A 65-year-old male with carcinoma of the colon presents for colon resection. He weighs 120 kg and is 157 cm tall (BMI 48 kg·m⁻²). He has a history of hypertension and obstructive sleep apnea. On airway examination, he has a Mallampati IV score; 3-cm mouth opening, a large tongue, full dentition, about 0.5 cm of mandibular protrusion, a receding mandible, decreased cervical spine extension, and has a short thick neck. His cricothyroid membrane is difficult to palpate. He has predictors of difficult direct laryngoscopy, difficult video-laryngoscopy, difficult bag-mask-ventilation, difficult extraglottic device (EGD) use, and a difficult surgical airway. He is likely to be intolerant of apnea. An awake bronchoscopic intubation was performed which was uneventful as was his subsequent surgery.

How Did Bronchoscopic Intubation Develop?

Transmission of a visual image through a flexible fiberoptic bundle was first reported by Hopkins and Kapany in 1954¹ and the first recorded endoscopic tracheal intubation was reported by Murphy in 1967.² In that case report, the trachea of a patient with Still’s disease was successfully intubated through the nose using a flexible choledochoscope.² The flexible fiberoptic bronchoscope was introduced into clinical practice in 1964, and although it was not developed for the purpose of airway management, its value as a device to facilitate endotracheal intubation was soon appreciated.^3,4 A series of 100 tracheal intubations using the flexible bronchoscope was reported in 1972, with a success rate of 96%.⁵ However, utilization of flexible fiberoptic technology for endotracheal intubation remained limited among health care providers throughout the 1970s and 1980s.⁶ Seventy-five percent of those who completed questionnaires at a series of fiberoptic bronchoscope workshops between 1984 and 1989 had either no or minimal experience with the technique.⁶ Following the publication of the ASA Guidelines on Difficult Airway Management in 1993,⁷ the use of flexible bronchoscopic intubation (FBI) among anesthesia practitioners greatly increased⁸ and the technique has come to play a pivotal role in the management of the difficult airway.^9–11

Although it has been advocated as the technique of choice in the management of the difficult intubation,^12–15 this view is not universally shared and a reluctance to perform awake bronchoscopic intubation continues to occur.^16,17 In 2011, the 4th National Audit Project of the Royal College of Anesthetists and the Difficult Airway Society (DAS)¹⁰ reported a failure to consider or employ awake bronchoscopic intubation as a first choice in difficult airway management when it was clinically indicated and that harm occurred as a result. However, surveys from the United States, France, and Denmark published between 1998 and 2003 confirm the widespread use of flexible bronchoscopes particularly for management of the anticipated difficult airway.^18–22 A Canadian survey published in 2005 (2066 surveys sent, 47% response rate) revealed that 91.5% of practicing anesthesiologists performed awake bronchoscopic intubation and 89.3% felt comfortable with the technique; 83.6% had performed asleep FBI and 82.7% were comfortable with the technique.²³ Anesthesiologists from teaching institutions and younger practitioners had more experience with FBI and were more comfortable with it. Wong et al.²⁴ repeated this survey with modifications in 2013 (2532 surveys sent, 39% response rate). Ninety-eight percent of respondents had performed awake FBI and 93% were comfortable with the technique. Ninety-one percent had performed asleep FBI and 88% were comfortable with the technique. When presented with an unanticipated difficult intubation with failed direct laryngoscopy, 41% chose FBI as the first choice alternative, whereas 90% chose a video-laryngoscope.²⁴ In a review of general anesthetics administered at a Canadian tertiary care center between 2002 and 2013, 146,252 patients underwent endotracheal intubation and of these intubations, 1554 (1.06%) were performed awake. A flexible bronchoscope was used in 99.2% of these awake intubations. The incidence of awake intubation did not change significantly over the period of the study.²⁵ An American study reported a decreasing use of bronchoscopic intubation over 12 years ending in February 2013. But, it is not clear if bronchoscopic intubation under general anesthesia (GA) was included.²⁶

When Is Bronchoscopic Intubation Indicated?

The primary indication for awake bronchoscopic intubation is in the elective (or at least nonemergency) management of the anticipated difficult airway. The difficult airway can be defined as one in which an experienced practitioner anticipates or encounters difficulty with any or all bag-mask-ventilation, direct or indirect (e.g., video) laryngoscopy and tracheal intubation, EGD use, or surgical airway.²⁷ If difficult intubation after induction of GA is predicted with the practitioner’s chosen device(s) and ventilation by face-mask or EGD is also predicted to be difficult, awake intubation should be strongly considered.²⁸ Contextual issues such as a predicted short safe apnea time, aspiration risk, and lack of skilled help may also favor an awake technique.²⁸ Although awake intubation can be performed using other devices or combination of devices, awake intubation of the elective surgical patient will most often be performed using a flexible bronchoscope.²⁸ FBI continues to be the accepted standard in elective airway management of the awake spontaneously breathing patient with an anticipated difficult airway,¹¹ and maintains a wide margin of safety.^29–31 NAP4 suggested that there is a need to decrease the threshold for considering awake bronchoscopic intubation as a first choice in difficult airway management.¹⁰

FBI can also be used in the unanticipated difficult airway as an alternative technique when intubation by a primary technique has failed but ventilation by face-mask or EGD is successful (can’t intubate, but can oxygenate).^27,32,33 The flexible bronchoscope may also be the preferred device for intubation after induction of GA by practitioners who are expert in its use.³³ However, NAP4 reported that bronchoscopic intubation under GA was technically more difficult than in an awake cooperative patient due to loss of muscle tone leading to upper airway obstruction.¹⁰ Bronchoscopic intubation was attempted in seven patients reported to the audit after induction of GA either as the primary technique or after failed direct laryngoscopy. The asleep bronchoscopic intubation failed in all seven patients and all seven required an emergency surgical airway.¹⁰

In general, if airway compromise or respiratory distress exists, awake intubation maintains a wide margin of safety.²⁹ However, in this circumstance, the urgency with which airway control must be achieved and the extent of the airway compromise may limit the choice of technique, and bronchoscopic intubation may not be feasible or appropriate. In addition, incomplete local anesthesia of the upper airway makes bronchoscopic intubation more difficult, as does the presence of blood and secretions in the airway. Complete airway obstruction has been reported following the topical application of local anesthesia to the airway and suctioning in preparation for awake intubation in a stridorous patient with recurrent neck carcinoma and radiation therapy.³⁴ Complete airway obstruction after application of topical local anesthesia to the upper airway was also reported by Shaw et al.³⁵ in a patient with a compromised airway secondary to goiter. Liistro et al.³⁶ demonstrated a transitory but profound obstruction at the level of the glottis or supraglottis during forced inspiratory and expiratory vital capacity maneuvers that was produced in normal subjects with local anesthesia of the upper airway. Beydon et al.³⁷ and Kuna et al.³⁸ also found a decrease in upper airway caliber following local anesthesia of the airway in normal subjects. Patients with severe airway obstruction due to edema or tumor must be approached with extreme caution if completion airway obstruction is to be avoided⁴ (see Chapter 3) and due consideration must be given to awake tracheostomy in this setting.²⁸

