Oxygen (O₂)

Oxygen should always be applied during assessment of the patient and before implementing airway management techniques. The application of supplemental oxygen can be lifesaving because oxygen deficiency is commonly encountered in critically ill patients suffering from respiratory failure. Furthermore, the concept of preoxygenation (increasing the alveolar oxygen concentration before tracheal intubation) is a critical tenet of emergency airway management.

Supplemental Oxygen

The primary reason for oxygen administration is the prevention or treatment of hypoxemia. Numerous causes of hypoxemia exist and all are improved with the administration of 100% O₂ (Table 49-2).

Table 49–2 Causes of Hypoxemia in Critical Illness Requiring Emergency Airway Management

Hypoxia is defined as oxygen deficiency at the tissue level. Anything that decreases oxygen delivery () may lead to hypoxia. Oxygen delivery depends upon cardiac output (), hemoglobin concentration (Hgb), and arterial oxyhemoglobin saturation (SaO₂), as follows:

Hypoxia occurs when decreases below adequate levels because of impaired myocardial function, anemia, or hypoxemia (due to decreased fraction of inspired O₂ [FIO₂] or increased shunt). Hypoxia can also occur secondary to increased metabolic rate or decreased utilization at the tissue level (e.g., cyanide poisoning). By administering oxygen to critically ill patients in respiratory failure, one can increase SaO₂, thereby improving until anemia, myocardial dysfunction, or right-to-left transpulmonary shunting abates.

Preoxygenation (Before Induction and Intubation)

Preoxygenation of the lungs is an essential component of any intubation technique that might involve a period of apnea. Preoxygenation is especially important for a rapid-sequence intubation because it allows for a reserve of oxygen in the lungs during apnea. For a patient who has been rendered apneic there is a finite period before arterial oxyhemoglobin desaturation. This period is related to the reservoir of oxygen in the lungs, or functional residual capacity (FRC), and is inversely related to the oxygen consumption (Fig. 49-1). Preoxygenation with 100% O₂ allows for up to 10 minutes of oxygen reserve following apnea (in a patient with healthy lungs); however, the patient who is preoxygenated with only room air (21% O₂) would have only about one fifth the time (or 2 minutes) before desaturation. Patients in respiratory failure frequently desaturate sooner owing to higher O₂ consumption, reduced FRC, and possibly lung disease with increased right-to-left transpulmonary shunting (Fig. 49-2).

Figure 49-1 FRC and relationship of oxygen reserve. This figure illustrates the factors that determine the time from apnea until desaturation, including the functional residual capacity (FRC), the concentration of oxygen in this reservoir (FIO₂), and the oxygen consumption () of the patient. The spirometric trace on the left side of the figure depicts the relative volumes of the FRC, tidal volume (V_T), residual volume (RV), and vital capacity (VC). The reservoir of oxygen in the lungs at end exhalation (FRC) in a normal 70 kg patient is approximately 2.5 L, and the resting is approximately 250 mL/min. If the patient is breathing 100% oxygen, then there is theoretically 10 minutes before desaturation. Whereas, if the patient is breathing room air (21% oxygen), there is only 2 minutes before desaturation. Furthermore, ICU patients are typically sicker with lower FRCs, increased, and increased shunting, all of which can cause more rapid desaturation following apnea.

(From Wilson WC: Emergency airway management of the ward. In Hannowell LA, Waldron RJ (eds): Airway Management. Philadelphia, Lippincott-Raven Publishers, 1996, pp 443-451; with permission.)

Figure 49-2 SaO₂ versus time of apnea (in minutes) for various types of patients. Time to hemoglobin desaturation with initial FIO₂ is 0.87. The physiologic characteristics of these patients can be obtained from the author upon request. The SaO₂ versus time curves were produced by the computer apnea model. The mean times to recovery from 1 mg/kg intravenous succinylcholine are shown in the lower right hand corner.

(From Benumof JL: Critical hemoglobin desaturation will occur before return to an unparalyzed state following 1 mg/kg IV succinylcholine. Anesthesiology, 1997;87:979-982, with permission.)

