Chapter 35. Airway Management

• The choice between noninvasive ventilation via mask versus ventilation via translaryngeal tracheal intubation is an increasingly critical branch point in the management of patients with respiratory failure.
• Shock, a failed trial of extubation, inability to protect and maintain one's own airway, need for larger minute ventilations or larger transpulmonary pressures, and transport of an unstable patient all remain indications for tracheal intubation.
• Assessment and adequate preparation of the patient prior to intubation are crucial to ensuring successful and safe intubation.
• Awake tracheal intubation with topical anesthesia remains the preferred technique, although skilled operators can perform rapid sequence induction and intubation with a high degree of success. General anesthesia and paralysis are associated with substantial risks in critically ill, hemodynamically unstable patients.
• The appropriate timing of tracheostomy remains poorly defined. Improved endotracheal tubes allow for prolonged intubation with a low risk of associated traumatic injury.
• Percutaneous tracheostomy and conventional tracheostomy are increasingly performed at the bedside to minimize the hazards associated with transporting a critically ill patient.

Tracheal intubation remains one of the most common and important procedures performed in the intensive care unit (ICU). When done well, tracheal intubation can be a lifesaving procedure. When done poorly, it may initiate a cascade of events that can lead directly or indirectly to trauma, severe complications, and death. The widespread adoption of noninvasive ventilation in the management of patients with type II acute-on-chronic respiratory failure (ACRF) and high-pressure pulmonary edema has created a population of patients who have failed moderate levels of ventilatory support and require emergent airway management (see Chap. 33). It is imperative that those who manage the airways in these patients have a high degree of knowledge, skill, and comfort in managing patients with little physiologic reserve. It is imperative that ICU physicians have knowledge and understanding of the indications for tracheal intubation, the assessment of the patient for tracheal intubation, the devices and techniques available for tracheal intubation, and the consequences and complications of tracheal intubation.1

The decision about whether to intubate a critically ill patient requires that a practitioner at the bedside synthesize all of the information they have at their disposal about a patient, compare it to their institutional practice patterns and resources, and decide how to proceed. These decisions are rarely clear-cut; reasonable practitioners can arrive at different decisions in identical circumstances. Patients who require intubation as part of the initial management of their respiratory failure include but are not limited to those with cardiopulmonary arrest, respiratory arrest, acute respiratory distress syndrome (ARDS) of almost any cause, and any patient who is unlikely to respond to noninvasive ventilation (Table 35-1). The decision to intubate a patient after noninvasive ventilation is even more difficult to make. Triggers to convert to an invasive airway include progressive hypercapnia in spite of adequate levels of support (such as a patient with sleep apnea who is worsening on biphasic positive airway pressure [BIPAP]), unacceptably high airway pressure, hypoxemia which persists in spite of moderate levels of continuous positive airway pressure (CPAP) and high fraction of inspired oxygen (FiO2), diminishing mental status, patterns of respiration which suggest evolving respiratory muscle fatigue or impending respiratory arrest, and unfavorable anatomy (which is present at the start of treatment, or which evolves) (Table 35-2).

In patients with airway compromise, two decisions need to be made at the time the patient is evaluated: (1) Does this patient require an artificial airway? and (2) Does this patient require a tracheostomy? It may be difficult or impossible to translaryngeally intubate the trachea in patients with an unstable cervical spine, airway tumor, unfavorable anatomy, or significant facial trauma. Preparation for tracheostomy should occur concurrently with preparation for translaryngeal tracheal intubation in such high-risk patients.

The decision to intubate patients in cardiopulmonary arrest is a simple one, as intubation is the safest and most effective way to both ensure adequate ventilation in these patients and to protect their airway. The goal of intubating the trachea in the patient in shock is to decrease the proportion of cardiac output devoted to perfusing their respiratory muscles, allowing this blood flow to be diverted to other vital organs.

All patients being evaluated for tracheal intubation should be treated with the highest FiO2 available. Oxygen saturation, blood pressure, heart rate, electrocardiography (ECG), and the frequency and strength of respiration should be closely monitored. Blood gas analysis may be helpful in facilitating the decision to intubate the patient, but has been largely supplanted by pulse oximetry, which is also essential for monitoring during intubation.

Patients requiring urgent intubation benefit from an expeditious but thorough assessment of their underlying medical conditions and airway anatomy (Tables 35-3 and 35-4). The possibility of increased intracranial pressure (ICP) or increased risk of intracranial hemorrhage is important to ascertain, since the presence of elevated ICP changes the emphasis in airway management from the maintenance of an adequate airway to the avoidance of further increases in ICP. Whereas most airway manipulation in the ICU can be done safely with patients awake, patients with elevated ICP and increased risk of intracranial hemorrhage (from unstable arteriovenous malformations or aneurysms) are best managed with intravenous general anesthesia for intubation. Laryngoscopy and tracheal intubation reliably produce myocardial ischemia in patients with coronary artery disease. Adequate anesthesia—topical and intravenous—can attenuate or prevent the myocardial ischemia associated with laryngoscopy and intubation. Inadequate anesthesia can elicit ischemia and associated arrhythmias. The use of intravenous agents in this setting is fraught with hazard. Too little intravenous agent can be associated with ischemia, while too much can cause hypotension, ischemia, hypoperfusion of vital organs, and a decreased rate of redistribution of the offending agent, prolonging its cardiovascular effects. The use of intravenous agents in these patients is thus best avoided if possible.

Intubation and positive pressure ventilation (PPV) will magnify the shock associated with intravascular hypovolemia. In hypovolemic patients, reflex sympathetic tone usually decreases venous capacitance, increases mean systemic pressure, and maintains venous return. Administration of sedative or anesthetic agents blunts this physiologic compensation. PPV increases intrathoracic pressure and therefore decreases the pressure gradient driving venous return. Singly or in combination, these effects can substantially reduce venous return, blood pressure, and tissue perfusion. In the setting of suspected hypovolemia, intravascular volume expansion may be desirable before intubation. In any case, preparation for rapid volume infusion should be made prior to intubation.

