Abstract
The flexible optical bronchoscope has unparalleled utility for difficult airway management and is part of every difficult airway management algorithm. The device can facilitate intubation for patients with airway tumours and bony or soft tissue abnormalities. It provides continuous visualisation of the airway during management, can be used to deliver local anaesthetics to the airway and is relatively less traumatic compared to other devices. Mastery of the device requires significant practice and the practitioner must use the device regularly to maintain skills. Several tips for success and pitfalls to be avoided are discussed.
Introduction
Flexible bronchoscopes and intubation scopes offer unparalleled utility for the safe management of patients with a difficult airway. Many centres have seen decreased use of flexible optical scopes after the introduction of videolaryngoscopes but it is imperitive that anaesthesia providers gain and maintain skills in using this invaluable airway management tool. Modern flexible bronchoscopes use a video camera at the tip of the scope rather than glass fibres to transmit the image. The term flexible optical bronchoscopes (FOBs) is used here to describe devices including flexible fibreoptic and flexible videoscopes used for tracheal intubation.
FOBs figure prominently in most airway management algorithms (see Chapter 4).
The FOB has many characteristics which make it an ideal tool for tracheal intubation and some disadvantages that must be understood for optimal use. Both are described in Table 16.1.
Table 16.1 Advantages and disadvantages of flexible optical bronchoscopic (FOB) intubation
Advantages
|
Disadvantages
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Successful FOB intubation requires several elements:
understanding the equipment
learning basic manipulations and hand–eye coordination
mastering upper airway endoscopy
correct tube selection
mastering tube delivery into the trachea
The Anatomy and Function of the FOB
The modern-day FOB consists of the following parts (Figure 16.1).
Figure 16.1 Flexible intubation scopes. The black scope is a fibreoptic bronchoscope that uses glass fibres to transmit the image from the objective lens at the end of the insertion cord to the eyepiece. The white scope is a single-use scope that uses a video camera chip at the end of the insertion cord and light emitting diodes to provide light.
Body
This is held in the palm of either hand; the thumb of the same hand is used to manipulate the control lever and the index finger activates the suction valve. The control lever is pressed down to move the tip of the scope anteriorly and up to move the tip posteriorly.
With traditional fibreoptic scopes, the body has an eyepiece, which can be focussed by a diopter ring to produce a sharp image. The eyepiece has a pointer which helps to orient the operator to the anterior direction of the tip. With videoscopes the image is projected on a video monitor. The body also has a port which accesses the working channel.
Insertion cord
This part of the scope is steered into the airway and acts as a flexible guide over which the tracheal tube is advanced, facilitating intubation. The outer diameter of the insertion cord determines the size of the smallest tracheal tube that can be easily passed over it. Neonatal scopes have an outer diameter of 2.2 mm, paediatric scopes and scopes used for double-lumen tube placement range from 3.5 to 4.0 mm and adult scopes range from 5.0 to 6.3 mm. It is desirable to use a tracheal tube with an internal diameter at least 1 mm greater than the outer diameter of the insertion cord, e.g. most adult scopes with insertion cord diameter of 4 mm will allow a tracheal tube of 5 mm or larger to easily pass over it. Most insertion cords are 55–60 cm long to allow passage of the tracheal tube once its tip is positioned in the trachea.
The insertion cord contains
In fibreoptic scopes: up to 10,000 image and light transmitting fibreoptic bundles
In videoscopes: wires that energise the light emitting diodes (LEDs) at the tip and transmit the image from the camera tip to the image processor
Mechanical wires connecting the control lever to the bending element, enabling anterior and posterior deflection of the tip
The Working Channel
This is a narrow channel that extends from a port in the body of the FOB to the distal end of the insertion cord. It can be used to insufflate oxygen or to instill drugs (especially local anaesthetics), to pass guidewires or (in larger FOBs) brushes or biopsy forceps. The effectiveness of the suction depends on the diameter of the channel. A typical adult scope has a 1.5 to 3.2 mm channel. Channels less than 2.0 mm are adequate but not very effective for removing viscous secretions.
Light Source
Traditional optical bronchoscopes have an external light source, usually a halogen lamp enclosed in a casing. This is connected to the body by a light guide cable. Videoscopes have LEDs at the tip of the scope to provide light.
Camera and Monitor
Traditional optical bronchoscopes may use a camera attached to the eyepiece which projects the image to a video monitor. Modern videoscopes have a camera chip at the tip of the scope which transmits the image directly to the video monitor. A video monitor facilitates training and optimises assistants’ efforts as they can see if their jaw thrust or other manoeuvres are effective. In addition, it is easier to keep the insertion cord straight and under a small amount of tension with a videoscope because the eyepiece does not need to be near the operator’s face.
Setting Up FOB Equipment
Here is an example of a simple checklist:
Ensure the FOB has been cleaned and disinfected before use.
Check that the tip moves in the appropriate direction when the control lever is moved and there is no slack between the control lever and tip motion.