Mask Ventilation Capability

It is critical to ensure the ability to apply oxygen in the CICU using positive pressure via a bag-valve-mask (BVM) device, along with oral and nasal airway adjuncts. BVM ventilation devices, such as an AMBU bag, deliver a significantly higher FIO₂ than either nasal cannulae or a mask alone (Table 49-3). Additionally, a BVM device enables one to ventilate a patient who is apneic or to assist ventilation in the patient with respiratory failure. The keys to using BVM devices are to provide adequate flow (10 to 15 L/min) and to ensure a tight seal between the mask and the patient’s face so as not to entrain any room air during ventilation.

Table 49–3 Actual FIO₂ Achievable with Commonly Used Oxygen Administration Devices in Patients with Normal Ventilatory Breathing Patterns

Intubation Equipment Check

Typically, the anesthesiologist, or other airway expert, brings the essential emergency intubation equipment to the resuscitation site in a “code box” (see Table 49-1). The user must inspect the “code box” each time he or she comes on call to make sure that the items listed in Table 49-1 are present and in working order before he or she is summoned to respond to a “code blue” situation and use the equipment.

All code box items need to be verified as present and in good working condition. The BVM device, styletted endotracheal tubes (ETT), and the laryngoscope, however, require some special notes about preparation and checkout.

The BVM device should be tested for integrity of the system and ability to generate positive pressure without leaks at connections. This can be done by using one’s thumb to occlude the 15-mm exit flow orifice of the elbow connector (where it connects to a mask) while flowing O₂ through the O₂ connection tubing. The bag should inflate at a rate proportionate to the O₂ gas flow until one’s occluding thumb is removed from the elbow connector exit flow orifice. If a self-inflating (AMBU) type of bag-mask device is used, pressure testing can be accomplished as already described, except that the bag will already be filled when the pressure test is begun.

The various sized styletted ETTs (balloon pretested) should be prepared as follows: An adult-sized ETT (size 7.0 or 8.0) should have a malleable stylet passed through its interior to a position just short of the tip (by approximately 5 to 10 mm). The malleable stylet allows the distal end of the ETT to be molded into a configuration that will most easily pass through the patient’s vocal cords. Additionally, a styletted 6.0 ETT (or 5.0 ETT) should be prepared as a backup for patients who have small glottic openings or a difficult airway. The smaller ETTs commonly pass through a swollen or small glottic opening and into the trachea when a larger tube will not.

The rigid direct laryngoscope (RDL) with several blades is another critical piece of equipment. First, one must make sure the laryngoscope handle is clean and that the electrical connections are free of any corrosion or debris. Next, one should check that the batteries are fresh and generating a bright beam of light when the laryngoscope blades are attached. There must be at least two sizes of Miller and Macintosh blades (No.3 and No.4) so that various types of airway problems can be solved.

All of the items listed in Table 49-1 are essential and constitute the minimum airway equipment that the anesthesiologist or other airway expert should bring to the “code blue” situation.

Suction

Patients in respiratory failure may have thick secretions and/or may have vomited. To protect against aspiration and to better visualize the laryngeal anatomy, suctioning of the airway is frequently required during a “code blue.” The suction apparatus should be continuous (not intermittent) and of sufficient force to allow rapid clearance of thick oropharyngeal secretions or vomitus. During initial airway management, a Yankauer suction tip should be used to suction debris out of the oropharynx. After tracheal intubation, however, endotracheal suction catheters may be useful to clear secretions and aspirated material out of the airways.

Functioning Intravenous Catheter

A functioning intravenous catheter (IV) is mandatory when airway control is urgent but not emergent. The ability to administer fluids and cardiovascular support drugs is essential. Thus, after application of O₂ by mask, assessment of the airway, and establishment of ventilation, an IV line should be established before any attempts at airway manipulation. In a patient in full arrest, the trachea must be intubated first, and IV access may be secured secondarily. All advanced cardiac life support (ACLS) protocol drugs can be administered via the ETT except for ionic compounds (calcium, bicarbonate, and magnesium).

