NASOTRACHEAL INTUBATION

Nasotracheal intubation was first described by Magill in the 1920s and the basic technique has changed little over the years. Modifications have been described that increase the success rate and limit complications. The tube may be placed blindly or with the aid of a laryngoscope or bronchoscope. Blind nasotracheal intubation can be one of the more technically demanding airway approaches, with the outcome being heavily dependent on the skill and experience of the operator. The primary advantage of blind nasotracheal intubation is that it minimizes neck movement and does not require opening the mouth.

General Indications and Contraindications
Nasotracheal intubation is technically more difficult than oral intubation, but it has definite advantages. It is especially suitable for the patient with a short, thick neck or other anatomic characteristics that would make orotracheal intubation difficult. Patients with clenched teeth or suspected cervical spine injury can be intubated with minimal preparation. Cervical spine films, jaw spreading, or paralyzing agents as preliminaries to airway control are unnecessary.
Blind nasotracheal intubation is possible with the patient in the sitting position, a distinct advantage when intubating the patient with congestive heart failure who cannot tolerate lying flat. In fact, patients in respiratory distress are the easiest to intubate blindly because their air hunger results in increased abduction of the vocal cords, which facilitates tube entry into the trachea. The drug overdose patient with a decreased level of consciousness is a candidate for nasotracheal intubation. These patients are often intubated before gastric lavage and may be sufficiently awake to make orotracheal intubation difficult without paralyzing agents.
A nasotracheal tube has advantages that extend beyond the immediate difficulties of airway control. The patient cannot bite the tube or manipulate it with the tongue. Oral injuries may be cared for without interference by the tube. A nasotracheal tube is more easily stabilized and generally easier to care for than an orotracheal tube. It is better tolerated by the patient, permitting easier movement in bed, and produces less reflex salivation than do oral tubes.
Nasal intubation should be avoided in patients with severe nasal or midface trauma. In the presence of a basilar skull fracture, a nasotracheal tube may inadvertently enter the brain through a basilar skull fracture. [41] The technique should be avoided in patients in whom thrombolytic therapy is being considered. Nasal intubation is relatively contraindicated if the patient is taking anticoagulants or is known to have a coagulopathy.

Blind Placement
Blind nasotracheal intubation is the most common form of nasotracheal intubation in the emergency setting. Danzl and Thomas reported a success rate of 92% in a large series of emergency department patients.

Indications and Contraindications
Any patient requiring airway control who has spontaneous respirations is a candidate for blind nasotracheal intubation. Specific indications that favor this approach over others are (1) short, thick neck, (2) inability to open the mouth, (3) inability to move the neck, (4) gagging or resisting the use of the laryngoscope, and (5) oral injuries.
Apnea is the major contraindication to blind nasotracheal intubation. Attempts to place the tube without respirations as a guide are futile. Relative contraindications include basilar skull fracture and nasal injury. Furthermore, significant bleeding may occur if the patient is receiving anticoagulants or has a coagulopathy. Blind nasotracheal intubation should be avoided in patients with expanding neck hematomas. Patient combativeness, if not controlled with sedation, is also a contraindication.
Some would argue that the inability to open the mouth is a relative contraindication, because emesis may be induced that could not be cleared. The operator must exercise judgment in the individual case and be prepared to use neuromuscular blocking agents or to bypass the upper airway with a surgical technique if such a complication develops.

Procedure
The patient is placed in the "sniffing" position with the proximal neck slightly flexed and the head extended on the neck. In preparation for intubation, the operator constricts the nasal mucosa of both nares, using either 0.25 to 1.0% phenylephrine drops, oxymetazoline (Afrin) spray, or 4% cocaine spray. Topical anesthesia of the nares, oropharynx, and hypopharynx with lidocaine spray (10%) is also indicated if time permits. If available, cocaine is ideal because it is both a vasoconstrictor and an anesthetic; caution is necessary in hypertensive patients. The most patent nostril is chosen. In the cooperative patient, this can be determined simply by occluding each nostril and asking the patient which one is easier to breathe through. The most patent nostril can also be identified by direct vision, or by gently inserting a gloved finger lubricated with viscous lidocaine, full length into the nostrils. If time is not an issue, an effective method to dilate the nasal cavity and administer the anesthetic is to pass a lidocaine gel-lubricated nasopharyngeal airway (nasal trumpet) into the selected nostril. This
airway is left in place for several minutes, and progressively larger trumpets are introduced.
After preparation of the nostril, a well-lubricated endotracheal tube with a 7.0 or 7.5 mm ID is inserted along the floor of the nasal cavity. The tube is not directed cephalad, as one might expect from the external nasal anatomy, but rather is directed straight back toward the occiput, corresponding with the nasal floor. Twisting the tube may help bypass soft tissue obstruction in the nasal cavity. It is sometimes recommended that the bevel of the tube be oriented toward the septum to avoid injury to the inferior turbinate. However, such an event is rare. At 6 to 7 cm, one usually feels a "give" as the tube passes the nasal choana and negotiates the abrupt 90° curve required to enter the nasopharynx. This is the most painful and traumatic part of the procedure and must be done gently. If resistance is encountered that persists despite continued gentle pressure and twisting of the tube, the passage of a suction catheter down the tube and into the oropharynx may allow for successful passage of the tube over the catheter. [44] If this fails, the other nostril should be tried. In an attempt to avoid this difficulty from the outset, a controllable-tip tracheal tube (Endotrol, Mallinckrodt Medical Inc, St Louis) may be used that allows the operator to increase the flexion of the tube and facilitates passage past this tight curve. One study found the Endotrol tube to enhance first attempt success with blind nasotracheal intubation.
As the tube is advanced through the oropharynx and hypopharynx and approaches the vocal cords, breath sounds from the tube become louder, and fogging of the tube may occur. At the point of maximal breath sounds, the tube is lying immediately in front of the laryngeal inlet. The tube is most easily advanced into the trachea during inspiration because that is when the vocal cords are maximally open. As the patient begins to breathe in, the tube is advanced in one smooth motion. If a gag reflex is present, the patient usually coughs and becomes stridulous during this maneuver, suggesting successful tracheal intubation. The absence of such a response should alert the operator to probable esophageal passage. If there is a delay in advancing the tube, oxygen can be added to the end of the tube to increase inspired oxygen. Once the tube is in the trachea, moaning and groaning should cease. If they continue, esophageal intubation is likely. Breath sounds coming from the tube and tube fogging are other signs of endotracheal placement. Reflex swallowing during blind nasotracheal intubation may direct the tube posteriorly toward the esophagus. If this occurs, the conscious patient should be directed to stick out the tongue to inhibit swallowing and prevent consequent movement of the larynx. Application of laryngeal pressure may also help avoid esophageal passage.
Following intubation, both lungs are auscultated while positive-pressure ventilation is applied. If only one lung is being ventilated, the tube is withdrawn until breath sounds are heard bilaterally. The optimum distance from the external nares to the tube tip is about 28 cm in males and 26 cm in females. After verification of tracheal placement, the cuff is inflated and the tube is secured.

