SUMMARY

The Authors examined advanced airway support

INTRODUCTION

Emergency physicians are routinely confronted by the high-stakes blend of cortical and limbic airway pressures. The evolutionary villain? Our common orifice for respiration and alimentation but then how else could you eat your own words?

This chapter reviews techniques to establish an airway and ventilate a patient after basic maneuvers have been utilized. The uses of oral and nasal airways, the bag-valve-mask unit, and various esophageal airways are discussed. The techniques of oral, nasal, and digital intubation; transillumination and fiberoptic laryngoscopy; retrograde tracheal intubation; translaryngeal insufflation; and cricothyrotomy are presented. Rapid sequence induction, neuromuscular blockade, and the role of respiratory support in cerebral resuscitation are discussed. Intubation in the setting of cervical spine trauma is presented. Finally, suctioning, extubation, and ventilator tricks of the trade are reviewed.

ORAL AND NASOPHARYNGEAL AIRWAYS. The oral airway, or oropharyngeal tube, lifts the base of the tongue off the hypopharynx. Adult, child, and infant sizes should be available. Use the oral airway only in patients without protective airway reflexes since it stimulates the gag reflex. A short oral airway functions as a bite block and helps to prevent trismic airway occlusion of an orotracheal tube. Two components of the triple airway maneuver, mouth opening and the jaw thrust, are accomplished with the oral airway. The third, head extension, is occasionally necessary to free the base of the tongue from the posterior pharyngeal wall.

The airway is placed over the tongue once the mouth is opened. The easiest technique is to insert it after depressing the tongue with a blade. Another method is to insert the tube with the convexity caudad and then rotate it. Improper insertion will increase airway obstruction by pushing the base of the tongue backward.

A variation of the oropharyngeal tube is the S tube. It is inserted just like an oral airway, and then the patient's head is extended. Ventilation is initiated after the nose is pinched and the flange sealed against the lips.

Nasal airways, or nasopharyngeal tubes, are easier to insert than oral airways. They are better tolerated by patients who are not deeply comatose and have active gag reflexes. The tube is advanced until maximal airflow is heard. If the tip is inserted too far it may stimulate laryngospasm or enter the esophagus. Insertion of a nasal airway may be a useful temporizing maneuver in patients with seizures, trismus, or cervical spine injuries. In addition, a nasogastric tube can be passed through a nasopharyngeal tube to prevent intracranial placement in patients with cribriform plate fractures.

THE BAG-VALVE-MASK (BVM) UNIT. The BVM unit includes a self-inflating bag, a nonrebreathing valve, and a face mask. The operator should check for adverse anatomic or pathologic facial conditions Depending on the operator's expertise, mouth-to-mask ventilation may be superior.

To deliver 100% oxygen, there must be a reservoir as large as the bag volume and an oxygen flow rate equaling the respiratory minute volume. The nonrebreathing valve at the mask or endotracheal (ET) tube allows air entry into the lungs with bag compression, while exhaled air exits through a separate port. Various sizes of transparent masks should be available.

Corrugated tubing reservoirs may be sensitive to variations in ventilatory technique and not deliver 100% oxygen. There are two more effective equipment options. Use a 2.5-L reservoir bag with an oxygen inflow of 15 L/min, or attach a demand valve to the reservoir port of the ventilating bag.

Before ventilating the patient, insert an oropharyngeal or nasopharyngeal tube and extend the stable neck. Then clamp the mask snugly to the face with your thumb and index finger on the mask, while the other fingers pull the chin upward. A major advantage of initially using a bag to ventilate via an ET tube is that you can better judge pulmonary compliance. Common errors in technique include air leaks around the mask and inadequate delivery of tidal volume.

Some alert patients with mild respiratory insufficiency who do not meet intubation criteria can be temporarily managed with continuous positive airway pressure (CPAP) through a snug-fitting face mask. This reduces the functional residual capacity and the work of breathing. Mask CPAP may thus delay or reduce the need for intubation. In patients with severe maxillofacial trauma and potential basilar skull fractures, pneumocephalus is a hazard.

ESOPHAGEAL AIRWAYS. The esophageal obturator airway (EOA) is a prehospital ventilatory adjunct when endotracheal intubation is not a viable option. It helps prevent gastric insufflation and regurgitation during positive pressure ventilation but is not a substitute for tracheal intubation. The only advantage of the EOA is that insertion does not require laryngeal visualization.

The EOA should be inserted only in apneic, comatose adult-sized patients. Patients with upper airway obstruction, known esophageal disease, or caustic ingestions require different airway management, as do patients with massive nasal or intraoral hemorrhage.

The original EOA design is a large-bore 34-cm tube with a rounded, occluded distal tip. A snap lock connects the tube through the center of a clear plastic oronasal mask. There are sixteen 3-mm openings in the proximal half of the tube below the mask at the hypopharyngeal level.

After attaching the mask to the proximal end of the tube, the patient's mandible and tongue are pulled forward with the head held in a neutral position. If a neck injury is excluded, slight neck flexion will decrease the incidence of inadvertent tracheal intubation. Once the mask is sealed by hand to the patient's face, ventilation is initiated. This forces air into the trachea, which is the only unobstructed orifice. Auscultation for bilateral breath sounds ensures esophageal placement of the tube. Then the cuff is inflated with 30 to 35 mL of air. The cuff must lie below the level of the carina or partial compression of the trachea will obstruct ventilation.

One variation of the original EOA is the esophageal gastric tube airway. The distal end of this tube is patent. There are two holes in the mask. The esophageal tube attaches to one, and a nasogastric tube can be passed down the tube through a valve into the stomach. This unit allows ventilation through the second hole.

Another modification of the EOA is the tracheoesophageal airway, which includes a standard ET tube. The modified face mask has two openings: one for the ET tube and the second for oropharyngeal ventilation. When the ET tube is in the esophagus it vents the stomach and facilitates gastric decompression. Applying cricoid pressure (Sellick maneuver) while the neck is held in extension facilitates tracheal placement.

In the field, a pharyngotracheal lumen airway (PTLA) is another option when endotracheal intubation is not possible. This two-tube two-cuff airway has a large low-pressure cuff that seals the oropharynx at the proximal airway.

Another permutation is the esophageal tracheal combitube. This plastic twin-lumen tube has one lumen resembling an EOA and the other an ET tube. The combitube has a proximal pharyngeal sealing balloon (100 to 140 mL air) that functionally replaces the EOA mask. The distal balloon holds 15 to 20 mL of air. Potential advantages of the pharyngeal cuff (combitube) over an oral cuff (PTLA) include a fairly consistent inflation volume to achieve a seal and less dental trauma to the cuff.

The laryngeal mask airway is another new device that is inserted blindly into the oropharynx. The patient is ventilated through a 12-mm inside diameter (ID) tube that is connected to an oval mask with an inflatable rim.

The amount of oxygenation initially possible with the EOA is similar to that provided with an ET tube. Ventilation is less efficient. The most common complication, seen in about 10 percent of EOA insertions, is inadvertent tracheal intubation. Subsequent asphyxia will occur unless this is quickly recognized.