Monitoring (Pulse Oximetry, Blood Pressure, Electrocardiogram)

The airway expert must ensure that the patient is monitored with pulse oximetry, blood pressure cuff, and electrocardiogram (ECG) before attempting to intubate the trachea (whenever time allows). Vital sign stability and adequate arterial oxyhemoglobin saturation are the goals of supportive measures before airway instrumentation and during and after intubation of the trachea.

Vasopressors and Inotropic Drugs

Vasopressors and inotropic drugs must be available for immediate use because hypotension is a common side effect of tracheal intubation. Hypotension can occur from the administration of anesthetic drugs, the use of positive pressure ventilation (PPV), or from relief of endogenous catecholamines elevated during respiratory failure and normalized following tracheal intubation. Furthermore, premorbid conditions in previously ill or elderly patients will further increase the likelihood of hypotension following intubation.

Airway Evaluation

Before attempting endotracheal intubation, the clinician should obtain historical and physical examination information to assess the patient’s airway for technical ease of ventilation/intubation. If evaluation reveals that the patient’s airway will be difficult to intubate, the patient should be intubated while awake. Several outstanding reviews on evaluation of the difficult airway exist.^2–4 In this section, a definition of the difficult airway is provided, and historical and physical examination keys for predicting airway difficulty are described.

Definition of Difficult Airway

Airway difficulty can occur during mask ventilation or during endotracheal intubation. The two are not synonymous, and indeed, some patients who are difficult to ventilate with a mask (edentulous, large-jawed) may be quite easy to intubate. The difficulty of maintaining gas exchange with mask ventilation can range from zero to infinite (Fig. 49-3, top).

Figure 49-3 Degree of airway difficulty continuum for mask ventilation and direct vision laryngoscopy at intubation. This illustration serves to provide a conceptual frame work for the definition of airway difficulty with mask ventilation (top) and direct vision laryngoscopy (bottom). The degree of difficulty ranges from zero degrees of difficulty to the impossible or infinitely difficult airway. The amount of difficulty can vary in the same patient with different anesthesiologists using various techniques. The grade of laryngoscopic view refers to grades defined by Cormack and Lehane (see Fig. 49-4).

(From Benumof JL: Management of the difficult airway. Anesthesiology 1991;75:1087, with permission.)

Difficulty of intubation using direct laryngoscopy proceeds along a similar continuum from easy to nearly impossible (Fig. 49-3, bottom). Difficult intubation has been defined as requiring multiple attempts with multiple maneuvers, including external laryngeal pressure, multiple blades, and/or multiple endoscopists.

Probably the best definition of difficult intubation for documentation (from one anesthesiologist to another) or for research purposes involves the grading of laryngoscopic views (Fig. 49-4): Grade I is visualization of the entire laryngeal aperture; grade IV is visualization of the soft palate only; grades II and III are intermediate views.³ Grade III or IV laryngoscopic views correlate well with difficult intubations in the vast majority of patients.^3,5 There are, however, some clinically relevant situations that provide exceptions to this rule. First, the skill of the endoscopist in manipulating the endotracheal tube and laryngoscope may have a significant effect on the grade of laryngoscopic view. Second, a grade III laryngoscopic view has been described differently by different investigators.^3,6 Third, the blade used for laryngoscopy affects the grade applied to the situation. A long floppy epiglottis may yield a high grade view (III or IV) with a MacIntosh blade and a relatively low grade (I or II) with a straight blade. Finally, traumatic conditions such as cervical spine injury (inability to move the neck into “sniffing” position), laryngeal fractures, or expanding hematomas may disassociate the laryngoscopic view from the difficulty of tracheal intubation.

Figure 49-4 Four grades of laryngoscopic view. The grading of laryngoscopic view is based upon the anatomic features that are visualized during the performance of direct laryngoscopy.

(From Cormack RS, Lehane J: Difficult tracheal intubation in obstetrics. Anesthesia 1984;39: 1105, with permission.)