Technical Difficulties
The nasotracheal tube may slide smoothly through the hypopharynx and into the trachea on the first pass. Unfortunately, this is not always the case; in the operating room, the first attempt was successful in <50% of cases. When the initial pass is unsuccessful, there are 4 potential locations of the tip of the tube: (1) anterior to the epiglottis in the vallecula, (2) on the arytenoid or vocal cord, (3) in the piriform sinuses, or (4) in the esophagus.
Observation and palpation of the soft tissues of the neck during attempted passage of the nasotracheal tube are helpful in determining the location of the misplaced tube. This is ideally done by the operator but may also be performed by an experienced attendant. Before reattempting placement, the tube is withdrawn slightly; it is not removed from the nose, because this will create additional trauma to the nasal soft tissues. The possibility of cervical spine injury must be kept in mind when considering corrective maneuvers. Any maneuver that moves the neck significantly should not be used if alternatives are available. Methods for achieving success when difficulties with tube placement are encountered include the following:

Anterior to the epiglottis.
Difficulty advancing the tube beyond 15 cm or palpation of the tube tip anteriorly at the level of the hyoid bone suggests an impasse anterior to the epiglottis in the vallecula. Withdrawing the tube 2 cm, decreasing the degree of neck extension, and readvancing the tube will frequently remedy this problem.

Arytenoid cartilage and vocal cord.
Contrary to the classic teaching, recent studies have demonstrated a propensity for a nasotracheal tube, when placed through the right nares, to lie posteriorly and to the right as it approaches the larynx. It is not surprising, then, that the most common obstacles to advancement of the nasotracheal tube are the right arytenoid and vocal cord. No data are available on the common obstacles encountered if the tube is placed in the left nares. If the tube appears to be hanging up on firm, cartilaginous tissue, withdraw the tube 2 cm, rotate it 90° counterclockwise, and readvance the tube. This maneuver orients the bevel of the tube posteriorly and frequently results in successful passage . Another technique is to pass a suction catheter down the tube; it often will pass through the larynx without difficulty and the tube can then be advanced over the catheter.

Piriform sinus.
Bulging of the neck lateral and superior to the larynx indicates tube location in a piriform sinus. The tube should be withdrawn 2 cm, rotated slightly away from the bulge, and readvanced. An alternate method is to tilt the patient's head toward the side of the misplacement and reattempt placement.

Esophageal placement.
Esophageal placement is indicated by a smooth passage of the tube with the loss of breath sounds. The larynx may be seen or felt to elevate as the tube passes under it. Assisted ventilation will usually produce gurgling sounds when the epigastrium is auscultated. The tube should be withdrawn until breath sounds are clearly heard, and passage should be reattempted while pressure is applied to the cricoid. Increased extension of the head on the neck during placement may help. If attempts continue to result in esophageal misplacement, the following maneuver may result in successful tracheal intubation: from the precise point at which breath sounds are lost, the endotracheal tube is withdrawn 1 cm. The cuff is inflated with 15 mm of air, resulting in an elevation of the tube off the posterior pharyngeal wall and angling it toward the larynx. The tube is then advanced 2 cm; continued breath sounds indicate probable intralaryngeal location. At this point, the cuff is deflated and the endotracheal tube is advanced into the trachea . This technique may be particularly useful in the patient with cervical spine injury, because it requires no manipulation of the head or neck. This maneuver, when used on the first pass in 20 patients in the operating room, was successful in 75% of cases. One should bear in mind, however, that these patients were paralyzed and thus did not experience the laryngospasm that may be encountered in a breathing patient. The use of topical anesthesia is recommended. Alternatively, if a controllable-tip endotracheal tube (Endotrol) is used, the tip can be flexed anteriorly to help avoid esophageal placement. Remember that the tip is very responsive to pulling on the ring. A common mistake is to exert too much force on the ring, resulting in the tube curling up short of the larynx, thus preventing tube advancement.

Laryngospasm.
Laryngospasm is common when attempting nasotracheal intubation. It is usually transient. The tube is withdrawn slightly and the operator should wait for the patient's first gasp; advancement of the tube at this precise moment is frequently successful, as the vocal cords are widely abducted during forced inhalation. Laryngeal anesthesia should also be assessed, and if IV and nebulized lidocaine have already been administered without success, transcricothyroid anesthesia (e.g., 2 mL of 4% lidocaine) should be considered. Occasionally, a jaw lift is necessary to break prolonged spasm. Another option is to use a smaller tube.

Placement Under Direct Vision
This technique combines elements of oral and nasotracheal intubation. The indications and precautions are similar, and the importance of considering cervical spine injury is identical. Likewise, the need for jaw opening by physical or pharmacologic means is unchanged. This method is preferred to orotracheal intubation if the presence of an orotracheal tube might interfere with the repair of an oral injury. It is also useful when blind nasotracheal intubation has failed.
Preparation of the nose and nasopharynx and passage of the tube into the oropharynx are the same as described for blind nasotracheal intubation. It is with the introduction of the laryngoscope that the technique changes.
Laryngoscopy, as described with orotracheal intubation, is used to visualize the vocal cords and the tip of the endotracheal tube. With the Magill forceps in the right hand, the endotracheal tube is grasped proximal to the cuff (to avoid damage to the balloon) and directed toward the larynx . An assistant advances the tube gently while the operator directs the tip into the larynx and trachea. Cricoid pressure may facilitate the passage. Often the larynx can be manipulated sufficiently with the laryngoscope so that the physician can advance the tube with the right hand and guide it between the cords without using the Magill forceps. Occasionally, the natural curve of the tracheal tube guides it through the cords without any manipulation. The cuff is inflated, and both lungs are auscultated to ensure ventilation. When placement is satisfactory, the tube is secured.

Complications
Epistaxis is the most common complication of nasotracheal intubation. However severe epistaxis was encountered in only 5 of 300 cases reported by Danzl and Thomas. [42] Tintinalli and Claffey reported severe bleeding in 1 of 71 cases and less serious bleeding in 12 others. [54] Bleeding is usually not a problem unless it provokes vomiting or aspiration, a serious potential problem in obtunded patients with a clenched jaw or a decreased gag reflex. Other immediate complications include turbinate fracture, intracranial placement through basilar skull fracture, retropharyngeal laceration or dissection, and delayed or unsuccessful placement. Unsuccessful placement may be minimized by selection of a smaller tube and by gentle technique.
Sinusitis in patients with nasotracheal tubes is common and can be an unrecognized cause of sepsis. Rare but potentially fatal delayed complications include mediastinitis following retropharyngeal abscess and massive pneumocephalus.
Because most of the complications occur during tube advancement through the nasal passage and proximal nasopharynx, the complications of blind nasotracheal intubation and placement under direct vision are largely the same. However, retropharyngeal laceration and esophageal intubation are more of a threat in blind placement techniques because they are more likely to go unrecognized. One unique problem associated with nasotracheal intubation is damage of the tube cuff with the Magill forceps.
Delayed nasotracheal placement under direct vision deserves special discussion. Manipulation of the endotracheal tube through the nose and with the Magill forceps during the direct vision technique involves additional steps that require time. Because time is of the essence in the resuscitation of the critically ill patient, orotracheal intubation may be preferable.

Summary
Nasotracheal intubation is being used less frequently than in the past, because practitioners are increasingly comfortable using oral intubation in the patient with potential cervical spine injury. In addition, emergency physicians frequently use paralytics to facilitate orotracheal intubation. Nevertheless, nasotracheal intubation remains an effective and potentially life saving approach to the difficult airway and should be a dependable part of the armamentarium of all providers who are active in emergency airway management.

