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Preparing to use the flexible fiber-optic laryngoscope
Sbecial Article 1
Preparing to Use the Flexible Fiber-optic Laryngoscope
James T. Roberts, MD* Departments Hospital
Study
Objective:
of Anaesthesia,
To describe a current method of teaching
Harvard
Medical School and Massachusetts
General
tubation may be taught safely using thiopental sodium and
jlexible fiber-optic lalyngosco$y.
succinylcholine by adhering to the guidelines outlined in this
Design: Review of a current technique. Setting: Inpatient surgery area at a university medical center. Patients: More than 1,000 ASA physical status I and II
paper.
patients requiring general endotracheal anesthesia for renal lithotripsy were intubated orally using a jlexible fiber-optic
Keywords: Flexible fiber-optic laryngoscope; laryngoscopy; intubation; anesthesia; airway; teaching; safety.
laryngoscope. Patients were given a sleep dose of thio-
Interventions:
pental sodium (4 mglkg) and paralyzed with a bolus of suc-
Introduction
cinylcholine (1 mglkg).
Measurements saturation,
and Main Results:
capnography,
Peri@eral
electrocardiography
tomated blood pressure (BP) measurements,
oqgen
(OJ
(EKG),
au-
and clinical re-
sponse of the patients were closely monitored by the attending anesthesiologist.
Three obese patients rapidly desaturated,
leading to abandonment
of the technique for teaching pur-
poses. After ventilation with 100%
02, all 3 patients were
rapidly intubated orally by the instructor using the flexible ,fiber-optic technique.
Conclusions:
Oral flexible fiber-optic laryngoscopy and in-
*Assistant Professor of. Anaesthesia, Harvard Medical School; Associate Anesthetist, Massachusetts General Hospital Address reprint requests to Dr. Roberts at the Department of Anesthesia, Massachusetts General Hospital, 32 Fruit Street, Boston, MA 02114, USA. Received for publication February 13, 1990; revised manuscript accepted for publication April 9, 1990. 0 1991 Butterworth-Heinemann
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The technique of flexible fiber-optic laryngoscopy is stirring the interest of anesthesiologists across the country. In the past 3 years, there has been a great response to the workshop on this technique offered at the annual meeting of the American Society of Anesthesiologists (ASA). Greater numbers of anesthesiologists are now developing and maintaining their skills with fiber optics by using this technique for routine intubations. In the author’s hands, the thiopental sodium-succinylcholine induction routine works as well for a fiber-optic intubation as it does for an intubation using a standard laryngoscope with a No. 3 Macintosh blade. After 20 intubations, the average resident can easily intubate a patient in less than a minute (Fi
Using the flexible fiber-optic
laygoscope:
Roberts
TIME (MINUTES] 71--------
0
L__-_ 0
I
._~, 5
10
15
20
INTUBATION Paw Ttmes
-
25
30
35
NUMBER RegressIon
Curve
Figure 1. Resident learning curve--times
of the first 30 intubation attempts. After 10 intubations, intubation time averages less than 2 minutes, and after 20 intubations, it averages less than 1 minute.
Figure 2. LF-1 laryngoscope. The important features include (A) the focusing ring on the eyepiece; (B) the thumb control lever; (C) the channel control valve; and (D) the oxygen connector.
the author chaired a workshop titled “Details That Make Fiberoptic Laryngoscopy Successful” in which he approached teaching fiber-optic laryngoscopy from three perspectives: preparation, equipment, and the patient. This article is organized in a similar fashion, not as a review of the history or development of flexible fiberoscopy in anesthesia but with a focus on the clinical use and appropriateness of the technique. The author has included a suggested reading list for those interested in the historical development of fiber-optic laryngoscopy.
Preparation Preparation means understanding the functioning parts of the fiber-optic laryngoscope (fiberscope), exploiting the features of the fiberscope to the patient’s advantage, knowing when (and when not) to use the scope, refreshing understanding of airway anatomy, practicing on a manikin prior to using the instrument on a patient, recognizing potential problems while anticipating their solutions, and avoiding common mistakes.