The incidence of esophageal rupture is unknown since most patients do not receive postmortem examinations. The probable cause of esophageal tears distal to the cuff is the increased intragastric pressure exerted against an occluded esophagus during cardiopulmonary resuscitation (CPR). Esophageal tears or perforation may also result from the direct trauma of the tube or postemesis (Mallory-Weiss syndrome).

Conscious patients may complain of shortness of breath, chest pain, and dysphagia. Physical findings include subcutaneous emphysema, pneumomediastinum, Hamman's crunch, and gastrointestinal hemorrhage. There will be an increased incidence of complications in patients who are not apneic or deeply comatose. They may vomit, aspirate, or develop laryngospasm or supraglottic obstruction.

When the patient arrives, insert a cuffed ET tube before removing the EOA. The use of esophageal airways is declining. Intubation of the trachea is rapidly becoming the prehospital technique of choice.

OROTRACHEAL INTUBATION. The most reliable means to ensure a patent airway, provide oxygenation and ventilation, and prevent aspiration is endotracheal intubation. Many conscious patients require emergency intubation. They may be unable to clear the airway spontaneously of secretions, require mechanical ventilation, have aspirated, or lack protective airway reflexes. Most are lying supine on gurneys. The poignant World War I aphorism "He who looks at heaven will soon be there" still holds.

The clinical assessment of oxygenation and ventilation is unreliable in a chaotic emergency department. Oximetry is the noninvasive bedside monitoring of arterial oxygen saturation. Remember that isolated oximetry yields no clue regarding the status of alveolar ventilation. Capnography allows estimation of the PaCO2 based on the waveform display of the end-tidal PCO2. Capnometry is the numerical display. In combination, both of these noninvasive modalities aid in determining the need for more aggressive airway interventions.

Capnography can also help verify tube placement in perfusing patients and thus prevent consequential esophageal intubation. A sudden drop in the end-tidal CO2 may reflect endobronchial tube migration. When electronic capnography is unavailable, consider using disposable capnometric devices.

Technique Take a brief time to evaluate the upper airway anatomy. Examination of the teeth, oral cavity size, mentum-cricoid distance, mobility and posterior depth of the mandible, and neck mobility may clue the operator to anticipate a difficult airway. The normal adult mouth opening is three finger breadths. Consider asking the alert sober patient to open the mouth as widely as possible and protrude the tongue in your direction. The ease of laryngoscopy correlates well with the ability of the physician to visualize the soft palate, uvula, and faucial pillars.

While calling for an assistant, check and arrange the necessary equipment. The appropriate-size tube and an additional tube 0.5 to 1 mm in size smaller should be selected, and the cuff checked for air leaks. Selecting a tube with the proper diameter is essential (Table 11-2). The second hole at the end of the tube above the bevel is called Murphy's eye. This permits some airflow if the tip is occluded. Most tubes need to be cut after orotracheal intubation or they will gradually creep into the carina.

Tubes with high-volume low-pressure cuffs are best for adults. In patients younger than 6 to 8 years, use uncuffed tubes. Note that lidocaine jelly can form a clear film and eventually occlude the lumen of small pediatric tubes. Thin-walled cuffs prevent aspiration when properly inflated better than medium-walled cuffs. Microcirculation to the tracheal mucosa will be impaired if the cuff pressure exceeds 40 cm H2O. After nasogastric decompression, the cuff pressure should initially be deflated to 15 to 20 cm H2O, or just to the point of eliminating audible air leaks. Cuff overinflation can compromise the ET tube lumen.

Test the light on the laryngoscope and pick your blade. The straight Magill blade directly and physically lifts the epiglottis. The curved Macintosh blade rests in the vallecula above the epiglottis and indirectly lifts it off the larynx because of traction on the frenulum. Developing expertise with both blades is desirable, since they offer differing advantages, depending on the clinical setting and body habitus. The curved blade may be less traumatic and reflex-stimulating since it does not directly touch the larynx. It also allows more room for adequate visualization during tube placement. The straight blade is mechanically easier to insert in many patients who do not have large central incisors. Simply aim the tip of the blade directly at the epiglottis and lift it. Selecting the proper size blade greatly facilitates intubation. In adults, the curved Macintosh no. 3 or 4, or the straight Miller no. 2 or 3, is most often ideal.

When all equipment is in order, the patient should be placed in the sniffing position. (Note: The novice laryngoscopist's most common reasons for failure—inadequate equipment preparation and poor patient positioning—occur prior to the use of the laryngoscope.)

Flexion of the lower neck with extension at the atlantooccipital joint (sniffing position) aligns the oropharyngeolaryngeal axis, allowing a direct view of the larynx. Placing a folded towel or small pillow under the occiput is often helpful.

If time permits, the patient should be oxygenated with 100% oxygen prior to intubation. Begin with the laryngoscope in the left hand and an ET tube or tonsil suction catheter in the right hand. After removal of dentures and any obscuring blood, secretions, or vomitus, the suction catheter is exchanged for the ET tube and inserted during the same laryngoscopy.

The blade is inserted into the right corner of the patient's mouth. If a curved Macintosh blade is used, the flange will push the tongue to the left side of the oropharynx. If the blade is inserted down the middle, the tongue forces the line of sight posteriorly yet another reason for the putative anterior larynx. After visualization of the arytenoids, lift the epiglottis directly with the straight blade or indirectly with the curved blade. The larynx is exposed by pulling the handle in the direction that it points, that is, 90° to the blade. Cocking the handle back, especially with the straight blade, risks fracturing incisors.

One can avoid the most common error, overly deep insertion of the blade, by looking for the arytenoid cartilages. If only the posterior commissure is visible, have an assistant apply pressure on the cricoid (the Sellick maneuver). Watch the cuff as it passes completely through the cords to avoid an error. Attempts at blind passage only invite anoxia. Always be willing to abort the attempt if visualization of the larynx is not successful, and resume mask ventilation. Continuous pulse oximetry during intubation can identify hypoxia quickly.

With proper technique and practice, malleable blunt-tipped metal or plastic stylets are not usually necessary. When the patient's anat-omy requires it, the proximal end of the stylet may be bent 45°, but the tip should not extend beyond the end of the ET tube nor exit Murphy's eye.

One aid to intubation with direct vision is the use of a thin, flexible intubation stylet. This type of stylet can be inserted blindly around the epiglottis into the trachea. Then the ET tube is threaded over it into the trachea and the stylet removed. The Eschmann stylet (gum elastic bougie) is a common choice. Another option is to use the tip on the laryngeal tracheal anesthesia kit. With either stylet, orient the tube so that Murphy's eye is in the twelve-o’clock position.

Visualization of the larynx prior to cervical spine clearance is difficult, since alignment of the oropharyngeolaryngeal axis is not possible. One way to move the tip of the tube anteriorly is to use a slightly flexed directional-tip tube (Endotrol) coupled with a Sellick maneuver. Another is a flexible stylet, the Flexiguide, that passes through the tube and has a trigger similar to the Endotrol. The final option is to aim the tip anteriorly with Magill forceps while an assistant advances the tube.

Never force the tube through the vocal cords. Often the tube is too large, or too warm and flexible, especially with an Endotrol. Translaryngeal or directed transoral anesthesia with lidocaine can help relax the cords. There are two other options. Try performing a Seldinger maneuver. A tube can be advanced over a nasogastric tube in the trachea and passed below the cords. On occasion, lining up the bevel with the glottic opening will also succeed.