MODIFIED OROTRACHEAL INTUBATION

Intubation with an Intermediate Airway in Place
Esophageal Obturator/Gastric Tube Airway in Place
The unconscious patient who requires ventilatory assistance may benefit from the temporary use of the esophageal obturator airway (EOA) or similar device. Although this may be an effective means of ventilation, it is at best a temporary measure. The patient experiencing upper airway hemorrhage with the EOA in place may have oropharyngeal blood insufflated into the trachea. Also, an endotracheal tube is the preferred airway, because with endotracheal intubation the airway is more secure and ventilation more convenient. Although the EOA may allow rapid airway support until cervical spine injury can be ruled out, it is recommended that the EOA not be left in place for more than 2 hours.
Replacement of the EOA with an orotracheal tube requires appropriate care. Removal of the esophageal cuff before placement of the endotracheal tube is fraught with danger. Spontaneous gastric regurgitation often occurs on EOA removal. The rescuer must therefore learn to perform endotracheal intubation around the EOA to protect the patient from aspiration.
The patient is hyperventilated through the EOA before intubation is attempted around it. The EOA mask is then removed, and the EOA tube is moved to the left side of the patient's mouth. Laryngoscopy and intubation are then performed in the usual fashion. If resistance to passage of the tracheal tube is met, the volume of the EOA balloon should be reduced, because the balloon may be producing distortion of the larynx. Next, the operator deflates the EOA balloon completely and slides it out of the patient's esophagus. If resistance is met, the operator must be sure that the esophageal cuff has been deflated completely.

Esophageal-Tracheal Combitube (ETC) in Place
Combitubes placed in the esophagus will generally require replacement with a tracheal tube. The inflated pharyngeal balloon prevents tracheal intubation around this airway. This proximal balloon must be deflated before attempting tracheal intubation. If intubation is still not possible, the ETC may need to be removed; the stomach should first be emptied via a gastric tube placed through the esophageal port of the airway. Suction is readied, the distal balloon is deflated, and the patient is quickly intubated. This maneuver poses an added risk over that associated with the esophageal obturator intermediate airway placement (i.e., EOA and EGTA) .

Laryngeal Mask Airway in Place
The trachea can often be intubated with the laryngeal mask airway (LMA) left in place.

Bullard Laryngoscope Use
A recent development for intubating the difficult airway is the Bullard laryngoscope, an anatomically shaped rigid fiberoptic laryngoscope that provides an indirect view of the larynx . It was design`ed to aid in intubating the difficult airway; and because no manipulation of the neck is necessary, it is especially well suited for the patient with potential cervical spine injury. Indeed, in the anesthetized patient, the Bullard laryngoscope has been found to cause less head extension and cervical spine extension than conventional laryngoscopes do. [36] The recent addition of an intubating stylet attached to the laryngoscope has resulted in increased ease and speed of intubation, and the technique appears to be effective regardless of the patient's head and neck anatomy. [37] Because alignment of the oropharyngeal and laryngeal axes is not required, the Bullard laryngoscope offers the advantage provided by a conventional fiberoptic scope but requires less training to gain proficiency in its use. [38]

Indications and Contraindications
The Bullard laryngoscope is indicated in patients with anticipated difficult airways who require definitive airway control. It can be used in awake as well as unresponsive patients. [39] The total inability to open the mouth is a contraindication to the use of this laryngoscope. However, because the Bullard laryngoscope follows the contour of the mouth and hypopharynx, only 2 cm of occlusal opening is necessary for the introduction of the scope plus endotracheal tube for intubation.

Procedure
The technique for introducing the Bullard laryngoscope blade is similar to that for direct laryngoscopy. The operator, who is at the head of the patient, opens the mouth with the left thumb while holding the head stable. As the scope blade is introduced into the oropharynx, the handle is rotated to follow the curve of the hypopharynx until the handle is fully vertical. The tip of the blade can be used to lift the epiglottis, but visualization of the larynx is usually possible without this maneuver. Only minimal force is exerted along the axis of the handle. Intubation of the larynx can be accomplished using a styletted endotracheal tube or an endotracheal tube with a directional tip (Endotrol; Mallinckrodt, Critical Care, Glens Falls, NY). The technique is generally successful when using the new Bullard intubating stylet. [37]
Awake intubation using the Bullard laryngoscope can be performed comfortably using topical anesthesia and light IV sedation. [39] Adult and pediatric Bullard laryngoscopes are available, and the scope has been used successfully in neonates. [38] The Bullard scope can also be used in conjunction with nasotracheal intubation and has the advantage of requiring only 6 mm of mouth opening through which to insert the blade. [40]

Complications
The major difficulty in using the Bullard laryngoscope is the inability to visualize the larynx because of blood, emesis, or secretions. Another reason for failure is the inability to place the blade tip under the epiglottis. [37]

Summary
The Bullard scope is useful in the difficult airway uncomplicated by blood and excessive secretions. In the all-too-common setting of blood and secretions, however, the inability to visualize the vocal cords significantly limits the utility of this device in emergency airway management.

OROTRACHEAL INTUBATION

Indications and Contraindications
Any clinical situation in which a definitive airway is necessary and limited neck motion is permissible is an indication for orotracheal intubation. Many of these situations, including cardiac arrest, airway compromise in infection and trauma, and airway obstruction are discussed in detail in Chapter 1 . Most orotracheal intubations are accomplished using a direct laryngoscope. An unstable cervical spine injury is a relative contraindication to direct laryngoscopy.

Equipment
Laryngoscope
Facility in the use of the direct laryngoscope is a prerequisite for orotracheal intubation. Various adult and pediatric blade sizes are available. There are two basic blade designs-- curved (MacIntosh) and straight (Miller and Wisconsin). Slight variations in laryngoscopic technique follow from one's choice of blade design, which is often a matter of personal preference. The tip of the straight blade goes under the epiglottis and lifts it directly, whereas the curved blade fits into the vallecula and indirectly lifts the epiglottis via the hyoepiglottic ligament to expose the larynx. Special blades designed for the anterior larynx include the Siker and the Belscope (Avulunga Pty Ltd, New South Wales, Australia).
Each blade type has advantages and disadvantages. The straight blade is usually a better choice in pediatric patients, in patients with an anterior larynx or a long floppy epiglottis, and in individuals whose larynx is fixed by scar tissue. It is less effective, however, in patients with prominent upper teeth, and it is more likely to break teeth. Use of the straight blade is also more often associated with laryngospasm due to its stimulation of the superior laryngeal nerve, which innervates the undersurface of the epiglottis. A straight blade may inadvertently be advanced into the esophagus and initially present one with unfamiliar anatomy until it is withdrawn. The blade has a light bulb at the tip that may slightly hamper vision. The wider, curved blades are helpful in keeping the tongue retracted from the field of vision, allowing for more room in passing the tube in the oropharynx, and they are generally preferred in uncomplicated adult intubations. Aside from patient considerations, some clinicians prefer the curved blade because they find it requires less forearm strength than the straight blade.