Attach the suction valve and catheter to the working channel port and ensure that the suction works when the suction valve is activated.
Plug the light guide cable to the light source and switch it on.
Defog the lens by wiping it with an alcohol swab.
For fibreoptic scopes: hold the tip of the scope 1 cm from an object and adjust the diopter ring until the image is sharp. Attach the camera to the eyepiece and set up the video monitor.
Lubricate the insertion cord (including the bending element but not the lens).
Load the tracheal tube onto the insertion cord, pulling it up to the body of the FOB, and secure it with a small piece of tape.
Learning Basic Manipulations and Hand–Eye Coordination Skills
Holding the FOB
The endoscopist holds the body of the scope in the palm of one hand using the thumb to manipulate the control lever and the index finger to activate the suction valve when required. The thumb and index finger of the other hand holds the insertion cord (Figure 16.2). It is important that the insertion cord is kept straight and slightly taut: if it becomes slack then rotation movements of the body are not effectively transmitted to the tip of the scope.
Figure 16.2 (a) The body of the intubation scope is held in the palm of one hand. The thumb manipulates the control lever and the index finger can be used to activate the suction valve. (b) The insertion cord is held straight and taut at all times, regardless of whether the scope uses video or fibreoptic technology.
Manipulating the Tip of the FOB
There are three degrees of freedom the endoscopist can use to advance the tip of the FOB into the trachea (Figure 16.3). These are: scope advancement (or withdrawal); tip deflection; and whole scope rotation. Advancing the whole FOB moves it towards the target: withdrawal is required if the scope has been advanced too far. The control lever moves the tip of the FOB anteriorly or posteriorly only: downward movement of the control lever bends the tip anteriorly (or away from the endoscopist), and upward movement bends the tip posteriorly (or towards the endoscopist). Sideways movements of the tip are achieved by rotation of the entire FOB towards the target while maintaining tip deflection. Most operators find it helpful to move their body when trying to achieve full rotation of the scope. In practice, good endoscopy technique involves performing the three basic manipulations simultaneously in order to bring the tip of the FOB towards the target.
Figure 16.3 Two-dimensional illustration of tip manipulation. The visual field is represented by a circle with four quadrants. The orientation marker is at the 12 o’clock position. Anterior tip deflection and rotation of the body in the clockwise direction are required to move the tip of the FOB from O (neutral position) to target A and posterior tip deflection with anticlockwise rotation of the body will move the tip from O to target P.
Position of the Endoscopist and the Patient
The operator will usually choose either to stand behind the patient’s head with the patient supine (more common in anaesthetised patient) or to stand in front of and face to face with the patient who is sitting upright (common in the awake patient). The latter is helpful if the patient is dyspnoeic, has a compromised airway from bleeding or oedema or has a full stomach. It is important to appreciate the differences in the observed anatomy when the operator is behind the patient rather than facing the patient.
The endoscopist should be comfortable when performing FOB endoscopy. Standing on a platform instead of standing on tip-toe may be useful to gain enough height to keep the insertion cord straight. If this is not done, the arms will fatigue rapidly and the insertion cord will slacken and bow.
Mastering Upper Airway Endoscopy
Use of the FOB is not intuitive. Practice is required to acquire and maintain a high skill level. Non-anatomical trainers can be used during early learning phases. Anatomical manikins and virtual reality trainers can be used to acquire and maintain higher skill levels (Figure 16.4). However, while these tools are educationally valuable, they are not a substitute for practice on patients for acquiring and maintaining the necessary skills.
Figure 16.4 FOB training devices. (a) The ‘Oxford’ Fibreoptic Teaching Box. (b) A trainee practising FOB manipulation skills on the Oxford box. (c) Practice using the ORSIM (Auckland, New Zealand) virtual reality airway trainer.
Flexible Optical Bronchoscopic Intubation
Intubation with an FOB involves guiding the tip of the FOB from the nose or the mouth into the trachea under continuous vision (Figure 16.5).
Figure 16.5 (centre) Upper airway anatomy during nasotracheal endoscopy. The endoscopist is standing behind a supine patient. (a) The right nostril is selected. (b) The tip of the FOB is advanced in the triangular space bounded by the nasal septum (left), inferior turbinate (bottom) and the lateral wall of the nose (right) of the visual field. (c) The FOB tip above the inferior turbinate, which is to the right of the visual field. (d) The posterior opening of the nasal cavity is indicated by the disappearance of the inferior turbinate (at the 5 o’clock) position. The posterior pharyngeal wall is seen at the centre of the visual field. (e) The soft palate is seen in the upper part and the base of the tongue in the lower part. (f) Epiglottis in view. (g) Laryngeal inlet with vocal folds, vocal cords, cuneiform and corniculate cartilages. (h) True and false vocal cords. (i) Trachea with tracheal rings. (j) Carina with openings of right and left main bronchi.
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