The tube should be advanced until the cuff disappears below the cords. Correct tube placement is about 2 cm above the carina. From the corner of the mouth, this is approximately 23 cm in men and 21 cm in women. The base of the pilot tube is usually at teeth level. The tube is also positioned by palpating its tip at the suprasternal notch and advancing it 2 to 3 cm.

After cuff inflation, insert an oropharyngeal airway or bite block and auscultate to verify bilateral lung expansion. Inadvertent endobronchial intubation is usually on the right side. Cut and secure the tube, being careful not to impede cervical venous return with the umbilical tape. Ideally use a modified clove-hitch knot or a commercial fixation. Avoid tying and kinking the pilot tube.

If the cuff leaks, tube replacement is possible with or without direct visualization. A length of nasogastric tubing two and one-half to three times the length of the ET tube can be inserted as a guide.

Complications Endobronchial or esophageal intubation will result in hypoxia or hypercarbia. Disposable capnographic devices can confirm ET tube placement. The syringe aspiration technique is another useful adjunct to the standard techniques for intratracheal tube confirmation. This may be especially useful in the prehospital setting. A catheter-tipped 60-mL syringe is snugly inserted through the adaptor at the proximal end of an ET tube. The tube must be at least size 7.0 ID. Resistance to aspiration reflects occlusion from esophageal collapse. If there is no resistance during aspiration, the tube is in the trachea. Commercial esophageal intubation detectors are also available. The adaptor on the detector's syringe fits over the 15-mm ET tube connector. The tube may be obstructed by a bulging cuff, secretions, kinking, or biting. Subsequent neck movement can also displace the tube.

Although they are uncommon, chronic complications of emergent endotracheal intubations do occur and may be quite debilitating. Arytenoid cartilage displacement, usually on the right, prevents the patient from phonating properly. Chordal synechiae may develop anteriorly, or commissural stenosis posteriorly. Subglottic stenosis is the most disastrous complication. Prevent tube motion in the larynx and trachea. This usually occurs in combative patients or those on ventilators.

NASOTRACHEAL INTUBATION Nasotracheal intubation is an essential skill that allows a flexible approach to airway management. In some locales nasotracheal intubation is a lost art. Despite the seductive pharmacologic alternative, this psychomotor skill can bail the clinician out of many difficult situations. As one example, many patients in respiratory distress may be easier to intubate in a semi-sitting position. There is always a calculated risk associated with pharmacologically extinguishing spontaneous respirations in nonfasting patients.

Technique Spray both nares with a topical vasoconstrictor-anesthetic. Then select a cuffed ET tube 0.5 to 1 mm in size smaller than that optimal for oral intubation. Check the tube cuff and firmly snug the tube adaptor. Despite universal precautions, secretions and blood may be expelled into the air and onto the intubator's face. Options include listening for air flow from a larger distance or through a section of IV tubing inserted into the ET tube. Alternatively, a protective filtering adaptor such as the Humid-Vent 1 (Gibeck Respiration, Sweden) can be attached to the proximal end of the ET tube.

Advance the tube, lubricated with a water-soluble (2% lidocaine, K-Y) jelly along the nasal floor on the more patent side. If the nares appear equal, try the right side. When the bevel faces the septum it helps prevent abrasions of the Kiesselbach plexus. Steady, gentle pressure or slow rotation of the tube usually bypasses small obstructions. If the right side is impassible, try the other side before resorting to a smaller tube.

In patients with intact protective airway reflexes, translaryngeal or directed transoral anesthesia often facilitates intubation. Translaryngeal anesthesia, not widely utilized in the emergency department, should always be considered when the initial intubation attempt is unsuccessful. After palpating the superior border of the cricoid cartilage in the midline, puncture the cricothyroid membrane with a 22- to 25-gauge 0.5- to 1-in needle. The needle should be perpendicular to the membrane in the midline, with the point of injection just cranial to the cricoid cartilage. Aspirate air, then swiftly inject 1.5 to 2.0 mL of 4% lidocaine (sterile for injection) and press the site firmly with a finger for a few seconds. Otherwise small amounts of subcutaneous emphysema would erroneously suggest laryngeal injury. In a review of 17,500 cricothyroid punctures with small-gauge needles, only eight minor complications were reported. Translaryngeal anesthesia is contraindicated if the landmarks are obscured by thyroid or tumor impingement on the cricothyroid membrane or in obese or combative patients.

Have an assistant immobilize the patient's head and initially maintain it in a neutral or slightly extended position. Stand to the side of the patient, with one hand on the tube and with the thumb and index finger of the other hand straddling the larynx. Advance the tube while rotating it medially 15° to 30° until you hear maximal airflow through the tube. Then gently but swiftly advance the tube during early inspiration. Entrance into the larynx may initiate a cough, and most expired air should exit through the tube even though the cuff is uninflated. Look for fogging of the tube.

Advancement toward the carina can be observed externally. The normal distance from the external nares to the carina is 32 cm in the adult male and 27 to 28 cm in the adult female. Auscultate to verify bilateral lung expansion and cuff inflation. Secretions or blood in the tube should be removed prior to positive pressure ventilation.

If intubation is unsuccessful, carefully inspect the neck to determine the malposition of the tube. Most commonly, it is in the pyriform fossa on the same side as the nares used. A bulge will be seen and palpated laterally. Withdraw the tube into the retropharynx until breath sounds are again heard. Then redirect while manually displacing the larynx toward the bulge. If there is no contraindication, flexion and rotation of the neck to the ipsilateral side will often help while rotating the tube medially.

The other most common tube misplacement is posteriorly in the esophagus. There will be no breath sounds through the tube, and the trachea will elevate slightly. Attempt redirection after extending the patient's head and performing a Sellick's maneuver. When cervical spine pathology is suspected, use a directional tip control tube (Endotrol) or a fiberoptic laryngoscope.

When tube passage is prevented by the vocal cords, shrill, turbulent air noises will be heard. Rotate the tube slightly to realign the bevel with the cords or squirt 2 mL of 4% lidocaine (80 mg) down the tube onto the cords if translaryngeal anesthesia was omitted. The use of continuous CO monitoring through an Endotrol during blind nasotracheal intubation can also help guide tube placement.

Congenital abnormalities in the nasopharynx, including pharyngeal bursae, may be anatomical causes of tube misplacement. With gentle technique, the obstruction can be felt and guided intubation accomplished. Hypertrophic adenoid tissue, polyps, and neoplastic lesions can also divert the tube.

Indications Nasal intubation is helpful in situations where laryngoscopy is difficult, neuromuscular blockade hazardous, or cricothyrotomy unnecessary. Severely dyspneic awake patients with congestive heart failure, chronic obstructive pulmonary disease, or asthma often cannot remain supine but do tolerate nasotracheal intubation in the sitting position. Nasotracheal tubes, in addition to being better tolerated by patients than oral tubes, are less traumatic to the tracheal mucosa since there is less intratracheal tube movement with head motion.

Patients often present with trismus from seizures, facial trauma, infection, tetanus, or decorticate-decerebrate rigidity. It may be impossible to align the oropharyngeolaryngeal axis in patients with arthritis, masseter spasm, temporomandibular dislocation, or recent oral surgical procedures. Agitated patients or those with a peculiar body habitus may be impossible to intubate orally.

