Many institutions make their own “intubating/airway kit.” It contains all the commonly used equipment in a portable container or cart that can be moved wherever required in the Emergency Department. While differences will exist between institutions, the kit commonly includes adult and pediatric laryngoscope handles, various sizes and types of laryngoscope blades, various sizes of oropharyngeal airways, various sizes of nasopharyngeal airways, tongue blades, malleable stylets, various sizes of ET tubes, syringes, tape, and commercially available devices to secure the ET tube. Some institutions may have a single kit, or separate kits for adult and pediatric patients.
The ET tube is a clear polyvinyl chloride disposable tube that is open on both ends (Figure 11-6). The proximal end contains a standard size (15 mm) connector that will attach to the bag-valve device, a ventilator, and other sources of positive-pressure ventilation. The distal end is beveled. It has a perforation, located approximately 0.5 to 0.75 cm from the tip and opposite the bevel, known as the Murphy eye. Printed on the tube are the size, a radiopaque line to aid in radiographic visualization, and 1 cm incremental marks beginning at the tip. An inflatable cuff is positioned proximal to the Murphy eye. A pilot balloon with an inflation port, to inflate the cuff, hangs from the proximal third of the ET tube. A syringe, filled with air, attaches to the inflation port to inflate and deflate the cuff.
The ET tube cuff is a high-volume, low-pressure balloon. It is designed to accommodate a high volume of air before the intracuff pressure rises. This is an extremely important feature. If the intracuff pressure rises, it is transmitted to the delicate tracheal mucosa where it can cause pressure necrosis and ischemia.
The choice of ET tube size will vary based on the patient's age, anatomic anomalies, body habitus, and airway anatomy (Table 11-1). The ET tube is sized based on the internal diameter (ID) measured in millimeters. The size is printed onto the surface of the ET tube for reference. The sizes begin with 2.5 mm and increase in 0.5 mm increments. Some generalities hold true in most patients. Adult males usually require a size 7.5 to 9.0 cuffed ET tube. Adult females usually require a size 7.0 to 8.0 cuffed ET tube.
ET tube selection in children can be made by one of several methods. A Broselow tape will identify the proper size tube. Visually select a tube with an ID that matches the size of the width of the nail of the patient's little finger, the width or diameter of the fifth finger, the diameter of the distal phalanx of the third finger, or the external nares luminal diameter. All these visual methods will approximate the same size ET tube. The following formula may be used to confirm the uncuffed ET tube size: (16 + child's age in years)/4. Tables based on the child's age, length (Broselow tape), or weight may be used to estimate the proper ET tube size. An uncuffed ET tube should be used in children under 28 days of age to prevent the complications of subglottic and tracheal stenosis. After determining the proper size ET tube, also select and prepare a tube that is one size smaller in case the patient's airway is smaller than expected.
Traditional teaching holds that cuffed ET tubes increase the risk of ischemic damage to the tracheal mucosa due to compression between the cuff and the cartilaginous rings, resulting in the old mandate to use uncuffed ET tubes in children younger than 8 years of age. There have been numerous advances in modern ET tubes that are changing this orthodoxy.41 Current American Heart Association Guidelines now recommend, but do not require, a cuffed ET tube for children older than 28 days of age. In the first 28 days of life, the cricoid narrowing functions as a cuff. For children over 28 days of age, the cuffed ET tube is just as safe as an uncuffed ET tube.25,26 The high volume, low pressure cuffs found on new ET tubes allow the cuff to produce a seal at much lower pressures. The use of cuffed ET tubes is becoming more common in pediatric ICUs and Emergency Departments. Several studies have shown no increase in postintubation stridor or reintubation when cuffed ET tubes are used in controlled settings with regular cuff pressure monitoring.
In addition to providing some protection from aspiration, other potential benefits resulting from the use of cuffed ET tubes in children include allowing ventilation at higher pressures, maintenance of more consistent ventilatory parameters, and fewer changes of inappropriately sized ET tubes. Cuffed ET tube size can be calculated using the equation (age in years/4) + 3, or by use of an ET tube one-half size smaller than the calculated uncuffed ET tube size.7,21
All ET tubes should be examined for defects before use. Attach a 10 mL syringe filled with air to the pilot balloon inflation port. Inject the air to inflate the cuff. The cuff should inflate symmetrically and have no air leak. Deflate the cuff completely. Leave the syringe attached to the pilot balloon in order to inflate the cuff after the ET tube has been inserted into a patient's airway. If an ET tube is defective, discard it and open a new ET tube.
The laryngoscope is a handheld device that is used to elevate the tongue and epiglottis to expose the glottis. It is a device that is held in the left hand regardless of which hand of the user is dominant. It consists of a handle (Figure 11-7) and a blade (Figures 11-8 & 11-9). The handle contains the battery for the light source. The distal end of the handle has a fitting where the handle connects to the blade. A transverse bar indicates where the indentation on the proximal blade attaches to the handle. There are many types of laryngoscope handles. They all have the same basic design, but are available in a variety of diameters and lengths (Figure 11-7). Smaller diameter (thinner) laryngoscope handles may be better suited for use with the smaller sized pediatric laryngoscope blades. Shorter, “stubby” laryngoscope handles may offer an advantage when proceeding with intubation of obese or barrel-chested patients, especially in cases where the neck cannot be manipulated. The shorter handle will not catch on the chest wall during attempts to place the laryngoscope blade in the patient's mouth.
A variety of laryngoscope handles.
The Macintosh laryngoscope blades.
The Miller laryngoscope blades.