Patients with respiratory failure require thoughtful assessment of their shunt, V/Q mismatch, and bronchospasm prior to airway manipulation. The more severe their pathology, the more rapidly they will become hypoxic or hypercarbic during airway manipulation. Patients with acute hypoxemic respiratory failure are usually hypoxemic in spite of a high FiO2, and frequently desaturate further during airway manipulation. Patients with type II respiratory failure may become hypoxemic, hypercapneic, or both during airway manipulation. The more severe the lung disease, the less likely it is that ventilation with a mask or laryngeal mask airway (LMA) will be successful. Patients with severe pulmonary edema or severe bronchospasm cannot generally be ventilated successfully with a mask or LMA because the pressures and flows required to maintain an acceptable minute ventilation cannot be generated with these systems.

Manipulation of the airway in the ICU is accompanied by a substantial risk of aspiration. Unlike patients undergoing airway manipulation in an elective setting, such as the bronchoscopy suite or operating room, patients in the ICU typically are at high risk of aspiration. Stomach contents may include enteral feedings, blood (from gastrointestinal hemorrhage), acid, and bacteria. Conditions that decrease emptying, such as diabetic gastroparesis, morbid obesity, and perhaps critical illness itself, require management as if the patient has a full stomach, even during elective airway management. Cricoid pressure (the Sellick maneuver) should be performed whenever possible on patients undergoing tracheal intubation in the ICU.1–4

The presence of a coagulopathy is a relative contraindication to nasal intubation and techniques that are associated with a risk of bleeding, such as transtracheal injection of anesthesia, superior laryngeal nerve blocks, and retrograde intubation techniques.

Finally, contraindications to the use of succinylcholine (see Table 35-3), the most commonly used muscle relaxant for airway management in the ICU, should be considered prior to any airway manipulation.

A variety of anatomic conditions are associated with increased difficulty of intubation by rigid laryngoscopy (see Table 35-4).5 A history of difficult intubation is perhaps one of the most important but least available elements of a patient's history. The presence of many anatomic conditions makes attempts at rigid laryngoscopy and intubation in the awake or asleep patient more difficult. This in turn increases the attractiveness of techniques which allow for the patient to be awake and spontaneously breathing, and that do not require direct laryngoscopy, such as fiberoptic intubation, blind nasal intubation, and techniques which utilize an intubating laryngeal airway. Patients with severely compromised airway anatomy may be best managed by either awake fiberoptic intubation or tracheostomy. When a difficult airway is anticipated, it is best to have equipment for performing a tracheostomy immediately available, and physicians skilled at performing the procedure at hand.

In spite of the vast array of available equipment, most tracheal intubation can be accomplished using a very small subset of the equipment and a very simple checklist (Table 35-5). A cart that is fully stocked with all of the equipment required to manage a difficult airway should be available to airway managers, but need not be brought to the bedside of every patient in crisis.6

Ideally, bags or boxes containing the equipment on the basic list for cardiac arrest are readily available to airway managers and can be brought by them to any situation in which they may be asked to manage an airway. The more complete equipment set for urgent and elective intubation can be kept in a cart stocked specifically for this purpose. Equipment should be checked at least daily and should be stored so that it is readily accessible. It is important that the equipment is checked by the person who will use it. This procedure ensures that the airway manager can focus on the patient during airway manipulation, and is not distracted by equipment failures, equipment checks, or preparation.

Pharmacologic Preparation and Use

The goals of pharmacologic preparation of the patient include creating conditions that allow safe intubation, providing relief from the discomfort and hemodynamic consequences associated with airway manipulation and tracheal intubation, and decreasing the hormonal and neurologic consequences of the procedure. The spectrum of pharmacologic preparation ranges from topical to intravenous general anesthesia. In the hands of experienced operators, most airway manipulations can be accomplished with topical anesthesia alone. Intravenous general anesthesia is indicated in the setting of elevated ICP and favorable airway anatomy (Table 35-6). There are many institutions where an intravenous general anesthetic is routinely administered for tracheal intubation, but this practice should be strongly discouraged. The majority of the literature suggests that the use of intravenous general anesthesia to facilitate airway management may be associated with a higher rate of failure and need for emergency tracheostomy/cricothyroidotomy.

Patients who require urgent intubation benefit from pharmacologic preparation when circumstances allow. The administration of 0.2 mg IV glycopyrrolate will dry the mouth and facilitate direct laryngoscopy or fiberoptic laryngoscopy. The oropharynx can be anesthetized topically with 4% lidocaine spray, followed by approximately 1 to 2 mL of 2% lidocaine jelly on an oral airway of appropriate size for the patient. The oral airway can also be used to direct topical anesthetic at the vocal cords. The use of lidocaine for topical anesthesia is preferable to benzocaine, as the latter can cause methemoglobinemia. Care should be taken to avoid giving high doses (>6 mg/kg) of lidocaine for topical anesthesia, since lidocaine is readily absorbed by the mucosa of the pharynx. Some practitioners routinely perform transtracheal and superior laryngeal nerve blocks to facilitate awake intubation, but these procedures add little or nothing to topical anesthesia, and can cause significant bleeding in coagulopathic patients. Topical/local anesthesia schemes that avoid anesthetizing the trachea have several advantages in the ICU setting. They allow the patient to retain some ability to protect themselves from aspiration, and they also allow confirmation of tracheal intubation when the patient coughs in response to introduction of the tube into the trachea.

The use of intravenous agents to facilitate tracheal intubation in the ICU is hazardous. The degree of hypovolemia, myocardial dysfunction, and shock that often exists in these patients is difficult to ascertain prior to manipulating the airway in an urgent situation. Doses of intravenous agents that are well tolerated or even subtherapeutic in healthy patients can precipitate respiratory arrest or circulatory collapse in critically ill patients, converting a serious situation into a desperate one. Intravenous lidocaine in a dose of 100 mg is frequently sufficient to induce general anesthesia in patients with shock. The use of intravenous agents such as midazolam, fentanyl, thiopental, etomidate, propofol, and ketamine should be restricted to experienced practitioners. When indicated, these agents may be used to either titrate up to an acceptable level of sedation (which will be accompanied by a corresponding decline in both hemodynamics and minute ventilation, with associated worsening of hypoxia and hypercapnia), or to deliberately induce brief general anesthesia.