Nasal intubation with a fiberoptic laryngoscope may be required when neoplastic lesions, lymphoid tissue, Ludwig's angina, peritonsillar abscess, or epiglottitis obstruct the pharynx. If the radiographic status of the neck in a traumatized patient is unknown, the nasal route is one of the noninvasive alternatives to cricothyrotomy or translaryngeal ventilation.

Contraindications Complex nasal and massive midfacial fractures, and bleeding disorders, are relative contraindications to nasotracheal intubation. However, oral intubation impedes prompt reduction and stabilization of some maxillary fractures. Since a LeFort I fracture does not extend to the cribriform plate, it is not a contraindication. Fiberoptic guidance is preferable when feasible for LeFort II and III fractures.

The risk of inadvertent intracranial passage of a nasotracheal tube is extremely low, unlike nasogastric tube insertion. Very poor technique in the setting of obvious massive head trauma would be required. Severe traumatic nasal or pharyngeal hemorrhage may necessitate orotracheal intubation or cricothyrotomy. Contamination of the spinal fluid is a hazard with some basilar skull fractures.

Complications Serious complications of nasotracheal intubation are rare. In a series of 1187 patients, there was no permanent laryngeal damage. Epistaxis is seen with inadequate topical vasoconstriction, excessive tube size, poor technique, or anatomic defects. Excessive force can damage the nasal septum or turbinates. Recheck the cuff for a potential puncture by a turbinate.

Frequent suctioning, especially if epistaxis or other upper airway hemorrhage is present, will help to prevent thrombotic occlusion of the tube or a mainstem bronchus. Retropharyngeal lacerations, abscesses, and nasal necrosis have been reported.

Paranasal sinusitis, especially occurring with prolonged nasotracheal intubation or severe cranial trauma, can be an unrecognized source of sepsis. Mucopurulent nasal drainage need not be present. The risk of postintubation sinusitis correlates with the duration of intubation, which often reflects the neurologic insult. In the setting of craniofacial trauma, any subsequent CT scans should include views of the paranasal sinuses. Other factors causing sinusitis include presence of a nasogastric tube, sinus hemorrhage or fracture, and administration of glucocorticoids. As with any route of intubation, one may observe stridor on extubation, tube obstruction or displacement, subglottic stenosis or edema, cuff overinflation, or tracheobronchitis.

DIGITAL INTUBATION. Visual landmarks may be impossible to identify because of patient positioning or anatomical disruption. Tactile digital intubation might avert cricothyrotomy when direct laryngoscopy has failed following neuromuscular blockade.

Success requires a deeply comatose patient, and even then consider inserting a molar bite-block. Lift the tongue and pull the mandible forward with a gloved hand. Insert the middle and index fingers of the other hand down the middle of the tongue. Palpate the epiglottis with the middle finger.

Then insert the ET tube, which has been shaped into a J configuration, with a malleable stylet. The tube slides along the middle finger which is in contact with the epiglottis. As the index finger guides the tube from behind, constant contact with the tip helps identify its position. Withdraw the stylet as resistance is felt when the tube enters the larynx.

TRANSILLUMINATION. Transillumination with a lighted stylet or light wand can be an intubation aid and help confirm ET tube placement and positioning. This technique is of particular assistance when direct laryngoscopy is anatomically impossible. Clinicians experienced with this technique use it to facilitate indirect visual oral or blind nasotracheal intubation.

Newer instruments can be used for either nasotracheal or orotracheal intubation. Oral intubation requires a rigid light wand. For nasal intubation, remove the trocar and insert the flexible instrument into a directional tip ET tube (Endotrol). After insertion, the intubator must discriminate between the light emanating from the larynx and that from the esophagus. Usually the circumscribed jack-o-lantern glow arising from the larynx or trachea will not be appreciated when the distal light source is in the esophagus. It may help to shield bright ambient light from the neck.

FIBEROPTIC ASSISTANCE. The flexible fiberoptic laryngoscope or bronchoscope is a valuable adjunct when there are anatomic or traumatic limitations that prevent visualization of the vocal cords. Clinical examples include conditions that prevent opening or movement of the mandible, congenital anatomic abnormalities, and cervical spine immobility. Fiberoptic instruments allow visualization of laryngeal structures and can enable difficult intubations, including those around expanding hematomas. Patients in need of an immediate airway or those with ongoing hemorrhage or copious secretions are poor candidates for fiberoptic intubation because of the time and skill needed for the technique.

Directed transoral or transnasal and translaryngeal topical anesthesia is essential. Spray the nasal mucosa with a vasoconstrictor. Dual suctioning capability is needed; attach one to a tonsil suction catheter for oral blood and secretions. Tongue extrusion and anterior mandibular displacement will be helpful if the oral route is chosen. Fragile equipment is more frequently damaged transorally. The nasal route is also more ideal because the optic tip can enter the glottis at a less acute angle.

Begin by focusing the eyepiece and lubricating the flexible shaft. Immerse the lens at the tip of the laryngoscope in warm water to prevent fogging. Continuously monitor pulse oximetry and be sure that the gag reflex has been eliminated. Attach oxygen tubing to the suction port. Consider intermittent insufflation of oxygen at 10 to 15 L/min to keep the optic tip clear, while maintaining a 1 to 2 L/min supplemental flow of oxygen. Insufflation is usually a better way to clear secretions than suction.

Remove the adaptor from an ET tube that is at least 7.0 mm ID in size. To prevent barotrauma when high-flow oxygen is insufflated, use at least a 7.5-mm (ID) tube. Then slip the lubricated ET tube over the shaft up to the handle. The distal end of the laryngoscope must extend beyond the end of the ET tube. Hold the laryngoscope with your left hand, and control the tip deflection while advancing it through the cords. The laryngoscope will function as a stylet for the tube. After the laryngoscope is in the trachea, advance the ET tube and remove the laryngoscope.

Another option is to insert a nasotracheal tube blindly into the posterior pharynx and stop about 1 to 2 cm proximal to the epiglottis. The scope is then inserted through this hollow conduit, and the fiberoptic tip can be directed into the glottis. Be careful not to pass the scope through Murphy's eye. If this occurs, it will be impossible to advance the ET tube.

The fiberoptic scope cannot be used as a stylet to guide the ET tube into the trachea. The stiffer ET tube will often deflect the thin scope tip posteriorly into the esophagus. In addition, keeping the concavity of the ET tube anteriorly toward twelve o’clock places the tube tip and Murphy's eye at three o’clock (90° to the right). The tip will then often abut the right arytenoid cartilage. Rotating the tube 90° counterclockwise lines up the tip with the upper triangular entrance into the trachea.

RETROGRADE TRACHEAL INTUBATION. Retrograde tracheal intubation (RTI) is yet another viable option when conventional airway approaches would fail. Use the same landmarks for the cricothyroid puncture as those used for translaryngeal anesthesia. Severe maxillofacial trauma, cervical or mandibular ankylosis, and upper airway masses are some of the conditions for which RTI is potentially useful.

RTI is not impeded by the blood that obscures fiberoptically guided intubation. Insertion of a retrograde translaryngeal catheter is a less invasive option than cricothyrotomy when the neck is im-mobilized and nasotracheal intubation fails. This technique can be time-consuming and must be avoided in apneic patients.

