide . The tube snugs up (encounters subtle resistance) as it enters the trachea, and palpation of the tube through the trachea provides further confirmation of correct placement. A styletted tube, shaped in the form of a J, is usually desired until familiarity with the procedure is achieved.
Complications
The risk of esophageal intubation is always present and, being a blind procedure in deeply comatose or cardiac arrested patients, the potential for esophageal misplacement is increased. If used in patients with a gag, induction of emesis with aspiration is a possibility. A high incidence of left main stem intubations was noted in a cadaveric study, but clinical confirmation is lacking. The greatest risk seems to be to the operator, whose fingers may be bitten.
Summary
While most of the recent experience with digital intubation in adults has been out of hospital, there is no reason why it should be confined to this setting. The majority of moribund emergency department patients who defy orotracheal intubation are never given a trial of digital intubation. This omission undoubtedly deprives some patients of expeditious airway management.
Lighted Stylet Intubation
This technique uses a battery-operated lighted stylet that is placed in an endotracheal tube and used to guide the tube into the trachea by transilluminating the soft tissues of the neck. First described in 1957 by MacIntosh and Richards, it was designed to aid in intubating the difficult airway. It has also been shown to be a useful means of determining the position of the tracheal tube.
In the operating room, the Tube Stat lighted stylet (Concept Corp, Clearwater, Fla) has been 99 to 100% successful. The requirement that the overhead lights be dimmed during the procedure has limited its use in most emergency settings. In a small out-of-hospital study, 88% of patients were successfully intubated by physicians using a lighted stylet. The majority of the failures occurred in the setting of bright sunlight and in patients who had vomited. A new device (Trachlight, Laerdal, Inc, Starger, Norway) with a brighter light source and adjustable length, appears to have solved this problem. In a series of 96 patients, many with a history of difficult intubation, all but 1 were successfully intubated in ambient light with this device using either the oral or nasotracheal route. Consistent with other series, the only failure was in a morbidly obese patient.
Indications and Contraindications
The patient with a difficult airway in whom direct laryngoscopy has failed is a candidate for light-guided tracheal intubation. A multiple trauma patient with airway bleeding is a prime example. The patient who has been pharmacologically paralyzed and cannot be intubated with direct laryngoscopy is another example. The lighted stylet may also be helpful in successfully completing a difficult nasotracheal intubation. One advantage of this technique over nasotracheal intubation is that it can be used in the apneic patient.
Because lighted stylet intubation is a blind approach, it should be avoided in patients with expanding neck masses and patients with airway compromise presumed due to a foreign body. Massive obesity has been shown to be the most common cause for failure with this technique because of the impossibility of transilluminating through the generous soft tissue.
Preparation
The function of the bulb of the lighted stylet should be checked before use. The patient's head should be placed in a neutral or, if cervical spine injury is not a concern, the sniffing position. The awake patient should have the oropharynx and hypopharynx sprayed with lidocaine and sedation should be administered as indicated.
Procedure
The lubricated lighted stylet is inserted into a tracheal tube (5.5 mm or larger) until the bulb lies just distal to the side port, not protruding from the end of the tube. This unit is bent in the shape of a hockey stick that approximates a 90° curve beginning just proximal to the tube cuff. The operator stands at the head of the patient. When this is not possible, the patient can be approached from the right or the left side. The tongue is grasped with gauze and pulled forward. Another means of exposing the oropharynx is to grasp the jaw between the thumb and the fingers . The light is turned on and the unit is inserted into the mouth, following the curve of the tongue into the oropharynx. A transilluminating glow indicates the location of the tube tip. Application of cricoid pressure may enhance transillumination. The overhead light should routinely be dimmed if feasible. Positioning is optimal when the glow emanates from the midline at the level of the hyoid bone. Holding the lighted stylet steady, the tube is slid off and advanced into the trachea. If the glow is located elsewhere, the unit should be withdrawn 2 cm or cocked back and repositioned as indicated by the light. If no light is seen, the tube is in the esophagus and should be pulled back, laryngeal pressure applied, and, if necessary, the head extended slightly. After passage, the tube should be checked for correct positioning and then secured.
Complications
Earlier reports noted complications resulting from an equipment failure and lost bulbs, but these problems have been corrected. No complications have been noted in the recent literature, but this may only reflect the limited use of this technique in uncontrolled settings.
Summary
Lighted stylet intubation is a safe, rapid, and highly successful method that has a definite place in the management of the difficult airway. Recent improvements in the device will increase its applicability to most settings in which emergency airway control is required.
Intubation over a Fiberoptic Bronchoscope
The use of the flexible fiberoptic bronchoscope as an aid to tracheal intubation is a recent addition in airway management in the emergency department. In this setting, success approximates 80%, with the most common cause of failure being the inability to visualize the glottis secondary to blood and secretions.
Flexible fiberoptic endoscopy is the best method for intubating the awake patient with a difficult airway. It can be accomplished using the nasal or oral route and is better tolerated than direct laryngoscopy. It also may be effective in the comatose patient when more conventional methods have failed. It provides excellent visualization of the airway and permits the evaluation of the airway prior to tube placement. The greatest obstacle to success is the inability to see through the scope secondary to blood, secretions, or fogging. The expense of the equipment, its fragility, and the time required to achieve technical proficiency are three other drawbacks.
Indications and Contraindications
Common indications for emergency fiberoptic intubation include the unstable cervical spine, expanding neck masses, upper airway infection, facial and airway burns, and anticipation of a difficult intubation due to anatomic constraints. It may also be helpful in guiding blind nasotracheal intubation that is initially unsuccessful.