Tracheal Tubes
The standard endotracheal tube is plastic and measures approximately 30 cm. Tube sizing is based on internal diameter (ID), measured in millimeters, and ranges from a 2.0 to a 20.0 mm tube, increasing in increments of 0.5 mm. The outer tube diameter is 2 and 4 mm larger than the internal diameter. Tube size is printed on the tube. There is also a scale, in centimeters, for determining the distance along the tube from the tip.
Adult men will generally accept a 7.5 to 9.0 mm orotracheal tube, whereas women can usually be intubated with a 7.0 to 8.0 mm tube. In most circumstances, tubes smaller than these should not be used, especially in patients with chronic obstructive lung disease who may be difficult to wean from the respirator due to excessive airway resistance from a small tube. However, in emergency intubations, particularly if a difficult intubation is anticipated, many clinicians
choose a smaller tube and change to a larger tube later if necessary. One exception is in the burn patient, in whom one places as large a tube as possible on the initial attempt because swelling may prohibit subsequent tube placement. For nasal intubation, a slightly smaller tube (by 0.5 to 1.0 mm) is chosen.
The cuff of a standard tracheal tube is high-volume and low-pressure. A clinical test for determining correct cuff inflation is to slowly inject air until no air leak is audible while the patient is receiving bag-tube ventilation. This usually occurs with 5 to 8 mL of air if the proper-sized tracheal tube has been selected. Many clinicians use the tension of the pilot balloon as a guide to cuff inflation; slight compressibility with gentle external pressure indicates adequate inflation for most clinical situations. For long-term use, cuff pressure should be measured and maintained at 20 to 25 mm Hg. Capillary blood flow is compromised in the tracheal mucosa when the cuff pressure exceeds 30 mm Hg.
In infants and children, the following formula is a highly accurate method for determining correct tracheal tube size:

Tube size = [4 + age (years)]/4

For most clinical situations, however, using the width of the nail of the little finger as a guide is sufficiently accurate and has been shown to be more precise than finger diameter 45911.
Correct tube size is especially important in the pediatric population, because most patients younger than 8 years are intubated with an uncuffed tube; adequate tube size is necessary to provide a good seal between the tube and the upper trachea and to prevent aspiration. A cuffed tube is used in children with decreased lung compliance who may require prolonged mechanical ventilation. In a child, the smallest airway diameter is at the cricoid ring rather than at the vocal cords, as in adults. Hence, a tube may pass the cords but go no farther. Should this occur, the next smaller sized tube should be passed after reoxygenation.
Adult endotracheal tubes will accept a standard adaptor on which the ventilator tubing will fit. Pediatric tubes require a special adaptor with a distal end small enough to accommodate the small tube size.

Preparing for Intubation
Before beginning intubation, a number of issues should be addressed. In chronologic order, they are (1) confirm that
the required intubation equipment is available and functioning; (2) position the patient correctly; (3) assess the patient for difficult airway; (4) establish intravenous (IV) access, time permitting; (5) draw up essential drugs, and; (6) attach the necessary monitoring devices. In the haste of the moment, it is a common error to fail to position the patient properly or to proceed with the procedure before the proper equipment is assembled and checked. Simple omissions, such as failing to restrain the patient's hands, removing dentures, or misplacing the suction device, can seriously hamper the performance of the procedure. A suggested pre-intubation checklist is presented in Table 2-2 .
In addition to the preparation necessary for optimum patient care, the operator should also minimize exposure to potentially infectious materials . Generally, the operator should be gloved and should wear eye and mouth protection to guard against exposure to patient secretions.
The endotracheal tube cuff should be checked for leaks by inflating the balloon before attempting intubation. The tube is prepared for placement by passing a flexible stylet down the tube to increase its stiffness and enhance control of the tip of the tube. The stylet should not extend beyond the end of the tube. The tube is then bent in a gradual curve with a more acute angling in the distal one-third to more easily access the anterior larynx. The tip and cuff of the tube are lubricated with viscous lidocaine or another water-soluble gel.
The patient should be positioned to optimally align the oral, pharyngeal, and laryngeal axes . The desired position was aptly described by Magill to make the patient appear to be "sniffing the morning air," with the head extended on the neck and the neck slightly flexed relative to the torso. A small towel under the occiput (to raise it 7 to 10 cm) may facilitate positioning. Positioning of the head and neck is a critical step; nonoptimal head positioning may be the sole reason for some intubation failures.

The Difficult Airway
The majority of difficult intubations are predictable. Perhaps the most frequently encountered condition associated with a difficult intubation is the agitated or combative patient. Fortunately, this condition can be readily eliminated through pharmacologic intervention. The classic parameters that predict a difficult intubation include a history of previous difficult intubation, prominent upper incisors, limited ability to extend at the atlanto-occipital joint, [5] poor visibility of pharyngeal structures when the patient extends the tongue (Mallampati's classification, or the tongue/pharyngeal ratio), [6] limited ability to open the mouth, [7] a limited direct laryngoscopic view of the laryngeal inlet, [7] and a short distance from the thyroid notch to the chin with the neck in extension . [8] Radiographic indicators of the ease of intubation include the mandibular length-to-height ratio [9] and the distance from the spine of the atlas to the occiput. [10] In emergency airway management, many of these predictors are not obtainable. An extensive history is rarely available, the patients are frequently uncooperative, and the presence of trauma limits movement of the neck. Fortunately, some of the key predictors are apparent simply by observing the external appearance of the patient's head and neck.
Patients with neck tumors, thermal or chemical burns, traumatic injuries to the face and anterior neck, angioedema and infection of the pharyngeal and laryngeal soft tissues, or previous operations in or around the airway suggest a difficult intubation because distorted anatomy or secretions may compromise visualization of the vocal cords. Facial or skull fractures may further limit airway options by precluding nasotracheal intubation. Patients with ankylosing arthritis or developmental abnormalities, such as a hypoplastic mandible or the large tongue of Down's syndrome, are difficult to intubate because neck rigidity and problems of tongue displacement can obscure visualization of the glottis.
Besides these obvious congenital and pathologic conditions, the short, thick neck poses the greatest difficulty for performing orotracheal intubation. In such individuals, the larynx is anatomically higher and more anterior, which makes it harder to visualize the vocal cords. These individuals are easily identified by observing the head and neck in profile. In such patients, apply laryngeal pressure and consider using the straight blade. Use of other options, including nasotracheal intubation, may be required.
It should be emphasized that some patients, despite normal-appearing anatomy and the absence of a complicating history, are unexpectedly difficult to intubate. One must be prepared for this rare but inevitable occurrence.

Procedure

Adults

Direct laryngoscopy.
The operator is stationed at the patient's head . The patient is generally supine with the head at the level of the operator's lower sternum. To maintain the best mechanical advantage, the operator keeps his or her back straight and does not hunch over the patient; any bending should occur in the knees. The left elbow is kept relatively close to the body and flexed to provide better support. In the severely dyspneic patient who cannot tolerate lying down, direct laryngoscopy can be performed with the patient seated semi-erect and the laryngoscopist on a stepstool behind the patient. [11]
The laryngoscope is grasped in the left hand with the blade directed toward the patient from the hypothenar aspect of the operator's hand. The patient's lower lip is drawn down with the right thumb, and the tip of the laryngoscope is introduced into the right side of the mouth. The blade is slid along the right side of the tongue, gradually displacing the tongue toward the left as the blade is moved to the center of the mouth. If the blade is initially placed in the middle of the tongue, the tongue will fold over the lateral edge of the blade and obscure the airway. Placing the blade in the middle of the tongue and failure to move the tongue to the left are two common errors preventing visualization of the vocal cords.
As the blade tip approaches the base of the tongue, the operator exerts a force along the axis of the laryngoscope handle, lifting upward and forward at a 45° angle. The epiglottis should come into view with this maneuver. It may help to have an assistant retract the cheek laterally to further expose the laryngeal structures. Do not bend the wrist; bending the wrist can result in dental injury because the teeth may be used as a fulcrum for the blade.
The step following visualization of the epiglottis depends on which laryngoscope blade is used. With the curved blade, the tip is placed into the vallecula, the space between the base of the tongue and the epiglottis. Continued anterior elevation of the base of the tongue and the epiglottis will expose the vocal cords. If the blade tip is inserted too deeply into the vallecula, the epiglottis may be pushed down to obscure the glottis. [6] When using the straight blade, the tip is inserted under and slightly beyond the epiglottis, directly lifting this structure. The jaw and larynx are literally suspended by the blade. If the straight blade is placed too deeply, the entire larynx may be elevated anteriorly and out of the field of vision. Gradual withdrawal of the blade should allow the laryngeal inlet to drop down into view. If the blade is deep and posterior, the lack of recognizable structures indicates esophageal passage; gradual withdrawal should permit the laryngeal inlet to come into view.
Proper neck positioning and pressure (cephalad, dorsally, and rightward) on the larynx by an assistant will facilitate visualization and intubation of an anterior larynx. If needed, suctioning is performed at this point. If the vocal cords are still not seen, consider using a tracheal tube introducer (Smiths Industries Medical Systems, Keene, NH). This device, also known as the "elastic gum bougie," is a long, semirigid introducer that is placed, using the laryngoscope, through the laryngeal inlet and into the trachea. [12A] The tracheal tube is then passed over the introducer and the introducer is withdrawn. If resistance is met in passing the tracheal tube, rotate the tube 90° counterclockwise and advance the tube.