Preoxygenate the patient, then administer translaryngeal anesthesia via an 18-gauge needle through the caudal aspect of the membrane. Align the needle bevel with the syringe markings. This will help determine the bevel direction after cricothyroid membrane puncture. After angling the needle 30° to 45° cephalad, advance a 70- to 75-cm flexible-tip guidewire. Grasp it in the oropharynx or nares with forceps unless, with luck, it exits spontaneously. Another option when hemorrhage is present is to insert a 75-cm central venous pressure catheter and insufflate. To locate the tip, go for the bubbles. Insertion of a J-wire, which can be slowly twisted once it arrives at the oropharynx, can also be easier to locate than a straight guidewire. Clasp the guidewire securely with a hemostat at the neck.

Next, thread the proximal end of the guidewire through the Murphy's eye on the ET tube. This allows more of the ET tube to enter the trachea before the guidewire is removed. Tighten the wire like a tightrope and advance the tube. When the ET tube will pass no further, cut the guidewire or catheter flush with the cricothyroid membrane to minimize soft tissue contamination. Advance the ET tube, and finally withdraw the wire or catheter from the proximal end of the ET tube.

TRANSLARYNGEAL VENTILATION. Percutaneous translaryngeal ventilation (PTLV) offers a temporizing alternative approach to airway management. It does not substitute for airway control with a cuffed tube. PTLV may prove valuable in the initial stabilization of patients not able to be intubated orally or nasally. In those with severe maxillofacial trauma and an unknown cervical spine status, PTLV can be initiated until cricothyrotomy is completed.

The equipment required for this technique is readily available in emergency departments. The required high-pressure oxygen source can be provided by either a 50-psi wall source with the flow meter set on flush or an oxygen cylinder without a secondary regulator valve. Demand valve devices limited to 50 cm H2O pressure (70 cm H2O = 1 psi) do not deliver sufficient tidal volume through large-bore intravenous (IV) catheters.

This technique involves puncture of the inferior aspect of the cricothyroid membrane at a caudal angle with a 12- to 14-gauge kink-resistant over-the-needle plastic catheter. Cannulae with side holes are preferable and lessen the risk of tracheal mucosal damage. After removing the needle, advance the catheter toward the carina.

The IV catheter and three-way stopcock can be directly attached to high-pressure oxygen tubing if the edges of the stopcock are trimmed. Another convenient way to allow exhalation is to interpose a section of an 18F to 20F suction catheter with control vent between the stopcock and the tubing.

The patient is ventilated for approximately 2 full seconds or until the chest begins to rise. The valve is then released for 4 to 5 s. This simulates an I:E ratio of 1:2. If exhalation is inadequate, a second venting catheter should be inserted through the cricothyroid membrane next to the first one. Intermittently uncover the second catheter with a finger to allow exhalation. Initially ventilate at 25 psi until the correct catheter position is verified; then increase to 50 psi.

This technique differs from high-frequency jet ventilation. Rapid jet ventilation through percutaneous translaryngeal catheters has been used for emergency ventilation with pulmonary dysfunction. There are several forms of high-frequency jet ventilation, all characterized by rapid rates of ventilation (>100 respirations/min), tidal volumes less than the dead space volume, and low peak airway pressure. These characteristics increase the functional residual capacity and improve oxygenation.

Complications. Complete expiratory obstruction of the airway complicates PTLV. Barotrauma, including air embolism, has been an experimental concern. Avoid attempts to intentionally disimpact an obstruction from below. Other complications of this technique include those reviewed with puncture of the cricothyroid membrane. If the catheter is misplaced or if exhalation is inadequate, massive subcutaneous emphysema from interstitial oxygen insufflation into tissue planes is possible. Esophageal laceration or rupture, pneumomediastinum, or pneumothorax can also occur as a result of excessive insufflation pressures.

CRICOTHYROTOMY AND TRACHEOSTOMY. Laryngotracheobronchial injuries and total upper airway obstruction often mandate a surgical airway. Initial symptoms include cough, dysphagia, dysphonia, odynophagia, and hoarseness. Peritracheal fascial sleeves may initially maintain a patent airway until an enlarging hematoma occludes it or the distal trachea retracts into the mediastinum. More commonly, these techniques are required because less invasive means of tracheal intubation have failed. Another scenario is the patient for whom neuromuscular paralysis of spontaneous respirations could be dangerous. Cricothyrotomy carries far fewer and less serious complications than does emergency tracheostomy.

Cricothyrotomy was initially condemned in 1921 by Chevalier Jackson for its allegedly high incidence of subglottic stenosis. Most of the patients in this preantibiotic-era study had high-pressure tubes placed in the setting of acute laryngeal disease. The complication rate for patients with emergency cricothyrotomies varies widely. In a series of 147 patients undergoing the procedure, the complication rate was 8.6 percent. In another series of 38 cricothyrotomies performed in the emergency department, the complication rate was 40 percent. Technical changes dropped this rate to 23 percent at the same site in a follow-up series. Nevertheless, in several large series of tracheostomies, the complication rate ranged from 28 to 65 percent and were of greater severity.

Indications Indications for immediate cricothyrotomy include severe, ongoing tracheobronchial hemorrhage, massive midfacial trauma, and inabil-ity to control the airway with the usual less invasive maneuvers. Less invasive procedures may be contraindicated or impossible with mechanical upper airway obstruction, facial or cervical trauma, or uncontrollable oral hemorrhage.

Further clinical situations requiring cricothyrotomy include oral or pharyngeal edema from infection, anaphylaxis, or chemical inhalation injuries. Patients with anatomic variants, occult foreign bodies, or obstructing lesions may be impossible to intubate.

Removal of blood or vomitus may not be possible in patients with trismus or masseter spasm. In addition, cricothyrotomy may be required if blind or fiberoptic nasotracheal intubation is unsuccessful.

Contraindications. This technique should not be used on patients who can be safely intubated orally or nasally. Emergency cricothyrotomy is relatively contraindicated in the presence of acute laryngeal disease due to trauma or infection. It should also be avoided if the patient has very recently been intubated for several days. Tracheostomy may be required in patients who develop airway obstruction after removal of an endotracheal tube in place for over 72 h.

In small children under 10 to 12 years of age, the small larynx lies much higher, at the C2-3 level rather than at the C5-6 level in adults. A 12- to 14-gauge catheter over the needle is safer than a formal cricothyrotomy or tracheostomy.

The patient must be completely immobilized because the incision site is 1.5 to 2 cm below the vocal cords and above the vascular thyroid isthmus. The esophagus is posterior and the carotid and jugular vessels lateral to the incision.

Cricothyrotomy, like blind nasotracheal intubation, can cause retraction of the distal trachea into the superior mediastinum in patients with laryngotracheal injuries. Since this is a technique of last resort, a hemorrhagic disorder is not an absolute contraindication. Hemostasis is certainly easier to achieve than with a tracheostomy. The management decision depends on operator experience and the degree of respiratory distress. Airway options include formal tracheostomy, endotracheal intubation over a flexible fiberoptic bronchoscope, insertion of a small (6- to 7-mm ID) orotracheal tube under direct vision, or low transtracheal insufflation.

