A worsening airway obstruction or an overall worsening condition of the child's respirations indicates the need for laryngobronchoscopy. In a stable patient in the office setting, direct laryngoscopy with flexible instrumentation can be performed under topical anesthesia. In a stable patient who requires a more thorough evaluation, laryngoscopy should be performed in the operating room as part of any airway endoscopic examination. These procedures enable a diagnosis to be made and assist in the planning of further treatment. If indicated, samples for bacteriological culture can be taken, and definitive treatment of an obstructing lesion can be performed under the same anesthetic.
For a child who has signs of respiratory distress, urgent endoscopic evaluation is mandatory. Early intervention in the setting of worsening stridor may avoid more extreme measures such as endotracheal intubation or a tracheostomy under critical conditions. It should be noted that once an endotracheal tube has been passed, the opportunity for diagnosis is greatly compromised.
If poor weight gain and difficulty in feeding are present in addition to concerns regarding airway compromise, endoscopy may be revealing of chronic conditions such as laryngomalacia or reflux-related irritation/inflammation.
Additionally, if imaging techniques such as computed tomography or echocardiography suggest an abnormality such as a vascular ring, endoscopy may confirm the diagnosis (Fig. 20-7).
A vascular ring is demonstrated on bronchoscopy in a young child with intermittent airway symptoms; these symptoms resolved after division of the ring and a concomitant aortopexy.
Careful inspection of the pharynx, larynx, trachea, and bronchi provides critical information on lumen size, vocal cord mobility, and the presence of dynamic compression, inflammation, or infection. Cooperation and teamwork between the surgeon and the anesthesiologist is absolutely imperative, as well as a surgical nurse/assistant who is familiar with the endoscopic equipment material. The preparation for airway endoscopy should include a discussion of an overall strategy and the resources required to handle all possible contingencies. The attending pulmonologist should also be available, especially when the patient has a history of pulmonary dysfunction or previous bronchoscopic procedures. The possible need for urgent airway access by cannula or a tracheostomy should be kept in mind for any airway procedure, and the appropriate instruments should be available in the operating room. A surgical cricothyrotomy is rarely advisable in young children; emergency airway access can be achieved faster and with less risk through the use of a large-bore angiocatheter (12- or 14-gauge) by direct, percutaneous tracheal puncture. Oxygenation can be performed through this intratracheal cannula using the hub of a 3-mm endotracheal tube connector attached to the bag valve mask or anesthesia circuit, until intubation or formal tracheotomy can be performed.
Utility and Limitations of Rigid and Flexible Bronchoscopy
Rigid and flexible bronchoscopy are complementary techniques used in various circumstances to assess airway anatomy and function, in some cases concurrently. Bronchoscopy may be diagnostic or therapeutic. Sometimes the diagnosis is already known, other times, there may be unexplained symptoms or undiagnosed disease that can be clarified only by direct examination of the airway. It is within the setting of airway obstruction or compromise that most difficulties occur. While both rigid and flexible bronchoscopy have advantages as well as disadvantages, both require an understanding of the unique anatomy of infants and children, and the potential risks involved in any attempt to visualize anatomical structures of the airway. Regardless of which endoscopic procedure is used, the importance of gentle technique cannot be overemphasized.
Rigid bronchoscopy has a more invasive character and is best utilized to visualize the oropharynx, larynx, vocal cords, and proximal tracheal bronchial tree. The procedure may be performed in an endoscopy suite with available anesthesia, but for most children it is more appropriately performed in the operating room under general anesthesia; it may be combined with flexible bronchoscopy for better distal airway visualization and suctioning.
The indications for rigid bronchoscopy usually involve severe or progressive airway obstruction, suspected foreign body aspiration, or a variety of surgical interventions, such as airway stent placement or dilation of tracheal or bronchial stenosis. The overall benefits to be gained from rigid bronchoscopy in children are shown in a large-scale study conducted by Wiseman over a 15-year period where the use of rigid bronchoscopy contributed to the final diagnosis in almost 90% of patients, with no mortality and a morbidity rate of only 3.5%.
The principal advantage of rigid over flexible bronchoscopy involves better control of the airway, but also allows access to instruments, removal of foreign bodies, or more effective suctioning capability.
Since the rigid bronchoscope can be placed only through the mouth, proper positioning requires neck hyperextension, usually upon a gently folded towel placed just below the occiput. This entails some risk for children with physical conditions that limit wide opening of the mouth or limited neck mobility, as seen in patients with Down syndrome or Arnold–Chiari malformation.