Tube passage.
Once the vocal cords have been visualized, the final and most important step, tube passage under direct vision through the vocal cords and into the trachea, is performed. The tube is held in the operator's right hand and introduced from the right side of the patient's mouth. The tube is advanced toward the patient's larynx at an angle, not parallel with or down the slot of the laryngoscope blade. This way, the operator's view of the larynx is not obstructed by the hand or the tube until the last possible moment before the tube enters the larynx. The tube should be passed during inspiration, when the vocal cords are maximally open. It enters the trachea when the cuff disappears through the vocal cords. The tube is advanced 3 to 4 cm beyond this point. It is not enough to see the tube and the cords; the tube must be seen passing through the vocal cords to ensure tracheal placement.
When the vocal cords are stimulated, laryngospasm-- the persistent contraction of the adductor muscles of the vocal cords--may prevent passage of the tube. Inadequate anesthesia is often the cause. Pretreatment with topical lidocaine decreases the likelihood of this occurring. Two percent or 4lidocaine is sprayed directly on the cords. An infrequent but effective route for achieving tracheal anesthesia is via transtracheal puncture, injecting a bolus of 3 to 4 mL of lidocaine through the cricothyroid membrane. Laryngospasm is usually brief and is often followed by a gasp. The operator should be ready to pass the tube at this moment. Occasionally, the spasm is prolonged and needs to be broken with sustained anterior traction applied at the angles of the mandible--the jaw lift. At no time should the tube be forced, because permanent damage to the vocal cords may result. Consideration should be given to using a smaller tube. Prolonged, intense spasm may ultimately require muscle relaxation with a paralyzing drug . The pediatric patient is far more prone to laryngospasm than is an adult. [12] In a child, if vocal cord spasm prevents tube passage, a chest thrust maneuver may momentarily open the passage and permit intubation.

Positioning and securing the tube.
The endotracheal tube should be secured in a position that minimizes both the chance of inadvertent endobronchial intubation and the risk of extubation. The tip should lie in the midtrachea with room to accommodate neck movement. Because tube movement with both neck flexion and extension averages 2 cm, the desired range of tip location is between 3 and 7 cm above the carina. [14]
On a radiograph, the tip of the tube should ideally be 5 ± 2 cm above the carina when the head and neck are in a neutral position. On a portable radiograph, the adult carina overlies the fifth, sixth, or seventh thoracic vertebral body. If the carina is not visible, it can be assumed that the tip of the tube is properly positioned if it is aligned with the T3 or T4 vertebra. In children, the carina is more cephalad than in the adult, but it is consistently situated between T3 and T5. In children, T1 is used as the reference point for the tip of the endotracheal tube. [15]
An estimate of the proper depth of tube placement can be derived from the following formulas, the lengths representing the distance from the tube tip to the upper incisors in children and from the upper incisors [18] or the corner of the mouth [19] in adults:
Adults: Tracheal tube depth (cm) = 21 cm (women)
Tracheal tube depth (cm) = 23 cm (men)
In adults, this method has been shown to be more reliable than auscultation in determining the correct depth of placement. [18]
The cuff is inflated to the point of minimal air leak with positive-pressure ventilation. In an emergency intubation, 10 mL of air is placed in the cuff, and inflation volume is adjusted after the patient's condition is stabilized.
After tracheal tube placement, both lungs are auscultated under positive-pressure ventilation. Care is taken to auscultate laterally because midline auscultation may lead to an erroneous impression of tracheal placement when the tube is actually in the esophagus. With the tube in position and the cuff inflated, the tube is secured in place. Commercial endotracheal tube holders, adhesive tape, or umbilical (nonadhesive cloth) tape can be attached securely to the tube and around the patient's head . The tube should be positioned in the corner of the mouth, where the tongue cannot expel it. This position is also more comfortable for the patient and allows for suctioning. A bite-block or oral airway to prevent endotracheal tube crimping or damage from biting is commonly incorporated into the system used to secure the tube.

Infants and Children
Appreciation of the anatomic differences between children and adults is helpful when intubating the pediatric patient . Infants' proportionately larger head naturally places them in the "sniffing position," so a towel under the occiput is rarely necessary. The large head can even result in a posterior positioning of the larynx that prevents visualization of the vocal cords; a small towel under the child's shoulders should correct this problem. The head also may be floppy, and it can be stabilized by an assistant during intubation. The child's increased tongue-to-oropharynx ratio and shorter neck hinder forward displacement of the tongue and, coupled with a long U-shaped epiglottis, can make visualization of the glottis difficult.
Consequently, direct laryngoscopy in the infant and young child is generally best performed with a straight blade: Miller size 0 for premature infants, size 1 for normal-sized infants, and size 2 for older children. The infant's larynx lies higher and relatively more anterior. One can have an assistant lightly apply laryngeal pressure, or the operator can use the little finger of the hand holding the laryngoscope blade for this purpose . If no laryngeal structures are visible after laryngeal pressure, the blade should be gradually withdrawn, because inadvertent advancement of the blade into the esophagus is a common error.