In the presence of potential cervical spine instability, no intubation technique has been shown to be clearly superior.^{11,29,30,39–43} However, movement of the cervical spine must be minimized during intubation if neurologic injury is to be avoided. FBI can be a valuable alternative in this setting and has been extensively utilized.^11,40,44 Complete airway obstruction has however been reported during attempted awake bronchoscopic intubation in this patient population.^44,45

In the presence of airway trauma, FBI can permit precise evaluation of the injury, facilitate placement of an endotracheal tube (ETT) beyond the level of the injury,¹¹ and has been said to be the method of choice for airway management in this setting.^11,46

Radiation treatment for head and neck cancers can cause edema and fibrosis which can limit mouth opening and neck mobility and distort the submandibular space making direct laryngoscopy difficult or impossible.^11,47 Neck radiation is also a predictor of difficult video-laryngoscopy, bag-mask-ventilation, EGD use, and cricothyrotomy^28,48; and it is the most significant clinical predictor of impossible mask ventilation.⁴⁹ In the patient who has had neck radiation, awake bronchoscopic intubation can be an invaluable option.

Ludwig’s angina is a rapidly progressive cellulitis of the floor of the mouth usually caused by odontogenic infection.^50,51 Spread of the infection into the submandibular space produces edema and swelling which cause superior and posterior displacement of the tongue.⁵⁰ Infection in the submandibular space can extend into the lateral and retropharyngeal spaces and thus encircle the airway.^50,52 Pus accumulation can occur.⁵⁰ The swelling can involve the larynx and the infection can reach the mediastinum.⁵⁰ Neck movement can be restricted.⁵⁰ Trismus can be severe and may not improve with neuromuscular blockade.⁵³ Although less advanced deep neck infection can be managed by antibiotics alone, true Ludwig’s angina typically requires definitive airway control and surgical drainage.⁵⁴ Face-mask-ventilation, EGD use, direct and video-laryngoscopy, and surgical airway can all be difficult.^53,54 Awake tracheotomy under local anesthesia has been considered the gold standard airway management in this setting, however awake FBI has also been used with a high success rate⁵⁵ and can be a feasible alternative.⁵²

FBI can also be used as an alternative to direct laryngoscopy in any patient for whom intubation is indicated, and in particular when a high risk of dental injury exists.⁴

When Is FBI Best Avoided?

Contraindications to FBI must be considered relative and weighed against the risks associated with alternative airway management techniques.²⁹ Some measure of patient cooperation is required for awake FBI, and the total absence of cooperation may preclude this technique, as can bleeding in the airway and massive tissue disruption.^4,29,11,28 Fixed laryngeal obstruction with stridor at rest implies a reduction in the caliber of the airway to 4.0 mm or less in diameter.⁵⁶ FBI is unlikely to be successful in this setting and at best will produce a higher grade of obstruction when the scope is passed through the involved area. In this setting, a surgical airway (e.g., awake tracheotomy) performed under local anesthesia is a better alternative.⁵⁷ FBI is contraindicated when immediate airway control is necessary and the time required to complete the procedure is not available.⁸

Patient refusal in the adult population without psychiatric disease is exceedingly rare if an appropriate explanation of the procedure has been provided.

How Do Flexible Bronchoscopes Work? What Is the Best Instrument for FBI?

The standard “adult” flexible bronchoscope remains unsurpassed as an instrument with which to perform bronchoscopic intubation in the vast majority of circumstances in the adult population. These bronchoscopes have a sufficient length (about 60 cm) to accommodate an ETT ensleeved proximally while leaving an adequate distal segment for maneuverability. Shorter flexible fiberscopes tend to make FBI more difficult. A bronchoscope with an outside diameter of 5.9 and 6.0 mm will readily accommodate a 7-mm internal diameter (ID) ETT and has adequate stiffness to function well as a stylet over which to advance the ETT (see Figure 10–1).^29,58 Bronchoscopes with thinner insertion cords tend to be more flexible and form a floppy stylet that is easily buckled away from the glottis as the ensleeved ETT is advanced into the airway (see Figure 10–2).³⁰

The flexible bronchoscope consists of a proximal handle and a distal insertion cord or shaft. An umbilical or universal cord is attached to the side of the handle and connects the bronchoscope to an external light source (see Figure 10–3). Modern flexible bronchoscopes include fiberoptic bronchoscopes, video bronchoscopes, and hybrid designs. Flexible bronchoscopes are also available with a battery-operated light source, which greatly improves portability. The handle of the bronchoscope is fitted with a lever which controls flexion of the tip of the scope (the bending section)^14,59 in a single plane; the movement of the tip being produced by two wires which connect the control lever to the tip of the scope (see Figure 10–3).¹⁴ The handle also contains the proximal port of the working channel which extends distally to the tip of the scope. This channel can be used to pass various instruments into the airway and can be used for irrigation, administration of medications, and suction. Oxygen insufflation has been used via the working channel; however gastric rupture has been reported with this technique.⁶⁰ Light is transmitted from the external light source to the tip of the insertion cord via a fiberoptic bundle made up of thin glass rods (see Figure 10–4).^14,59,61 In the flexible fiberoptic scope, light reflected from the object being viewed is focused by a lens located at the tip of the insertion cord onto the distal end of a second fiberoptic bundle which then transmits the image to a second lens located in the eye piece.^14,59 The glass fibers in this image transmission bundle remain in the same relative location along the length of the bundle (coherent bundle) such that a mosaic image is accurately reconstructed at the eye piece.^14,59 The image seen through the scope is focused by means of a control located in the handle. In the video bronchoscope, a charged coupled device or silicone chip is located at the distal tip of the insertion cord and is used to sense and transmit the image (see Figure 10–5).⁵⁹ The image data are then transmitted electronically through the bronchoscope to an external video processing unit.⁵⁹ The image is then displayed on a screen and can be printed, stored electronically, or transmitted to a remote location.⁵⁹ A video camera can be coupled to the eye piece of a conventional fiberoptic bronchoscope; however, the image obtained is inferior to that provided by the video bronchoscope.⁵⁹ A video bronchoscope with a shaft that can be rotated relative to the handle has recently been introduced, although this feature is unlikely to make maneuvering the scope easier during bronchoscopic intubation.