Airway Examination Principles

Three Easy Airway Evaluation Tests

Missed signs of a difficult airway can be minimized if one looks carefully for both pathologic and anatomic abnormalities. Investigators have sought to determine anatomic characteristics that correlate with intubation difficulty. Three airway evaluation tests that are easy to perform have emerged as highly predictive indicators of intubation difficulty: Mallampati class, thyromental distance, and atlanto-occipital (AO) extension. When these three tests are used in the same patient, their combined predictive power becomes quite substantial.

Relative Tongue/Pharyngeal Size (Mallampati Class)

Mallampati and associates⁸ in 1985 proposed the size of the tongue in relation to the size of the oral cavity as a clinical sign of the difficulty of tracheal intubation (Fig. 49-5). Lewis and colleagues⁹ have demonstrated that the Mallampati classification is best obtained with the patient in the sitting position, with the head in full extension, with tongue out, and with phonation, because the test is more predictive and easier to perform under these conditions.

Figure 49-5 Mallampati classification. Classification of the upper airway relating to the size of the tongue to the pharyngeal space based upon the anatomic features seen with the mouth open and the tongue extended.

(Modified from Mallampati, SR et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can J Anaesth 1985;32:429, with permission.)

Thyromental Distance or Mandibular Space

Space anterior to the larynx—thyromental distance—greater than 6 cm suggests that direct laryngoscopy will be relatively easy.¹⁰ Because the tongue must be moved anteriorly and caudad (in a supine patient) by the laryngoscope, the mandibular space must be large enough to accommodate the tongue and allow exposure of the glottis.

Atlanto-Occipital Joint Extension

Normally, 35 degrees of atlanto-occipital (AO) extension are possible at the AO joint. Bellhouse and Dore¹¹ have demonstrated that AO joint extension can be easily measured clinically, and that the measurement is highly predictive of the ease of intubation.

Patient Preparation and Positioning

Regardless of whether an awake, topicalized technique or a rapid-sequence technique is chosen, proper patient positioning and preparation are important.

“Sniffing” Position (Preparation for Rapid-Sequence Technique)

The “sniffing” position is the optimum position for direct laryngoscopy and endotracheal intubation using a rapid-sequence technique. One of the most common reasons for difficulty with laryngoscopy and intubation is failure to place the patient in an adequate sniffing position. The sniffing position involves forward flexion of the neck on the chest and atlanto-occipital extension of the head at the neck. This maneuver aligns the oropharyngeal, laryngeal, and tracheal axes (Fig. 49-6). The easiest way to accomplish this is to place at least two folded towels under the head of the supine patient. The first attempt at laryngoscopy should be a well-prepared one. Once the patient is placed in an adequate sniffing position, a helper should apply cricoid pressure to protect against regurgitation of gastric contents.

Figure 49-6 Head position and the axis of the upper airway. This diagram demonstrates the various head and neck positions in the supine patient and the corresponding oral axis (OA), pharyngeal axis (PA), and laryngeal axis (LA) in four different head positions. Each head position is accompanied by an inset that magnifies the upper airway and superimposes the continuity of these three axes within the upper airway. The upper left panel (A) shows the head in the neutral position with marked nonalignment of the various axes. In the upper right panel (B), the head is resting on a pillow, which causes forward flexion of the neck on the chest and serves to align the pharyngeal axis and the laryngeal axis. However, the oral axis remains nonaligned. The lower right panel (D) shows extension of the head on the neck without concomitant elevation of the head on the pad resulting in nonalignment of the oral pharyngeal with the laryngeal and pharyngeal axes. The lower left panel (C) shows the head resting on a pad that flexes the neck forward on the chest along with extension of the head on the neck, which brings all three axes into alignment (sniff position). This position allows for a direct view from the oral pharynx to the larynx providing the tongue and soft tissues are elevated out of the way with a rigid direct laryngoscope.

(From Benumof JL: Conventional (laryngoscopic) orotracheal and nasotracheal intubation (single lumen type). In Benumof JL (ed): Clinical Procedures in Anesthesia and Intensive Care. Philadelphia JB Lippincott Co, 1992, p 123, with permission.)