Muscle Relaxants and Airway Management in the Intensive Care Unit

The use of muscle relaxants to facilitate airway management in the ICU remains controversial. Although these agents are routinely administered to facilitate airway management in the operating room, their use in ICU patients is not essential. The use of intravenous induction agents to initiate general anesthesia is motivated by the desire to produce intubating conditions quickly and to minimize unpleasant recall. Most patients undergoing elective surgery tolerate the hemodynamic consequences of intravenous anesthetic agents well and can be readily oxygenated and ventilated with a bag and mask. When anesthesiologists are confronted with patients who have abnormal airway anatomy or who may be impossible to oxygenate or ventilate with a bag and mask, they tend to opt for awake intubation strategies, as outlined in this chapter. Muscle relaxants, including succinylcholine, vecuronium, mivacurium, rocuronium, and cisatracurium should be used only by those who are experienced in managing the airway with an Ambu bag and mask, and who are thoroughly versed in techniques used to manage the difficult airway. The reason for this stipulation is that once these agents are administered, it is imperative that a definitive airway be obtained within minutes. Attempts at ventilating most patients in respiratory failure with an Ambu bag and mask are often difficult and frequently futile, since the decreased compliance of the lungs and/or increased airway resistance makes it difficult to maintain adequate minute ventilation. Among muscle relaxants available to facilitate airway management, succinylcholine remains the agent of first choice in ICU and ER patients for whom it is not contraindicated.7

There is an evolving literature about the use of intravenous anesthetic agents and muscle relaxants to facilitate airway management in both the field and the emergency department.8–18 This literature suggests that the use of intravenous agents can both improve intubating conditions and cause hypotension, although brain-injured traumapatients have worse outcomes.19,20 Airway management utilizing muscle relaxants in these reports is associated with a success rate in the range of 94% to 99%, with 1% of patients requiring a surgical airway of some kind. At first glance, this appears to be conspicuous success, but compared to airwaymanagement in the operating room, it is a very high rate of failure, and a very high rate of requirement for a surgical airway. No doubt some of the need for surgical airways in these patients is a consequence of their pathology, their anatomy, and the circumstances surrounding their airway management. Nevertheless, it seems plausible if not certain that the requirement for a surgical airway in some of these patients is a consequence of the use of either intravenous anesthetics or muscle relaxants as part of their airway management.

Compared to the operating room environment, arterial oxygen desaturation occurs quite rapidly in most patients undergoing intubation in the ICU, even if the patient has been preoxygenated with 100% oxygen. Factors that contribute to desaturation include an increased alveolar-arterial gradient, decreased functional residual capacity (FRC), and increased metabolic rate. Nevertheless, all patients undergoing airway management in the ICU should be preoxygenated.

The presence and help of well-trained assistants increases safety and success of intubation. Assistants might include other physicians, ICU nurses, respiratory therapists, and others trained in airway management and routinely engaged in the bedside care of critically ill patients. Ideally, the person managing the airway in the ICU has several helpers, one to help position the patient and apply cricoid pressure, one to hand off equipment, and one to monitor the patient and administer IV drugs as necessary.

Patients in cardiopulmonary arrest are relatively straightforward to intubate, as they are typically unconscious and flaccid. No drug therapy is necessary to facilitate airway management in these patients. Direct laryngoscopy should be attempted immediately, and the largest possible appropriate-sized endotracheal tube (ETT) should be inserted into the trachea. Many patients will have aspirated oral secretions or gastric contents prior to or after their cardiopulmonary arrest, and the necessity of suctioning using a rigid catheter (Yankauer) to achieve adequate visualization should be anticipated. Patients receiving cardiopulmonary resuscitation (CPR) do not typically deliver much carbon dioxide to their lungs, and attempts to confirm endotracheal intubation with CO2 monitors may therefore be futile. The ability to detect carbon dioxide in the exhaled gases of such patients is usually a sign of the recovery of a spontaneous circulation. Cervical instability is the only coexisting condition that requires serious consideration during the intubation of a patient receiving CPR. All other medical and anatomic considerations are secondary in this situation.

In the past few years, there have been several clinical studies that have demonstrated an association between nasal intubation and the evolution of sinusitis, and between sinusitis and the development of ventilator-associated pneumonia (VAP) (see Chap. 43). Given this, it is probably the case that the oral route of intubation is preferable in most critically ill patients. Nasal intubation may still be desirable in a select population of patients with normal immunity, normal coagulation status, and relative contraindications to oral intubation.

Orotracheal Intubation

Advantages of oral intubation include the requirement for less equipment (a laryngoscope), less trauma and bleeding, a lower incidence of sinusitis and VAP, and a high success rate independent of patient respiratory effort.21,22 The disadvantages of oral intubation include the substantial stimulus associated with direct laryngoscopy, risk of dental and cervical trauma, difficulty securing the tube, difficulty of maintaining oral hygiene, and the occasional problem of a patient biting the tube. Patients must generally be supine to undergo orotracheal intubation. Orotracheal intubation is far more difficult to accomplish than it appears to the casual observer, especially in the less-than-ideal conditions that are typical of airway management in the ICU.

