Indications for Airway Endoscopy

A severe stridor generally goes hand in hand with significant airway obstruction. It is important to know how much air the patient is moving. If there is no movement of air through the airway, because of a severe obstruction, the symptom of a stridor will not be noticeable. Whenever possible, flexible endoscopy should be considered as a first step in assessing the larynx in any patient with a moderate to severe stridor. This test can provide the diagnosis, and a rigid endoscope can be used if necessary.

The best way to make a good assessment is with laryngoscopy or with flexible or rigid bronchoscopy prior to endotracheal intubation, because afterward the opportunity for a good diagnosis decreases.

If the stridor and airway obstruction are progressive—and to this can be added a weight increase and difficulty in feeding—rigid endoscopy is generally indicated not only for diagnosing the pathology but also with the aim of applying immediate treatment. For example, this can occur with laryngomalacia.

Endoscopy is often complemented with x-rays, while computerized axial tomography can also be useful when the endoscopic study suggests the presence of an abnormality, such as a vascular ring. In children with symptoms of severe obstruction, radiographic or magnetic resonance tests that require sedation should not be done before the diagnosis has been established by means of rigid endoscopy. As with the diagnosis of a foreign object, upper airway lateral and anteroposterior plaques do not provide sufficient resolution to rule out a large number of common pathologies. Consequently, direct visual observation by flexible or rigid endoscopy is more useful than imagery for assessing the airway in pediatrics.

When Is Rigid Endoscopy, Rather than Flexible Endoscopy, Appropriate?

Rigid and flexible endoscopy are complementary. Flexible endoscopy is used to examine the larynx of a child who is awake, and it allows useful information to be obtained about cordal mobility and laryngeal dynamics.

Lesions in the pharynx and lower airway can be viewed only with rigid endoscopy. If necessary, with general anesthesia after suspension of the larynx, the vocal cords can be viewed with a binocular microscope, providing a stereoscopic view. Rigid endoscopy allows for a good and detailed view, while control of the airway is maintained. Flexible bronchoscopy does not allow for absolute control of the airway and can obstruct it entirely in small children. The quality of the image with a rigid Hopkins rod-type telescope is superior to that obtained with a flexible bronchoscope, and its documentation is undoubtedly much clearer.

Rigid Instruments

Laryngoscopy and Bronchoscopy

Laryngoscopes

There are a wide variety of laryngoscopy approaches and devices, and they can be divided into those that are designed for suspension and those that are not. It is important to know how to employ the different types, including those for intubation. There are two types of nonsuspension laryngoscope: straight bladed and curved bladed (Fig. 16.1). The straight blades are more compatible with rigid endoscopy. Among the straight blades are the Miller, Wis-Hipple (or Wisconsin), and Philips; the Philips provides the most space in the oropharynx to pass the endoscope and facilitate intubation. An important feature of suspension laryngoscopes is that they have a xenon light source and consequently provide more illumination than intubation laryngoscopes do. Suspension is also necessary for endolaryngeal surgery with a microscope. The most commonly used suspension laryngoscope in pediatrics is the Parsons type (Karl Storz), of which there are several sizes for all ages, and it is partially open, allowing for its use in suspension or intubation. It is also useful to have small closed laryngoscopes to view the anterior of the larynx, such as the Hollinger anterior commissure laryngoscope. Finally, the closed Benjamin–Lindholm laryngoscope, which is available in many sizes for all ages, offers the possibility of a broad posterior view.

Bronchoscopes

Telescopes

In 1966, Hopkins introduced the long telescope with different lenses, which improved the resolution and the angle of viewing, and revolutionized pediatric bronchoscopy, providing the potential to see into very small spaces. For example, a 4.0 mm by 20 cm zero-degree telescope is ideal for passing through a laryngoscope in the subglottis or trachea.

A Hopkins rod telescope alone (bare) or with a ventilating bronchoscope can be used for rigid assessment of the upper airway. Both visualize the larynx, trachea, and bronchi with magnification. The advantage of using the telescope alone is that it minimizes the trauma to the airway walls, given that the diameter of the endoscope is less than that of the ventilating bronchoscope. The diameters of Hopkins rod telescopes (the most widely used) are 1.9, 2.7, and 4 mm, while the lengths vary. There are also lenses with 30- and 70-degree angles. When a bare telescope is used, the patient cannot be actively ventilated, and so the endoscopy is usually conducted under spontaneous ventilation (see below for more information on this).

A ventilating bronchoscope is much wider and thicker than a bare telescope, given that the Hopkins rod is inserted inside the bronchoscope light. The size of the telescope that is inserted depends on the size of the bronchoscope. Sometimes it is useful that the telescope is longer than the bronchoscope, because more peripheral areas can be examined. Ventilating bronchoscopes allow for ventilation of the patient while therapeutic maneuvers are being conducted in the trachea. These bronchoscopes are characterized in the following manner:

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   Connection of a closed gas system to the anesthesia circuit so that the bronchoscope also acts as an endotracheal tube, which can serve to provide spontaneous ventilation and positive ventilation

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