Structure and Function of a Fiberscope Because the author regularly uses the Olympus LF-1 fiberscope (Olympus Corporation, Tokyo, Japan), it will be used as an example to discuss the functional components of a fiberscope (Figure 2). A convex glass
Figure 3. A close-up of the fiberbundle tip demonstrates one noncoherent light-carrying bundle, one coherent image-transmitting bundle, and a channel for administration of oxygen or drugs.
lens having a 60-degree angle of view and a composition that is unaffected by repeated cleaning and sterilization in a glutaraldehyde solution is fused to the distal end of a coherent fiber-optic bundle, (Figure 3). The coherent fiber-optic bundle transmits an image from the distal lens to the proximal eyepiece. Individual fibers occupy similar positions at the distal and proximal ends of the bundle. Use of glass fibers accounts for the exceptional clarity of the image from the tiny bundle. The entire length of the fiber-optic bundle is passively flexible except for the distal 2 cm, J. Clin. Anesth., vol. 3, January/February
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65
which may be moved within a vertical plane through the long axis. Rotating the eyepiece focuses the scope with the normal focusing depth indicated by a white line on the band (Figure 2A). The flange of the eyepiece helps keep extraneous light from entering the image path and is designed so that a teaching adapter or a television camera may be attached for additional monitoring capability. Movement of the distal tip is controlled by two wires in the fiber-optic bundle. Moving the thumb level forward, away from the laryngoscopist, moves the tip vertically by actuating a cam that places tension on the upper wire while at the same time releasing tension on the lower wire. Moving the thumb lever toward the laryngoscopist reverses the tension and (Figure 28). To ensure that bends the tip downward the plane of movement is truly in a vertical and not a diagonal plane, the bundle must be kept fully extended while in use (Figuw 4). A handle encases the cam mechanism, protects the junction of the fiberbundle with the eyepiece, and aligns concentrically with the axis of the fiber-optic bundle, making it easy to rotate the scope around its long axis. A separate, noncoherent fiber-optic bundle transmits light from the light source through a side extension, permitting use of the fiberscope at some distance from the light source. Oxygen (0,) may be directed through the open
channel in the fiber-optic bundle sheath. ‘I’he chamlel also may be used to guide drugs or a biopsy wire to the tip of the bundle or permit suctioning of secretions from the area in front of the lens. The control valve of the open channel resides in the upper part of the 2C). 0, is directed through the scope handle (F&w channel by occluding the openings of the control valve with the index finger (Figure 2B). A rigid metal connector for 0, or suction tubing projects from the left side of the scope (Figure 20). A smooth covering protects the instrument during repeated sterilizations and enhances movement oft he endotracheal tube along the scope. Circular- white markings 5 cm apart indicate depth of insertion in the nose or mouth (Figure 4).
Manipulating
the Fiberscope
Four manipulations of the fiberscope facilitate intubation. The laryngoscopist may (1) bend the tip up or down, (2) rotate the entire instrument (clockwise or counterclockwise) along its extended axis, (3) advance or withdraw the scope, or (4) put the channel to use. Tip flexion and bundle rotation interact to change the field of view through the fiberscope. ‘l’he field of (Figure 5). view may be divided into four quadrants If the bundle is rotated without bending the tip, the fiberscope acts exactly like a rotating telescope--i.e., there is no change in the field of view. To change the field of view from one quadrant to another, the tip must be bent while the fiberscope is rotated. For example, if the laryngoscopist wishes to direct the tip of the scope, and consequently the field of (ix., center the left view, to the left upper quadrant
UP CLOCKWISE
C-CLOCKWISE
Figure 4. Fully extended fiberscope. When the fiberscope is not kept fully extended, the fiberbundle torques, possibly confusing orientation. The white circular lines mark 5 cm increments from the tip. The fiberbundle is initially held at the second (10 cm) white ring as it is inserted into the mouth. 66
,J. Clin. Anesth., vol. 3, JanuaryiFebruarv
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CLOCKWISE
DOWN
C-CLOCK WISE d
Figure 5. Four-quadrant field of view. ‘l&e figure demonstrates how to manipulate the fiberscope to change the field of view to a new location.