Most patients can be successfully intubated with topical anesthesia alone. Most patients will benefit from treatment with 0.2 mg of glycopyrrolate as a drying agent, and topical anesthesia using a combination of lidocaine spray (4%) and jelly (2% to 4%). Topical anesthesia usually begins with spraying the oropharynx with lidocaine, obtaining as much coverage of the oro- and hypopharynx as possible to obliterate the gag reflex. An appropriately sized oral airway (9 mm is a good default) is then covered with lidocaine liquid or jelly and inserted into the pharynx. The patient is instructed to suck on the airway. Lidocaine can also be sprayed through the oral airway directly towards the larynx. The importance of the oral airway as a mechanism to administer topical lidocaine requires emphasis, as it is the quality of the hypopharyngeal anesthesia that allows direct laryngoscopy to be performed. An adequately prepared patient will permit placement of a laryngoscope blade or even a more uncomfortable device such as an intubating LMA. Once the operator is assured that the airway has been adequately prepared, laryngoscopy (direct or fiberoptic) is performed, and intubation is attempted. Direct laryngoscopy in adults is usually performed using a Macintosh no. 3 or 4 blade, although straight blade designs (such as the Miller) are popular with some operators. The curved blades are generally easier to use, but the straight blades may be more useful in the event of difficulty obtaining an adequate view. It is desirable for those who manage airways in the ICU to be comfortable with both designs. Although circumstances are frequently less than ideal, the operator should do everything possible to ensure successful laryngoscopy. If possible, the head of the bed should be removed, and the bed moved away from the wall. The patient should be positioned in the sniffing position using pillows and rolled blankets as necessary. Failure to adequately position the patient is a common cause of repeated intubation attempts in the ICU setting. Once the patient has been intubated, it is imperative that the airway manager hold the tube firmly in place until the tube has been secured. Oral ETTs must be secured at least with tape; they may be wired to secure teeth in circumstances in which the use of tape is undesirable or impossible. Importantly, the pressure in the cuff of the tracheal tube should be maintained at 20 to 22 cm H2O pressure from the time it is inserted to minimize the risk of VAP.23

Successful tracheal intubation can be confirmed by a variety of techniques in the spontaneously breathing patient, including the appearance of humidified gases in the tube, audible breath sounds at the end of the tube, breath sounds synchronous with Ambu bag ventilation, and carbon dioxide detected via capnography or capnometry.

Nasotracheal Intubation

The disadvantages of nasal intubation are the increased risk of associated purulent sinusitis, VAP, and bleeding.24,25 Advantages of nasal intubation include ease of securing the tube, free access to the mouth, greater stability relative to oral intubation, and absence of biting-associated obstruction. Nasal intubation can be accomplished with the head in a neutral position (or in traction) and with the patient sitting upright in bed. Nasally intubated patients are less likely to self-extubate than orally intubated patients.26,27 Blind nasal and fiberoptic nasal intubation are readily accomplished in patients with air hunger. Other disadvantages include the greater length of the ETT and trauma to the nasal mucosa, septum, and turbinates. Relative contraindications to nasal intubation include coagulopathy, compromised immune function, and suspected or known skull-base trauma.

Nasal intubation can be performed either blindly, with direct laryngoscopy, or fiberoptically. Larger-bore tubes, such as 8.0 mm ETTs, should be used in nasal intubation, as they can be inserted as readily as smaller tubes in most patients, present substantially less resistance to air movement than do smaller tubes, and are large enough to allow fiberoptic bronchoscopy to be performed.28

Nasal intubation can be successfully performed without sedation, provided that adequate topical anesthesia is used. Many experienced operators prepare both nares simultaneously, so if an anatomic complication arises in attempts to use the first one, the second one can be used without delay. Those who desire to vasoconstrict the nasal mucosa prior to manipulating it can do so with 0.5% phenylephrine spray.29 Topical anesthesia such as 4% lidocaine can then be sprayed into both nostrils. Following this step, a nasal trumpet lubricated with 2% lidocaine jelly is introduced into one of the nares. Successful introduction of the trumpet confirms the presence of a passage patent enough to allow an ETT to be passed. If the operator encounters any difficulty in passing the nasal trumpet, the attempt to intubate the trachea through that nostril should be abandoned. Once the trumpet is successfully inserted, lidocaine is then sprayed through the trumpet onto the vocal cords. It is best to use ETTs intended for use in the nose (such as the Endotrol tube) when performing nasal tracheal intubation, as conventional tubes may be too short and too rigid to be used safely for this purpose. The ETT is lubricated with 2% lidocaine jelly and passed into the nasopharynx. If any resistance is encountered as the tube is advanced, the operator should stop immediately. Attempts to advance the tube past substantial resistance are associated with mucosal tears, polypectomies, turbinatectomies, crushed and perforated nasal septa, and tunneling of the ETT underneath the mucosa, all of which can be associated with exuberant bleeding and other major complications. If fiberoptic intubation is planned, the bronchoscope is introduced through the tube into the nasopharynx and is advanced into the trachea. The bronchoscope is used as a stylet to advance the ETT into the trachea. Tracheal intubation can be confirmed by observing the carina and presence of tracheal rings beyond the tip of the ETT. If the plan is to perform nasal intubation under direct laryngeal visualization with a rigid laryngoscope, the oropharynx should be anesthetized concurrently with the nose. Direct laryngoscopy is then performed, and a Magill forceps may be used to guide the tube into the trachea. If blind nasal intubation is planned, then the ETT is advanced slowly, with inspiration, while the operator listens at the end of the tube for breath sounds. As the end of the tube gets close to the glottis, the breath sounds become louder. The tube is advanced into the trachea while the patient is instructed to take a deep breath. The sensation of the tube popping through the cords followed by efforts at a cough by the patient suggest successful introduction of the tube into the trachea. The disappearance of breath sounds suggests that the esophagus has been intubated. If this occurs, the tube should be withdrawn until breath sounds are heard again. The patient's head should then be repositioned and another attempt made to pass the ETT. If an Endotrol tube is being used, tension should be applied to the ring to redirect the tip of the tube more anteriorly before another attempt is made.