Unlike rigid bronchoscopy, flexible fiber-optic bronchoscopy can be carried out under topical anesthesia with or without intravenous sedation. Its use extends to settings beyond a hospital operating room, such as an intensive care unit. In addition, since flexible bronchoscopes can be passed through mouth or naris, this technique may be useful in evaluating children with anatomic anomalies or maxillofacial trauma that make passage of a rigid scope difficult. Since the airway of patients who undergo flexible bronchoscopy through an endotracheal tube can be obstructed during the endoscopic examination, careful attention must be paid to oxygen saturation and carbon dioxide levels during the procedure in order to ensure physiological stability.
The standard pediatric flexible bronchoscope has a 3.5 to 3.7 mm outside diameter and a 1.2-mm suction channel. This instrument can be used in infants weighing as little as 700 g, and most term newborns can breathe around it spontaneously for short periods. To minimize the risk of hypoxia, small infants can undergo bronchoscopy through a face mask adapter, either breathing spontaneously or being manually ventilated by an anesthesiologist. Examination of the distal airways in intubated infants usually requires extubation, use of a rigid bronchoscope, or possible use of a very small flexible bronchoscope.
Ultrathin flexible bronchoscopes offer many advantages for examination of the lower airways of infants and small children. The most important of these is the ability to pass through small endotracheal or tracheostomy tubes while maintaining effective gas exchange. Ultrathin flexible bronchoscopes can be used for other purposes as well, including in situ evaluation of (the placement of) tracheostomy tubes and the dynamics of the posterior trachea near the tip of tracheostomy tubes, and for retrograde direct laryngoscopy in infants with tracheostomies. They have also been used to direct the placement of balloon catheters for dilation of bronchial stenoses, to examine peripheral airways beyond the subsegmental bronchi in infants, and for intraoperative assessment of bronchial patency during pulmonary resection. Despite this wide array of possible uses, ultrathin flexible bronchoscopes provide only limited working channels and limited suction capability.
While visualization of airway patency and management of obstructive lesions are best accomplished using a rigid bronchoscope with the patient under general anesthesia, the use of a flexible bronchoscope with the patient under sedation and local anesthesia allows a more dynamic view of the airway. Although tracheoesophageal fistulae are best identified and their location is assessed by rigid endoscopy (Fig. 20-8), other conditions such as tracheomalacia are best assessed in a dynamic state. When rigid endoscopy is used to assess dynamics of airway motion, anesthesia must be lightened to allow for spontaneous respiration and assess collapse from tracheomalacia.
A newborn with esophageal atresia demonstrated a distal tracheoesophageal fistula at the level of the carina. A routine bronchoscopic evaluation prior to a thoracotomy provided important information, revealing the presence of a proximal fistula and providing an estimation of the distal esophageal length.
The widespread use of flexible bronchoscopy by nonsurgeons may lead to confusion regarding its value or role in diagnosis or management. Wood reported the use of flexible bronchoscopy in 1000 children undergoing laryngoscopy or bronchoscopic procedures over a 5-year period. He found endoscopic information of direct relevance to the suspected diagnosis in 75% of patients and demonstrated other unsuspected abnormalities in 15%; normal findings were encountered in only 9% of the patients studied. As in the Wiseman study cited earlier, Wood reported no mortality and a morbidity rate of only 3%, the major complications being abscess formation, laryngospasm, and pneumothorax. Accordingly, when used by well-trained individuals familiar with pediatric airway issues, both flexible and rigid bronchoscopic techniques have unique advantages and specific limitations.
Sudden onset of respiratory distress is highly suggestive of foreign body aspiration, particularly in toddlers and younger children. The average age for fatal events from aspiration is only 15 months; 75% of aspiration events occur in children younger than 4 years. Endoscopy for evaluation and management of airway foreign bodies should be performed only in the operating room setting with surgical and anesthesia teams in attendance (Fig. 20-9). If foreign body aspiration is suspected, general anesthesia should be induced in a manner that minimizes the effects on spontaneous ventilation. Should assisted ventilation be necessary, avoiding positive airway pressure may reduce the chance of foreign body dislodgement or distal migration, both of which could have potentially disastrous results.
Layout for rigid bronchoscopy. Layout for rigid bronchoscopy in a pediatric patient is demonstrated. Note that the patient is positioned with the neck slightly hyperextended on a folded towel, the eyes taped and protected, and the chest exposed for visualization. Induction of anesthetic can usually be performed without intubation, allowing the surgeon a first look at most noncritical airways. An anterior commissure laryngoscope, which provides excellent visualization in difficult pediatric airway cases, is shown. Nursing personnel skilled in equipment use and in the performance of this procedure are necessary. Organization of the entire team to review the proposed “game plan” prior to such procedures is essential, especially in cases of anticipated difficult airway access.