upper quadrant in the field of view), he or she should first bend the tip of the scope slightly upward, then rotate the scope counterclockwise. If the laryngoscopist wishes to direct the scope to the lower left quadrant, he or she bends the tip downward and rotates the instrument clockwise. This process is simplified once the user develops a mental image of the tip motion. Frequently, the author observes residents moving from side to side, lifting and twisting their shoulders as they manipulate the scope. This body movement does nothing to improve control of the scope; in fact, it destroys the laryngoscopist’s optimal alignment with the patient. The user is cautioned not to advance the scope against resistance. This approach may result in breaking of fibers (seen as black dots), which leads to costly repairs. The instrument should be guided to the center of the base of the patient’s tongue under direct vision; the user should not look through the scope while initially inserting it through the bite block. New laryngoscopists commonly advance the fiberscope too far into the mouth, past the laryngeal opening, and then wonder why they cannot identify laryngeal structures. A general rule for oral intubation is to advance the scope through a bite block, aligning the fiber-optic bundle with the center of the tongue. The scope should be advanced until the second white line ( 10 cm) is level with the upper lip. The user may then begin to look through the scope. When one sees nothing but pink through the scope, its tip usually is against the tongue, the posterior oral pharynx, or the piriform fossa or is in the upper portion of the esophagus. A solution to this problem may be to lift the mandible, bend the tip of the scope, and/ or rotate or straighten the fiber-optic bundle. If the user still cannot identify structures, he or she should slowly and gently withdraw the scope until he or she can do so. The fourth manipulation uses the scope’s channel. A connector to the channel is located on the side of the fiberscope ~Fig~re 2). 0, should be introduced through this port; suction should not be applied. It is important to remember that control of 0, flow through the channel is achieved by occluding both holes on the 0, control valve on the upper aspect of the scope cF@ure 2A). Directing O:, into the channel has more advantages than suctioning secretions through it. As a dry gas, 0, defogs and blows secretions away from the distal lens. Directing 0, into the channel helps oxygenate the patient, as opposed to sucking secretions toward the lens and thus obstructing the field of view. Occasionally, the laryngoscopist may wish to use the channel to administer a drug such as lidocaine.
Topicalizing the larynx via this route is particularly useful for performing an awake intubation on a patient with a cervical collar, since the collar prevents cutaneous access to the superior laryngeal nerves (see the section on anatomy for substitute methods of blocking the superior laryngeal nerves). Although the channel was originally designed for suctioning, this should not be its primary use. Secretions should be aspirated with a suction separate from the fiberscope. Rarely should the channel be used for a biopsy wire or to retrieve a foreign body such as a chip from a tooth.
Indications for Using the Fiberscope The original indication for using the flexible fiberoptic laryngoscope was a difficult airway problem, which may be identified in the patient’s history or by physical examination of the patient. Physical attributes suggesting a difficult airway problem include temporal mandibular arthritis, an anterior larynx, inability to open the mouth, cervical injury, or blood in the oral cavity. Patients with an unsuspected difficult airway are the most disconcerting. Having the necessary fiberscope immediately available and sterile is imperative for proper management of these patients. It is gratifying to hear former residents cite specific instances in which the flexible fiber-optic laryngoscope bailed them out. It is not a good idea to teach the technique on a patient who is known to have a difficult intubation problem. In the author’s teaching program, oral flexible fiber-optic intubation is used on almost every ASA physical status I and II patient requiring endotracheal intubation. This approach gives the residents experience under controlled conditions that are safe for the patient. During his or her month in the author’s service, a resident can expect to perform up to 30 oral intubations. The author emphasizes the oral endotracheal route because it is more difficult than the nasal approach. Once a resident masters oral fiber-optic intubation, he or she can easily manage a nasal intubation, since the nasal passages tend to guide the fiberscope to the laryngeal opening.
Contraindications
to Using the Fiberscope
Although rare in occurrence, patient refusal constitutes an absolute contraindication to oral or nasal intubation. Hemorrhage in the oral cavity is a relative contraindication to fiber-optic intubation because J. Clin. Anesth.,
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Special Article
blood may obliterate the field of view through the instrument. Obesity is a relative contraindication to teaching the elective oral flexible fiber-optic approach because obese patients develop 0, desaturation faster than nonobese patients, and they also are anatomically more difficult to intubate. Agitated awake patients must be appropriately sedated and the oral cavity and larynx properly anesthetized. In general, patients requiring rapid-sequence intubation should not be intubated with the fiberscope except following failed attempts at standard laryngoscopy. A fungating laryngeal tumor may be a contraindication to oral or nasal intubation, with the preferred technique being early elective tracheostomy.
