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blade may inadvertently be advanced into the esophagus and initially present one with unfamiliar anatomy until it is withdrawn.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.

INTERMEDIATE AIRWAYS

Intermediate airways are those interventions that go beyond the maintenance of a patent airway. They represent a midpoint between airway establishment and true airway control. Airway control is secured by maneuvers such as tracheal intubation and tracheotomy, in which an endotracheal cuff isolates the trachea. The devices described in this section occlude the esophagus and allow ventilation across the larynx. The devices discussed are the esophageal obturator airway (EOA), the esophageal gastric tube airway (EGTA), the laryngeal mask airway (LMA) and the esophageal-tracheal Combitube (ETC) airway (Sheridan Catheter Corp., Argyle, NY). Two are designed to occlude only the esophagus (EOA and EGTA), one (LMA) seals the larynx at the hypopharynx level, and one ETC offers the versatility of use whether placed into the esophagus or the trachea. Each is designed for use in the unconscious patient who requires positive-pressure ventilation. The esophageal cuff or seal built into these devices reduces gastric content aspiration. The EOA and EGTA have fallen into general disfavor in recent years due to the gravity of errors in placement. Complications including esophageal rupture and tracheal intubation have led many to prefer the ETC or LMA as an intermediate airway.
Esophageal Obturator Airway and Esophageal Gastric Tube Airway
The EOA and the EGTA maintain airway patency in ways similar to the oral and nasal airways, but they also protect
the airway by occluding the esophagus to reduce gastric distention and regurgitation. The face mask permits use of these airways as positive-pressure ventilating devices. Air insufflated through the airway traverses the upper airway before crossing the larynx and entering the trachea. Ventilation from the EOA exits the airway through numerous ports in its hypopharyngeal portion . Ventilation from the EGTA is identical to mask ventilation, with the addition of esophageal occlusion. A port is available on the EGTA to vent the stomach. The attractiveness of the EOA and the EGTA for use in the apneic patient stems from their retention of much of the simplicity of the artificial airway with the addition of an important feature of more complicated airways--some protection against regurgitation and reduction of gastric distention.

Indications and Contraindications
Speed and simplicity are advantages of the esophageal airway over tracheal intubation. Trained individuals can successfully place an esophageal airway in an average of 5 seconds, whereas the same individuals may need 20 seconds to perform a tracheal intubation. In one out-of-hospital study, failure to intubate was much higher with the endotracheal tube (19.4%) than with the EOA (1.7%). [19] Neck motion is not as necessary with the esophageal airway as it is with tracheal intubation. For these reasons, the EOA may be an effective adjunct in the management of the unconscious injured patient who requires respiratory assistance. Hypercarbia may occur more commonly with EOA ventilation as compared with endotracheal ventilation. The most difficult aspect of this form of ventilation is securing a tight fit with the mask. Dentures should be left in place to give support to the lips. Adequate tidal volume must be delivered to ventilate the lungs.
There are various contraindications to the use of the EOA and the EGTA. Because the airway is not protected from pharyngeal secretions, the presence of active oropharyngeal bleeding and excessive secretions represent a relative contraindication to EOA and EGTA use. Because of attendant discomfort, the devices cannot be used in the awake patient. Size specifications preclude their use in the pediatric patient; 16 years is the age usually cited as the lower limit for EOA and EGTA use. The actual limiting factors are the size of the esophagus and the face; an adult-sized 14-year-old would certainly tolerate an EOA or EGTA if necessary. However, a small adult may not receive an appropriate fit. Other contraindications include esophageal injury or conditions predisposing to perforation. A patient who has ingested a caustic agent or one with a known esophageal stricture should not undergo esophageal intubation. As a precaution against pressure-related complications, it is recommended that the device not be left in place for longer than 2 hours. It must be recognized that the EOA and the EGTA are temporary forms of airway control. This form of airway control is most often used in out-of-hospital care.

Placement of EOA/EGTA
The head is in the neutral position during placement of the EOA and the EGTA. Neck motion is unnecessary. The rescuer grasps and pulls the jaw forward. At this point, the rescuer inserts the assembled airway with the mask attached. The obturator tip is directed into the patient's posterior pharynx with gentle, steady pressure. The obturator is advanced down the esophagus until the mask rests flush against the face of the patient. Figure 1-9 (Figure Not Available) A illustrates the correct position at placement. The cuff should lie in the esophagus just distal to the carina of the trachea. The rescuer postpones inflation of the balloon until proper position is confirmed. The patient is ventilated with a tight mask seal on the face, and the lungs are auscultated. For effective ventilation, the mask seal must be tight. Breath sounds should be audible bilaterally. Unilateral breath sounds or failure of auscultation should lead the rescuer to reassess the airway placement. Pneumothorax or hemothorax may explain unilateral sounds, as may inadvertent main stem bronchus intubation. Tracheal intubation will result in the absence of breath sounds. The possibility of bronchial or tracheal intubation requires removal and replacement of the airway. Once satisfactorily placed, the esophageal balloon is inflated to 20 to 25 mL.