Alternative Plan and Extra Help

After assessing the airway and evaluating the patient’s underlying pathologic condition, one must devise a plan for intubation. If there is any concern that the patient’s airway will be difficult to intubate, an awake technique with spontaneous ventilation should be chosen. Regardless of the primary plan, there must always be a “plan B.”

Whenever securing the airway, one must make sure to have extra help available. The expert should communicate with the patient and the assistants to ascertain that everyone understands the plan.

Mask Ventilation

Mask Ventilation Technique

The face mask must be applied firmly to the patient’s face to ensure an adequate seal, although care must be taken not to injure the bridge of the nose with excessive pressure. A single-hand technique is acceptable if the airway is easy to ventilate (Fig. 49-7). If, however, ventilation is not easy, two hands should be used to hold the mask in place while another person depresses the bag in an attempt to ventilate the patient (Fig. 49-8). Frequently, the application of jaw thrust (backward and upward pull of the jaw in a supine patient) opens an airway and allows ventilation.

Figure 49-7 Mask ventilation one-hand technique. This figure shows the one-handed technique in holding a mask properly on a patient’s face. The top figure (A) demonstrates the standard one-handed grip of the mask on the face. The thumb encircles the upper part of the patients mask while the second and third finger are applied to the lower portion of the mask with the fourth and fifth fingers pulling the soft tissue under the mandible up toward the mask. The lower panel (B) demonstrates the one-handed mask grip while maintaining jaw thrust. The hand positions are altered such that only the thumb and the second finger encircles the mask while the third, fourth, and fifth fingers maintain upward and backward pull of the mandible “jaw thrust.” Typically an oral airway would have been placed in the patient’s oropharynx before manipulating the mandible with the “jaw thrust” maneuver.

(Modified from McGee JP, Vender JS: Nonintubation management of the airway. In Benumof JL (ed): Clinical Procedures in Anesthesia and Intensive Care. Philadelphia JB Lippincott Co, 1992, p 107, with permission.)

Figure 49-8 Two-hand mask ventilation technique. With the two-handed technique, the thumbs are hooked over the collar of the mask while the lower fingers maintain jaw thrust and the upper fingers are pulling the mandible into the mask while extending the head (arrows indicate direction of force).

(Modified from McGee JP, Vender JS: Nonintubation management of the airway. In Benumof JL (ed): Clinical Procedures in Anesthesia and Intensive Care. Philadelphia JB Lippincott Co, 1992, p 109, with permission.)

Oropharyngeal and Nasopharyngeal Airways

When the tongue and other soft tissues are maintained in the normal forward position, the posterior pharyngeal wall remains nonobstructed, and the airway is generally open (Fig. 49-9, A).

Figure 49-9 Normal airway, soft tissue obstruction, and use of laryngeal and nasopharyngeal airways. This series of four panels describes in sequence the normal (unobstructed) airway (A), the obstruct airway (B), and use of the oral (C) and nasal (D) airways. The normal airway (A) maintains the tongue and other soft tissues in the forward position, allowing unobstructed passage of air. The next panel (B) demonstrates the typical obstructed airway of an unconscious supine patient. The tongue and epiglottis fall back to the posterior pharyngeal wall and occlude the airway. In panel C, the use of oral pharyngeal airway is demonstrated. The oral pharyngeal airway follows the curvature of the tongue and pulls it and the epiglottis away from the posterior pharyngeal wall providing a channel for air passage. In the last panel (D), the use of the nasal pharyngeal airway is demonstrated. This airway passes through the nose and ends at a point just above the epiglottis clearing the air passage.

(Modified from Stone DJ, Gal TJ: Airway management. In Miller RD (ed): Anesthesia, 4th ed. New York, Churchill Livingstone 1994; 1403–1436, with permission.)

The most common cause of airway obstruction is falling back of the tongue and epiglottis in supine, unconscious patients (Fig. 49-9, B). This can be alleviated by the jaw thrust maneuver. Regardless of whether jaw thrust is successful, an oral or nasal airway as an adjunct to bag-mask ventilation can open up a closed airway.