Contraindications to fiberoptic nasotracheal intubation are those ascribed to nasotracheal intubation in general: severe midface trauma and coagulopathy. Although there are no clear contraindications to fiberoptic orotracheal intubation, active airway bleeding and vomiting are relative contraindications because successful fiberoptic intubation is rarely achieved in this setting. If the operator is inexperienced in fiberoptic intubation, apnea is another relative contraindication to its use.
Equipment
Fiberoptic scopes are graded according to their external diameter (in millimeters). A convenient intubating scope is 3.5 mm. Although it is physically possible to pass a 4.0 mm (0.5 mm larger) tracheal tube over the scope, the fit is quite tight. As a rule, the tracheal tube should be at least 1 mm larger than the intubating scope. The size of the working channel--the port to which suction or oxygen is applied and through which fluid or catheters may be passed--is another important dimension when evaluating fiberoptic scopes. Large working channels are desirable.
Procedure
The optimal positioning of the neck is in extension, as opposed to the cervical flexion desired when using direct laryngoscopy. Extension allows for better visualization of the
glottis by elevating the epiglottis off the posterior pharyngeal wall. This is especially pertinent in the comatose patient who lacks the muscle tone necessary to maintain an open airway. Problems with the tongue and soft tissues falling back and obscuring fiberoptic scope view are effectively managed by applying a jaw lift or pulling the tongue forward and away from the soft palate and posterior pharyngeal wall. This maneuver also moves the epiglottis away from the posterior pharyngeal wall facilitating exposure of the cords. Extending the head on the neck may accomplish the same objective.
Nasotracheal approach.
The nasal approach is preferred to the oral approach because the angle of insertion allows for easier visualization of the larynx and because patient cooperation is not as critical. Also, in the unconscious patient, the tip of the scope is less likely to impinge on the base of the tongue with a nasal approach.
The nose is prepared using a vasoconstrictor and topical anesthetic agent as described for nasotracheal intubation. Using an aerosolized anesthetic agent, it is important to obtain sufficient hypopharyngeal anesthesia to minimize gagging and laryngospasm once the procedure begins. The well-lubricated endotracheal tube may be placed in the nostril first, and the scope passed through it, or the endotracheal tube can be mounted over the scope and the scope first passed through the nostril. The advantage of the former is that it avoids the possibility of nasal secretions covering the scope and obscuring the view. The disadvantage is that nasotracheal placement may cause bleeding as well as that in some patients, the tube may not make the bend into the nasopharynx.
The most patent nostril is prepped and the endotracheal tube is advanced until it makes the bend into the nasopharynx in the manner described under nasotracheal intubation. If negotiating this bend is difficult, a well-lubricated fiberoptic scope can be placed through the tube and into the oropharynx to serve as a guide for the endotracheal tube. Once the tracheal tube is in the oropharynx, thorough oropharyngeal suctioning should be performed prior to introduction of the scope into the endotracheal tube. The fiberoptic scope is then advanced toward the larynx; the epiglottis and vocal cords are seen with little or no manipulation of the tip of the fiberoptic scope in 90% of patients. As the scope is advanced, the cords are kept in view by frequent minor adjustments of the scope tip.
In the comatose or obtunded patient, the tongue and other soft tissue may obscure the view of the larynx; this can be alleviated by having an assistant pull the tongue forward or apply a chin or jaw lift. The scope is advanced through the larynx to the level of the midtrachea and the endotracheal tube is passed over the firmly held fiberoptic scope into the trachea . It is helpful to remember that in adults the average distance from the naris to the epiglottis is 16 to 17 cm; if the scope has been advanced much beyond this distance and the glottis is still not seen, the scope is probably in the esophagus. If the scope meets resistance at about this same level and only a pink blur is visible, the scope tip is probably in a piriform sinus; transillumination of the soft tissues may be present to confirm this as well as to indicate what corrective maneuvers are necessary.
The greatest impediment to successful fiberoptic intubation is the inability to visualize the larynx because blood or secretions have covered the optical element and cannot be removed. The best time to suction is before introducing the fiberoptic scope, actively suctioning the oropharynx just prior to scope insertion. Once the scope is in place, minor secretions can be suctioned through the fiberoptic suction port. Significant blood and secretions, however, are best removed by insufflation of oxygen through the suction port and out the tip of the scope, serving simultaneously to remove blood and secretions, defog the tip, and increase the inspired O2 content. The set-up required for insufflation should be immediately available, if not already attached to the suction port prior to scope insertion. Once the scope has entered the trachea, difficulty may be encountered in advancing the endotracheal tube into the trachea. The tip of the tube most commonly catches on the right arytenoid cartilage or vocal cord; withdrawing the tube 2 cm, rotating it counterclockwise 90°, and readvancing the tube should result in successful tracheal intubation.
Orotracheal approach.
Oral fiberoptically guided intubation is indicated when contraindications to nasal intubation are present, the most common being severe midface trauma, or when the operator is more comfortable with this approach. The oral approach is more difficult than the nasal approach because the path of the scope is less defined by the surrounding soft tissue and the tip of the scope is more likely to impinge on the base of the tongue or vallecula. Attention to keeping the scope in the midline and elevating the soft tissue by pulling the tongue forward or applying the jaw lift will minimize this difficulty. Another disadvantage of the oral approach is that the oropharyngeal axis is not as well aligned with the laryngeal axis as in the nasal approach and thus requires more scope manipulation to visualize the larynx.