should increase the bulk of the sterile cotton (Figure the local anesthetic and/or 8) to facilitate spreading astringent over a wide area in the nasal passage. The posterior oropharynx is innervated by the glossopharyngeal nerves. A glossopharyngeal nerve block at the styloid process almost always affects the spinal accessory nerve. It is, therefore, easier to topicalize locally, either with a spray or by allowing 5% lidocaine ointment to melt in the patient’s mouth while in the supine position. Gargling a 4% lidocaine solution achieves a similar result. The base of the tongue, epiglottis, piriform fossa,
Airway Anatomy To anesthetize the airway for an awake fiber-optic intubation, the laryngoscopist should know the distribution (sensory and motor) of the nasopharyngeal, oropharyngeal, laryngeal, and tracheal nerves. Sensory innervation of the nasal passages is provided by the following nerves: anterior superior alveolar, olfactory, anterior ethmoid, sphenopalatine, and infraorbital (Figures 6 and 7). Multiple nerves necessitate distributing the topical anesthetic over the entire nasal passage. This action may be accomplished by spraying or application with a cotton applicator stick. The user
6. Sensory distribution of’ the nasal passage. Multiple nerves must be anesthetized to achieve total topical anesthesia. The lateral wall is innervated primarily by the (A) anterior ethmoid, (B) infraorbital, (C) anterior superior alveolar, (D) olfactory, (E) maxillary and sphenopalatine ganglion, and (F) middle and inferior turbinates. (Reproduced with permission from Fundamentals of Tracheal Intubation by James T. Roberts, published by Grune and Stratton, New York, 1983.)
7. Sensory innervation of the nasal septum: (A) anterior ethmoid, (B) infraorbital, (C) olfactory, (D) nasopalatine, and (E) nasopharynx (glossopharyngeal). (Repro duced with permission from Fundamentals of Tracheae/ Intubation by James T. Roberts, published by Grune and Stratton, New York, 1983.) Figure
Figure
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Figure 8. Large cotton swabs are not commercially available but can be made from a cotton swab and the center of a Topper gauze pad.
Using the flexible fiber--optic laqngoscope: Roberts
and vallecula receive sensory innervation from the superior laryngeal nerves (Figure 9). These nerves are easily blocked by any of three approaches: percutaneously, just anterior to the superior horn of the thyroid cartilage, anteriorly, through the notch of the thyroid cartilage; or intraorally, in the piriform recess. A special needle with a 45-degree bend facilitates intraoral injection. The laryngoscopist should avoid injecting the carotid artery, since as little as 1 ml of 1% lidocaine can increase the arterial lidocaine concentration above 5 pg/ml and induce a grand ma1 seizure. The sensory mucosa supplied by the superior laryngeal nerves also can be anesthetized by simply spraying the oral mucosa with 4% lidocaine. Bilateral recurrent laryngeal nerves innervate the trachea (Figure 10). Blocking these nerves, or inadvertently cutting both nerves during thyroid surgery, results in obstruction of the airway by unopposed activity of the motor division of the superior laryngeal nerve. The superior laryngeal nerve innervates only one muscle, the cricothyroid, which is a tensor of the cords (Figure IO). All other intrinsic muscles of the larynx are supplied by the recurrent laryngeal nerves. The trachea may be topically anesthetized by spraying via the oral cavity, by a midline percutaneous injection, or by inhalation of a vaporized lidocaine solution. Each of these approaches produces satisfactory local anesthesia of the trachea.
Airway Physiology Reflex constriction of the bronchial smooth muscles is of concern whenever a foreign body is purposely or accidentally introduced into the trachea. The laryngoscopist should be prepared to administer a bronchodilator, an intravenous (IV) narcotic to suppress reflex coughing, or an agent such as atropine to suppress secretions.
Manikin Practice An excellent anatomical model suitable for either oral or nasal intubation training is available through the
lnterna I Laryngeal Nerve /
Recurrent Laryngeal Nerve
10. The superior laryngeal nerves supply motor innervation of the cricothyroid muscle by its external branch and sensory innervation by its internal branch. Note the recurrent laryngeal nerves lying posteriorly lateral to the trachea. These nerves supply sensory innervation to the trachea and motor innervation to all intrinsic muscles of the trachea except the cricothyroid.