Confirmation of Tracheal Intubation

Clinical Assessment
The best assurance of tracheal placement is for the operator to see the tube pass through the vocal cords . Absent or diminished breath sounds, vocalization, increased abdominal size, and gurgling sounds during ventilation are clinical signs of esophageal placement. However, esophageal placement is not always obvious. One may hear "normal" breath sounds if only the midline of the thorax is auscultated. One way to clinically assess tracheal placement after a ventilation or during spontaneous respiration is to note whether air is felt or heard to exit through the tube following cuff inflation. If the tidal volume is adequate, the exit of air should be obvious. It is important to note that when an appropriately sized tube is placed in the trachea, the patient cannot groan, moan, or speak. Any vocalization suggests esophageal placement.
Asymmetrical breath sounds indicate probable main stem bronchus intubation. Due to the angles of takeoff of the main bronchi and the fact that the carina lies to the left of the midline in adults, right main stem intubation is most common and is indicated by decreased breath sounds on the left side. When asymmetrical sounds are heard, the cuff should be deflated and the tube withdrawn until equal breath sounds are present. Bloch and colleagues report accurate pediatric tracheal positioning if after noting asymmetrical breath sounds, the tube is withdrawn a defined distance beyond the point at which equal breath sounds are first heard--2 cm in children younger than 5 years and 3 cm in older children. [20]

Esophageal Detector Device
An aspiration technique used to determine endotracheal tube location was first described by Wee in 1988. [21] The technique takes advantage of the difference in tracheal and esophageal resistance to collapse during aspiration to determine location of the tip of the tracheal tube. Following intubation, a large syringe is attached to the end of the endotracheal tube and the syringe plunger is withdrawn. If the tube is correctly placed in the trachea, the plunger will pull back without resistance as air is aspirated from the lungs. However, if the tracheal tube is in the esophagus, resistance is felt when the plunger is withdrawn, because the pliable walls of the esophagus collapse under the negative pressure and occlude the end of the tube. Another device using the same principle as syringe aspiration is the self-inflating bulb (e.g., Ellick's device).
Wee first reported use of an esophageal detector device in the operating room. [21] The tube was correctly identified in 99 of 100 cases (51 esophageal, 48 tracheal). The device result was considered equivocal in the remaining tracheal tube. The tube was removed and found to be nearly totally occluded with purulent secretions. Slight resistance was noted in one patient with a right main stem intubation; resistance decreased when the tube was pulled back. Before use, the esophageal detector device must always be checked for air leaks. If any connections are loose, the leak may allow the syringe to be easily withdrawn, mimicking tracheal location of the tube.
Wee recommends the following guidelines in using the aspiration technique: apply constant, slow aspiration to avoid tube occlusion from tracheal mucosa drawn up under high negative pressure. If the tracheal tube is correctly placed, 30 to 40 mL of air can be aspirated without resistance. If air was initially aspirated and then some resistance is encountered, the tracheal tube should be pulled back between 0.5 and 1.0 cm and partially rotated. This takes the tube out of the bronchus, if it has been placed too deeply, and changes the orientation of the bevel if the tube has been temporarily occluded with tracheal mucosa. Air is easily aspirated if the tube was in the trachea, but repositioning will make no difference if the tube was in the esophagus. The syringe aspiration technique can be used before or after ventilation of the patient. Continuous cricoid pressure should be applied pending tube confirmation. Inflation of the tube cuff will have no effect on the reliability of the test. [22] This device is reliable, rapid, inexpensive, and easy to use. Jenkins reported good success with physician use of the aspiration technique to confirm placement of emergency department and out-of-hospital intubations. [23]
A squeeze-bulb aspirator can be used as an alternative to the syringe technique. [24] [25] The bulb is attached to the endotracheal tube and squeezed; if the tube is in the esophagus, it is often accompanied by a flatus-like sound followed by absent or markedly delayed refilling. Insufflation of a tube in the trachea is silent, with instantaneous refill. An early study with the Ellick's evacuator bulb device reported that 87% of esophageal tubes were identified. [24] A later study using a slightly different bulb device (Respironics, Murrysville,Pa) found that all 45 esophageal tubes were detected. [25] The device is cheap and easy to use and can be operated single-handedly in <5 style="font-weight: bold;">End-Tidal CO2 Detector Devices
A high level of CO2 in exhaled gas is the physiologic basis for capnography and the principle on which end-tidal CO2 (ETCO2 ) detectors was developed. The most commonly available devices for emergency use are colorimetric indicators responding to CO2 levels of gas flowing through the device when placed on the tracheal tube adapter. The typical device displays two extreme colors indicating a low level of CO2 in esophageal intubation and another color in tracheal intubation. An intermediate color is indeterminate. Hand-held quantitative or semiquantitative electronic CO2 monitors are also available.
A multicenter study of a colorimetric device demonstrated an overall sensitivity of 80% and a specificity of 96%. [26] In patients with spontaneous circulation and the tracheal tube cuff inflated, the sensitivity and specificity rose to 100%. The poor sensitivity seen in cardiac arrest (69%) is due to the fact that low exhaled CO2 levels are seen in both very-low-flow states and in esophageal intubation. The device must therefore be used with caution in the cardiac arrest victim. Levels of CO2 return to normal after return of spontaneous circulation in these patients. Further, colorimetric changes may be difficult to discern in reduced lighting situations, and secretions can interfere with the color change. Regardless of the monitoring device, patients in cardiac arrest should be ventilated for a minimum of 6 breaths prior to taking a reading, because recent ingestion of carbonated beverages can result in spuriously high CO2 levels with esophageal intubation. [27]

Comparison of Detector Devices
In the setting of spontaneous circulation, both syringe aspiration and ETCO2 detection are highly reliable means of excluding esophageal intubation. A comparison of the techniques with clinical assessment was carried out in the animal laboratory, with measurement of the speed and accuracy of determination of tube placement. [28] Both the syringe esophageal detector device and ETCO2 detection were highly accurate, approaching 100%. The esophageal detector device was more rapid with determination in 13.8 seconds vs 31.5 seconds for ETCO2 detection. The detector device remained accurate when air was insufflated into the esophagus for 1 minute, simulating unrecognized esophageal placement. Clinical assessment alone yielded an alarming 30% rate of misidentifying an esophageal tube as being in the trachea. In the setting of cardiac arrest, the aspiration method is more reliable than CO2 detection, because its accuracy is not dependent on the presence of blood flow.