The drawbacks of the oral approach can be minimized by using an oral intubating airway. This adjunct resembles an oropharyngeal airway but is longer and has a cylindrical passage through which the fiberoptic scope and tracheal tube are passed. The tip of this airway lies just cephalad to the epiglottis and assures midline positioning and a predictable place from which to advance the scope.
The patient must be adequately anesthetized or obtunded to minimize the gag reflex. Topical anesthesia is achieved by spraying a 4 or 10% solution of lidocaine into the oropharynx. A degree of laryngeal and tracheal anesthesia may be achieved by a transoral spray using the laryngeal tracheal anesthetic (LTA) set. A well-lubricated fiberoptic scope, premounted with an endotracheal tube, is placed through the oral intubating airway and the trachea is fiberoptically intubated. The endotracheal tube is advanced over the scope into the trachea, frequently requiring the same counterclockwise manipulation as described with the nasal approach. After successful intubation, the intubating device can be left in place as a bite block, or it can be removed over the endotracheal tube after removal of the tube adapter. Some oral intubating airways can be removed from the mouth without disconnecting the endotracheal tube adapter.
Complications
Complications of fiberoptic orotracheal intubation include prolonged intubation attempts and vomiting and laryngospasm in the underanesthetized patient. Oxygen saturation monitoring should alert the operator to hypoxemia from prolonged intubation attempts. The majority of complications seen with fiberoptically guided nasotracheal intubation are associated with the passage of the endotracheal tube through the nasopharynx. Epistaxis is most common, followed by other nasopharyngeal injuries seen with nasotracheal intubation in general. A rare but potentially significant complication may result if on blind advancement of the fiberoptic scope through the endotracheal tube, the tip of the scope inadvertently exits out through the distal side port (Murphy's eyes) as it is being advanced through the larynx into the trachea. [74] Attempts at passing the endotracheal tube through the larynx will fail because the tube tip, now extending off the midline, will catch on the laryngeal structures. This complication is avoided if the scope is introduced prior to tracheal tube placement.
Summary
The primary advantage of fiberoptic intubation is its ability to negotiate difficult airway anatomy. It is noninvasive and well tolerated. Its major limitation in the emergency setting is lack of visibility in the presence of blood and secretions. The fiberoptic scope requires more practice than other methods of airway management; the first experience using the scope should not be in the setting of an emergency airway problem. Once familiarity and facility with the scope are acquired, fiberoptic intubation can be used early in the management of the difficult airway rather than as a last resort after repeated failed attempts using conventional techniques.
Retrograde Intubation
Retrograde orotracheal intubation is a technique of guided endotracheal intubation using a wire or catheter placed percutaneously through the cricothyroid membrane or high trachea and exiting through the mouth or nose. An endotracheal tube is then passed over this guide and advanced through the vocal cords into the trachea. Introduced by Butler and Cirillo in 1960, the technique has undergone several recent modifications that have enhanced its value as a means of establishing a definitive airway when more conventional techniques have failed.
Indications and Contraindications
Retrograde intubation is indicated when definitive airway control is required and less invasive methods have failed. Indications include trismus, ankylosis of the jaw or cervical spine, upper airway masses, unstable cervical spine injuries, and maxillofacial trauma. It can be used to convert transtracheal needle ventilation into a definitive airway. It has been described in a 1-month-old with developmental abnormalities. It is particularly helpful in the trauma patient with airway bleeding that prevents visualization of the glottis. A striking example of the efficacy of this technique is presented in an article by Barriot and Riou describing successful out-of-hospital retrograde intubation in a series of trauma patients in whom attempts at conventional intubation failed.
Contraindications to this procedure include the ability to control the airway by less invasive means. The inability to open the mouth is another contraindication. A relative contraindication is the apneic patient who cannot be effectively ventilated using the bag-valve-mask; in this setting it is advisable to first establish transtracheal needle ventilation before attempting retrograde intubation or to go directly to cricothyrotomy.
Equipment
Needed materials include the following: (1) local anesthetic and skin preparation materials, (2) 18-ga needle, (3) 60 cm epidural catheter-needle combination or 80 cm (0.88 mm diameter) spring guide wire (J-tip preferred), (4) hemostat, (5) long forceps (e.g., Magill) for grasping wire in pharynx, (6) endotracheal tube of appropriate size, (7) syringe for tube cuff, and (8) materials for securing tube. A prepackaged alternative is the Cook Retrograde Intubation Set (Cook Critical Care, Bloomington, Ind), which also contains a sheath.
Procedure
Three anatomic landmarks must be located by palpation: the hyoid bone, thyroid cartilage, and cricoid cartilage. The skin overlying the cricothyroid membrane is prepped and anesthetized. Next, the lower half of the cricothyroid membrane is punctured with a needle directed slightly cephalad. The bevel should also face cephalad. Air is aspirated to confirm needle tip position within the lumen of the larynx. An alternative entry point is the high trachea, usually through the subcricoid space, using the same steps as described for the cricothyroid membrane.
The syringe is removed and the wire is then passed through the needle and advanced until it is seen in the patient's mouth, with the help of the laryngoscope, or until it exits out the nose. If the wire is found in the hypopharynx, it is grasped with the Magill forceps and drawn out through the mouth. The needle is removed from the neck and the end of the wire is secured at the puncture site with a hemostat. The oral end of the wire is then threaded in through the endotracheal tube side port--not the end of the tube--and advanced up the tube until it can be grasped by a second hemostat. Threading the wire through the side port allows the tube tip to protrude 1 cm beyond the point at which the wire enters the larynx. The wire is then pulled taut and moved back and forth to ensure that no slack remains.