Bronchoscopes are produced by a number of different manufacturers and are available with insertion cord diameters ranging from 2.2 to 6.3 mm.⁵⁹ In general, minimizing the discrepancy between the outer diameter (OD) of the bronchoscope and the ID of the ensleeved ETT facilitates passage of the tube through the larynx over the scope.^{3,4,30,62–68} Bronchoscopes with smaller diameter insertion cords have allowed FBI to be performed in the pediatric population, and very thin scopes such as the Olympus BF-N₂O with a shaft diameter of 2.2 mm can be used in infants. However, use of “pediatric” bronchoscopes to perform FBI of the adult, in general, makes the procedure more difficult.³⁰ The use of a pediatric bronchoscope to perform awake intubation in the adult with severe upper airway obstruction may be complicated by complete obstruction and must be approached with great caution.^4,34,57,69

Bronchoscopes are delicate instruments and must be handled with care if damage to the instrument is to be avoided. Damage to the bronchoscope is not only costly to repair but it also means that the scope is unavailable for clinical use for a period of time.¹⁴ Striking the distal tip of the insertion cord against a hard surface or excessive bending or twisting of the shaft of the scope can damage the lens and fiberoptic bundles, respectively.⁵⁹ If the external shaft of the insertion cord or the working channel wall is punctured, fluids can enter the inside of the scope and lead to a degradation or loss of the image transmitted.⁵⁹

Flexible bronchoscopes with shaft diameters of 3.5 and 4.0 mm can readily be passed through the lumen of a #35-Fr or larger double lumen tube and are invaluable for the precise tube placement required for lung isolation.

In 2010, Ambu^® (Ballerup, Denmark) launched a disposable single use video endoscope designed for intubation of adult patients.^70,71 This first generation Ambu aScope™ had an insertion cord with a maximum OD of 5.3 mm, a working length of 63 cm, and a 100⁷¹ or 120 degree⁷⁰ up and down bending section.⁷¹ It was equipped with a charged coupled device sensor and a light-emitting diode that provided an 80-degree field of view^70,72 and had a working channel 0.8 mm in diameter.⁷¹ It was connected to a separate 6.5 inch color liquid crystal display (LED) monitor (Ambu aScope™ Monitor) which had a resolution of 640 × 480 pixels. The operation time of the aScope is electronically limited to 30 minutes within an 8-hour period.^70,73 Missaghi et al.⁷¹ used the aScope™ to perform 10 orotracheal intubations and noted fogging of the camera system and secretions obscuring the view. Piepho et al.⁷⁰ compared the aScope™ with a standard flexible intubating fiberscope during easy and difficult intubations in the manikin. They also used the aScope™ successfully to nasally intubate three awake patients with predicted difficult airways and performed oral intubation on two patients who had unanticipated difficult airways after induction of GA. The authors felt that an acceptable view of the anatomical landmarks was obtained in the simulated airway and all the patients but the failed intubation rate was higher in the difficult airway simulation as compared with the standard flexible bronchoscope. They noted that image resolution on the aScope™ monitor was inferior and that the ability to use suction was limited.⁷⁰ Kristensen and Fredensborg⁷³ subsequently used the aScope™ to orally intubate the tracheas of 20 patients under GA. Intubation was successful on the first attempt in all 20 patients and the image quality was “acceptable” or “good.” Following this pilot phase of the study, 40 patients scheduled for awake intubation were randomized to aScope™ or reusable video bronchoscope groups. Intubations were performed orally under local anesthesia and sedation. The time required for administration of local anesthesia and intubation was longer in the aScope™ group. In two cases in the aScope™ group the image became blurred immediately after injection of local anesthetic through the scope and required the use of a new aScope™. Image quality was found to be inferior with the aScope™. An updated Ambu aScope™, the Ambu aScope™2 was developed with a better quality optical system.⁷⁴ Krugel et al.⁷² compared this second-generation aScope™ with a standard reusable fiberscope in a study that included 100 patients who were randomized to aScope™ and reusable scope groups. The intubations were performed orally under GA with the neck immobilized in a semirigid collar.⁷² All tracheal intubations were successful with the assigned scope, although intubation times were significantly longer, the quality of vision was significantly inferior, and jaw thrust was needed more often in the aScope™ group.⁷² Chan et al.⁷⁵ compared the Ambu aScope™2 with a conventional flexible bronchoscope in a randomized controlled trial that included 60 adult patients requiring oral tracheal intubation under GA. Two blinded independent observers rated the video recording of the intubation using a global rating scale (GRS). There was no significant difference in the GRSs between the two groups. Although the number of intubation attempts was lower in the aScope™ group, there was no significant difference in the success rates and intubation times between the groups. The authors supported the use of the aScope™ as an alternative to the reusable fiberscope. A third-generation aScope™, the Ambu aScope3 is now available (see Figure 10–6). The aScope3 has an insertion cord with an external diameter of 5.0 mm and a working channel with a diameter of 2.2 mm. A slim version, the aScope3-Slim has an insertion cord diameter of 3.8 mm and a working channel of 1.2 mm. A new monitor, the Ambu aView delivers 800 × 480 resolution and has improved the quality of the image.⁷⁵ Melookaran and Rosenblatt evaluated the aScope3 in a nonrandomized, non-blinded, noncontrolled cohort of 10 patients who were evaluated as difficult to intubate. The primary anesthesia practitioner and an independent anesthesia practitioner scored the intubation using a visual analogue scale.⁷⁶ One patient had incomplete data and was removed from analysis. The aScope™ was thought to perform comparably to a reusable flexible intubation scope. Greig and Wisely also evaluated the aScope3 during 20 bronchoscopic intubations in which the intubation was predicted to be difficult. Fifteen intubations were performed orally and 5 nasally; 4 awake and 16 following induction of GA. Ten 5.0-mm and ten 3.8-mm scopes were evaluated. Functionality and performance were rated as satisfactory in all procedures and the aScope3 was evaluated by the two investigators who performed the intubations as able to replace the existing non-disposable system in all cases.⁷⁷

The cost of a bronchoscopic intubation using reusable bronchoscopes includes the purchase cost of the scopes, repairs, maintenance, and labor.⁷⁸ An adequate number of scopes must be purchased to ensure availability when clinically needed. Cost analysis comparing traditional reusable bronchoscopes and the aScope2 concluded that costs are approximately the same per procedure in a department performing a high volume of bronchoscopic intubations, whereas in departments that perform bronchoscopic intubation occasionally, costs associated with the use of the disposable scope may be lower.⁷⁵ Tvede et al.⁷⁹ determined that the break-even point at which the cost of using disposable and non-disposable flexible scopes was identical at their institution was 22.5 intubations per month.

Another advantage of single use disposable bronchoscopes is elimination of the possibility of infection transmission that is associated with the use of non-disposable scopes (see section “Disposable versus Reusable Devices Considerations for Difficult Airway Carts” in Chapter 62).

How Are Flexible Bronchoscopes Disinfected?