Fiberoptic Intubation

Fiberoptic tracheal intubation is increasingly performed in critical care units.6 There are a variety of explanations for this, including the proliferation of fiberoptic bronchoscopes, increased familiarity and comfort with their use, and increased recognition of their utility as the technique of first choice in the patient with an anticipated difficult airway. Because the technique can be made difficult or impossible by the presence of blood or secretions, it requires meticulous preparation of the airway with drying agents, suctioning of secretions, and careful avoidance of any trauma which might cause bleeding. The technique is more successfully performed in awake patients, because their airway muscle tone maintains airway patency, which is important for good viewing conditions.30

Preparation for performing fiberoptic intubation consists of warming the ETT, if possible, to soften it and make it easier to advance through the vocal cords. The ETT is then placed on the fiberoptic scope in position to be slid forward when the scope is advanced into the trachea. The airway is prepared with topical anesthesia as discussed previously. Specialized oral airways, such as the Ovassapian airway are very useful, as they keep the tube midline, displace the tongue anteriorly, and prevent biting on the bronchoscope (Fig. 35-1). For optimal viewing conditions, it is imperative that a competent assistant either provide a vigorous jaw thrust or pull on the tongue, delivering it anteriorly. The fiberoptic bronchoscope is then passed through the vocal cords, down the trachea to the carina. The tube is then threaded into the trachea, over the scope with a smooth twisting motion. Tracheal intubation is confirmed with the bronchoscope as it is withdrawn from the trachea. The distance from the carina to the tip of the tube is determined by measuring how far the bronchoscope must be withdrawn from the carina before the tip of the tube becomes visible. Difficulty advancing the tube is usually from the tube catching laryngeal structures, and can be corrected by pulling the tube back and advancing with a twisting motion. Rarely, the tube may be too large for the glottic opening, requiring the bronchoscope to be withdrawn and a smaller tube to be placed instead. Of note, cricoid pressure may decrease the time and difficulty of fiberoptic intubation.30

The technique for nasal fiberoptic intubation is similar in most regards. Most operators will introduce the tube through the nose and into the nasopharynx, thus proving patency of the nose and allowing the tube to be used as a guide through the nose for the bronchoscope. Viewing conditions for the nasal approach are also improved by either the jaw thrust or the tongue-tug, especially in unconscious or sedated patients.

Intubating with a Laryngeal Mask Airway

Laryngeal mask airways in their various forms have become a critical component of airway management, especially in difficult-to-intubate patients (Fig. 35-2).31 A variety of LMAs (e.g., the classic, Fastrach, and ProSeal) have been designed to facilitate ventilation and intubation under the most difficult conditions. As with most airway management skills, the use of such devices appears to be deceptively easy and unskilled practitioners will have a high rate of failure.32,33

The intubating LMA is designed to facilitate tracheal intubation with a large size ETT. It has a rigid anatomically curved tube made of stainless steel with a standard 15-mm connector, and an epiglottic elevating bar (EEB). The caudal end of the EEB is not fixed, allowing it to elevate the epiglottis when an ETT is passed through the aperture. The tube is large enough to accept a cuffed 8-mm ETT, and is short enough to ensure passage of the ETT cuff beyond the vocal cords. The Fastrach is fitted with a rigid handle to facilitate one-handed insertion, removal, and adjustment of the device's position.

The device permits single-handed insertion from any position without moving the head and neck from a neutral position and without placing fingers in the mouth. Ventilation and oxygenation may be continued during intubation attempts, lessening the likelihood of desaturation. Prior to insertion of the LMA-Fastrach, the cuff should be tightly deflated using a syringe so that it forms a smooth spoon shape without any wrinkles on the distal edge. Lubricant is applied to the posterior surface of the LMA before insertion. The LMA cuff is inflated with 20, 30, and 40 mL of air for size 3, 4, and 5 tubes, respectively.

The application of cricoid pressure reduces the chances of successfully positioning the LMA and intubating the trachea by 30%.34 For this reason, and because LMAs do not protect against aspiration, the intubating laryngeal mask airway is more properly used as a rescue device than an approach of first choice in any ICU patient who may have a full stomach. In the settings of upper airway bleeding or copious secretions and failed rigid laryngoscopy, it is reasonable to attempt to use an intubating LMA.

The Difficult Airway

The difficult airway is far more commonly encountered in the ICU and emergency room than in the operating room. Under these emergent conditions of airway management, multiple attempts at laryngoscopy are common (25% to 35%), and between 0.5% and 2% of patients require a surgical airway. Copious secretions and inadequate positioning are common obstacles encountered in the ICU, but not in the operating room. The American Society of Anesthesiologists' Difficult Airway Algorithm outlines the options available to practitioners faced with a difficult airway (Fig. 35-3).31 Choices for proceeding include: ventilate with the bag and mask, summon help in the form of another operator, reposition, attempt laryngoscopy with a different blade, and apply other techniques as appropriate. Ideally, a competent operator will ventilate the patient with an Ambu bag as the operator prepares for their next attempt to secure the airway. If the patient can be adequately oxygenated with mask ventilation, then the operator has a variety of options for how to proceed. Changing the operator or laryngoscope blade will sometimes permit successful intubation where previous attempts have failed. Straight blades, such as the Miller blade, are especially useful in patients with prominent maxillary teeth, a small mandible, an anterior larynx, a floppy epiglottis, or trismus.

LMAs are useful as a bridge to oxygenate patients who cannot be intubated, but cannot be counted on to do so in the presence of abnormal lung mechanics or very abnormal anatomy.35

Care must be taken when using classic LMAs in such situations; a malpositioned LMA can insufflate the esophagus and increase the risk of aspiration. Even when properly inserted, inflation pressures over 20 cm H2O can cause both leaks and esophageal and gastric insufflation. The LMA-ProSeal is a better option than a classic LMA under these conditions.

The LMA-ProSeal is an advanced form of the classic LMA and has four components: cuff, inflation line with pilot balloon, airway tube, and drain tube (see Fig. 35-2). The drain tube communicates with the upper esophageal sphincter and permits blind insertion of gastric tubes and venting of the stomach. The LMA-ProSeal introducer is provided to aid insertion of the LMA-ProSeal without the need to place fingers in the mouth. The technique of LMA-ProSeal placement with the introducer is similar to LMA-Fastrach placement.

The features of the LMA-ProSeal provide more patient management options. While the classic LMA may be used with low-pressure PPV, the LMA-ProSeal has been designed for use with PPV at higher airway pressures. The drain tube will direct the regurgitated fluid to the outside, avoiding aspiration of gastric contents; however, it is not as effective as an ETT in preventing aspiration.