Technique Instruments required for emergency cricothyrotomy include a curved Mayo scissors and hemostat, a dilator, a tracheal hook, and a no. 11 scalpel blade.

Have an assistant maintain cervical immobilization. After identification of the anatomic landmarks and palpation of the cricothyroid membrane, digitally stabilize the larynx. This is critical. A vertical 3- to 4-cm incision is made through the skin. Start at the superior border of the thyroid cartilage and incise caudally toward the suprasternal notch. Alternatively, puncture the membrane caudally with a needle, which may provide a temporizing airway and guide for the incision. The blade is then rotated to make a horizontal stab through the infe-rior aspect of the membrane after it has been repalpated.

Stabilize the larynx by inserting the tracheal hook into the cricothyroid space and retracting upon the inferior edge of the thyroid cartilage. With the blade tip left in the larynx, scissors points or a hemostat is inserted beside the blade and spread horizontally. Then the scalpel is removed and a dilator (LaBorde, Trousseau) or hemostat is inserted and spread vertically. Remove the tracheal hook it could puncture the balloon. The largest tracheostomy tube that does not injure the larynx is placed, usually a no. 4 Shiley in an adult (inner diameter 5.0 cm; outer diameter 8.5 mm). The average fiber-elastic adult cricothyroid membrane measures 9 to 10 mm by 22 to 30 mm. Do not slide the tube into the anterior mediastinum.

The cuff is then inflated and the tube securely tied. Alternatively, a small-cuffed (5-mm) endotracheal tube may be cut short and inserted. It should be electively removed after location of a curved tracheos-tomy tube, which is less traumatic to the posterior tracheal wall.

A vertical midline skin incision decreases the incidence of marginal vessel hemorrhage and certainly seems to help with exposure of landmarks. A vertical incision can always be extended. Horizontal incisions would be cosmetically preferable in elective situations. The cricothyroid membrane should be punctured interiorly and at a caudal angle, since the cricothyroid arteries anastomose superiorly over the membrane.

In patients with massive neck swelling, the hemorrhage, subcutaneous emphysema, edema, or fat may make identification of normal landmarks impossible. In such cases, more formal exposure or tracheostomy may be necessary. Tracheostomy is most often necessary in pediatric patients or those with subglottic stenosis. Airway problems caused by traumatic tracheal transection, laryngeal fracture, or a zone III hematoma cannot be managed via cricothyrotomy.

An alternative approach involves location of the hyoid bone. Estimate the distance from the angle of the mandible to the chin. Insert a blade in the midline of the neck down half of that distance from the chin. Attach a skin hook to the hyoid and vertically incise inferiorly.

Several cricotomes are commercially available. These percutaneous devices allow insertion of a needle or stylet into the trachea. A functional airway is then inserted after dilatation of the tract. There is insufficient clinical experience reported to comment on their safety, particularly in children.

Complications. Immediate complications of cricothyrotomy include prolonged execution time, excessive hemorrhage, aspiration, and unsuccessful or incorrect tube placement. The most common misplacement is superior to the thyroid cartilage through the thyroid membrane. Inferior tracheotomy placement has also been reported.

Other potential complications include mediastinal or subcutaneous emphysema or creation of a false passage into the trachea. Adjacent vascular, neural, endocrine, esophageal, or pulmonary structures may be injured. Long-term complications include dysphonia from thyroid cartilage fractures, transient dysphagia, or voice changes. Infection and perichondritis may occur.

The postoperative surgical airway management is critical. Correct head positioning, aggressive humidification, and frequent suctioning prevent acute tube occlusion. Replacement of a tube prior to epithelialization of the tract is very difficult. Secure the tube and protect it with restraints as needed. Monitor for chronic complications including infection and tracheal stenosis, which is rare with correct tube size and cuff pressure.

RAPID SEQUENCE INDUCTION. Complex airway emergencies in select nonfasted patients may require rapid sequence induction (RSI). This couples sedation to induce unconsciousness (induction) with muscular paralysis. Intubation follows laryngoscopy while maintaining cricoid pressure to prevent aspiration. The principle contraindication is any condition preventing mask ventilation or intubation.

Some agitated and combative patients can only be reasoned with pharmacologically. Repeated 5-mg aliquots of haloperidol will control severe agitation. Droperidol, another butyrophenone, is a more potent and rapid onset agent. Titrate with 2.5- to 5-mg aliquots IV. Droperidol can blunt the cardiovascular response to intubation. Hypotension is rare, and there are fewer dystonic reactions than with haloperidol. Since it is a potent antiemetic, it is ideal as a premedication or for neuroleptanalgesia.

Thiopental is a short-acting barbiturate sedative. An IV dose(Thiopental) of 3.0 to 5.0 mg/kg will induce unconsciousness in 30 to 40 s and last about 10 min. It is the most widely used induction agent. An ultrashortacting barbiturate is methohexital. It is twice as potent as thiopental with half the duration of action. Avoid these cerebroprotective agents if systemic hypotension is a problem. Thiopental and methohexital are also contraindicated in status asthmaticus, and methohexital reduces the seizure threshold.

Opioids are also reversible potent induction agents. Fentanyl 2-10 mg/kg has an onset of action usually under a minute. The ideal dose (Fentanyl) is highly variable. Consider using this agent in head-injured patients. Rapid injection of high doses (Fentanyl) may cause chest wall rigidity. Alfentanil is more potent and has a more immediate onset of action. Opioids are the preferred induction choice when patients require analgesia in addition to sedation.

Another pharmacologic alternative is a short-acting benzodiazepine. Midazolam at a dose (Midazolam) of 0.1 mg/kg is another viable option since the antagonist flumazenil is available. If time permits, titrate with 0.5-mg increments. Finally ketamine is a potent bronchodilator to be considered in difficult hypotensive or bronchospastic patients. Since ketamine increases the blood pressure, it has been popular in hypovolemic situations. However it will increase the intracranial pressure (ICP) in head trauma patients.

NEUROMUSCULAR BLOCKADE. Neuromuscular blocking agents facilitate management of selected patients in the emergency department. The most commonly used agents are succinylcholine, vecuronium bromide, pancuronium, and atracurium. Succinylcholine allows persistent depolarization to occur at the neuromuscular endplate, mimicking acetylcholine. In contrast, vecuronium, pancuronium, and atracurium are nondepolarizing curariform agents. They compete with acetylcholine at the myoneural endplate receptors. The blockade is reversible with acetylcholinesterase inhibitors.In the emergency department, neuromuscular blockade can improve mechanical ventilation and help control intracranial hypertension. Paralysis improves oxygenation and decreases peak airway pressures in a variety of disorders, including refractory pulmonary edema and respiratory distress syndrome. Patients with refractory status asthmaticus; status epilepticus; or tetanic spasms resulting from clostridial infections or a variety of toxins, including strychnine, may improve with blockade.

In addition, extremely violent, agitated patients who jeopardize aeromedical personnel or their own airway security, spinal cord integrity, or fracture stability may require pharmacologic restraint. Be certain to maintain attempts to correct hypoxia and hypovolemia, coupled with physical restraints.

For the conditions mentioned above, nondepolarizing agents are preferable to succinylcholine. Although the onset of action is delayed, there are fewer adverse cardiovascular and histaminic effects, coupled with a longer duration of paralysis.