In general, the issue of sterilization of bronchoscopes is addressed by infection control and risk management personnel in each health care facility.⁵⁹ Specific recommendations for sterilization are also provided by each manufacturer.^14,59 Accurate reprocessing of flexible endoscopes is a multistep procedure which includes manual cleaning followed by high-level disinfection (HLD), rinsing, drying, and appropriate storage.⁸⁰ Reprocessing can be performed using automated endoscope reprocessors (AERs) and manual methods according to a strict protocol. Most flexible endoscopes are classified as semicritical devices which come into contact with intact mucous membranes and should undergo at least HLD. Flexible endoscopes used for therapeutic procedures, and reusable accessories such as biopsy forceps, are classified as critical devices and must be sterilized after each procedure.⁸⁰ Ethylene oxide and hydrogen peroxide plasma sterilization have reliable efficacy as compared to HLD but can damage the flexible endoscopes. Gas sterilization with ethylene oxide may fail in the presence of organic debris or biofilm. As of 2013, there were no data demonstrating that sterilization resulted in a lower frequency of post-endoscopic infection as compared to HLD. Manual cleaning precedes sterilization or HLD and includes brushing of the external surfaces of the scope, including the channels, ports and removable parts, and immersion in a detergent solution.^80,81 This is followed by irrigation of internal channels with a detergent, inspection for damage, and a leak test. HLD is then performed manually or by using an AER. Use of an AER is recommended. Agents appropriate for HLD include 2% to 4% glutaraldehyde, peracetic acid, orthophthaldehyde, and superoxidized and electrolyzed acid water. Glutaraldehyde can, however, coagulate and fix proteins and fail to eliminate atypical bacteria within standard contact times.⁸⁰ Peracetic acid is the agent usually used for HLD of flexible scopes in AERs. After disinfection, the disinfectant must be removed from the exterior and the internal channels of the scope by rinsing with bacterium-free water. This is followed by flushing of the channels with ethyl or isopropyl alcohol. The flexible scope should then be dried with filtered compressed air manually or in an AER between procedures (short drying cycle) and at the end of the day (intensive final drying). The scope is then stored hung vertically in a dust-free drying cabinet with laminar airflow.

It has been shown that routine cleaning and autoclaving do not remove protein material, including prions (protein particles without nucleic acid), from reusable airway devices,⁸² and concern has been expressed with respect to the possible transmission of infection with subsequent usage.⁸³ The true incidence of bronchoscopy-associated infections is unknown in part due to inadequate surveillance and episodic reporting.^81,80 Although the risk of infection transmission in gastrointestinal endoscopy has been quoted to be 1 in 1.8 million,^80,81 others have said that the true incidence of infection transmission is impossible to determine.^78,80,84 The emergence of variant Creutzfeldt–Jakob disease (vCJD) which is transmitted by prions as an important pathogen in humans has further complicated the issue of decontamination.^78,80 Prions are highly resistant to routine methods of sterilization and decontamination. Dry heat, glutaraldehyde, and ethylene oxide are ineffective and recommended chemical methods include a decontamination step with concentrated sodium hydroxide, sodium hypochlorite, or formic acid and prolonged steam sterilization.⁸⁰ Most contemporary flexible endoscopes cannot withstand heat sterilization and disinfection with high concentrations of disinfectants without sustaining severe damage.⁸⁰ A recent review has suggested that flexible endoscopes that have been used in patients with CJD should be discarded.⁸⁰

How Is the Bronchoscope Maneuvered? What Are the Key Aspects of Technique for Fast, Successful Bronchoscopic Intubation?

The bronchoscope is most easily maneuvered by holding the handle of the scope in the palm of the dominant (usually right) hand with the thumb placed on the flexion lever (see Figure 10–7). The fingers should comfortably encircle the handle of the scope and the index finger can be used to activate the suction mechanism, although suction is rarely required during FBI if antisialogogues are used. When the scope is held such that the flexion lever is in the 6 o’clock position, moving the lever downward (toward the shaft of the scope) flexes the tip of the scope upward toward the 12 o’clock position. Conversely, moving the lever up toward the proximal aspect of the handle flexes the tip downward toward the 6 o’clock position (see Figure 10–8). Movement of the flexion lever (thumb flexion) then flexes the tip of the scope in a single plane. To flex the tip in any other plane, the entire instrument must be rotated clockwise or counterclockwise using the wrist and hand holding the handle of the scope. This wrist rotation is the second important and perhaps not intuitively obvious movement required when manipulating the bronchoscope during FBI (see Figure 10–9A and B). The tip of the bronchoscope can then be manipulated to view objects in any plane within the scope’s field of vision by a combination of wrist rotation and thumb flexion. Some bronchoscopes have a triangular marker or divot^8,85 located at the 12 o’clock position at the periphery of the scope’s field of vision (see Figure 10–10). This marker helps the practitioner maintain spatial orientation as the tip of the scope always flexes in the diametrical plane of the marker. When a video camera is coupled to a fiberoptic bronchoscope, the divot must be adjusted to the 12 o’clock position (opposite the flexion lever on the handle) to maintain correct orientation.⁸⁵ The practitioner’s nondominant (usually left) hand holds the shaft or insertion cord of the bronchoscope a few centimeters proximal to the tip with the forearm pronated (see Figure 10–11). The shaft should be held lightly between the tips of the thumb and index finger, and can be stabilized between the ring and middle finger or some other combination of digits if desired. The hand holding the distal shaft of the scope must feed the scope forward into the airway in a controlled manner without excessive (shaky) movement that can make visualization difficult. During FBI, the scope must travel about 21 cm from the incisors to the mid trachea. If the shaft is held at about 20 cm proximal from the tip, then feeding can be minimized.

Generally it is easier to rotate the bronchoscope using the dominant (usually right) hand positioned at the handle. The nondominant hand holding the distal aspect of the shaft must allow the shaft to rotate, and therefore the shaft cannot be gripped tightly. If the distal aspect of the shaft is held tightly, rotation at the handle twists the insertion cord, the scope fails to go in the desired direction, and the components in the shaft can be damaged. Although rotation of the scope is usually more easily controlled by the hand positioned at the handle, the nondominant hand holding the distal shaft can also be used to rotate the instrument. In that maneuver, the hand at the handle must follow the movement and allow the entire instrument to rotate as a single unit, or again, twisting of the shaft will occur and the scope fails to go in the desired direction (see Figure 10–9A and B). As experience is gained in handling of the scope, the shaft does not need to be held taut to maneuver the tip. However, holding the shaft of the scope relatively straight can be useful to maintain orientation and control movement. The most important concepts to master are thumb flexion and wrist rotation. During FBI, movements of the scope (flexion, rotation, and forward feeding) should be small, slow, and deliberate. Over steering of the scope is a common error.