Complications
A 5% incidence of inadvertent tracheal intubation has been reported by Don Michael in experience with 29,000 placements. In a subsequent smaller sample, a 2.9% (5 of 170) incidence was reported with a 100% mortality among the 5 patients. One study comparing out-of-hospital EOA placement with endotracheal tube placement found that the occurrence rate for complications of the EOA that prevented resuscitation (tracheal placement, tube kinking) was nearly three times higher for the EOA (8.7% vs 2.6%). If not quickly rectified, tracheal intubation with the EOA or tube kinking are disastrous complications that produce occlusion of the patient's airway. Disciplined examination for bilateral breath sounds is critical.
Esophageal lacerations of undetermined depth were found in 8.5% of autopsies of patients in whom the EOA was used.Esophageal rupture has been found and reported in case histories. Since Scholl and Tsai first reported esophageal ruptures in 1977, the recommended balloon inflation volume was reduced from 35 to 20 mL. No further ruptures or leakage around the cuff have been reported. However, factors other than balloon inflation volume that theoretically can contribute to rupture include careless balloon removal without deflation and forceful attempts at placement when obstruction is met.
Tracheal intubation should be performed BEFORE removal of the EOA, because vomiting often occurs following deflation of the balloon and EOA removal. If the EOA cuff has been overinflated, it may partially occlude the trachea and make intubation difficult. In such cases, the balloon is partially deflated to facilitate tracheal intubation.

The Laryngeal-Mask Airway
The laryngeal-mask airway (LMA) (Intavent International SA, Henley-on-Thames, England) functions intermediately between an oropharyngeal airway and an endotracheal tube. It was developed for use in the operating room as an alternative for endotracheal intubation, but it has also been recommended for use in difficult intubations. It consists of a tube fitted with an oval mask, rimmed with an inflatable cuff. Contrary to usual mask design, the mask is intended to reside in the hypopharynx rather than on the face. It is inserted digitally until its tip meets resistance in the upper esophageal sphincter. The cuff is then inflated, forming a seal around the glottic opening. The result is a relatively secure airway. However, it cannot be considered to protect against gastric regurgitation. Leakage of the hypopharyngeal mask allows aspiration of emesis and gastric distention may occur with misplacement. Although the device may be used for prolonged periods under appropriate conditions, it is usually considered a temporary adjunct until tracheal intubation is established.

Indications and Contraindications
The LMA is indicated for patients requiring an airway who cannot be endotracheally intubated. The most frequently cited example is a patient whose anatomy prevents visualization of the larynx. Contraindications include the inability to open the patient's mouth and vomiting.

Placement of LMA
The LMA is first checked for possible air leaks by inflating and deflating the cuff. If the patient has a gag reflex, deep oropharyngeal topical anesthesia or conscious sedation must be administered. With the patient's head in the sniffing position, the mask is lubricated and oriented so the mask opening is facing the tongue. With the index finger of the dominant hand placed on the proximal aspect of the mask, the mask is inserted into the mouth, firmly against the hard palate. The index finger (or thumb) may also be used as a guide during advancement. With one smooth motion, the mask is advanced until resistance is encountered. With the tip of the mask thus seated in the upper esophageal sphincter, the cuff is inflated. The lungs are auscultated to confirm correct placement.
While the sniffing position is desirable, it has been shown that LMA placement was 95% successful when the patient was placed in the neutral position with in-line immobilization, simulating a trauma setting.
After successful placement of the LMA, several methods are available to achieve subsequent endotracheal intubation. The first method is simply to pass an appropriately sized endotracheal tube down through the lumen of the LMA, rotate the tube 90° so that the tip easily passes through the fenestrations, and advance it through the larynx to the trachea . This has been found to be successful in 90% of attempted cases. The second method involves the use of a tracheal tube exchanger. The exchanger is passed blindly down the lumen of the LMA and into the trachea. The LMA is then removed and an endotracheal tube is passed over the tracheal tube exchanger. This method of tube placement must be combined with confirmation of exchanger location, because it has been shown to pass into the esophagus in up to 70% of attempts. Confirmation of endotracheal tube location should be made . The third and most dependable method of intubation with an LMA in place is via a fiberoptic scope. A lubricated, appropriately sized endotracheal tube is mounted over a fiberoptic scope, and this combination is advanced through the lumen of the LMA out through the mask and through the larynx. The scope is then removed, but the LMA may be left in place with the cuff deflated. If the LMA must be removed after a tracheal tube has been successfully placed through it, pass a tracheal tube exchanger down the tube, remove the tracheal tube/LMA combination, and replace it with a tracheal tube.