If the patient cannot be either intubated or oxygenated with less invasive means, then a surgical airway is indicated. This decision cannot be made lightly, as emergency surgical airways (such as tracheostomy) have a complication rate of 30%.36 Tracheostomy is preferable to cricothyroidotomy, but requires the timely availability of both skilled personnel and appropriate equipment. Tracheostomy provides a large-bore cuffed airway that both protects against aspiration and can be used for mechanical ventilation. A wide variety of kits are commercially available for these procedures, and are preferable to ad-hoc kits because they contain all of the necessary equipment and supplies, are sterile, and have a variety of training aids. Individuals who anticipate the possibility of using such kits as part of their airway management practice should obtain training in their use. Needle cricothyroidotomy and jet ventilation is increasingly viewed as the approach that is most likely to succeed when attempts to ventilate and secure an airway via laryngoscopy fail.37

Changing the Endotracheal Tube

Changing the endotracheal tube is frequently more hazardous than original insertion, because the patient may have evolved significant facial and airway edema, and may require both very high FiO2 and positive end-expiratory pressure (PEEP). The most common indications for changing ETTs include failure of the cuff to retain volume and pressure, occlusion of the tube by inspissated secretions and clots, and the requirement for a different tube than the one originally inserted (e.g., one of a larger diameter, or a different type such as a single- rather than a double-lumen tube). Tube changes motivated by complete occlusion or cuff rupture in the face of high PEEP may be dire emergencies; most other endotracheal tube changes are not.

Practitioners called on to change an endotracheal tube have the advantage that the patient already has an artificial airway, and hence the ease or difficulty of obtaining an airway has been discovered at least once for the patient. If laryngoscopy was easily accomplished before, and the patient's airway anatomy has not changed appreciably (e.g., as a result of edema), many practitioners elect to perform endotracheal tube changes with direct laryngoscopy under deep sedation and paralysis. This practice is safe when the old tube is withdrawn simultaneously with the introduction of the new tube into the trachea. Many operators prefer to perform endotracheal tube changes with the patient breathing spontaneously, reasoning that attempts at ventilation by the patient will delay the onset of hypoxia and hypercarbia in the event of difficulty in inserting the new airway. Withdrawing the old tube prior to attempting laryngoscopy, or when the view is difficult, can produce a cannot-intubate, cannot-ventilate situation, which can quickly become a crisis.

A variety of semirigid catheters are available for use as tube changers. Although they can be helpful in difficult circumstances, they can become dislodged from the trachea, and in some cases it is impossible to thread the new tube over them. Such tube changers may be best used in combination with direct laryngoscopy when the anatomy is challenging. Tube changers with a central lumen may be used to attempt to jet ventilate patients in the event that a more permanent airway cannot be established immediately. In patients with substantial facial and neck edema or burns, several assistants will be required for successful tube changes. Fiberoptic-guided exchange of tracheal tubes requires both excellent preparation of the airway (including treatment with drying agents such as glycopyrrolate and aggressive suctioning), and a high degree of skill by the operator, but can produce success where most or all other approaches would yield failure.38

Tracheal intubation has a range of important physiologic consequences. These are not complications of the procedure per se, but are consequences of the presence of an artificial airway and mechanical ventilation.

Tracheal intubation and the institution of positive pressure ventilation can cause a variety of changes in circulatory physiology. Laryngoscopy and tracheal intubation are frequently accompanied by hypertension and tachycardia.

Endotracheal tubes may cause an increase in airway resistance. An 8.0-mm endotracheal tube causes a 20% increase in airway resistance in the normal airway, all of it in the central airways and nonresponsive to therapy with inhaled bronchodilators. Smaller tubes have exponentially higher resistances.39 A 7.0-mm endotracheal tube has twice the resistance of an 8.0-mm tube, whereas a 9.0-mm tube has one-third the resistance of an 8.0-mm tube. The airways resistance associated with a particular tube increases as inspissated secretions accumulate in the tube, decreasing its diameter and increasing the turbulence of flow. Tracheal intubation can also precipitate bronchospasm in susceptible individuals, which can further increase airways resistance.

Hypotension frequently evolves after the establishment of tracheal intubation and mechanical ventilation, and has many contributing factors.40 First, these usually entail a change in mean intrathoracic pressures from large negative pressures to large positive pressures, with a corresponding fall in venous return and cardiac output. Mechanical ventilation is also frequently associated with a resolution of hypoxia, hypercapnia, and dyspnea, and a proportionate decline in circulating catecholamines.41 Patients with obstructive lung disease can develop high levels of auto-PEEP very quickly during vigorous ventilation with an Ambu bag, which can be associated with hypotension.42,43 Finally, high levels of PEEP can increase the pulmonary vascular resistance, with an associated shift of the interventricular septum into the left ventricle.44,45

Airway manipulation in critically ill patients is a necessarily hazardous undertaking (Table 35-7). Death, circulatory collapse, arrhythmias, hypoxia, airway trauma, aspiration, and failed intubation can all occur, even when the airway is managed flawlessly.

Right mainstem intubation is a common consequence of intubation in the ICU. It can be avoided in many cases by taping tubes at 23 cm at the lip in males and 21 cm at the lip in females of average stature (using the average tooth-to-carina distance, which is 28 cm in the average male and 24 cm in the average female).46 Tooth-to-carina distance varies; a tube taped at 24 cm at the lip might be in perfect position for the average 180-cm male, but might not even be in the trachea of a very tall patient. Correct positioning of the endotracheal tube is difficult to verify clinically and requires fiberoptic bronchoscopy or a chest radiograph for confirmation.47,48

In spite of assertions that it should never happen, esophageal intubation remains an inevitable complication of airway management. In theory, it should be quickly recognized and the offending tube removed expeditiously. In practice, it will occur in circumstances in which auscultation of the breath sounds is difficult and where endotracheal intubation cannot be confirmed with capnography, including patients with severe bronchospasm (especially children), and in adults in full cardiopulmonary arrest.49

Gastric aspiration that occurs around the time of intubation in the ICU can cause pneumonia and precipitate acute respiratory distress syndrome; it occurs approximately 4% of the time.10 In less controlled settings, such as in trauma patients, aspiration may occur in up to 30% of patients around the time they are intubated.50 The application of cricoid pressure and manipulation of the airway with the patient awake are the two most effective strategies to avoid this problem.