The ETT can be precut to a desired length (usually about 28 cm) to maximize the length of the insertion cord beyond the tube and thereby optimize maneuverability.²⁹ The inside of the tube can be lubricated using lidocaine spray or sterile water. The tube is then ensleeved proximally and fixed to the handle with an elastic band (see Figure 10–12).²⁹ A lubricant jelly placed on the cuff of the tube may facilitate glottic entry. Lubricating the shaft of the scope is unnecessary and makes it difficult to handle.

Is Bronchoscopic Intubation More Easily Performed from the Head of the Bed or from the Patient’s Right Side? What Instructions Should be Given to the Patient During the Procedure?

Awake FBI can be performed with the practitioner standing at the head of the bed, and for those who are most familiar with visualization of the airway by direct laryngoscopy, this position preserves the spatial orientation of the airway structures as they are viewed through the scope.^29,30 However, this position requires the practitioner to negotiate an S-shaped curve to the trachea (see Figure 10–13) and the patient to be supine or nearly supine. Standing at the patient’s right side facing cephalad facilitates negotiation of the natural C-shaped curve of the airway (see Figure 10–14), permits easy visualization of patient monitors, and as eye contact can be readily maintained this position may be less intimidating for the patient.^29,30 The patient may be supine or in the semi-sitting or sitting position.³⁰ The semi-seated or sitting position may also be less intimidating for the awake patient and may better maintain the patency of the pharyngeal lumen.^30,86 Lai et al.⁸⁷ report that they can often obtain a superior view during bronchoscopic intubation with the patient in the sitting position. Extension at the atlanto-occipital joint moves the epiglottis anteriorly away from the posterior pharyngeal wall and facilitates passage of the bronchoscope through the pharynx.^{4,30,68,88,89} Neck flexion, however, tends to produce pharyngeal obstruction and can make FBI more difficult.^30,88–90 For awake oral FBI, the author prefers to be positioned at the semi-seated or sitting patient’s right side (see Figure 10–15). The light source is to the practitioner’s left, and the video screen is located in front of or slightly to the left of the practitioner. Oxygen can be administered by nasal prongs. An assistant is positioned at the patient’s left side and provides gentle tongue traction using a piece of gauze.³⁰ Use of a bite block tends to push the tongue posteriorly and cephalad into the oropharyngeal isthmus, can make passage of the scope into the oropharynx more difficult, and is not necessary if adequate local anesthesia has been achieved.³⁰ The lens can be defogged using silicone solution or simply by holding the tip of the scope in warm water, or against the buccal mucosa for a few seconds to warm it and thereby prevent condensation.^29,30 The scope should be inserted into the oral cavity to the level of the dental arches in the midline, and then advanced a few centimeters posteriorly over the dorsum of the tongue following the midline groove toward the first midline landmark, the uvula, seen in the superior aspect of the scope’s field of vision (see Figure 10–10).³⁰ Gently resting the hand holding the shaft of the scope on the patient’s chin may help keep the scope in the midline but requires the shaft to be held close to the tip and necessitates more feeding as compared to holding the shaft at about 20 cm from the tip.^30,68 If the uvula is in contact with the dorsal aspect of the tongue, the patient can be instructed to take a deep breath, thereby elevating the uvula and opening the oropharyngeal isthmus.^29,30 The scope is then advanced slowly forward just past the uvula and flexed caudally to visualize the second midline landmark, the epiglottis, seen inferiorly in the scope’s field of vision (see Figure 10–16).^29,30 If the epiglottis is oriented posteriorly or is in contact with the posterior pharyngeal wall, the awake patient can again be instructed to take a deep breath and thereby move the epiglottis anteriorly to create an air space through which to pass the scope.^29,30 The scope is then passed, posterior to the epiglottis to visualize the third midline landmark, the vocal cords (see Figure 10–17).^29,30 If the bronchoscope is passed behind the epiglottis in the midline, then it is naturally lined up for the approach to the larynx. Conversely, if the bronchoscope is off midline at the level of the epiglottis, the approach to the larynx can be much more difficult. The scope is then advanced in the midline through the glottis and positioned proximal to the carina.^29,30 As the scope is advanced through the larynx, the patient is again instructed to take a deep breath to maximally abduct the vocal cords and thereby facilitate passage of the scope. As the bronchoscope is passed from the level of the dental arches to the trachea, flexion and rotation movements should be small and deliberate such that the scope can be kept in the midline and advanced along the C-shaped curve of the airway, analogous to staying in a given lane during highway driving using small movements of the steering wheel. Unnecessary touching of the mucosa by the bronchoscope should be avoided. Having positioned the tip of the bronchoscope in the mid to distal trachea, the practitioner should then look directly at the patient and advance the ETT over the scope being careful to aim for the midline and to follow the natural curve of the airway (see Figure 10–15).^29,30 The bronchoscope must be kept stationary as the tube is advanced¹² in order to avoid inadvertent contact with the carina, cannulation of a mainstem bronchus, or premature removal of the scope from the trachea. Again, as the tube is advanced, the patient should be instructed to take a deep breath to move the epiglottis anteriorly away from the advancing tube and to maximally abduct the vocal cords.^29,30 The correct intratracheal position of the ETT can be confirmed endoscopically before the scope is removed.^29,30 However the presence of both the bronchoscope and ETT in the trachea produce a degree of airway obstruction that can be distressing for the awake patient, and the bronchoscope should be removed expeditiously once the ETT is in proper position. Correct position can be further confirmed by listening to and feeling gas exhaled via the ETT and by capnography.

How Can Difficulty in Passing the Ensleeved ETT into the Trachea Over the Flexible Bronchoscope be Minimized?

Difficulty in passing the ensleeved ETT through the larynx has been variously reported to occur in 0% to 90% of FBIs,^{62,65,91–95} in awake patients, as well as those under GA, and with both the nasal and oral routes of tracheal intubation. During oral FBI, as the tube is advanced with the concave aspect of the tube facing anteriorly and the bevel facing toward the patient’s left, the leading edge of the tube may meet resistance at the right arytenoids, aryepiglottic fold, or interarytenoid soft tissue (see Figure 10–18).^93,96–98 Rotation of the tube 90 degrees counterclockwise orients the bevel posteriorly and the leading edge into the anterior position and has been advocated to improve passage of the ETT through the larynx.^97–101 Sharma et al. randomized 70 patients undergoing awake bronchoscopic intubation to conventional tube orientation with the bevel facing the patient’s left or bevel facing posteriorly. The first attempt success rate in the bevel posterior group was 100% as compared to 60% in the bevel left group.¹⁰² In the 14 of 35 patients in the bevel left group in whom intubation was unsuccessful on the first attempt, all were intubated successfully on the second attempt with the bevel rotated 90 degrees counterclockwise.¹⁰² Rotation of the tube counterclockwise may also keep the leading edge in closer contact with the bronchoscope and provide less of a gap between the two with which to catch a laryngeal structure.^62,103 Migration of the tube into the hypopharynx as it was advanced over a 4-mm fiberscope and pushed the mid segment of the scope into the hypopharynx in patients under GA and muscle paralysis has also been observed, as has impaction of the tube on the epiglottis.¹⁰⁴