The laryngoscope blade may have a removable bulb attached to its distal third. A fiberoptic bundle within the blade transfers power from the handle to the bulb. Other laryngoscope blades only contain fiberoptic bundles which transmit light, with the light source located within the handle. The choice of the type and size of laryngoscope blade will vary with physician experience and preference. The best blade is one that the intubator feels comfortable and confident using. The curved Macintosh blade is most commonly used (Figure 11-8). It is the easier blade to use for those with little experience with orotracheal intubation. Many feel that it requires less forearm strength to use as compared to the straight blade. The large flange allows for easier control of the tongue and the flat curved shape of the spatula fits the natural curve of the tongue. The straight Miller blade is often reserved for those experienced with the blade and with orotracheal intubation (Figure 11-9).
The tip of the curved Macintosh blade fits into the vallecula and indirectly lifts the epiglottis to expose the vocal cords (Figure 11-10). A size 2 blade is used for 3 to 6 year olds. A size 3 blade is used for children starting at about age 6, for women, and for small to average-size males. A size 4 blade is usually reserved for large males.
Use of the Macintosh blade. It is inserted into the vallecula to elevate the mandible, tongue, and epiglottis as a unit.
The tip of the straight Miller blade goes directly under the epiglottis to lift it and the tongue to expose the vocal cords (Figure 11-11). Use the straight blade, if possible and the intubator is familiar with its use, to intubate patients under 2 years of age. A straight blade makes controlling the epiglottis and tongue easier than with a curved blade. It also makes visualization of the vocal cords easier due to its smaller flange profile. A size 0 blade is used for premature babies and neonates up to approximately 1 month of age. A size 1 blade is used for children from approximately 1 month of age to toddlers up to 2 years of age. A size 2 blade is used for children 3 to 6 years of age. Children between 6 and 12 years of age may require either a size 2 or 3 blade depending on their body size. A size 3 blade is used for adolescents, women, and average-size males. A size 4 blade is rarely used, and then primarily for large males.
Use of the Miller blade. It is inserted below the epiglottis to elevate the mandible, tongue, and epiglottis as a unit.
If one cannot remember the proper blade size, it can be determined based on patient anatomy.20 Place the base of the blade, excluding the handle insertion block, at the level of the patient's upper incisor teeth. The tip of the blade should be located within 1 cm proximal or distal to the angle of the patient's mandible. Correct blade size allows for approximately 90% of first attempt intubations to be successful versus 57% if the blade is too small.20
There are a wide variety of laryngoscope blades commercially available. They tend to be variations of the curved Macintosh or Straight Miller blades. The McCoy blade is a curved blade with a hinged tip. The tip can be flexed by depressing a lever on the laryngoscope handle. This flexion augments indirect elevation of the epiglottis by stretching the hypoepiglottic ligament. The Flexiblade (Arco-Medic Ltd., Omer, Israel) laryngoscope also has a levering blade. The extra lift provided by these blades may improve visualization of the vocal cords.8,9 The Propper Flip-Tip laryngoscope blade (Propper Manufacturing Co., Long Island, NY) has a lever that elevates its tip up to 90° to lift the epiglottis. Other variations of the Macintosh blade include the incorporation of a variety of prism or mirror systems. These modifications allow for indirect visualization of otherwise obscured vocal cords. The Belscope (International Medical Inc., Burnsville, MN), Truvue EVO2 (Truphatek International Ltd, Netanya, Israel), Lee-Fiberview (Anesthesia Medical Specialties, Beaumont, CA), and Viewmax (Rusch, Duluth, GA) blades are examples of these types of modifications.8,10,11
There have also been many variations of the straight laryngoscope blade. Today, the Miller is the most popular straight blade. Other variants include the Phillips and Henderson blades. These modify components such as the cross section, the blade channel width, tip style, and light source placement. These modifications represent efforts to avoid such problems as dental trauma, laceration of the ET tube cuff, improve tongue displacement, minimize tip trauma, and obscuration of the light source by secretions.
In addition to traditional metal laryngoscope blades, plastic single-use blades are also available. These single-use plastic blades were developed, in part, to concerns regarding possible transmission of infectious agents by incompletely sterilized metallic blades. A study comparing plastic versus metallic Macintosh laryngoscope blades in 1177 patients found that metallic blades had higher first attempt intubation rates, fewer cases of difficult intubation, and used alternative airway interventions less often than when intubation was attempted with a plastic blade.12 Plastic blades cause less dental trauma when used on dental models.16 The rates of dental trauma in patients when compared to metal blades are not known. The use of single-use disposable plastic blades cannot be recommended at this time unless circumstances do not allow proper cleaning of metallic laryngoscope blades.
The stylet is a semirigid piece of metal that is bendable (Figure 11-12). It is often plastic coated. It inserts into the lumen of the ET tube. It should be lubricated with a water-soluble lubricant or an anesthetic jelly prior to insertion into the ET tube. The tip of the stylet should be 1 cm proximal to the tip of the ET tube to prevent injury to the patient's airway. The ET tube, with a stylet, can be bent to maintain a specific shape. The stylet is used to facilitate passage of the ET tube through the vocal cords. It is commonly bent into a “hockey stick” or “J” shape for most intubations. A greater curvature is often used for intubations when the larynx is “anterior,” in difficult intubations, and in “blind” intubations.
The intubating stylet. It may be bent into any required shape. When inserted into an ET tube, it will form the ET tube into the desire shape. The most common shapes are the “J” and the “hockey stick.”
A modification of the traditional stylet is the Parker Flex-It™ Directional Stylet (Parker Medical, Highlands Ranch, CO). This is a plastic articulating stylet that requires no prebending. The stylet has a built-in gentle curve. It has a button on its proximal end that extends from the ET tube. When pushed with the thumb, it allows the curvature of the ET tube to be continuously adjusted during intubation attempts.