Complications
Although the LMA works well in most cases, this airway has several significant drawbacks. Aspiration is always a possibility, because the cuff does not provide a watertight seal. Laryngospasm can occur if adequate anesthesia is not achieved. A significant air leak around the cuff may occur when high airway pressures exist, leading to poor ventilation. Finally, success rates in the operating room range from 94 to 98%; success rates in difficult emergency airway management are unknown, but they are undoubtedly lower.

Conclusion
The LMA is a blindly placed intermediate airway that should be considered in patients who require establishment of an emergency airway but cannot receive endotracheal intubation. The technique is quick and simple, requires a minimum amount of training, and appears effective in the hands of paramedics, nurses, and respiratory therapists.

The Esophageal-Tracheal Combitube
The ETC is a noninvasive airway device that is placed blindly. It allows for effective ventilation and oxygenation when placed in either the esophagus or the trachea. The device has two lumina running parallel to each other. One is perforated at the level of the pharynx and occluded at the distal end, similar to the EOA. The second lumen is open at the distal end, resembling an endotracheal tube. The device has two balloons: a proximal pharyngeal balloon that occludes the oropharynx by filling the space between the base of the tongue and the soft palate and a smaller, distal cuff that serves as a seal in either the esophagus or trachea . The Combitube has compared favorably with the endotracheal tube with respect to ventilation and oxygenation in cardiac arrest situations. It is also placed more rapidly.

Indications and Contraindications
The ETC is superior to other intermediate airways, because no face mask seal is necessary. It may be preferable to tracheal intubation in certain situations, because it can be placed blindly and is also effective in the esophageal or tracheal position. It is, therefore, more easily placed than an endotracheal tube and is indicated in situations in which tracheal intubation is difficult, neck motion is impossible, or the rescuers are not skilled in tracheal intubation.
The ETC should not be used in patients with an intact gag reflex and is not recommended in patients younger than 16 years or less than 5 feet in height. It is contraindicated in suspected caustic poisonings or proximal esophageal disorders.

Placement of ETC
The device is held in the dominant hand and gently placed caudally into the pharynx while the nondominant hand grasps the tongue and jaw between the thumb and index finger. The tube is passed blindly to a depth where the printed rings on the proximal end of the tube lie between the patient's teeth or alveolar ridge. The pharyngeal balloon is then filled with 100 mL of air, and the distal cuff is subsequently filled with 10 to 15 mL of air. The large pharyngeal balloon serves to both securely seat the ETC in the oropharynx and to create a closed system in the case of esophageal placement. Because approximately three-quarters of placements are esophageal, ventilation is begun through the longer (blue plastic) connector associated with the esophageal lumen. Chest rise and good breath sounds without gastric insufflation confirms effective placement in the esophagus. However, gastric insufflation without breath sounds and chest rise indicate a tracheal positioning of the tube and require changing the ventilation to the shorter (clear plastic) tracheal lumen. Auscultation of breath sounds over the lateral lung fields confirms endotracheal placement of the Combitube. If the tube is in the esophageal position, gastric suctioning can be accomplished by passing a catheter through the open lumen into the stomach while the patient is being ventilated via the other port.
An alternative method to identify position is to attach an aspirating device to the tracheal or clear plastic shorter tube. The inability to easily aspirate air confirms esophageal placement necessitating ventilation via the longer blue esophageal tube. In the patient with ventilatory effort, CO2 detector devices also may be useful.
A patient who has been successfully resuscitated with an ETC positioned in the esophagus should ultimately receive a definitive airway. The steps required to place a tracheal tube in this setting are detailed in Chapter 2 but consist generally of deflating the large pharyngeal balloon and, with the distal balloon still inflated, intubating around the ETC.