Both oral (Fig. 49-9, C) and nasal (Fig. 49-9, D) airways restore airway patency by separating the tongue from the posterior pharyngeal wall. A rigid oral airway may elicit a gag response from an awake patient, which may be followed by emesis. Soft nasal airways provoke less gag response than rigid oral airways. Soft nasal airways are commonly inserted in patients suffering from ventilatory failure, who are more awake and prone to gagging on the rigid oral airway. Coagulopathies and nasal or basilar skull fractures are relative contraindications to nasal airways.

Laryngeal Mask Airway (LMA)

Ventilatory obstruction above the level of the cords (supraglottic) can be alleviated by the LMA because of its supraglottic placement (Fig. 49-10). However, the LMA is not an effective ventilatory device in cases of periglottic or subglottic pathology (e.g., laryngospasm, subglottic obstruction).¹⁴

Figure 49-10 LMA. The normal anatomic position of the laryngeal mask airway. The proximal portion of the laryngeal mask rests upon the epiglottis, whereas the distal end extends into the pharynx at the upper end of the esophagus. The opening on the laryngeal mask overlies the laryngeal inlet. This figure demonstrates a prototypical LMA and is not meant to represent any particular commercially available device.

(Modified from Brain AJJ: The laryngeal mask: a new concept in airway management. Br J Anaesth 1983;55:801, with permission.)

The LMA is inserted blindly into the oropharynx forming a low pressure seal around the laryngeal inlet, thereby permitting gentle positive pressure ventilation with a leak pressure in the range of 15 to 20 cm H₂O. Therefore, LMA is relatively contraindicated in the presence of a known supraglottic hematoma or other expanding lesion (e.g., abscess) that might rupture. However, it can be very useful in other supraglottic obstructive conditions such as those due to swelling, edema, or redundant tissues. Placement of an LMA requires a completely anesthetized airway or an anesthetized patient.¹⁵ The LMA has been shown to rapidly restore efficient ventilation in numerous cannot intubate-cannot ventilate situations.^15–17

Rigid Direct Laryngoscopy

Before performing laryngoscopy, the airway expert should test the laryngoscope blade and handle to ensure proper functioning. The laryngoscope is held in the left hand, so that the right hand is free to place the styletted endotracheal tube through the cords and into the trachea. The patient’s mouth is opened by simultaneously extending the head on the neck with the right hand, and using the small finger of the left hand (while holding the laryngoscope) to push the anterior part of the mandible in a caudal direction and opening the mouth (Fig. 49-11).

Figure 49-11 Opening the mouth for laryngoscopy: use of the little finger. The mouth can be opened wide by concomitantly extending the head on the neck with the right hand while the small finger and the medial border of the left hand pushes the anterior aspect of the mandible in a caudad direction. The laryngoscope is held in the left hand while opening the mouth with this technique. As the blade approaches the mouth, it should be directed to the right side of the tongue. Gloves should be worn during laryngoscopy and the hands should be kept out of the oral cavity to limit contact with the patient’s secretions.

(From Benumof JL: Conventional (laryngoscopic) orotracheal and nasotracheal intubation (single lumen type). In Benumof JL (ed): Clinical Procedures in Anesthesia and Intensive Care. Philadelphia JB Lippincott Co, 1992, p 124, with permission.)

As the blade enters the oral cavity, gentle pressure is applied on the tongue, sweeping it leftward and anteriorly (Fig. 49-12) so as to expose the glottic aperture. Two basic types of blades are in common use: a curved (MacIntosh) blade and a straight (Miller and Wisconsin) blade. The curved MacIntosh blade (Fig. 49-13) tip is placed in the vallecula after the tongue is slid leftward and anteriorly and while the laryngoscope handle is lifted in a forward and upward direction (stretching the hyoepiglottic ligament). This causes the epiglottis to move upward, exposing the arytenoid cartilages and eventually the vocal cords. The straight Miller blade (Fig. 49-14) is inserted until the epiglottis is visualized, and then the epiglottis is elevated to expose the glottic aperture.

