The procedure in which the vocal cords are visualized for placement of an et tube is called direct

Tracheal Tube Introducer (Bougie)

If DL does not bring the vocal cords fully into view, a tracheal tube introducer may be used to facilitate intubation. This adjunct is a long, thin, semirigid introducer that, with the aid of a laryngoscope, is passed through the laryngeal inlet and over which an ET tube is advanced through the cords and into the trachea. The technique, originally described more than 60 years ago by Macintosh,144 was recommended for patients in whom visualizing the vocal cords was difficult. It has also been shown to be effective when the laryngeal inlet cannot be visualized at all.145 It is the most common airway adjunct used in British EDs for complicated intubations.146 Its efficacy has been demonstrated prospectively during difficult intubations in the operating room, as a pivotal component of a difficult airway algorithm in the operating room, and when compared with conventional laryngoscopy in the ED.53,147,148

A variety of tracheal tube introducers are available today (Fig. 4.18). The original adjunct was called the gum elastic bougie, or simply “the bougie,” and is currently available in a reusable form for both adult and pediatric patients (Eschmann Tracheal Tube Introducer, Portex Sims, Kent, UK). The adult size comes in two forms: a 60-cm (15-Fr) version with a short, 40-degree hockey-stick curve at the end, and a straight one that is 70 cm. The adult version can accommodate a 5.5-mm ET tube. The pediatric version is 70 cm (10-Fr) and straight and can accommodate a 4.0-mm tube. A polyethylene introducer designed for single use is also available and comes only in the 60-cm version (Flextrach ET Tube Guide, Greenfield Medical Sourcing, Austin, TX). A variation of this concept is the FROVA Introducer (Cook Critical Care, Bloomington, IN), a plastic introducer with a similar profile to the others except that it has a hollow lumen through which the patient can be ventilated when an accompanying adapter is attached.

Consider using a tracheal tube introducer when a difficult airway is anticipated; it can also be helpful in all intubations when visualization of the laryngeal inlet is limited. A trauma patient with cervical spine precautions is a typical example. The presence of blood and vomitus rarely prevents placement of the bougie into the trachea. Its safety record is impressive despite decades of use, and reports of complications are rare.149

Shaping the introducer may not be necessary in many cases, but with difficult laryngeal views, create a 60-degree bend in the distal introducer (seeFig. 4.18D).150 Ideally, tracheal tube introducer-assisted intubation is a two-person procedure (Fig. 4.19). As laryngoscopy begins, the assistant has both a styletted ET tube and bougie prepared and available. The intubator performs laryngoscopy in the normal fashion to obtain the best possible view of the larynx. If the cords are in full view, proceed with intubation using a styletted ET tube. If the view is suboptimal, an assistant can pass the tracheal tube introducer to the operator for placement anterior to the arytenoids and into the larynx. If only the epiglottis is visible, place the introducer, with a 60-degree distal bend, just under the epiglottis and direct it anteriorly. With the laryngoscope still in place and the introducer stabilized by the operator, the assistant slides the ET tube over the introducer. Pass the tube through the larynx. Just before entering the larynx, rotate the tube 90 degrees counterclockwise to avoid having the tip of the ET tube get caught on the laryngeal structures (Fig. 4.20).74 Withdraw the laryngoscope and confirm proper tube placement. While securing the ET tube, ask the assistant to remove the introducer.

Tracheal Tubes

Tracheal tubes weigh a few grams and are typically made from polyvinyl chloride plastic, latex rubber, or silicone elastomer, all of which are flammable. Laser-resistant tracheal tubes often contain one or more of these materials. Although they are resistant to certain laser wavelengths, these tubes may be flammable under other conditions, such as during exposure to different laser wavelengths or other heat sources (e.g., an electrocautery pencil), or they may have flammable parts, such as the cuff or inflation tube.

The combustion of a tracheal tube, as demonstrated in Figure 12-6, delivers flames, smoke, and hot gases into the airway and lungs. Tracheal-tube fires typically produce an intraluminal fire that generates fuel and heat to produce an extraluminal free-end flame. The tracheal tube in Figure 12-7 ignited and burned severely during a tracheostomy when the surgeon cut through the tracheal rings with the flat-blade electrosurgical electrode. The patient died 2 weeks after the incident from the severe tracheal burns that were sustained.