During nasal FBI, it has been postulated that the tube tends to impinge on the epiglottis.^93,97,103 However the usual point of obstruction during nasal tracheal intubation may also be the right arytenoid.¹⁰³ Improved success rates have been reported for glottic cannulation during nasal FBI, using a 90-degree counterclockwise rotation of the tube.⁹³ Conversely, others have said that counterclockwise rotation of the tube may not be effective during nasal bronchoscopic intubation.^62,91 Nasal FBI performed with the bevel up has also been advocated such that impingement on the epiglottis may be avoided.¹⁰¹ In addition to the right arytenoid and epiglottis, impingement can occur at the posterior pharyngeal wall or other laryngeal structures.⁹⁵

The larger the discrepancy between the outside diameter of the bronchoscopic insertion cord and the ID of the ensleeved ETT, the greater is the chance that the tube may impinge on laryngeal structures and resist entry into the trachea (see Figure 10–19).^{3,4,30,64,65,96} Therefore, this discrepancy should be minimized by choosing the largest bronchoscope which will easily fit into the ETT to be used.^30,67,68 In the adult, a bronchoscope with an OD of 5.9 to 6.0 mm works well when used with a 7.5- to 8.5-mm ID ETT. When the combination of a relatively large bronchoscope and an ETT are both present in the trachea, the practitioner must be aware that a degree of airway obstruction has been produced⁶³ and the bronchoscope should be removed without delay following tube placement and confirmation. If the bronchoscope must remain inside the tube positioned in the trachea for a relatively long period as during diagnostic or therapeutic bronchoscopy, then the concentric airway remaining must be adequate to permit ventilation to occur.^30,63,105 Wire reinforced spiral tubes are more flexible than polyvinyl chloride (PVC) tubes and may more easily follow the curve of the bronchoscope as it passes through the larynx.^{30,96,105–108} Although flexible wire reinforced tubes were reported to be associated with a lower rate of impingement in the larynx than a standard tube,¹⁰⁶ subsequent studies reported frequent laryngeal impaction with spiral tubes.^91,92 Various methods to minimize the discrepancy between the OD of the bronchoscope and the ID of the ETT have been proposed. These include the interposition of a smaller ETT between the scope and the larger ETT to be positioned in the trachea (see Figure 10–20),^62,108 or the use of a sleeve such as an airway exchange catheter,¹⁰⁸ split nasogastric tube,¹⁰⁹ or a custom-designed conical-shaped PVC sleeve.¹¹⁰ The use of a Cook Airway Exchange Catheter passed alongside the bronchoscope through the ETT into the trachea to “centralize” the tube and facilitate glottic cannulation has also been reported.¹¹¹ Preformed PVC ETTs can also be warmed to increase flexibility although the effect of warming on ease of insertion is unclear.^14,29,62,30 Laryngeal cannulation with the ensleeved ETT may also be facilitated by using a tube with a modified tip design.^29,30,96,99 The silicone wire-reinforced tube for the Intubating Laryngeal Mask Airway (ILMA) is reusable and has a soft hemispherical bevel that has a leading edge in the midline (see Figure 10–21).⁹⁶ Greer et al.⁹⁶ found that the incidence of difficulty in passage of the ETT was significantly less using the ILMA tube as compared to the flexometallic tube during oral FBI under GA. Barker et al.⁹¹ found the Intravent Orthofix ILMA tube to be superior to both the reinforced and standard PVC tubes during nasotracheal intubation under GA. All 15 Intravent tubes were easily passed through the larynx on the first attempt, whereas difficulty in passing the ensleeved tube was encountered in 8/15 in the standard-tube group, and 6/15 in the flexible-tube group.⁹¹ The Parker Flex-Tip tube (see Figure 10–22) has a flexible tip that points toward the center of the distal lumen and the convex side of the tube and a bevel that faces posteriorly.^62,65 Kristensen⁶⁵ has reported a greater incidence of initial success with passage of the tube through the larynx as compared to a standard PVC ETT in a series of 76 patients who underwent oral FBI under GA. A higher cuff pressure was required with this Parker Flex-Tip tube to establish a seal. However, in a recent randomized prospective study involving 111 patients with difficult airways or unstable cervical spines, Joo et al.¹¹² did not find any significant difference in the success rate between the Parker Flex-Tip tube and the PVC tube for awake oral FBI. Baraka et al.¹¹³ modified the 7.5-mm Parker tube by cutting the anterior Flex Tip. They then compared the ease of advancement of the Parker Flex-Tip tube over a 4-mm FB with a standard Mallinckrodt tube (group 1) and the modified Parker tube with the Mallinckrodt tube (group 2) in 27 patients under GA. The success rate of advancing the tube on the first attempt was significantly higher with both the Parker and the modified Parker tubes as compared to the Mallinckrodt tubes but there was no significant difference between the Parker and the modified Parker tubes. The authors concluded that the improved ease of passage seen with the Parker tube may be due to the posteriorly facing bevel.¹¹³ Difficulty in advancing the ETT through the larynx may be encountered as well in the awake patient without obtunded laryngeal reflexes.⁴

Difficulty with passage of the ETT through the larynx is exceedingly rare in the awake cooperative patient in the sitting position with adequate topical anesthesia of the airway, when an optimally sized bronchoscope is used relative to the ETT, and the tube is advanced during a deep inspiration.

Are Oral Intubating Airways Useful or Necessary?

Various oral intubating airways are available and can be used during FBI. The purpose of these airways is to keep the bronchoscope in the midline and align it with the glottic opening, displace the tongue anteriorly and the soft palate superiorly thus opening the pharyngeal space, and to protect the scope from bite damage.^85,114

The Berman Intubating Pharyngeal Airway, also known as the Berman Breakaway Airway (see Figure 10–23), is cylindrical and has a longitudinal opening along its side which permits its disengagement (“breakaway”) from the ETT.¹⁴ The maneuverability of the bronchoscope is limited when inside the airway, and if the airway is not in line with the glottis, visualization requires manipulation of the device.¹⁴

The Patil-Syracuse Endoscopy Airway (see Figure 10–24) is made of aluminum and is available in two sizes (adult and pediatric). A central groove is located on the lingual surface for the bronchoscope, but manipulation of the bronchoscope is restricted.⁸² An ETT will not pass through the airway.¹⁴

The Williams Airway Intubator has a cylindrical proximal half, whereas the distal half of the device has an open lingual surface (see Figure 10–25).^14,85 The airway is available in two sizes (90 and 100 mm ID) which admit 8.0- and 8.5-mm ID ETTs, respectively.^14,85 Manipulation of the bronchoscope inside the airway is limited.¹⁴ If the distal aspect of the airway is not aligned with the glottis, visualization of the vocal cords can be difficult.^14,85

The Ovassapian Fiberoptic Intubating Airway has a flat lingual surface at the proximal half of the device which minimizes its movement (see Figure 10–26).^14,85 The distal half of the airway has a wide curve designed to prevent the tissues of the anterior pharyngeal wall from moving posteriorly. The posterior distal aspect of the airway is open.