The dosage of pancuronium is 0.10 to 0.15 mg/kg IV. After documentation of the neurologic examination, including pupil size, pre-sedation is advised unless there is a significant head injury. Muscle relaxants are neither anxiolytics nor analgesics. Omission of sedation is a common error, and patients then remain aware of their paralysis. An increased sympathetic tone can exacerbate arrhythmias. Consider pancuronium or ketamine in irreversible status asthmaticus.

Vecuronium bromide is another nondepolarizing agent. This curariform drug is approximately one-third more potent than pancuronium. The duration of action is one-third to one-half as long. Vecuronium does not cause the degree of tachycardia commonly seen after pancuronium, since it has one-twentieth of the vagolytic effect. This simplifies interpretation of a tachycardia developing in the trauma patient. Hypersensitivity reactions are rare, doses are only mini-mally cumulative, and excretion is biliary. Despite the lack of histamine release, hypotension may occur through two other mechanisms. Sympathetic ganglia blockage occurs, and venous return is decreased from both absent muscle tone and the positive-pressure ventilation.

The usual dose of vecuronium is 0.08 to 0.1 mg/kg IV. Maximal paralysis occurs within 3 to 5 min, with full blockade lasting for 25 to 40 min.

Atracurium is another agent more suited for patients with hepatic or renal failure. Elimination is via ester hydrolysis and Hoffman degradation, a nonenzymatic process. This nondepolarizing agent's elimination half-life is approximately 20 min, versus 65 to 75 min with vecuronium. Recovery time is consistent and unaffected by anticonvulsants. Consider this agent for intubated patients requiring brief diagnostic or therapeutic procedures. Atracurium also offers advantages when continuous infusion is essential to maintain a required level of neuromuscular blockade precisely. The risk with prolonged infusion is accumulation of laudanosine, a neuroexcitatory metabolic byproduct.

The reversal of nondepolarizing muscle relaxants should not be attempted prior to some sign of motion or spontaneous recovery. Ideally, a train of four twitches should be elicited with a neuromuscular stimulator. Reversal requires 0.01 mg/kg of atropine IV, followed by 0.5 to 1.0 mg/kg of edrophonium IV. The onset of action is 30 to 60 s, with a duration of 10 to 30 min. This reversal may be shorter than the duration of the muscle relaxant. Edrophonium is an acetylcholinesterase inhibitor with a faster onset and fewer muscarinic side effects than the longer-acting neostigmine. Prophylactic atropine given before the cholinergic agonist edrophonium helps prevent muscarinic side effects.

When the indication for blockade is tracheal intubation, succinylcholine is the most commonly used agent. It has a more rapid onset (30 to 60 s) and shorter duration of action (average 5 to 6 min) than does vecuronium or pancuronium. After a brief fasciculation, complete relaxation occurs at 60 s with maximal paralysis at 2 to 3 min.

The dosage of succinylcholine is 1.0 to 1.5 mg/kg IV for adults and 2.0 mg/kg for children under 12 years. Be prepared to obtain an airway surgically if intubation attempts fail. Succinylcholine produces adequate intubation conditions in the emergency department, despite some significant risks.

The other alternatives for decreasing the time to intubation involve administration of a small priming dose (10 percent of the actual dose)of vecuronium or high-dose (0.15 to 0.28 mg/kg) vecuronium. These may prove viable alternatives in the emergency department despite their intermediate duration of action.

Approximately 2 to 3 percent of intubations prove impossible with standard techniques. Emergency physicians selecting neuromuscular blockade must anticipate difficult intubations despite time-limited assessment of the patient's physiognomy.

Before injection of succinylcholine, 0.01 mg/kg of atropine IV may attenuate the muscarinic vagal effects, especially in children and vagotonic adults. Serious arrhythmias are not rare. An additional pretreatment to consider is a subparalytic dose (Vecuronium bromide)(Vecuronium)(Norcuron) of 0.01 mg/kg vecuronium to prevent the initial muscle fasciculations that may cause long-bone fractures to become displaced. This is most pronounced in muscular adolescents.

Intraocular pressures also increase. In addition, increased intragastric pressure predisposes to aspiration. ICP increases are another concern with succinylcholine. This increase in ICP is greater in patients with central nervous system (CNS) neoplasms than in those with acute CNS hemorrhage or trauma. If the intubation is rapid, immediate hyperventilation may compensate. Pretreatment with vecuronium and a short-acting barbiturate can attenuate transitory intracranial hypertension, which occurs during tracheal intubation of some patients with significant head trauma.

Avoid barbiturates, including thiopental, unless the cranial trauma is isolated. There is the potential for systemic hypotension, especially with associated injuries. Topical laryngeal and/or IV lidocaine (1.5 mg/kg) may minimize the increase in the ICP.

There are other, less preventable side effects of succinylcholine. The serum potassium will transiently rise an average of 0.5 mEq/L with succinylcholine. Hyperkalemia is even more pronounced hours after muscle trauma or burns. Avoid depolarizing agents in patients with burns, muscle trauma, myopathies, rhabdomyolysis, narrow-angle glaucoma, renal failure, or neurologic disorders. Any patients with denervated musculature (e.g., Guillain-Barré syndrome) are particularly at risk. Genetically susceptible individuals may develop acute malignant hyperthermia. Have dantrolene sodium available.

Patients with an atypical pseudocholinesterase will require prolonged ventilatory support, as will those with burns, cirrhosis, or carcinomas who have low plasma pseudocholinesterase levels.

Effective oxygenation and ventilation during cerebral resuscitation often requires neuromuscular blockade. Autoregulation of cerebral blood flow (CBF) over a range of perfusion pressures may be impaired. As a result, CBF becomes pressure-dependent (CBF = CPP/CVR, where CPP is cerebral perfusion pressure and CVR is cerebral vascular resistance). Autoregulation is usually intact when the CPP ranges between 50 and 130 mmHg. The CPP equals the mean arterial pressure minus the ICP. Ideally, it should be kept well over 70 mmHg.Therefore, respiratory support of the bucking or posturing patient becomes critical. After blockade, select an FIO2 sufficient to maintain an arterial PO2 of 100 mmHg, fully saturating hemoglobin. Institute prophylaxis against atelectasis with positive end-expiratory pressure (PEEP) of up to 5 cmH2O. Higher levels impair cerebral venous drainage because of the elevated intrathoracic pressure. Avoid other modalities that also increase the ICP, including excessively tight ET tube straps, tight cervical collars, or Trendelenburg positioning.

The optimal PaCO2 following blockade for the individual patient with intracranial hypertension is frequently unknown. Hyperventilation will decrease cerebral blood volume while cerebral vasoconstriction is intact. Postresuscitation, cerebral vasospasm may decrease CBF, and thus overzealous hyperventilation could be harmful. Always avoid hypercapnia, generally maintaining the PaCO2 around 28 to 30 mmHg.

INTUBATION IN CERVICAL SPINE INJURY. Airway management of patients with the potential to have an unstable cervical spine injury challenges clinical judgment. There is no single best algorithm. The reported incidence of injury ranges from 1 to 12 percent. Cervical spine radiography without a thorough and reliable neurologic examination does not clear the neck. From 20 to 30 percent of cervical spine injuries are not appreciated on a single cross-table lateral view. Spinal cord injury without radiographic abnormal-ity (SCIWORA) is an important consideration, especially in children.