Laryngeal Tube and Esophageal-Tracheal Combitube

The laryngeal tube (VBM Medizintechnik GmbH, Sulz, Germany) is another SGA device.178,179 Laryngeal tubes are manufactured from either silicone or polyvinylchloride (PVC) and have ventilation apertures between a proximal oropharyngeal cuff and a distal esophageal cuff. The laryngeal tube is inserted into the oropharynx until resistance is met, which should result in positioning of the ventilation apertures directly above the glottic opening. These devices are reported to provide seal pressures similar to those with the ProSeal LMA (40 cm H2O) and insertion times and success rates comparable to those of the LMA.180 The Laryngeal Tube-S (LTS) contains a second lumen that can be used for drainage of the stomach.181 The LTS has been used successfully after a failed intubation and ventilation in a patient undergoing emergency cesarean delivery.182

The esophageal-tracheal Combitube (ETC) (Sheridan Catheter Corporation, Argyle, NY) is a twin-lumen plastic tube with an outer diameter of 13 mm. One lumen has an open distal end and thus resembles a tracheal tube (i.e. the tracheal lumen), and the other (esophageal) lumen has a closed distal end. The ETC has a 100-mL proximal pharyngeal balloon; when the ETC is correctly positioned, the pharyngeal balloon fills the space between the tongue base and soft palate. When inflated, the proximal balloon seals the oral and nasal cavities. Distal to the pharyngeal balloon, but proximal to the level of the larynx, are eight perforations in the esophageal lumen. A smaller 15-mL distal cuff, similar to that on an ETT, seals either the esophagus or trachea when inflated. The ETC is inserted, with or without the aid of a laryngoscope, but its insertion does not require visualization of the larynx. Indeed, in the usual clinical context, the larynx cannot be visualized. The ETC enters the esophagus 96% of the time, allowing ventilation through the esophageal lumen perforations.183 If the ETC enters the trachea, the patient's lungs can be ventilated directly through the tracheal lumen. Therefore, regardless of whether the distal end of the ETC enters the trachea or esophagus, the anesthesia provider can ventilate the lungs, assuming correct identification of which lumen should be used for ventilation.

The ETC allows adequate ventilation while preventing aspiration of gastric contents. If the distal end of the ETC enters the esophagus, the ETC can assist in removing gastric fluids through suction applied to the “tracheal” lumen. When long-term ventilation is anticipated or required, the ETC should be exchanged for an ETT.

Use of the ETC in the out-of-hospital setting has been associated with a notable incidence of serious complications, including upper airway bleeding, esophageal laceration and perforation, and mediastinitis.184 Although a lower incidence of serious complications would be expected in the more controlled operating room environment with an anesthesia provider using a laryngoscope to facilitate placement, the stiffness and the anterior curvature of the ETC, as well as the potential for balloon overinflation, still represent potential sources of airway and esophageal injury.

Endobronchial Intubation with a Standard Tracheal Tube

A tracheal tube can be inserted into either main bronchus with the use of bronchoscopic guidance or fluoroscopic guidance. In small neonates, an uncuffed tracheal tube can provide adequate isolation of the lungs. In older infants and children, a cuffed tracheal tube maintains an effective seal of the lungs while maintaining the tube in a proximal position within the main bronchus. A tube with a distally placed cuff facilitates this placement. The major disadvantage of selective endobronchial intubation is that it is not possible to quickly change from one-lung ventilation to two-lung ventilation because it requires repositioning the tracheal tube from the bronchus into the trachea and vice versa. Furthermore, with unintentional movement of the tracheal tube and minimal cephalad displacement, selective intubation may be lost because of bronchial extubation, a phenomenon that occasionally happens with surgery around the hilum of the lung.

Answers

1.

Concerning tracheal tubes

False. An RAE tube is a normal size preformed tracheal tube. It does not allow good visibility of the larynx because of its large diameter. A microlaryngeal tracheal tube of 5–6 mm ID is more suitable for microlaryngeal surgery, allowing good visibility and access to the larynx.

True. Because the shape of these tubes is fixed, they might not fit all patients of different sizes and shapes; e.g. a small, short-necked patient having an RAE tube inserted is at risk of an endobronchial tube position.