The endotracheal tube is then advanced over the wire until resistance is met. This is the most critical point in the procedure; because this is a blind technique, it may be difficult to determine whether the tube has entered the trachea or is hung up on more proximal structures. If the endotracheal tube has successfully passed through the vocal cords and it is being restricted by the guide wire as it traverses the anterior laryngeal wall, one should feel some caudally directed tension on the wire at its laryngeal insertion point. If this does not occur, the tip of the endotracheal tube may be proximal to the vocal cords, either in the vallecula, the piriform sinus, or abutting the narrow anterior aspect of the vocal cords. If in doubt, pull the tube back 2 cm, rotate it 90° counterclockwise, and readvance the tube. This will usually result in successful passage through the larynx. [73] When satisfied that the tube has entered the trachea, the tube should be stabilized and the guide wire pulled out through the mouth. The tube is then advanced further into the trachea.
The classic method of retrograde intubation, as described above, has undergone modifications that facilitate the passage of the endotracheal tube through the glottis. A significant advance has been the addition of a plastic sheath that is passed antegrade over the wire until it meets resistance at the point at which the wire penetrates the laryngeal mucosa . This sheath needs to be stiff enough to effectively guide an endotracheal tube, yet small enough to easily pass through the vocal cords without impinging on supraglottic or glottic structures. Once the sheath comes to rest against the anterior laryngeal wall, the wire is withdrawn from the mouth and the sheath is advanced. With the sheath well within the trachea, the endotracheal tube is passed over the sheath. Any resistance that may be encountered at the arytenoids or vocal cords can usually be remedied by pulling the tube back 1 to 2 cm and rotating it counterclockwise 90°. One advantage of the antegrade sheath is that it lies freely in the larynx, allowing for a more posterior passage through the widest distance between the cords. The wire, however, pulls the endotracheal tube anteriorly toward the narrow commissure of the vocal cords and is more likely to result in impingement of the tube on the cords. Also, the use of the sheath permits unrestricted advancement of the endotracheal tube, whereas a wire entering the larynx 1.0 to 1.5 cm below the vocal cords prevents the tube from advancing more than this distance prior to removal of the wire.
If no sheath is available, one should consider placing the needle inferiorly in the subcricoid space, thereby increasing the distance the endotracheal tube can be advanced before being stopped by the wire. This will decrease the likelihood of dislodging the endotracheal tube tip when the guide wire is withdrawn.
Up to this point, blind retrograde intubation has been described. A further modification of the technique allows for visualization using a fiberoptic scope. In addition to the scope, an extra long guide wire (e.g., 125 cm, 0.025 cm Teflon-coated J-wire) is also required. The procedure is the same as previously described up to the point at which the wire is withdrawn from the mouth. At that point, with a endotracheal tube mounted on a lubricated fiberoptic scope, the long guide wire is passed retrograde up through the end of the fiberoptic scope and out the suction port. The fiberoptic scope is then advanced over the guide wire and through the cords, coming to rest against the anterior laryngeal wall. The wire is withdrawn from the suction port and the scope is advanced into the trachea. The endotracheal tube is then passed over the fiberoptic scope, and visualization guarantees correct endotracheal placement. The scope is then withdrawn and the lungs are auscultated.
Complications
The complications of retrograde intubation are largely related to cricothyroid membrane puncture. Hemorrhage is minimized by taking care to puncture the cricothyroid membrane in its lower half (to avoid the cricothyroid artery). Subcutaneous emphysema may occur, but it is of no clinical significance because no air is insufflated during this technique. A small incidence of soft tissue infection is reported with translaryngeal needle procedures, but this can be minimized by ensuring that the wire is withdrawn from the mouth rather than the neck.
The final complication, the failure to achieve intubation, has been mitigated by the addition of the antegrade sheath over the wire.
Summary
Retrograde intubation is an underused technique for achieving endotracheal intubation in a patient who cannot be intubated by less aggressive means. It is more invasive than fiberoptic intubation but requires less skill. Whereas retrograde intubation usually takes several minutes to complete, [81] the patient can undergo bag-mask ventilation through much of the procedure. Recent modifications in the technique guarantee this method a prominent place in the management of the difficult airway, particularly when active bleeding compromises the airway.
Digital intubation is a technique that uses the index and middle finger to blindly direct the endotracheal tube into the larynx. It is particularly well adapted to the out-of-hospital situation in which a trapped victim cannot be positioned for intubation. An out-of-hospital series of 66 digitally intubated patients demonstrated an 89% success rate.
Indications and Contraindications
Digital intubation is indicated in the deeply comatose patient whose larynx cannot be visualized and who has a contraindication to nasotracheal intubation. Advantages include speed and ease of placement, immunity to anatomic constraints and other difficulties visualizing the larynx, and little neck movement. Contraindications are primarily precautions to protect the operator: digital intubation should not be attempted on any patient who presents a significant risk of biting. This includes the calm and awake patient as well as the agitated patient.