Figure 49-12 Inserting the laryngoscope blade into the right side of the mouth. This figure demonstrates the proper head and neck positioning for insertion of a curved (Macintosh) laryngoscope blade. The inset shows the blade entering the right side of the oral cavity so that the tongue will be moved toward the left side of the mouth with the large flange on the Macintosh blade thereby creating a view of the larynx.

(From Benumof JL: Conventional (laryngoscopic) orotracheal and nasotracheal intubation (single lumen type). In Benumof JL (ed): Clinical Procedures in Anesthesia and Intensive Care. Philadelphia JB Lippincott Co, 1992, p 125, with permission.)

Figure 49-13 Correct position of the Macintosh laryngoscope blade in the vallecula. This figure demonstrates the correct position of the curved (Macintosh) laryngoscope blade in the vallecula and the angle of pressure that should be applied (45 degrees from the patient’s axial line). The inset demonstrates the laryngeal view obtained when the Macintosh blade is used. 1 = epiglottis, 2 = vocal cords, 3 = cuneiform part of arytenoid cartilage, and 4 = corniculate part of arytenoid cartilage.

(From Benumof JL. Conventional (laryngoscopic) orotracheal and nasotracheal intubation (single lumen type). In Benumof JL (ed): Clinical Procedures in Anesthesia and Intensive Care. Philadelphia JB Lippincott Co, 1992, p 127, with permission.)

Figure 49-14 Laryngoscopic technique with a straight (Miller) blade. A straight (Miller) laryngoscope blade should pass underneath the laryngeal surface of the epiglottis; then the handle of the laryngoscope blade should be elevated at a 45-degree angle similar to that used with a Macintosh blade. By lifting up the epiglottis, the laryngeal aperture should come clearly into view.

(From Benumof JL: Conventional (laryngoscopic) orotracheal and nasotracheal intubation (single lumen type). In Benumof JL (ed): Clinical Procedures in Anesthesia and Intensive Care. Philadelphia JB Lippincott Co, 1992, p 128, with permission.)

Six common errors can occur during RDL use. First, the blade can be inserted too far into the pharynx, elevating the entire larynx which exposes the esophagus instead of the glottis. Second, for optimal laryngoscopy, the tongue must be completely swept to the left side of the mouth with the flange on the RDL blade. This is slightly more difficult to accomplish with the Miller blade because the flange is less prominent. Third, novice laryngoscopists frequently rock the RDL in the patient’s mouth using the upper incisor as a fulcrum in a self-defeating attempt to visualize the glottis. This can chip the patient’s upper incisors and moves the glottic aperture further anterior out of view. The correct approach is to lift the handle anterior and forward at an approximately 45^o angle (see Fig. 49-14). Fourth, proper sniffing position is not always achieved or indicated. Fifth, in obese barrel-chested patients and large breasted women, it can be difficult to insert the blade in the mouth. Use of a short handled RDL or removal of the blade from the scope handle and reattaching once the blade is positioned in the mouth helps with this predicament. Finally, improper blade selection may hinder laryngoscopy and intubation. If the patient has a long floppy epiglottis, a Miller blade may be best; a large wide tongue may be best managed using a Macintosh blade.

Numerous developments have been made in the last decade combining fiberoptic technology with various configurations of the laryngoscope, with the goal of improving intubation success, and decreasing the need to move the neck when manipulating the airway. Such laryngoscopic devices as the Bullard Laryngoscope (Circon, ACMI, Stamford, Conn.) and the WuScope (Achi Corp., Dublin, Calif.) are representative of this approach and have been in use for more than a decade. More recent innovations include the GlideScope (Verathon, Inc., Bothell, Wash.) (Fig. 49-15, 49-16). In recent studies of simulating easy and difficult airways with novice GlideScope users, the laryngoscopic view was either the same or superior in the difficult intubation scenario.¹⁸

Figure 49-15 GlideScope video laryngoscope Cobalt. Single-use, sterile Cobalt GVL Stat with reusable Video Baton.

(Images courtesy of Verathon, Inc.)

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