True. Some anaesthetists use the laryngeal mask in nasal surgery with a throat pack. This technique has a higher risk of aspiration.

False. RAE stands for the initials of the designers (Ring, Adair and Elwyn).

False. The Oxford tube is one of the few tracheal tubes with a front-facing bevel. This might make intubation more difficult as it obscures the larynx.

Laryngeal masks

False. Laryngeal masks do not protect the airway from the risks of aspiration.

False. The bars in the cuff are designed to prevent the epiglottis from blocking the lumen of the tube.

True. The laryngeal mask has a large ID, in comparison with a tracheal tube. This reduces the resistance to breathing which is of more importance during spontaneous breathing. This makes the laryngeal mask more suitable for use in spontaneously breathing patients for long periods of time.

False. The laryngeal mask can be autoclaved up to 40 times. The cuff is likely to perish after repeated autoclaving. A record should be kept of the number of autoclaves.

False. The standard laryngeal mask has a metal component in the one-way inflating valve. This makes it unsuitable for use in MRI. A specially designed laryngeal mask with no metal parts is available for MRI use.

Double lumen endobronchial tubes

False. The Robertshaw double lumen tube does not have a carinal hook. The Carlens double lumen tube has a carinal hook.

False. Left-sided tubes do not have an eye in the bronchial cuff to facilitate ventilation of the left upper lobe. This is because the distance between the carina and the upper lobe bronchus is about 5 cm, which is enough for the bronchial cuff. Right-sided tubes have an eye to facilitate ventilation of the right upper lobe because the distance between the carina and the upper lobe bronchus is only 2.5 cm.

True. Carlens double lumen tubes have relatively small lumens in comparison to the Robertshaw double lumen tube.

True. CPAP can be applied to the deflated lung to improve oxygenation during one lung anaesthesia.

True. It is sometimes difficult to ensure correct positioning of the double lumen endobronchial tube. By using a fibreoptic bronchoscope, the position of the tube can be adjusted to ensure correct positioning.

Concerning the tracheal tube cuff during anaesthesia

False. The design of the low-pressure/high-volume cuff allows wrinkles to be formed around the tracheal wall. The presence of the wrinkles allows aspiration of gastric contents to occur.

False. The rise in the intracuff pressure is mainly due to the diffusion of N2O. Minimal changes are due to diffusion of oxygen (from 21% to say 33%) and because of increase in the temperature of the air in the cuff (from 21°C to 37°C). The diffusion of inhalational agents causes minimal changes in pressure due to the low concentrations used (1–2%). New design material cuffs prevent the diffusion of gases thus preventing significant changes in pressure.

True. The high pressures achieved by the high-pressure/low-volume cuffs, especially during nitrous oxide anaesthesia, can cause necrosis to the mucosa of the trachea if left in position for a long period.

True. Because of the design of the low-volume cuffs, a seal can be maintained against a relatively small area of the tracheal wall. In the case of the high-volume/low-pressure cuffs, a large contact area on the tracheal wall is achieved.

False. The pressure in the cuff may decrease because of a leak in the cuff or pilot balloon’s valve.

Concerning tracheal tubes

False. The ID is measured in millimetres.

False.

False. An armoured tube should not be cut, as that will cut the spiral present in its wall. This increases the risk of tube kinking.

False. A Murphy eye allows pulmonary ventilation in the situation where the bevel of the tube is occluded.

False. The bevel of the tube is usually left-facing to allow easier visualization of the vocal cords. The tracheostomy tube has a square-cut tip.

Concerning tracheal tubes

False. A left-facing bevel improves view at laryngoscopy.

False. Reinforced tubes have a spiral of wire running through the wall to resist crushing and kinking.

True.

True. They have a thicker than usual wall to prevent kinking but this reduces ID.

True.

Tracheostomy tubes

False. Tracheostomy tubes are cut horizontally.

False. Fenestrated inner tubes can be used to allow phonation.

True.

True.

False. This is a relative contraindication; ultrasound or cross-sectional imaging should be considered to identify if percutaneous tracheostomy can be safely attempted.

Concerning airway adjuncts

False. 9 sizes are available, but they are numbered 000 to 6.