Figure
distribution of the superior laryngeal nerves supplying the base of the tongue, epiglottis, vallecula, and piriform recesses down to the vocal cords. (Reproduced Figure
9. Sensory
with permission from Fundamentals of Tracheal Intubation by James T. Roberts, published by Grune & Stratton, New York, 1983.)
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Special Article
Olympus Corporation (Lake Success, NY). An acceptable routine for manikin practice is as follows. The adapter from an appropriate endotracheal tube is removed, and the lubricated fiberscope is threaded through the endotracheal tube. The adapter is too large to fit through the Olympus mouthpiece. The laryngoscopist positions himself or herself at the head of the patient and places one of the many available mouth bites between the teeth to protect the fiberscope. The fiberscope is inserted through the mouth bite, following the center of the tongue. The tip of the scope is flexed, then guided past the base of the tongue. The scope is inserted until the 10 cm white ring is adjacent to the upper lip, then the tip is straightened. The laryngoscopist should now begin looking through the scope to guide it to the laryngeal opening. When the laryngeal opening is immediately in front of the scope tip, the tip is guided into the trachea by bending it slightly downward, or posteriorly (FZgure 11). The center of the trachea is kept in the center of the field of view as the scope is advanced. The scope should be advanced until the carina is clearly in view. At this point, the handle of the fiberscope is turned 180 degrees and placed above the umbilicus (Figure 12). With the fiberscope still in place, the endotracheal tube is advanced over the scope, which now acts as a stylet. In a patient, the laryngoscopist may encounter resistance to advancing the endotracheal tube. This resistance is usually due to the Murphy tip of the endotracheal tube hanging up on the right arytenoid
Figure 12. After the fiberscope tip is inserted to the level of the carina, rotating the scope 180 degrees places the handle above the patient’s umbilicus and allows the natural curve of the endotracheal tube to match the natural curve of the oropharynx.
(corniculate) cartilage (Figure 13). To pass the tube beyond this point, the tube is withdrawn 1 cm or so, rotated exactly 90 degrees counterclockwise, and advanced again. The tube now will pass easily into the trachea. The tube should be positioned so that the 22 cm mark is at the upper teeth, then the fiberscope is withdrawn without moving the endotracheal tube. The mouth bite is removed, and the endotracheal tube adapter that was previously removed is inserted and connected to the anesthesia circuit. The cuff is inflated and positioned just distal to the vocal folds, then taped securely in place. Both oral and nasal approaches are repeated during the manikin practice becomes second until manipulation of the fiberscope nature.
Preparing
the Appropriate Equipment
Sterile Fiberscope. A common routine for sterilizing the fiberscope is to soak it in a glutaraldehyde solution for at least 10 minutes, then wash it with sterile water and store it in a sterile environment. Figure 11. Sagittal section of cadaver showing oropharynx and upper trachea. Arrow indicate the fiberscope path curving around the tongue and then angling posteriorly into the trachea. (Photo modified from one appearing in Emergency Airway Management by Michael Gorback, M.D., published by B.C. Decker, Philadelphia, 1990.) 70
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Oxygen to the Scope. O2 is connected directly to the scope through the side port. Seven liters per minute has been ideal for directing secretions away, helping defog the lens, and oxygenating the patient.
Using the flexible Jibrr-optic la~yngoscofw:Robert>
Williams bite block (Anesthesia Associates, San Marcos, CA) surrounds the endotracheal tube.
A second light source should be available as a backup to a lamp that burns out at a critical moment. Dual light sources are available through Applied Fiberoptics (Southbridge, MA).
Backup Light Source.
Second Suction.
thesia machine,
In addition to the suction to the anesan oral suction is mandatory.
The pulse oximeter allows for the safe teaching of oral fiber-optic laryngoscopy by the thiopental sodium-succinylcholine method. With 5 minutes of preoxygenation and hyperventilation, the ASA physical status I and II patients who tend to desaturate are the obese patients. Obese patients are not, therefore, selected for routine fiber-optic intubation.
Pulse Oximeter.