A split Guedel airway has also been used for FBI.¹³

Randell et al.¹¹⁵ found that the Berman airway was superior to the Ovassapian Fiberoptic Intubating Airway during FBI. However, only 1 of 63 bronchoscopies failed using the Ovassapian airway. Greenland et al.¹¹⁴ compared the Williams Airway Intubator and the Ovassapian Fiberoptic Intubating Airway in 60 Asian patients who underwent oral FBI under GA. They reported that the Williams airway provided an unobstructed view of the glottis in 68.3% of cases, whereas the Ovassapian airway provided an unobstructed view in 25%. Four bronchoscopies failed using the Williams airway and 26 using the Ovassapian airway. Intubating conditions with either airway were similar when the glottis was visible.¹¹⁴ In a randomized clinical trial, Rosenstock et al.¹¹⁶ compared awake video-laryngoscopic and awake bronchoscopic intubation in a group of patients with anticipated difficult intubation. A Berman II airway was used in the bronchoscopic group. Of the 43 patients in the bronchoscopic group, a Cormack–Lehane (CL) I view was obtained in 22 and a CL 2 in 12. The CL view was 3 or worse for the rest of the patients. Asai and Shingu⁶² suggest that it may be better to remove an airway intubator after the bronchoscope has been positioned in the trachea as it may interfere with the advancement of the ETT.

Airway intubators can be used to facilitate FBI. However, the great advantage of FBI is that the instrument is flexible and restricting its flexibility seems counter intuitive. FBI can be rapidly achieved without the use of these devices and the emphasis should be on the development of skill with bronchoscopic manipulation and topical anesthesia of the airway.

Is Nasal Bronchoscopic Intubation Easier? Which Nostril Is the More Appropriate for Intubation?

If the nasal route is chosen for FBI, an attempt to identify the more patent nostril can be made by asking the patient to assess airflow through each nasal cavity in turn during exhalation, and by feeling airflow from the nostril.¹¹⁷ However, these simple diagnostic tests have been shown to have a failure rate of about 45%.¹¹⁷ Some degree of nasal obstruction can be present in the absence of a history of nasal trauma, surgery, or obstruction and can interfere with the attempted passage of a nasal tube. The mucosa over the turbinates is easily traumatized.¹¹⁷ Endoscopic examination of the nasal cavity may be helpful in identifying the more appropriate nostril for intubation.¹¹⁷ Administration of a nasal vasoconstrictor may also increase the caliber of the nasal airway. In the absence of a history of nasal obstruction, it is controversial whether the left or right nostril should be used for nasal intubation as it is not known whether the bevel or the tip of the tube is more responsible for potential damage to the nasal mucosa (see section “Blind Nasal Intubation” in Chapter 12).

During nasal FBI, either the ETT or the bronchoscope can be passed initially through the nasal cavity.^3,29,30,61 If the tube is passed first, it can be advanced along the floor of the nose using a gentle alternating clockwise–counterclockwise motion to facilitate its passage until the tip of the tube exits the choana and enters the nasopharynx.^3,30 The scope can then be passed through the lubricated tube and as it exits the distal aspect of the tube, the glottis is usually in view (see Figure 10–27). If on exiting the tip of the ETT the view is obstructed, the tube may be in contact with the pharyngeal mucosa or the tip of the scope may be covered with blood or debris. The scope can be removed, the tip cleaned and warmed, and then reinserted into the tube. If on exiting the distal aspect of the tube, still no recognizable structures are visualized, then the scope and tube should be slowly retracted together until pharyngeal or laryngeal landmarks (the uvula, epiglottis, or vocal cords) are identified.²⁹ If the epiglottis is oriented posteriorly against the posterior pharyngeal wall, the patient can be instructed to take a deep breath and thereby move the epiglottis anteriorly and create an adequate airspace for the scope to pass behind it, without touching mucosa and losing the visual field.³⁰ The flexible bronchoscope is then advanced into the trachea and the ETT advanced over the scope as for oral intubation during a deep inspiration, optimally with the patient in the semi-sitting or sitting position.^29,30 Alternatively, the flexible bronchoscope can be passed first through the nasal cavity and on into the trachea under endoscopic vision and then the ensleeved ETT passed over the scope (see Figure 10–28). On advancing the ETT over the flexible bronchoscope, the leading edge of the tube may impact on the laryngeal structures and resist further advancement.⁹³ The most likely site of impingement during nasal FBI is controversial.^97,103 Rotating the tube such that the bevel faces anteriorly,¹⁰¹ or posteriorly,⁹³ or advancing with a twisting motion^30,63,97 may facilitate glottic entry. A lubricated nasopharyngeal airway can be inserted temporarily into the nose before subsequent insertion of the ETT to explore the nasal cavity such that an appropriately sized ETT can be chosen.³⁰ Further decompression of the nasal mucosa may also be thereby achieved¹¹⁸ and trauma due to the more rigid ETT may be reduced. Alternatively, a nasopharyngeal airway split longitudinally can be inserted into the nasopharynx and used as a guide through which to pass the bronchoscope.^30,118 The split nasopharyngeal airway can then be removed before subsequent passage of the ETT. On occasion, the caliber of the nasal cavity may be such that it will permit passage of the ETT or nasopharyngeal airway but not the bronchoscope through the tube or airway due to external compression.^29,30 Conversely, the nasal cavity may permit initial passage of the scope but not the tube over the scope.^29,30 In this circumstance, it may be necessary to use a smaller scope, a smaller tube, the other nostril, oral intubation, or another means of airway management Nasotracheal intubation produces less stimulation of the gag reflex^3,7,57 and requires less patient cooperation, but is generally more uncomfortable for the awake patient. Kundra et al.¹¹⁹ compared nebulized lidocaine with combined regional lidocaine blocks for awake nasotracheal bronchoscopic intubation under conscious sedation. Thirteen of 24 patients in the nebulizer group reported mild discomfort and 5 were “uncomfortable” during the procedure; 12 of 24 in the CRB group reported mild discomfort and 3 were “uncomfortable.”¹¹⁹ If the nasal cavity can be readily cannulated, nasotracheal intubation using a flexible bronchoscope is technically somewhat easier than oral FBI.