Complications
Inappropriate balloon inflation and incorrect ETC placement can lead to air leaks during ventilation. The most common placement error is an improper insertion angle. A more caudal, longitudinal direction is recommended, as opposed to an anteroposterior direction of insertion. Another caveat is that the ETC must be maintained in the true midline position during insertion to avoid blind pockets in the supraglottic area, which prevent passage of the tube. Attention to the ring markings on the tube at the level of the incisors ensures proper positioning of the tube. One must remember to first inflate the oropharyngeal balloon before inflating the distal balloon. Although unlikely, esophageal injury is theoretically possible with the overinflation of the distal balloon.

BAG-VALVE-MASK VENTILATION

Indications and Contraindications
Correctly performed, the BVM method of ventilation appears to be simple and effective. Still, it is fraught with difficulty and therefore deserves special mention. Bag-valve-mask ventilation should be used by experienced individuals who are able to ensure a tight mask seal in situations requiring positive-pressure ventilation. The BVM is often used with an oropharyngeal or nasopharyngeal airway in place.
Inexperience is a relative contraindication to the use of a BVM. A rescuer who is not skilled with the BVM will achieve much better ventilation with mouth-to-mouth or mouth-to-mask breathing than with a BVM. However, concern regarding transmission of infectious diseases has reduced the willingness of the lay public and health professionals to perform mouth-to-mouth ventilations. Although BVM ventilation may provide excellent respiratory support in the anesthetized, paralyzed patient in the operating room, the device frequently is of marginal value during cardiopulmonary resuscitation (CPR), during an ambulance run, or in the combative patient. A tight mask seal is mandatory to prevent loss of air volume during ventilation. Another hazard of BVM ventilation occurs when vomitus, blood, or other debris is present in the mouth or pharynx. The foreign material may be insufflated down the trachea if it is not cleared before ventilation. The three major problems encountered with BVM ventilation are inadequate tidal volumes, inadequate oxygen delivery, and gastric distention.

Ventilation Technique
Achieving adequate tidal volume with BVM ventilation requires a tight mask seal and adequate compression of the bag. Even trained paramedics practicing on manikins have difficulty delivering tidal volumes above 650 mL, which is well below the 10-15 mL/kg recommended by the American Heart Association. A variety of mask configurations are available to facilitate a tight seal, but none substitutes for the practiced skill of the rescuer. For the single rescuer, only one hand can be used to achieve the seal because the other must squeeze the bag. The rescuer's hand must be large enough
to apply pressure anteriorly while simultaneously lifting the jaw forward. The thumb and index finger provide anterior pressure while the fifth and fourth fingers lift the jaw. Care must be exercised to deliver an adequate tidal volume by full compression of the bag. Dentures generally should be left in place to help ensure a better seal with the mask.
It has been suggested that effective BVM ventilation during CPR requires two hands and, therefore, two rescuers. We suggest using the two-rescuer technique whenever it is practical. The presence on the BVM device of a pop-off valve may further frustrate ventilation efforts in the patient with reduced compliance.
All BVM devices should be attached to a supplemental oxygen source (with a flow rate of 15 L/min) to avoid hypoxia. A significant problem with the BVM method is the low oxygen saturation achieved with various reservoirs. The amount of delivered oxygen is dependent on the ventilatory rate, the volumes delivered during each breath, the oxygen flow rate into the ventilating bag, the filling time for reservoir bags, and the type of reservoir used. The commonly used corrugated tube reservoir is the least effective of those examined by Campbell and colleagues. [14] It is too sensitive to ventilatory technique and does not alert the clinician to changes in oxygen flow. A 2.5-L bag reservoir and a demand valve are the preferred supplementation technique during BVM ventilation.
Pediatric BVM devices should have a minimum volume of 450 mL. Pediatric and larger bags may be used for ventilation of infants with the proper mask size, but care should be taken to administer only the volume necessary to effectively ventilate the infant. Pop-off valves should be avoided because airway pressure under emergency conditions may often exceed the pressure of the valve.

Complications
Hypoventilation often occurs because of the difficulty of carrying out the technique properly. Three mechanisms can result in complications: poor mask seal, failure to achieve airway patency, and low tidal volume. Practiced skill development is necessary to avoid these errors. Gastric distention can also result from poor airway patency. Air is insufflated down the esophagus, which inflates the stomach. Consequently, the risk of regurgitation and aspiration increases. When assistance is available, the application of firm posterior pressure on the cricoid ring helps reduce gastric inflation during BVM ventilation. [15] [16] The technique must be used carefully in infants, whose airway is more pliable and subject to obstruction with excessive cricoid pressure. Even with proper BVM technique, aspiration can occur. The rescuer must be vigilant to recognize complications early and take corrective action.