When the author first began performing routine oral intubations by the fiber-optic method, he found increases in arterial blood pressure (BP) after intubation. Upon measuring the expired carbon dioxide (CO,) by capnometry, he discovered that arterial CO, tension (PaCO,) increased at an average rate of approximately 4 mmHg/min. With an initial value of 30 mmHg, 3 minutes of complete apnea gives a final value of 42 mmHg, hardly enough to explain the increase in BP. These BP increases were easily controlled by adding a volatile anesthetic immediately after paralysis with succinylcholine and before the intubation attempt. A paper record from the CO, analyzer allows accurate timing of the intubation process from last mask breath to first intubated breath.
Carbon Dioxide Analyzer.
13. Since the fiberscope occupies the center of the laryngeal opening, advancement of the concentrically placed endotracheal tube is frequently interrupted by the right corniculate cartilage. This problem may be overcome by (1) withdrawing the endotracheal tube 1 cm to free it from the corniculate cartilage but not removing it from under the epiglottis, then (2) rotating the endotracheal tube 90 Figure
degrees counterclockwise past the vocal cords.
before (3) advancing the tube tip
Dinamap,
Several oral bite blocks are available. The Olympus bite block (Olympus Corporation, Lake Success, NY) is designed primarily to protect the fiberscope from the patient’s teeth. The Patil airway (Anesthesia Associates, San Marcos, CA) is a metal airway designed not only to protect the fiberscope from the teeth but also to guide the tip of the scope toward the laryngeal opening. The Ovassapian airway (The Kendall Company, Boston, MA) is a disposable plastic airway designed to protect the fiberscope, guide the tip of the fiberscope toward the laryngeal opening, and allow easy removal of the endotracheal tube. The Oral Bite Blocks.
EKG,
IV,
Drugs,
and
Anesthesia
Ma-
The author has grouped these items together because they are standard equipment for all intubation attempts. An automated BP apparatus frees one’s hands for the intubation process. The author has no specific drug preference suggestions. A variety of sedatives and narcotics are satisfactory, and the author leaves the nuances of drug interaction to be argued by others. chine.
Accessories. Teaching scopes that attach to the head of the fiberscope are available to allow the
Teaching
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Figure 14. A teaching fiberbundle is easily attached to the eyepiece, allowing an additional person to view the
image through the fiberscope.
Figure 15. A video camera attachment allows simultaneous viewing and videotaping of fiber-optic laryngoscopy. The videotape provides legal proof of intubation.
attending physician to view the intubation and guide it if necessary (Figure 14). A video camera also may be attached to the fiberscope to permit video monitoring of the intubation and a permanent record to be made (Figure 15). To improve teaching of flexible fiber-optic laryngoscopy, it is possible to expose the larynx with a new monitoring laryngoscope that lifts the tongue. This also allows the attending physician to observe and comment on the resident’s manipulations of the tip of the flexible fiberscope (Figure 16).
Preparing the Patient A preoperative interview and physical examination help to answer three basic questions prior to selection of fiber-optic intubation for a patient. First, is the patient to be intubated orally or nasally? Second, is the patient to be asleep under general anesthesia or awake with sedation and regional anesthesia to the airway? Third, if the patient is to be operated on under general anesthesia, is it reasonable to use muscle relaxants? Fiber-optic intubations are commonly done under all of the above conditions.
For teaching purposes, the nasal approach has been traditional. While there are definite advantages to this approach, the author has chosen to teach flexible fiber optics by the oral route for the following reason: since the oral approach is more difficult, once his residents learn to intubate by this method, nasal intubations are effortless. This finding is borne out by resident learning curves. One may consider using the endotracheal tube as Oral or Nasal Intubation?