Procedure
The patient's head and neck are placed in neutral position. The operator stands at the patient's right side, facing the patient. The operator's left index and middle fingers are introduced into the right angle of the patient's mouth and are slid along the surface of the tongue until the epiglottis is palpated. The tip of epiglottis is palpated at 8 to 10 cm from the corner of the mouth in the average adult. The use of a stylet in the tube is optional; the largest reported series had good success without a stylet. For the operator with short fingers or a patient with an anterior larynx, a stylet is advantageous. If a stylet is used, it is placed in the tube and bent into the form of an open "J" with the distal end terminating in a gentle hook. A lubricated tube is introduced from the patient's left between the tongue and the rescuer's 2 fingers . The tube is cradled between 2 fingers and the tip is guided beneath the epiglottis. Gentle anterior pressure directs the tube into the larynx. If the operator has sufficiently long fingers, they can be placed posterior to the arytenoids, acting as a "backstop" for the tube to both avoid esophageal passage and to assist in laryngeal placement. If a stylet has been used, it is withdrawn at this time while simultaneously advancing the tube. An alternative to using a stylet for directing the tube anteriorly is to select an endotracheal tube with a controllable tip (Endotrol, Mallinckrodt Medical Inc, St Louis).
A variation on the technique of digital intubation has been described for intubating the newborn. Only the index finger is used to guide the tube intraorally into the larynx. The end of the tube is bent and both the tube and the finger are moistened with sterile water. The index finger of the nondominant hand follows the tongue posteriorly to easily palpate the epiglottis and paired arytenoid. The thumb of the same hand may be used to apply cricoid pressure to steady the larynx. The endotracheal tube is held in the dominant hand and advanced using the nondominant index finger as a guide . The tube snugs up (encounters subtle resistance) as it enters the trachea, and palpation of the tube through the trachea provides further confirmation of correct placement. A styletted tube, shaped in the form of a J, is usually desired until familiarity with the procedure is achieved.
Complications
The risk of esophageal intubation is always present and, being a blind procedure in deeply comatose or cardiac arrested patients, the potential for esophageal misplacement is increased. If used in patients with a gag, induction of emesis with aspiration is a possibility. A high incidence of left main stem intubations was noted in a cadaveric study, but clinical confirmation is lacking. The greatest risk seems to be to the operator, whose fingers may be bitten.
Summary
While most of the recent experience with digital intubation in adults has been out of hospital, there is no reason why it should be confined to this setting. The majority of moribund emergency department patients who defy orotracheal intubation are never given a trial of digital intubation. This omission undoubtedly deprives some patients of expeditious airway management.
Lighted Stylet Intubation
This technique uses a battery-operated lighted stylet that is placed in an endotracheal tube and used to guide the tube into the trachea by transilluminating the soft tissues of the neck. First described in 1957 by MacIntosh and Richards, it was designed to aid in intubating the difficult airway. It has also been shown to be a useful means of determining the position of the tracheal tube.
In the operating room, the Tube Stat lighted stylet (Concept Corp, Clearwater, Fla) has been 99 to 100% successful. The requirement that the overhead lights be dimmed during the procedure has limited its use in most emergency settings. In a small out-of-hospital study, 88% of patients were successfully intubated by physicians using a lighted stylet. The majority of the failures occurred in the setting of bright sunlight and in patients who had vomited. A new device (Trachlight, Laerdal, Inc, Starger, Norway) with a brighter light source and adjustable length, appears to have solved this problem. In a series of 96 patients, many with a history of difficult intubation, all but 1 were successfully intubated in ambient light with this device using either the oral or nasotracheal route. Consistent with other series, the only failure was in a morbidly obese patient.
Indications and Contraindications
The patient with a difficult airway in whom direct laryngoscopy has failed is a candidate for light-guided tracheal intubation. A multiple trauma patient with airway bleeding is a prime example. The patient who has been pharmacologically paralyzed and cannot be intubated with direct laryngoscopy is another example. The lighted stylet may also be helpful in successfully completing a difficult nasotracheal intubation. One advantage of this technique over nasotracheal intubation is that it can be used in the apneic patient.
Because lighted stylet intubation is a blind approach, it should be avoided in patients with expanding neck masses and patients with airway compromise presumed due to a foreign body. Massive obesity has been shown to be the most common cause for failure with this technique because of the impossibility of transilluminating through the generous soft tissue.
Preparation
The function of the bulb of the lighted stylet should be checked before use. The patient's head should be placed in a neutral or, if cervical spine injury is not a concern, the sniffing position. The awake patient should have the oropharynx and hypopharynx sprayed with lidocaine and sedation should be administered as indicated.
Procedure
The lubricated lighted stylet is inserted into a tracheal tube (5.5 mm or larger) until the bulb lies just distal to the side port, not protruding from the end of the tube. This unit is bent in the shape of a hockey stick that approximates a 90° curve beginning just proximal to the tube cuff. The operator stands at the head of the patient. When this is not possible, the patient can be approached from the right or the left side. The tongue is grasped with gauze and pulled forward. Another means of exposing the oropharynx is to grasp the jaw between the thumb and the fingers . The light is turned on and the unit is inserted into the mouth, following the curve of the tongue into the oropharynx. A transilluminating glow indicates the location of the tube tip. Application of cricoid pressure may enhance transillumination. The overhead light should routinely be dimmed if feasible. Positioning is optimal when the glow emanates from the midline at the level of the hyoid bone. Holding the lighted stylet steady, the tube is slid off and advanced into the trachea. If the glow is located elsewhere, the unit should be withdrawn 2 cm or cocked back and repositioned as indicated by the light. If no light is seen, the tube is in the esophagus and should be pulled back, laryngeal pressure applied, and, if necessary, the head extended slightly. After passage, the tube should be checked for correct positioning and then secured.
Complications
Earlier reports noted complications resulting from an equipment failure and lost bulbs, but these problems have been corrected. No complications have been noted in the recent literature, but this may only reflect the limited use of this technique in uncontrolled settings.