A variety of tissue injuries are associated with airway management in the ICU setting.51–54 These injuries are more likely to occur in uncooperative patients, seizing patients, and patients with anatomically difficult airways.55 Dental injury and tooth fragment aspiration remain a complication of airway management. Tracheal and esophageal lacerations can also occur. At least some bleeding is likely to occur in coagulopathic patients and in patients with friable tissues. The vocal cords and arytenoid cartilages can also be traumatized during intubation. Prolonged tracheal intubation can also impair swallowing, which increases the risk of aspiration in these patients after extubation.56 Residual muscle paralysis is an important risk factor for aspiration in perioperative patients, and perhaps in critically ill patients as well.57

A variety of cardiac complications may occur around the time of airway manipulation. Myocardial ischemia can be precipitated by the stress response to airway manipulation. The amount of ischemia precipitated can be minimized with adequate topical anesthesia and by matching the sedation given to the degree of stimulation created. Ventricular premature beats are a common consequence of the stress response in the setting of airway manipulation. Ventricular tachycardia and ventricular fibrillation can occur in patients susceptible to these arrhythmias. Bradycardia can also occur, particularly in young patients with high vagal tone.

Death occurs around the time of endotracheal intubation in approximately 3% of critically ill patients.10 In some patients, issues of airway management will contribute to the sequence of events that result in death; an expeditious intubation averts death in the vast majority of patients.

The role of tracheostomy continues to evolve in critically ill patients. The improved design of endotracheal tubes and careful attention to sedation has minimized the traumatic consequences of intubation, making translaryngeal intubation for weeks both safe and tractable. On the other side, the improved techniques for performing tracheostomy, and the increasing ability to perform tracheostomy at the bedside has made tracheostomy safer and more available than it has been previously. Tracheostomy continues to have immediate and long-term complications that intensivists manage.

Indications for Tracheostomy

The least controversial indication for tracheostomy is upper airway obstruction, especially long-term or permanent airway obstruction. Tracheostomy is also widely accepted as preferable to transglottic intubation for long-term mechanical ventilation. Tracheostomy is also indicated when a patient will be unable to clear their airway secretions for a long period of time. Finally, tracheostomy is frequently used to facilitate liberation from mechanical ventilation.

Tracheostomy has several benefits in patients who will require long-term mechanical ventilation. It allows easier and safer access to the mouth, which allows improved oral hygiene. It is substantially more comfortable than translaryngeal intubation, so the need for both analgesics and sedation may be significantly reduced. Specially designed tracheostomy tubes allow for speech and even normal eating in patients who are either continuously or intermittently ventilated. There was a time when patients underwent tracheostomy after only very brief periods of translaryngeal intubation and mechanical ventilation (e.g., 7 to 10 days). The decision to perform a tracheostomy on a patient in these circumstances should not be motivated as much by the time that has already elapsed on mechanical ventilation, but rather by the amount of time it can be foreseen that they will require mechanical ventilation. If the patient will obviously require ventilation for the coming weeks, then it is quite reasonable to perform a tracheostomy for both their safety and comfort.58,59 Patients at high risk of the complications of translaryngeal intubation, such as diabetics, may benefit from earlier tracheostomy.

Tracheostomy has the great benefit of reducing the anatomic dead space, resulting in substantially greater alveolar ventilation for any given minute ventilation. This benefit may be of critical importance in patients whose strength is very closely matched to their requirement for minute ventilation, and who might not otherwise be easy to liberate from the ventilator. The ease of reinstituting mechanical ventilation, and the wide bore and short length of tracheostomy tubes are also of benefit in these circumstances.

Percutaneous versus Surgical Tracheostomy

There is a large and growing literature which clearly demonstrates that percutaneous and surgical tracheostomy are equally successful and safe in competent hands.60–62 Interestingly, the sum of the patients in all of the prospective studies published thus far is less than 600, limiting the statistical power of inferences about rare complications, such as death, pneumothorax, and posterior tracheal wall perforation, but certainly allowing the conclusion that the success rates and overall complication rates of the two procedures are very similar. Mortality of either procedure is now less than 1%, which is significantly lower than that reported in older literature. When performed at the bedside in the ICU, both percutaneous and surgical tracheostomy are significantly less expensive and easier to arrange than tracheostomy in the operating room. The difference in cost between the two procedures performed at the bedside is small, and likely to be outweighed by other institutional factors and considerations.

A variety of techniques for percutaneous tracheostomy have been described and are in widespread use. Briefly, after appropriate sedation, the patient's neck is extended to open the tracheal interspaces. The skin over tracheal interspaces below the cricoid cartilage is then anesthetized, prepped with an appropriate cleansing agent, and draped in the usual sterile fashion. A 2-cm horizontal incision is made, and the neck is bluntly dissected down to the trachea. The existing tracheal tube is then withdrawn to a position just below the vocal cords. A needle is then inserted into the trachea (usually under bronchoscopic guidance), and a wire threaded into the tracheal lumen. The tract is then mechanically dilated, and an appropriately sized tube inserted into the trachea. Commercially available kits are now available that replace multiple dilators with a single dilator (e.g., Blue Rhino PDT from Cook Critical Care, Bloomington, IN), which may save time and reduce the risk of the procedure as well. Two of the advantages of the percutaneous technique are the minimal sharp dissection involved, and the use of dilation to create the tract for the tracheostomy tube, both of which limit the bleeding associated with the procedure.