As a result, determine whether immediate airway intervention is needed. There is a large selection of airway options to consider while attempting to maintain cervical spine immobilization. The selection is far less critical than the timing. When there is evidence of a cervical cord injury or significant intracranial hypertension, consider blind nasotracheal intubation or rapid sequence induction and oral intubation. Oral intubation appears safe when achieved without hyperdistraction, flexion, or extension of the neck. Maintenance of cervical spine immobilization is the paramount issuenot the approach to secure the airway.

The need for in-line cervical stabilization should not be considered a license for axial in-line traction. In the near-hanging victim, at-tempting to radiographically visualize C7 by countertracting on the head and shoulders is indiscreet. Attempt to block any further in-crease in the ICP.

Patients not in urgent need of an airway should be neurologically and radiographically evaluated as thoroughly as is practical, given the patient's condition. The presence of systemic hypotension or intracranial hypertension guides the selection of sedatives or induction agents.

SUCTIONING. A variety of conditions render patients unable to clear their own secretions. Aspiration usually occurs when the tone of the lower esophageal sphincter is insufficient to deal with increased intragastric pressure and protective laryngeal airway reflexes are depressed. Common iatrogenic causes include BVM ventilation, nasogastric tubes, and pharmacologic neuromuscular paralysis. Predisposing conditions include trauma, bowel obstruction, obesity, overdose, pregnancy, and hiatus hernia.

Attention to technique reduces the risk. A rigid-tip plastic tonsil suction catheter works best for large quantities of oropharyngeal secretions, including blood and vomitus. Clear the pharynx either with the tonsil suction catheter or digitally. When necessary, place the patient in a left lateral Trendelenburg position. This gets the tongue out of the laryngoscopist's way. Perform endotracheal suctioning immediately.

To suction the nasopharynx and tracheobronchial tree, use a well-lubricated, soft, curved-tip catheter. Straight catheters will usually pass into the right mainstem bronchus. If a curved-tip catheter is available, turning the head to the right in addition to catheter rotation will facilitate passage into the left bronchus.

Select a suction catheter of a size no larger than half the diameter of the tube to be suctioned. This will prevent pulmonic collapse from insufficient ventilation during suctioning. Oxygenate the patient before and after suctioning to avoid transient desaturation. Insert the catheter without suctioning, and then remove, suctioning with rotation over 10 to 15 s.

Complications of suctioning include hypoxia, cardiac arrhythmias, hypotension, pulmonic collapse, and direct mucosal injury. The magnitude of the ICP increase during endotracheal suctioning may be related to the increase in intrathoracic pressure with coughing. Consider topical laryngeal or intravenous lidocaine.

Continued airway patency is not assured after ET tube insertion. Suctioning clears clotted blood or inspissated secretions. In addition, mechanical obstruction from tumors or vascular malformations may be detected.

Endobronchial ball-valve obstruction can occur with a clot. This will impair ventilation and produce hyperinflation of individual lobes. Cuff displacement or overinflation has also resulted in ball-valve obstruction of the airway. Cuffs inflated in the field during frigid conditions will expand with warming. Recheck for unequal breath sounds or asymmetrical chest expansion. Elevated inspiratory pressures develop and exhalation is prevented, ultimately resulting in tension pneumothorax.

Deflate the cuff when tracheal ball-valve obstruction is suspected. If the tube is blocked, deflation will allow exhalation. Specific diagnosis and relief of endobronchial obstruction requires bronchoscopy.

MECHANICAL VENTILATORY SUPPORT. Ventilators are pressure-cycled or volume-cycled. Pressure-cycling is usually limited to pediatrics and does not control the volume delivered. Most emergency departments will have volume-cycled ventilators. Other decisions regarding mechanical ventilatory support in the emergency department include the mode, FIO2 minute ventilation, and use of PEEP or CPAP.

There are three common ventilator modes or methods of providing the tidal volume: controlled mechanical ventilation (CMV), assist-control (A/C), and intermittent mandatory ventilation (IMV). Use the control mode for apneic patients. The A/C mode allows the patient to trigger a cycle by inhaling and lowering the air pressure, which can be adjusted by the ventilator's trigger sensitivity (1 to 3 cmH2O). The ventilator will provide a nontriggered controlled breath unless one is triggered during the selected time cycle. Finally, a predetermined number of ventilator-generated tidal volumes can be assured either unsynchronized (IMV) or more commonly synchronized to patient effort (SIMV). In the emergency department, the A/C or SIMV is the preferred initial mode except with an apneic patient.

The initial FIO2 should be guided by the oximetry. Set the tidal volume at 10 mL/kg ideal body weight and adjust the rate accordingly. Maintain the peak airway pressure (PAP) below 40 to 45 cmH2O to prevent barotrauma. The tidal volume can be increased up to 15 mL/kg to adjust the PaCO2 unless it elevates the PAP.

PEEP or CPAP should be considered if the decreased pulmonary compliance prevents delivery of an adequate tidal volume or if hypoxemia persists despite an FIO2 of 100 percent. Even low levels (3 to 5 cmH2O) of PEEP/CPAP usually render ventilator sighs (1.5 ´ tidal volume) unnecessary. If hypotension develops, adjust the respiratory rate and PEEP to lower the mean airway pressure.

EXTUBATION. Extubations are always potentially hazardous. While patients are recovering their protective airway reflexes, they may fight the tube. Injection of 1 to 2 mL of 4% lidocaine (sterile for injection) down the ET tube will decrease bucking. Absorption of lidocaine via the airway yields sustained levels, while the maximum serum level is slightly lower than that from an equivalent intravenous dose (lidocaine).

Prior to extubation, rule out metabolic or circulatory abnormalities and check for respiratory insufficiency. Prior nasogastric decompression is advised. On command, the patient should have an inspiratory capacity of 15 mL/kg. There should be no intercostal or suprasternal reactions, and the patient's grip should be firm.

After suctioning secretions, assure adequate oxygenation of the patient with 100% oxygen. Explain the procedure to the patient. Ventilate with positive pressure, using the BVM unit to exsufflate secretions while the cuff is deflated. At the end of a deep inspiration, to prevent secretory reaccumulation, remove the tube and oxygenate by mask.

Observe the patient closely for stridor. Postextubation laryngospasm is initially treated with oxygen by positive pressure. If necessary, nebulized racemic epinephrine (0.5 mL 2.25% in 4-mL saline) often helps. Rarely, neuromuscular blockade to facilitate reintubation or cricothyrotomy is necessary.

BIBLIOGRAPHY

1. Benumof JL: Management of the difficult adult airway. Anesthesiology 75:1087, 1991.
2. Dailey RH, Simon B, Young GP, Walls RM: The Airway: Emergency Management. St. Louis, Mosby Year Book, 1992.
3. Schuster DP: A physiologic approach to initiating, maintaining, and withdrawing mechanical ventilatory support during acute respiratory failure. Am J Med 88:268, 1990.
4. Storer DL: The pharmacology of airway control. Emerg Care Q 7:69, 1991.
5. Yealy DM, Stewart RD, Kaplan RM: Myths and pitfalls in emergency translaryngeal ventilation: Correcting misimpressions. Ann Emerg Med 17:690, 1988.