Summary
Lighted stylet intubation is a safe, rapid, and highly successful method that has a definite place in the management of the difficult airway. Recent improvements in the device will increase its applicability to most settings in which emergency airway control is required.
Intubation over a Fiberoptic Bronchoscope
The use of the flexible fiberoptic bronchoscope as an aid to tracheal intubation is a recent addition in airway management in the emergency department. In this setting, success approximates 80%, with the most common cause of failure being the inability to visualize the glottis secondary to blood and secretions.
Flexible fiberoptic endoscopy is the best method for intubating the awake patient with a difficult airway. It can be accomplished using the nasal or oral route and is better tolerated than direct laryngoscopy. It also may be effective in the comatose patient when more conventional methods have failed. It provides excellent visualization of the airway and permits the evaluation of the airway prior to tube placement. The greatest obstacle to success is the inability to see through the scope secondary to blood, secretions, or fogging. The expense of the equipment, its fragility, and the time required to achieve technical proficiency are three other drawbacks.
Indications and Contraindications
Common indications for emergency fiberoptic intubation include the unstable cervical spine, expanding neck masses, upper airway infection, facial and airway burns, and anticipation of a difficult intubation due to anatomic constraints. It may also be helpful in guiding blind nasotracheal intubation that is initially unsuccessful.
Contraindications to fiberoptic nasotracheal intubation are those ascribed to nasotracheal intubation in general: severe midface trauma and coagulopathy. Although there are no clear contraindications to fiberoptic orotracheal intubation, active airway bleeding and vomiting are relative contraindications because successful fiberoptic intubation is rarely achieved in this setting. If the operator is inexperienced in fiberoptic intubation, apnea is another relative contraindication to its use.
Equipment
Fiberoptic scopes are graded according to their external diameter (in millimeters). A convenient intubating scope is 3.5 mm. Although it is physically possible to pass a 4.0 mm (0.5 mm larger) tracheal tube over the scope, the fit is quite tight. As a rule, the tracheal tube should be at least 1 mm larger than the intubating scope. The size of the working channel--the port to which suction or oxygen is applied and through which fluid or catheters may be passed--is another important dimension when evaluating fiberoptic scopes. Large working channels are desirable.
Procedure
The optimal positioning of the neck is in extension, as opposed to the cervical flexion desired when using direct laryngoscopy. Extension allows for better visualization of the
glottis by elevating the epiglottis off the posterior pharyngeal wall. This is especially pertinent in the comatose patient who lacks the muscle tone necessary to maintain an open airway. Problems with the tongue and soft tissues falling back and obscuring fiberoptic scope view are effectively managed by applying a jaw lift or pulling the tongue forward and away from the soft palate and posterior pharyngeal wall. This maneuver also moves the epiglottis away from the posterior pharyngeal wall facilitating exposure of the cords. Extending the head on the neck may accomplish the same objective.
Nasotracheal approach.
The nasal approach is preferred to the oral approach because the angle of insertion allows for easier visualization of the larynx and because patient cooperation is not as critical. Also, in the unconscious patient, the tip of the scope is less likely to impinge on the base of the tongue with a nasal approach.
The nose is prepared using a vasoconstrictor and topical anesthetic agent as described for nasotracheal intubation. Using an aerosolized anesthetic agent, it is important to obtain sufficient hypopharyngeal anesthesia to minimize gagging and laryngospasm once the procedure begins. The well-lubricated endotracheal tube may be placed in the nostril first, and the scope passed through it, or the endotracheal tube can be mounted over the scope and the scope first passed through the nostril. The advantage of the former is that it avoids the possibility of nasal secretions covering the scope and obscuring the view. The disadvantage is that nasotracheal placement may cause bleeding as well as that in some patients, the tube may not make the bend into the nasopharynx.
The most patent nostril is prepped and the endotracheal tube is advanced until it makes the bend into the nasopharynx in the manner described under nasotracheal intubation. If negotiating this bend is difficult, a well-lubricated fiberoptic scope can be placed through the tube and into the oropharynx to serve as a guide for the endotracheal tube. Once the tracheal tube is in the oropharynx, thorough oropharyngeal suctioning should be performed prior to introduction of the scope into the endotracheal tube. The fiberoptic scope is then advanced toward the larynx; the epiglottis and vocal cords are seen with little or no manipulation of the tip of the fiberoptic scope in 90% of patients. As the scope is advanced, the cords are kept in view by frequent minor adjustments of the scope tip.
In the comatose or obtunded patient, the tongue and other soft tissue may obscure the view of the larynx; this can be alleviated by having an assistant pull the tongue forward or apply a chin or jaw lift. The scope is advanced through the larynx to the level of the midtrachea and the endotracheal tube is passed over the firmly held fiberoptic scope into the trachea . It is helpful to remember that in adults the average distance from the naris to the epiglottis is 16 to 17 cm; if the scope has been advanced much beyond this distance and the glottis is still not seen, the scope is probably in the esophagus. If the scope meets resistance at about this same level and only a pink blur is visible, the scope tip is probably in a piriform sinus; transillumination of the soft tissues may be present to confirm this as well as to indicate what corrective maneuvers are necessary.