The literature about percutaneous tracheostomy clearly documents that it can be accomplished successfully and safely in the hands of competent practitioners. Some techniques incorporate bronchoscopic guidance, incurring additional expense, time delay, and need for additional operators to provide some increase in the safety of the procedure. Although simultaneous bronchoscopy is advocated by some authorities, many more experienced operators rarely if ever use it to facilitate the procedure. The speed with which percutaneous tracheostomy without the use of a bronchoscope can be accomplished is impressive, making it attractive as a procedure to emergently secure the obstructed airway in institutions with readily available kits and highly skilled operators. Morbid obesity and previous tracheostomy are frequently cited contraindications to percutaneous tracheostomy, but there are case series which suggest that the procedure can be performed safely in select patients with either diagnosis.63,64 There is no doubt that as with any other procedural skill, there is and will be significant variation across practitioners and institutions, which makes prescriptions about percutaneous tracheostomy inappropriate.

Minitracheostomy

Minitracheostomy is a procedure that is sometimes performed in select critically ill patients to facilitate clearance of bronchial secretions.65 Minitrach allows repeated suctioning of the trachea below the cords without passing a tube through them at the cost of undergoing the procedure (which is generally performed at the bedside) with its attendant complications. The procedure itself is very similar to that described for percutaneous tracheostomy, except that it does not result in an airway. Minitracheostomy has been demonstrated to reduce the incidence of radiographic collapse, but has not otherwise been proven to improve outcomes.66,67 Minitracheostomy is commonly done at some centers, rarely done at most, and never done at others. This is unlikely to change unless studies demonstrating more dramatic benefit to the procedure are published.

Complications of Tracheostomy

The immediate complications of tracheostomy include hemorrhage, malpositioning of the tracheostomy tube, and pneumothorax/pneumomediastinum. Hemorrhage can occur as a consequence of bleeding from subcutaneous vessels, neck veins, and the thyroid gland. Most postoperative bleeding is venous in origin, and it may take hours for a noticeable hematoma to form. A hematoma in the neck can compress the trachea or cause it to deviate, resulting in increased airway pressures, a sensation of dyspnea on the part of the patient, and hypoventilation. Airway obstruction caused by a hematoma is best treated by decompression/evacuation, as all other therapies will fail to interrupt the cascade of events leading to deterioration and will allow the underlying process to progress.

Rarely, tracheostomy tubes may be placed into tissue planes in the neck instead of the trachea. Monitoring end-tidal carbon dioxide concentrations after the tube is inserted will aid in the timely recognition of this problem, allowing it to be quickly corrected. Tracheal positioning of the tracheostomy tube can be verified with auscultation, capnography, and fiberoptic bronchoscopy.

Pneumothorax and pneumomediastinum are consequences of invasion of these tissue planes, which can extend superiorly into the neck in some patients (particularly those with chronic obstructive pulmonary disease or on high amounts of PEEP). These complications are more likely to occur in situations in which the anatomy is difficult, such as patients with morbid obesity, previous neck surgery, or goiter. These complications are usually recognized on the routine chest radiograph taken postoperatively in these patients to confirm adequate positioning of the new tracheostomy tube.

Long-Term Complications of Tracheostomy

Tracheostomy tubes are frequently left in patients for months and occasionally years. This situation puts the patient at risk of complications due to chronic irritation or erosion of the trachea, including tracheoesophageal fistula, tracheoinnominate fistula, tracheomalacia, and tracheal stenosis.

The absence of a large epidemiologic database, the heterogeneity of patient populations undergoing tracheostomy in the ICU, and the high mortality in some patient populations that undergo the procedure make discussion of the complications of tracheostomy difficult.68 Tracheal stenosis is diagnosed in 40% to 60% of patients who have undergone tracheostomy, but it is unclear if this is a complication of their tracheostomy or their prior transglottic tracheal intubation.69,70 The high cuff pressures thought to be the major cause of the tissue injury that drives this process are more likely to be present during the early, acute phase of critical illness, when high airway pressures are present.71 On the other hand, the disruption of the tracheal cartilages caused by the presence of the tracheostomy tube may lead to instability, which may in turn cause tissue injury, which may be worsened by the immune response to both the tracheostomy tube and the purulent secretions that contaminate its tract. Given this, it is unsurprising that a majority of the tracheal stenoses attributed to tracheostomy occur at the level of entry into the trachea.

Tracheoinnominate fistula occurs in less than 1% of patients, typically within 1 month of undergoing insertion of a low-lying tracheostomy. Either the tip of the tube or its cuff erodes through the wall of the trachea and into the vessel, causing life-threatening bleeding which requires immediate surgical repair. Tracheoesophageal fistula occurs via the same mechanism, but entails erosion through the posterior wall of the trachea into the esophagus. Tracheoesophageal fistula is frequently difficult to diagnose, as it can present as recurrent pneumonia in a ventilated patient. Other more obvious symptoms include cuff leak refractory to inflation, aspiration of large quantities of tube feeds in spite of an appropriately inflated tracheostomy cuff, and gastric distention with large quantities of air. The diagnosis of a tracheoesophageal fistula can be established with either barium swallow or computed tomography scan. Treatment is usually surgical, although a variety of stents have been employed as an alternative.72

The place to learn basic airway management skills is the operating room, not the ICU. Basic airway management skills, although apparently very simple, in fact take a great deal of time and experience to master. These basics are best learned in an environment in which patients will generally have normal anatomy, circulation, and lung mechanics. Elective procedures in the operating room present ideal opportunities to learn the basics of mask ventilation, laryngoscopy, fiberoptic laryngoscopy, nasal intubation, and insertion of laryngeal mask airways. Outpatient bronchoscopies present excellent opportunities to learn how to adequately topically anesthetize the nasopharynx and oropharynx. Literature from a wide variety of fields supports the contention that most practitioners tasked with managing the airway are either inadequately trained, or will predictably benefit from more training.73,74 Once the basics of airway management have been mastered in the elective setting, they can be applied in airway management under adequate supervision in the ICU. Attempts to teach the basics of airway management at the bedside in the ICU should be discouraged, as critically ill patients do not tolerate the high rates of failure that typically occur as practitioners learn these skills. Participating in airway management workshops and the practice of various airway management techniques in models and simulators is extremely valuable, especially for procedures such as fiberoptic bronchoscopy, which requires hours of practice to attain facility manipulating the bronchoscope. The wide variety of things that skillful airway managers take into account at the bedside or consider as they proceed are given in Table 35-8.