Nasotracheal intubation has been considered to be contraindicated in the presence of a coagulopathy, intranasal abnormalities, paranasal sinusitis, extensive facial fractures, and basal skull fracture.^120–123 Conversely, basal skull fracture has been said not to be a contraindication to nasotracheal intubation.¹²⁰ Complications peculiar to nasotracheal intubation include epistaxis,^41,121–126 damage to the nasal or nasopharyngeal mucosa with creation of a false passage^4,124 and potential abscess formation,¹²¹ bacteremia,^4,41,123 damage to nasal polyps or adenoidal tissue with possible dislodgement and aspiration, nasal necrosis,^4,41,121,123 sinusitis,^41,121,123 and otitis.^4,41,123 Minimal epistaxis has been reported in 11% to 40% of emergency nasotracheal intubations^124,126 and moderate to severe bleeding in 7%.¹²⁶ In a series of 99 patients undergoing maxillofacial surgery, nasotracheal intubation was associated with mild epistaxis in 5 patients and bleeding sufficient to produce a visible accumulation of blood in the pharynx in 1 patient.¹²⁵ Of 175 participants who underwent nasotracheal intubation at an awake bronchoscopic intubation training course, minor nasal bleeding was seen during endoscopy or after extubation in 20.¹²⁷ None of these 20 participants required suction to clear the airway and the bleeding did not interfere with endoscopy.¹²⁷

When Is Bronchoscopic Intubation Under GA Indicated? What Are the Problems with This Technique?

FBI under GA can be performed as easily as intubation by direct laryngoscopy in patients with normal airway anatomy.⁴ Oral FBI has also been successfully performed following simulated rapid sequence induction (RSI),¹²⁸ and FBI under GA has been used for training purposes.^129,130 FBI of the anticipated and unanticipated difficult intubation under GA has also been reported, although some intubation failures did occur.^13,131 This technique may be particularly useful in uncooperative patients.¹³²

As consciousness is lost, loss of tone in the submandibular muscles allows the tongue and epiglottis to move posteriorly and potentially obstruct the airway at the level of the pharynx and larynx, respectively.^133,134 The soft palate also approximates the posterior pharyngeal wall.¹³³ The degree of airway obstruction produced is influenced by variations in airway anatomy, body habitus, and depth of coma.^30,89 In the unconscious individual, this reduction in the caliber of the pharyngeal lumen can make endoscopic visualization more difficult.^4,30,135 Contact of the bronchoscope lens with the mucosa results in loss of the visual field, and the practitioner’s ability to maneuver past an epiglottis in contact with the posterior pharyngeal wall is limited.^30,58,63,135 In the supine individual under GA, lingual traction with Duval’s forceps has been shown to move the tongue away from the uvula and soft palate better than the jaw thrust maneuver, whereas jaw thrust moved the epiglottis away from the posterior pharyngeal wall more effectively than tongue traction.¹³⁴ Jaw thrust and tongue traction applied simultaneously opened the airway at the soft palate and epiglottic level in all patients studied.¹³⁴ These combined maneuvers require two assistants.¹³⁴ Intubating airways such as the Berman or Ovassapian airway can also be used to keep the pharyngeal airway open as well as to direct the flexible bronchoscope toward the larynx; however multiple manipulations may be required, the intubation may be prolonged, and failure can occur.¹³⁴ Ching et al.¹³⁶ evaluated the effect of lingual traction on bronchoscopic intubation in patients with anticipated difficult airways under GA. Intubation was successful in 29 of 39 patients on the first attempt without tongue traction and 36 of 39 with tongue traction. All patients in both groups were successfully intubated after the application of tongue traction, although some required three attempts.¹³⁶ Anterior displacement of the tongue base using the rigid laryngoscope may also improve visualization,^3,4,30,58 as can placing the patient in the semi-left lateral position with the head turned to the left.¹³⁷ If resistance is encountered in passing the ETT over the bronchoscope despite rotation of the tube, digital manipulation may be useful to facilitate glottic entry.⁶⁸ Jaw thrust has also been shown to facilitate tube passage during bronchoscopic intubation under GA.¹³⁸ An endoscopy mask fitted with a diaphragm permits endoscopy during positive pressure mask-ventilation,¹³⁹ and can be used in conjunction with an intubating airway.^4,8,14,139 The nasotracheal route can also be used in the unconscious individual.^3,135

In the presence of apnea or suboptimal ventilation, arterial desaturation imposes a time limit on bronchoscopic techniques.^4,29,30 Denitrogenation creates an oxygen reservoir in the lungs and in healthy adults can extend the duration of apnea before oxygen desaturation occurs from 1 to 2 minutes to 8 minutes.^33,140 Denitrogenation in the 20-degree head up position has been shown to increase the apnea time before oxygen desaturation to 95% as compared to the supine position.¹⁴¹ The apnea time before oxygen desaturation to 92% in severely obese patients was similarly shown to be increased after denitrogenation in the 25-degree head up position as compared to the supine position.¹⁴² Passive oxygenation during the apneic period (apneic oxygenation) can also prolong the duration of apnea before desaturation occurs.³³ During apnea oxygen uptake from the alveoli into the blood stream exceeds carbon dioxide excretion from the blood stream into the alveoli.^143,144 This creates subatmospheric pressure in the alveoli which generates a mass flow of gas from the pharynx to the alveoli provided the upper airway is patent.^143,144 Oxygen can be delivered to the pharynx during apnea using nasal cannulae at flow rates of 5 to 15 L·m⁻¹.¹⁴³ Specialized high-flow nasal cannulas that humidify the oxygen allow flow rates up to 40 L·m⁻¹.¹⁴³ Patel and Nouraei¹⁴⁴ used the Optiflow nasal cannula to deliver oxygen at 70 L·m⁻¹ during 10 minutes of denitrogenation and then during apnea following the induction of GA and muscle relaxation in 25 adults undergoing hypopharyngeal or laryngotracheal surgery. The median apnea time was 14 minutes and no patient had oxygen saturation less than 90%.¹⁴⁴

FBI of a patient under GA can be difficult¹⁴⁵ and arterial oxygen desaturation can occur.^146,10 Although the technique has been used with high levels of success,^{128,131,138,136,147} failure of FBI following induction of GA has also been reported.^10,138,147 Bronchoscopic intubation under GA was attempted in seven patients reported to NAP4 either as the primary technique or after failed direct laryngoscopy.¹⁰ The asleep bronchoscopic intubation failed in all seven patients and all seven required an emergency surgical airway.¹⁰ If FBI is planned under GA, denitrogenation and administration of oxygen by nasal cannula during the procedure can extend the apnea time before oxygen desaturation occurs. Tongue traction and jaw thrust can open the pharyngeal airway and improve visualization.