Complications
Prolonged efforts to intubate may result not only in hypoxia but also in cardiac decompensation. Pharyngeal stimulation can produce profound bradycardia or asystole; when it is feasible, an assistant should view the cardiac monitor during intubation of a patient who has not suffered cardiac arrest. Atropine should be available to reverse vagal-induced bradycardia that may occur secondary to suctioning or laryngoscopy. Prolonged pharyngeal stimulation also may result in laryngospasm, bronchospasm, and apnea.
The maximum interval allowable for routine intubation of the apneic patient is 30 seconds. As a guide, one should limit the time of an intubation attempt to the amount of time a single deep breath can be held. This is especially important in a child, because the functional residual capacity of a child's lungs is less than that of an adult. Failure to achieve control within this time frame demands an interval of bag-valve-mask ventilation before intubation is attempted again. The use of preoxygenation to minimize hypoxia is strongly recommended. An oxygen saturation monitor can also be used to monitor explicitly for hypoxia. Assuming optimal preoxygenation of the patient to >98% O2 saturation, attempts at intubation should be halted until the patient is reoxygenated whenever the O2 saturation drops below 92%, equal to a PO2 of about 60 to 65 mm Hg. When ventilation is not achievable, irreversible brain damage can result within minutes. Therefore, the maximum interval allowable for conservative airway management maneuvers is about 3 minutes; one must then choose alternative methods .
One should check for loose or missing teeth before and after orotracheal intubation. Any avulsed teeth not found in the oral cavity warrant a postlaryngoscopy chest film to rule out aspiration of a tooth. Swallowed teeth are of no consequence. In a study of 366 patients, McGovern and coworkers found broken teeth to be the most common complication of laryngoscopy. [29] Laceration of the mucosa of the lips, especially the lower lip, may occur if adequate care is not taken. Tracheal or bronchial injuries are rare but serious, usually occurring in infants and the elderly as a result of decreased tissue elasticity. [30] Vomiting with aspiration of gastric contents is another serious complication that can occur during intubation.
The most devastating complication of tracheal intubation is unrecognized esophageal intubation. Assessment of tube position should be the first step in the emergency department evaluation of patients who have undergone out-of-hospital intubation. The best assurance of tracheal placement is for the operator to see the tube pass through the vocal cords. Techniques to assess tube placement are discussed earlier. Another method of reliably determining tracheal tube location uses the fiberoptic scope. Passage of the scope through the tube with visualization of tracheal rings confirms endotracheal placement as well as the position within the trachea. The placement of a lighted stylet down the tracheal tube and successful transtracheal illumination also reliably predicts tracheal positioning. [31]
A chest radiograph should be taken shortly after the intubation to confirm tube placement and position. Bissinger and coworkers noted that endobronchial intubation was clinically unrecognized without a chest film in 7% of out-of-hospital intubations. [32] In addition to hypoxia, delayed tube repositioning can lead to unilateral pulmonary edema. [33] Persistent asymmetrical breath sounds after appropriate tube positioning suggests unilateral pulmonary pathology (e.g., main stem bronchus obstruction, pneumothorax, or hemothorax).
If an endotracheal tube is removed from the esophagus, vomiting may occur. This should be anticipated and suction readied. Cricoid pressure should be applied during tube removal and maintained until intubation is successful. Alternatively, the first tube can be left in the esophagus to serve as temporary gastric venting until tracheal intubation is achieved.
A persistent air leak during ventilation usually means one of three things: (1) the cuff is leaking because of damage to the balloon, (2) the cuff is positioned above or between the vocal cords, or (3) the pilot balloon is leaking. If the cuff is leaking, the tracheal tube must be replaced (see Changing Tracheal Tubes). If the pilot balloon is determined to be leaking, however, this can usually be remedied without changing the tube. [34] An incompetent 1-way balloon valve can be fixed by placing a stopcock into the inflating valve. Reinflation of the cuff followed by shutting off the stopcock should solve the problem. If the leak involves the pilot balloon itself, or if the distal inflation tube has been inadvertently severed, cut off the defective part and slide a 20-ga catheter into the inflation tube. Then connect the stopcock to the catheter, inflate the cuff, and close the stopcock.
Tracheal stricture used to be a significant late complication of long-term intubation with low-volume high-pressure cuffs. The standard use of high-volume low-pressure cuffs has markedly decreased the incidence of this complication. [35] Tubes with high-pressure cuffs are obsolete and should be avoided.

Summary
Orotracheal intubation is the mainstay of definitive airway management. In the comatose patient, it is usually accomplished rapidly and without difficulty. The easy intubation is frequently successful in the hands of the novice; the difficult intubation often proves challenging even for the experienced operator. Rapid-sequence intubation has increased the use of orotracheal intubation as the first-line approach in a variety of clinical situations and settings (see Chapter 3) . Once the patient's breathing and protective reflexes are removed, however, the operator has the supreme responsibility of safely reestablishing them. A mastery of the technique of orotracheal intubation is essential.

Tracheal Intubation

Tracheal intubation is generally considered the most definitive means of airway control. The decision to tracheally intubate must consider the patient's physiologic status, anticipated patient care needs, operator experience, and features related to preparation for the procedure. This chapter discusses the indications for tracheal intubation in greater detail as well as the preparation for intubation and the key steps and modifications of the actual procedure.

GENERAL PREPARATION
Preparation is the key to successful airway management. Two general areas of preparation should be addressed before undertaking the first attempt at definitive airway management in a clinical setting. The first is mental and physical preparedness. The second is the assembly of essential intubation equipment.
Mental and physical preparation comes from reading about the procedures, discussing the principles and details with instructors, practicing the techniques on intubation mannequins or in the animal laboratory, and finally performing the technique under supervision in a controlled clinical setting. Studies addressing various approaches to tracheal intubation are generally performed under optimal conditions (i.e., with equipment available and appropriate preparatory training). Also, often hidden within the study findings are individual learning curves. Therefore, it is overly optimistic to expect to match the success reported in the literature when first attempting a new intubation technique. However, the goal of preparation is to be as high on the learning curve as possible prior to the first clinical application of a new intubation technique. Further, continued rehearsal and application of the techniques that have been learned are important for skill maintenance.
Each approach to tracheal intubation has a preferred training format. Orotracheal intubation, for example, may be simulated with a mannequin, whereas retrograde intubation is best learned using an animal or cadaver model. Orotracheal intubation is likely to be successful on the first attempt, whereas considerable practice is required for facile use of the scope for fiberoptic intubation. In preparation for managing critical airway problems, maximal hands-on training is desirable.
The second general area of preparation is material preparedness (i.e., the immediate availability of all essential equipment required to optimally perform the airway maneuvers that are within the capabilities of the care provider). This may be accomplished by the wall-mounting of essential resuscitation equipment. [1] Alternatively, dedicated adult and pediatric airway carts may be used for placement of the equipment in an open, organized, and labeled manner that can be regularly checked. [2] The worst moment to realize that a vital piece of equipment is missing is when a patient's life depends on it. The importance of this concept cannot be overstated. Technical expertise cannot substitute for the lack of essential equipment.
In airway management, failure has ominous consequences. Mental, physical, and material preparation maximizes the chances of success.

AIRWAY ANATOMY
Requisite for a discussion of procedures in airway management is a common understanding of airway anatomy and its terminology . The following terms are used frequently :

Arytenoid cartilages
the paired cartilages forming the posterior aspect of the laryngeal inlet nasal cavity, from the external nares to the choana.

Nasopharynx
from the end of the nasal cavity (choana) to the level of the soft palate.

Oropharynx
soft palate to the upper border of the epiglottis.

Hypopharynx (laryngopharynx)
epiglottis to the lower border of the cricoid cartilage.

Vallecula
the space at the base of the tongue formed posteriorly by the epiglottis and anteriorly by the anterior pharyngeal wall.

Laryngeal inlet
the opening to the larynx bounded anterosuperiorly by the epiglottis, laterally by the aryepiglottic folds, and posteriorly by the arytenoid cartilages.

Piriform fossae (recesses)
the pockets on both sides of the laryngeal inlet separated from the larynx by the aryepiglottic folds.

Corniculate cartilage
the posteromedial portion of the arytenoid cartilage.

Cuneiform cartilage
the anterolateral prominence of the arytenoid cartilage.

Glottis
the vocal apparatus, including the true and false cords and the glottic opening.

Glottic opening (rima glottidis)
the opening into the trachea as seen from above through the vocal cords.

SPECIAL CONSIDERATIONS

Cardiac Arrest
Mouth-to-mouth and BVM ventilation may suffice for out-of-hospital care with short transport times or for the initial few minutes of ventilation in cardiac arrest. However, optimal BVM ventilation during CPR is impossible. Mouth-to-mouth and BVM ventilation are adequate and effective in the anesthetized or paralyzed patient with an empty stomach in the absence of chest compression, but they are inadequate for prolonged ventilation in the patient in cardiac arrest.
Proper BVM ventilation is probably harder to master than tracheal intubation, and prolonged attempts during CPR usually only distend the stomach and give the uninitiated a false sense of security. Patients in cardiac arrest should be orotracheally intubated. Most cardiopulmonary arrests are not associated with cervical spine injury. When there is suspicion of cervical injury, the following precautions should be followed.