The greatest impediment to successful fiberoptic intubation is the inability to visualize the larynx because blood or secretions have covered the optical element and cannot be removed. The best time to suction is before introducing the fiberoptic scope, actively suctioning the oropharynx just prior to scope insertion. Once the scope is in place, minor secretions can be suctioned through the fiberoptic suction port. Significant blood and secretions, however, are best removed by insufflation of oxygen through the suction port and out the tip of the scope, serving simultaneously to remove blood and secretions, defog the tip, and increase the inspired O2 content. The set-up required for insufflation should be immediately available, if not already attached to the suction port prior to scope insertion. Once the scope has entered the trachea, difficulty may be encountered in advancing the endotracheal tube into the trachea. The tip of the tube most commonly catches on the right arytenoid cartilage or vocal cord; withdrawing the tube 2 cm, rotating it counterclockwise 90°, and readvancing the tube should result in successful tracheal intubation.
Orotracheal approach.
Oral fiberoptically guided intubation is indicated when contraindications to nasal intubation are present, the most common being severe midface trauma, or when the operator is more comfortable with this approach. The oral approach is more difficult than the nasal approach because the path of the scope is less defined by the surrounding soft tissue and the tip of the scope is more likely to impinge on the base of the tongue or vallecula. Attention to keeping the scope in the midline and elevating the soft tissue by pulling the tongue forward or applying the jaw lift will minimize this difficulty. Another disadvantage of the oral approach is that the oropharyngeal axis is not as well aligned with the laryngeal axis as in the nasal approach and thus requires more scope manipulation to visualize the larynx.
The drawbacks of the oral approach can be minimized by using an oral intubating airway. This adjunct resembles an oropharyngeal airway but is longer and has a cylindrical passage through which the fiberoptic scope and tracheal tube are passed. The tip of this airway lies just cephalad to the epiglottis and assures midline positioning and a predictable place from which to advance the scope.
The patient must be adequately anesthetized or obtunded to minimize the gag reflex. Topical anesthesia is achieved by spraying a 4 or 10% solution of lidocaine into the oropharynx. A degree of laryngeal and tracheal anesthesia may be achieved by a transoral spray using the laryngeal tracheal anesthetic (LTA) set. A well-lubricated fiberoptic scope, premounted with an endotracheal tube, is placed through the oral intubating airway and the trachea is fiberoptically intubated. The endotracheal tube is advanced over the scope into the trachea, frequently requiring the same counterclockwise manipulation as described with the nasal approach. After successful intubation, the intubating device can be left in place as a bite block, or it can be removed over the endotracheal tube after removal of the tube adapter. Some oral intubating airways can be removed from the mouth without disconnecting the endotracheal tube adapter.
Complications
Complications of fiberoptic orotracheal intubation include prolonged intubation attempts and vomiting and laryngospasm in the underanesthetized patient. Oxygen saturation monitoring should alert the operator to hypoxemia from prolonged intubation attempts. The majority of complications seen with fiberoptically guided nasotracheal intubation are associated with the passage of the endotracheal tube through the nasopharynx. Epistaxis is most common, followed by other nasopharyngeal injuries seen with nasotracheal intubation in general. A rare but potentially significant complication may result if on blind advancement of the fiberoptic scope through the endotracheal tube, the tip of the scope inadvertently exits out through the distal side port (Murphy's eyes) as it is being advanced through the larynx into the trachea. [74] Attempts at passing the endotracheal tube through the larynx will fail because the tube tip, now extending off the midline, will catch on the laryngeal structures. This complication is avoided if the scope is introduced prior to tracheal tube placement.
Summary
The primary advantage of fiberoptic intubation is its ability to negotiate difficult airway anatomy. It is noninvasive and well tolerated. Its major limitation in the emergency setting is lack of visibility in the presence of blood and secretions. The fiberoptic scope requires more practice than other methods of airway management; the first experience using the scope should not be in the setting of an emergency airway problem. Once familiarity and facility with the scope are acquired, fiberoptic intubation can be used early in the management of the difficult airway rather than as a last resort after repeated failed attempts using conventional techniques.
Retrograde Intubation
Retrograde orotracheal intubation is a technique of guided endotracheal intubation using a wire or catheter placed percutaneously through the cricothyroid membrane or high trachea and exiting through the mouth or nose. An endotracheal tube is then passed over this guide and advanced through the vocal cords into the trachea. Introduced by Butler and Cirillo in 1960, the technique has undergone several recent modifications that have enhanced its value as a means of establishing a definitive airway when more conventional techniques have failed.
Indications and Contraindications
Retrograde intubation is indicated when definitive airway control is required and less invasive methods have failed. Indications include trismus, ankylosis of the jaw or cervical spine, upper airway masses, unstable cervical spine injuries, and maxillofacial trauma. It can be used to convert transtracheal needle ventilation into a definitive airway. It has been described in a 1-month-old with developmental abnormalities. It is particularly helpful in the trauma patient with airway bleeding that prevents visualization of the glottis. A striking example of the efficacy of this technique is presented in an article by Barriot and Riou describing successful out-of-hospital retrograde intubation in a series of trauma patients in whom attempts at conventional intubation failed.
Contraindications to this procedure include the ability to control the airway by less invasive means. The inability to open the mouth is another contraindication. A relative contraindication is the apneic patient who cannot be effectively ventilated using the bag-valve-mask; in this setting it is advisable to first establish transtracheal needle ventilation before attempting retrograde intubation or to go directly to cricothyrotomy.
Equipment
Needed materials include the following: (1) local anesthetic and skin preparation materials, (2) 18-ga needle, (3) 60 cm epidural catheter-needle combination or 80 cm (0.88 mm diameter) spring guide wire (J-tip preferred), (4) hemostat, (5) long forceps (e.g., Magill) for grasping wire in pharynx, (6) endotracheal tube of appropriate size, (7) syringe for tube cuff, and (8) materials for securing tube. A prepackaged alternative is the Cook Retrograde Intubation Set (Cook Critical Care, Bloomington, Ind), which also contains a sheath.