True.

False. The tip should be inferior to the soft palate.

True.

False. Nasopharyngeal airways do not require tape. A flanged end or safety pin prevents migration into the nose.

e.

c.

b.

6 Entrapment

The tracheal tube may become entrapped due to an inability to deflate the cuff,44,45 or there may be difficulties with the pilot tube.46,47 Difficulties include a crimped pilot tube, a defective pilot valve, and fixation of the tracheal tube by Kirschner wires,48 screws,49 ligatures,50 or entanglement with other devices.51,52 Entrapment can also occur during a percutaneous tracheostomy.53 Mechanical obstruction of an entrapped tube is a life-threatening complication. Partial transection of the tracheal tube by an osteotome during a maxillary osteotomy has resulted in the partially cut tube forming a barb that caught on the posterior aspect of the hard palate.54 One report of tube entrapment with fatal consequences involved a Carlens tube that was inadvertently sutured to the pulmonary artery.55 Lang and colleagues recommended routine intraoperative testing for tracheal tube movement when fixation devices are used in proximity to the airway.49 Uncertainty about tube movement should prompt fiberoptic examination before emergence from general anesthesia.

Armoured tracheal tube

Armoured tracheal tubes are made of plastic or silicone rubber (Fig. 5.12). The walls of the armoured tube are thicker than ordinary tracheal tubes because they contain an embedded spiral of metal wire or tough nylon. They are used in anaesthesia for head and neck surgery. The spiral helps to prevent the kinking and occlusion of the tracheal tube when the head and/or neck is rotated or flexed so giving it strength and flexibility at the same time. An introducer stylet is used to aid intubation.

Because of the spiral, it is not possible to cut the tube to the desired length. This increases the risk of bronchial intubation. Two markers, situated just above the cuff, are present on some designs. These indicate the correct position for the vocal cords.

Tracheal Tubes

The art of anesthesia using a tracheal tube is more than 100 years old. The first orotracheal intubation anesthetic was performed in 1880 by Glasgow surgeon Sir William Macewen.23–28

Indications for tracheal intubation include positive-pressure ventilation, pulmonary toilet, and airway protection. Tracheal tubes (TTs) initially were made of rubber and were reusable. However, these devices were prone to kinking and were unsuitable for patients sensitive to latex. Tracheal tubes today are made of many materials, although the most commonly used material is polyvinylchloride (PVC). PVC is inexpensive, the tubes conform to patient’s anatomy through thermoplasticity, and the tubes are more resistant to kinking.29 Tracheal tubes must conform to the International Organization for Standardization (ISO) (standard ISO 5361:2016) which include specifications for internal diameters (IDs) and outer diameters (ODs), distance markers from the distal end to anesthesia circuit adapter, material toxicity, angle and direction of the bevel, size and shape of the Murphy eye, and radius of the tube curvature.30 Tracheal tubes may either be cuffed or uncuffed; the cuff provides a seal between the TT and trachea, thereby protecting the trachea from aspiration of gastric contents and facilitating positive-pressure ventilation. Tracheal tubes in use today have high-volume, low-pressure cuffs that disperse force on the tracheal tissues (Fig. 14.9).

Respiration

The tracheal tube can end in a bronchus, or in the esophagus; the blocking balloon can lie in the pharynx compressing the vocal cord. Two tubes can be present (Figure 11) – the first was left in the esophagus to facilitate the placement of the second tube.

Air bubbles and emphysema (and bleeding) indicate injuries of the pharynx, the mucosa, and the trachea. Pharynx tubes with two balloons are supposed to be more secure than simple tracheal tubes; however, detailed analysis in PMCT shows that there is not always a free airway to the trachea.

Tracheotomy may fail. In small children, the trachea is sometimes difficult to enter. In adults, the posterior wall of pharynx can be perforated; the tracheostomy tube can end outside the lumen.

Mask ventilation and ventilation via a tube in the esophagus inflate the gastrointestinal tract (meteorism). If this is visible, the intubation probably has been difficult, even if the tube is finally in the correct position. Similarly, neck emphysema (with a tracheostomy tube in correct position) points to difficulties performing the tracheostomy. In both cases, the time span prior to ventilation might have been extended significantly.