Potential Cervical Spine Injury
Any patient who has sustained a significant injury has the potential for cervical spine injury. Approximately 1.5 to 3.0% of initial survivors of all types of major trauma seen in emergency departments have significant cervical spine injury. It is interesting to note that this prevalence is not increased in the setting of significant head injury. Falls from heights and motor vehicle crashes are also common causes of spinal instability.
In patients with multiple injuries, the possibility of cervical spine injury warrants caution when considering tracheal intubation involving the use of the laryngoscope. It is prudent to provide adequate oxygenation while limiting neck extension until cervical spine injury is disproved. If the patient is severely hypoxic or apneic, immediate tracheal intubation may be necessary with in-line manual stabilization of the neck (without axial traction) by an assistant. When done cautiously, oral intubation of the unconscious spinal cord injured patient may be as safe as other techniques, including intubation with fiberoptic guidance.
Note that mouth-to-mouth and BVM ventilation frequently require some degree of neck extension to open the airway. A cadaver study demonstrated increased neck motion with BVM ventilation when compared to various intubation techniques, including oral intubation, lighted stylet guided oral intubation, and nasotracheal intubation. BVM techniques may, therefore, be less desirable than the other methods of securing the airway and ventilating the patient.
Many institutions and some out-of-hospital systems use pharmacologic adjuncts, in-line cervical stabilization, and orotracheal intubation before cervical spine films are initiated. In the patient who is comatose, combative, or in severe respiratory distress without definite evidence of spinal cord injury, this approach is advocated, because it may be life saving. Precautions during intubation of the patient with known cervical spine fracture or its potential should include in-line stabilization of the cervical spine with attempts to minimize traction or lateral neck motion during the intubation procedure. Clinical experience is accumulating that supports the safety of this approach.

Potential Epiglottitis/Supraglottitis
Epiglottitis is often considered a disease of children between the ages of 2 and 8 years, but it is being recognized in adults with increasing frequency. The typical presenting picture is that of an adult or child sitting upright, drooling, or spitting up oral secretions rather than swallowing. The voice may sound muffled. There is a history of a relatively abrupt onset of a sore throat that rapidly becomes more painful. Children commonly present with a high temperature, but adults usually are only mildly febrile. The disease is especially treacherous in children because of their small airways and their tendency to panic when an oral examination or insertion of an IV line is attempted.
Small children are most calm when allowed to sit on a parent's lap. An oxygen mask with oxygen flowing at 10 L/min can be held by the parent several centimeters from the child's face. If the child is using accessory muscles to breathe, every attempt should be made to keep the child calm. If a lateral radiograph of the neck taken on inspiration can be obtained without disturbing the child, it will often establish the diagnosis. On radiography, the inflamed epiglottis often appears thickened and rounded. The hypopharynx is dilated above the obstruction.
In cases of respiratory compromise, an epiglottitis protocol should be implemented rapidly. A preestablished protocol can save many minutes of time otherwise spent trying to reach all of the personnel needed to manage this critical emergency. When a child is suspected of having epiglottitis based on history and clinical presentation, the safest course of action to establish the airway should be pursued. The emergency physician should accompany the child at all times until the airway is secure and be prepared to intervene. Otolaryngologist notification should be included in the protocol because a tracheostomy may be necessary. When operating room space or personnel are not available immediately, emergency department personnel must be prepared to manage the airway.
If the child lapses into a coma or stops making ventilatory efforts, the first step is to attempt to force oxygen past the obstruction by using mouth-to-mouth respiration or a BVM apparatus. Because the obstruction is edematous supraglottic tissue and epiglottis, positive-pressure ventilation often can displace the edema enough to allow adequate ventilation. If this effort is unsuccessful, the emergency physician should attempt oral intubation. However, a normal larynx will not be visible because of the edema. The operator should attempt to pass an endotracheal tube through the slit-like opening that remains for the supraglottic airway. An assistant can compress the chest to force bubbles through the airway, as a means of locating the airway. The assistant can also palpate the larynx and the trachea to detect the tube's entry into the trachea. If orotracheal intubation fails, the intubator should go directly to transtracheal needle ventilation (TTNV) . The obstruction of epiglottitis is mainly inspiratory, so there should be no difficulty with chest hyperinflation with intermittent TTNV. This method should ease subsequent orotracheal intubation, because the path of the airway should be readily apparent as exhaled gases pass through it.
It is recommended that all children with acute epiglottitis receive tracheal intubation. If the child is not in distress, an IV line can be established before intubation for appropriate drug administration, although some operators prefer to delay IV placement until after inhalation anesthesia.
Adults and cooperative older children with suspected epiglottitis can be examined directly. It is good practice to visualize the epiglottis and the vocal cords of the stable older patient with laryngeal tenderness who is complaining of a severe sore throat or difficulty swallowing. A mirror, fiberoptic scope, or a right-angle scope can be used to do this. In epiglottitis, the pharynx and tonsils usually do not appear inflamed, a finding that might otherwise explain the symptoms. Adults with epiglottitis do not always
need to be intubated if rigorous monitoring can be accomplished, a skilled intubator is immediately available, and the patient is not in distress. Orotracheal intubation for epiglottitis is not as difficult in adults as it is in small children. Transtracheal needle ventilation can also be used in adults who are difficult to intubate.

Jaw Clenching
Hypertonus induced by neurologic dysfunction is a common complicating factor of airway management, especially in the patient with multiple injuries, drug overdose, or seizures. Jaw clenching may be a lethal complication when it prevents clearing of blood, vomitus, or foreign bodies in the airway. No more difficult airway problem exists than occlusion of the nasal and oral passages by vomitus while the patient's teeth are tightly clenched. Respiratory efforts may lead to severe aspiration, and although the hypertonus gradually gives way as the brainstem becomes progressively hypoxic, the cerebrocortical hypoxic insult sustained in the process may be irreversible. Various disease states can lead to a similar scenario in which the jaws are clenched in the presence of upper airway hemorrhage or the accumulation of secretions.
Jaw clenching and cervical spine injury can, of course, occur together. At times, the blind nasotracheal route of intubation may be adequate for airway management while minimizing the risk of further spine injury. However, at least a small degree of spontaneous air movement should be present for the blind nasotracheal approach to be successful. Although a serendipitous success may occur in the apneic patient, it is recommended that time not be wasted on this approach in the completely apneic patient.
Neuromuscular blocking agents are generally an effective means to overcome jaw clenching in the breathing patient. Both neuromuscular depolarizing and nondepolarizing agents may be administered IV to induce paralysis and allow orotracheal intubation.

Apnea with Airway Obstruction
Despite the many nonsurgical approaches to tracheal intubation discussed in this chapter, the patient who is apneic secondary to deep airway obstruction may be served best by a surgical airway. When maneuvers to relieve airway obstruction are unsuccessful and direct laryngoscopy is not possible or cannot rapidly alleviate the obstruction and permit ventilation, the operator should rapidly move to a surgical airway approach.

CONCLUSION
Airway management is the most fundamental aspect of emergency care. Every rescuer must know basic airway maneuvers and be able to use them instinctively. When basic maneuvers fail, airway management rapidly becomes more complex. Familiarity with the ingenious intermediate airway devices can often reverse a deteriorating situation and provide the rescuer with a temporary solution to an airway dilemma. When basic and intermediate maneuvers fail, complexity, risk, and exigency mount. Choices become more critical and complications more likely. Advance consideration of situations represented in the airway management algorithms is a wise practice for the emergency physician. It may hasten accurate decision-making when time becomes critical. In this chapter we have described basic and intermediate airway techniques and offered a logical schema for their use in the patient with an acutely compromised airway. Subsequent chapters deal with the more advanced airway techniques of tracheal intubation and cricothyrotomy.