Procedure
Three anatomic landmarks must be located by palpation: the hyoid bone, thyroid cartilage, and cricoid cartilage. The skin overlying the cricothyroid membrane is prepped and anesthetized. Next, the lower half of the cricothyroid membrane is punctured with a needle directed slightly cephalad. The bevel should also face cephalad. Air is aspirated to confirm needle tip position within the lumen of the larynx. An alternative entry point is the high trachea, usually through the subcricoid space, using the same steps as described for the cricothyroid membrane.
The syringe is removed and the wire is then passed through the needle and advanced until it is seen in the patient's mouth, with the help of the laryngoscope, or until it exits out the nose. If the wire is found in the hypopharynx, it is grasped with the Magill forceps and drawn out through the mouth. The needle is removed from the neck and the end of the wire is secured at the puncture site with a hemostat. The oral end of the wire is then threaded in through the endotracheal tube side port--not the end of the tube--and advanced up the tube until it can be grasped by a second hemostat. Threading the wire through the side port allows the tube tip to protrude 1 cm beyond the point at which the wire enters the larynx. The wire is then pulled taut and moved back and forth to ensure that no slack remains.
The endotracheal tube is then advanced over the wire until resistance is met. This is the most critical point in the procedure; because this is a blind technique, it may be difficult to determine whether the tube has entered the trachea or is hung up on more proximal structures. If the endotracheal tube has successfully passed through the vocal cords and it is being restricted by the guide wire as it traverses the anterior laryngeal wall, one should feel some caudally directed tension on the wire at its laryngeal insertion point. If this does not occur, the tip of the endotracheal tube may be proximal to the vocal cords, either in the vallecula, the piriform sinus, or abutting the narrow anterior aspect of the vocal cords. If in doubt, pull the tube back 2 cm, rotate it 90° counterclockwise, and readvance the tube. This will usually result in successful passage through the larynx. [73] When satisfied that the tube has entered the trachea, the tube should be stabilized and the guide wire pulled out through the mouth. The tube is then advanced further into the trachea.
The classic method of retrograde intubation, as described above, has undergone modifications that facilitate the passage of the endotracheal tube through the glottis. A significant advance has been the addition of a plastic sheath that is passed antegrade over the wire until it meets resistance at the point at which the wire penetrates the laryngeal mucosa . This sheath needs to be stiff enough to effectively guide an endotracheal tube, yet small enough to easily pass through the vocal cords without impinging on supraglottic or glottic structures. Once the sheath comes to rest against the anterior laryngeal wall, the wire is withdrawn from the mouth and the sheath is advanced. With the sheath well within the trachea, the endotracheal tube is passed over the sheath. Any resistance that may be encountered at the arytenoids or vocal cords can usually be remedied by pulling the tube back 1 to 2 cm and rotating it counterclockwise 90°. One advantage of the antegrade sheath is that it lies freely in the larynx, allowing for a more posterior passage through the widest distance between the cords. The wire, however, pulls the endotracheal tube anteriorly toward the narrow commissure of the vocal cords and is more likely to result in impingement of the tube on the cords. Also, the use of the sheath permits unrestricted advancement of the endotracheal tube, whereas a wire entering the larynx 1.0 to 1.5 cm below the vocal cords prevents the tube from advancing more than this distance prior to removal of the wire.
If no sheath is available, one should consider placing the needle inferiorly in the subcricoid space, thereby increasing the distance the endotracheal tube can be advanced before being stopped by the wire. This will decrease the likelihood of dislodging the endotracheal tube tip when the guide wire is withdrawn.
Up to this point, blind retrograde intubation has been described. A further modification of the technique allows for visualization using a fiberoptic scope. In addition to the scope, an extra long guide wire (e.g., 125 cm, 0.025 cm Teflon-coated J-wire) is also required. The procedure is the same as previously described up to the point at which the wire is withdrawn from the mouth. At that point, with a endotracheal tube mounted on a lubricated fiberoptic scope, the long guide wire is passed retrograde up through the end of the fiberoptic scope and out the suction port. The fiberoptic scope is then advanced over the guide wire and through the cords, coming to rest against the anterior laryngeal wall. The wire is withdrawn from the suction port and the scope is advanced into the trachea. The endotracheal tube is then passed over the fiberoptic scope, and visualization guarantees correct endotracheal placement. The scope is then withdrawn and the lungs are auscultated.
Complications
The complications of retrograde intubation are largely related to cricothyroid membrane puncture. Hemorrhage is minimized by taking care to puncture the cricothyroid membrane in its lower half (to avoid the cricothyroid artery). Subcutaneous emphysema may occur, but it is of no clinical significance because no air is insufflated during this technique. A small incidence of soft tissue infection is reported with translaryngeal needle procedures, but this can be minimized by ensuring that the wire is withdrawn from the mouth rather than the neck.
The final complication, the failure to achieve intubation, has been mitigated by the addition of the antegrade sheath over the wire.
Summary
Retrograde intubation is an underused technique for achieving endotracheal intubation in a patient who cannot be intubated by less aggressive means. It is more invasive than fiberoptic intubation but requires less skill. Whereas retrograde intubation usually takes several minutes to complete, [81] the patient can undergo bag-mask ventilation through much of the procedure. Recent modifications in the technique guarantee this method a prominent place in the management of the difficult airway, particularly when active bleeding compromises the airway.
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