When removing large or dangerous foreign bodies that might result in occlusion of the airway or injury to delicate tissues, conversion to a tracheostomy may need to be considered. Thoracotomy should be reserved for the rare complications of endoscopic removal (eg, airway perforation or a major injury to the trachea or bronchus) or cases where the foreign body cannot be removed by endoscopic techniques and must be extracted by bronchotomy or through lung parenchyma. A lobectomy may be required in rare cases when a foreign body has caused a pulmonary abscess, the destruction of parenchyma, or chronic bronchiectasis.
The significant risks involved in removing foreign bodies without secure airway control and less than optimum instrumentation mandate against attempts to use any technique other than rigid endoscopy in an operating room setting. As noted by Kelly and Mantor, if occult foreign bodies are found during flexible bronchoscopy, conversion to rigid instrumentation should be carried out before attempting foreign body removal. It is important to note that foreign body aspiration can masquerade as other pediatric respiratory illness, as illustrated by a study conducted by Wood and Gauderer showing foreign bodies in 1% of all patients undergoing flexible endoscopy for a wide variety of reasons.
We have found flexible and rigid bronchoscopy to be complementary instruments in the operating room setting for occasional foreign bodies that are so distally located that then cannot be reached by flexible bronchoscopy alone. In such a case, the removal of demonstrable foreign bodies can occur under rigid instrumentation under the same general anesthetic. When used in conjunction with rigid bronchoscopes, flexible scopes assist not only in the diagnosis for borderline cases but also in the removal of difficult or fragmented objects from those distal airways.
Treatment with Laser Therapy
Lasers can be useful for resection or fulguration of a number of airway lesions (Fig. 20-10). Although a carbon dioxide laser provides a superficial depth of penetration making it safe for routine airway use, the laser beam cannot be passed through a fiber-optic cable; special laser bronchoscopic tubes are required to focus the beam directly on the target tissue (Fig. 20-11). This is a major drawback since the smallest such bronchoscopic tube is 7 mm in diameter, too large for most infants. In contrast, the YAG laser beam can pass through a fiber-optic cable and is easily inserted via the instrument channel of rigid bronchoscopes. However, its depth of penetration is significantly greater, thus increasing the risk of tracheal penetration or deep tissue injury. Its use should involve the minimal effective power setting with a short duration of laser burst. The KTP laser incorporates elements of both the carbon dioxide and YAG lasers with lesser tissue penetration, while allowing beam transmission via a fiber-optic cable.
An adolescent presented with a long history of airway difficulties dating to infancy when a tracheostomy was done because of respiratory distress. Subsequent decannulation was also performed. Over subsequent childhood years he did well, although he demonstrated severe dyspnea on exertion. A bronchoscopic evaluation showed a thick web in the distal trachea (A), presumably from the distal tracheostomy cannula, leaving a tracheal lumen of only a 4- to 5-mm diameter. Resection of this dense web was accomplished with a YAG laser; there was significant enlargement of the tracheal lumen (B) and complete resolution of symptoms.
Laser bronchoscopy. Equipment for laser bronchoscopy includes a carbon dioxide laser bronchoscope and housing, shown in the center. Because a carbon dioxide laser beam cannot be passed down a fiber-optic cable, it must be transmitted directly through the special bronchoscope by a series of mirrors; manipulation of the joystick moves the laser beam. As shown, fiber-optic cables can be passed down the instrument channel of a Storz bronchoscope to allow the use of a KTP or YAG laser.
Concerns pertaining to anesthesia during laser surgery on airway include minimizing thermal injury and using the lowest possible inspired oxygen concentration (preferably less than 30%) compatible with adequate oxygen saturation as well as avoiding nitrous oxide, which supports combustion. Flammable items in the airway such as endotracheal tubes or stents must be shielded from exposure to the laser beam to prevent laser fire from ignition. The safest techniques involve the use of metal airways, the use of a laser through the rigid bronchoscope, or the use of insufflation anesthesia or jet ventilation with a suspension laryngoscopy apparatus, although laser ignition of normal tissue can still occur with prolonged periods of lasering, especially on high energy settings.
Children with airway lesions, including foreign bodies, may present with symptoms ranging from subtle to dramatic and with varying indications for endoscopic evaluation and treatment. Familiarity with basic tenets of bronchoscopic techniques and equipment for use in children is mandatory prior to undertaking airway evaluation of any child. Once anesthesia has been induced, surgeons are dependent on their own skills and the assistance of the anesthesiologist and nursing staff in attendance to ensure a successful outcome and avoid potentially disastrous complications.