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Figure 16. The Roberts adjustable, monitoring, and recording (AMR) laryngoscope has a pivoting handle, a blade that may be lengthened or shortened while in the mouth, a coherent fiber-optic bundle for imaging, and a noncoherent fiber-optic bundle for light transmission. By adding a video camera, the attending physician can view as well as videotape exactly where the laryngoscopist places the endotracheal tube.
a guide to advancing the fiberscope through the nose. There are advantages and disadvantages to this method. One advantage is that prior insertion of the endotracheal tube guides the fiberscope to the glottic opening. Disadvantages include greater duration of patient discomfort during awake intubations, since the endotracheal tube remains in the nasal passage while the laryngoscopist searches for the glottic opening with the fiberscope. Preinsertion of the endotracheal tube increases the chance of inducing bleeding and thus the chance of obstructing the laryngoscopist’s view. There is also a greater chance of inhibiting the passage of the fiberscope through the endotracheal tube once the tube is bent into position in the nasal passage. If it is necessary to move the fiberscope back and forth inside the endotracheal tube to effect passage, there is a greater chance of smearing some of the lubricant on the lens tip and obstructing one’s view. If the fiberscope is initially passed into the trachea, the endotracheal tube is introduced over the fiberscope, and discomfort to an awake patient is only momentary until the thiopental sodium takes effect. Another consideration is whether the patient should be awake or asleep. Intubation of an awake patient has the advantage that the patient is breathing spontaneously and is comfortable with proper topical anesthesia and/or nerve blocks and sedation. (Topical anesthesia and nerve blocks are dis-
Awake or Asleep?
Using the /lexible fiber-@tic
cussed under anatomy.) The awake intubation legitimately conjures up fear in most patients, so the physician must use his or her own judgment in deciding whether to use it. Awake intubation enables orthopedic patients to help situate themselves in difficult positions, such as the knee-chest position with the Tarlov frame. The anesthetized patient may be intubated while breathing spontaneously or while paralyzed. Spontaneous ventilation is helpful but requires a longer induction time prior to intubation.
By learning to use the thiopental sodium-succinylcholine oral fiber-optic tube, one can easily and safely use the flexible fiberscope without delaying a busy operating room schedule. Paralyzed muscles of the mandible and larynx relax their tone and tend to collapse inward. It is mandatory to have
Relaxation.
another person closely observing and recording the monitoring values while the laryngoscopist’s attention is focused on the eyepiece. This
person also may help by lifting the patient’s mandible, although this action is easily accomplished by the laryngoscopist. Reflex cord closure often occurs under general anesthesia as the fiberscope bundle approaches the laryngeal opening. Once the fiberscope induces reflex cord closure, a judicious amount of succinylcholine (20 mg) should be administered. This action will relax the laryngeal muscles and allow the fiberscope to pass through the cords and into the trachea.
Eight Potential Problems A problem is defined as a source of perplexity, distress, or vexation. Eight problems are discussed here and listed in Table 1. Perhaps the most common prob-
Table
1.
lem in using the flexible fiber-optic laryngoscope is fogging of the lens caused by the warm, humid air in the oral cavity condensing on the cooler fiberscope. This fogging is prevented by inserting the fiberscope tip into warm sterile saline to warm the lens prior to insertion in the patient’s mouth. Sterile defogging solution also may be applied to the distal lens. The author’s method is to direct 100% 0, through the scope channel at a rate of 7 L/min. The dry gas nicely dehumidifies the lens. Another problem is the presence of blood secondary to oral trauma or because of preexisting blood in the nasal passages, possibly from the laryngoscopist’s trying a blind nasal intubation before attempting it with the fiberscope. If blood blocks the field of view, the fiberscope must be removed and cleaned. If blood is present but not on the lens, a separate suction can be used to remove it (suction should not occur through the fiberscope). Suctioning through the fiberscope brings blood to the lens. A third and more common problem occurs when a patient’s secretions obstruct the view through the fiberscope. Secretions are removed by suctioning the oral cavity before inserting the fiberscope, pretreating with an anticholinergic, and/or directing them away with 0, channeled through the fiberscope. In the author’s experience, the last method is most useful. Another indication of trouble is when one sees only pink through the fiberscope. When this situation occurs, the liberscope should be c ecked to see that it follows the midline of the tongu t exactly. The fiberscope often tracks along the side of the tongue into the piriform recess. The fiberscope also should be fully extended. When it is not, the fiberbundle may be torqued. When torquing occurs, orientation through the scope is distorted, since the mark seen at 12 o’clock remains at 12 o’clock in spite of the direc-
Summary of Eight Potential Problems and Their Solutions Problem
1. Lens fogs Blood blinds view Secretions blind view Unrecognized view Endotracheal tube cannot be advanced 6. Turbinates visible in oral approach 7. Instructor cannot see 8. Black dots appear in field of view 2. 3. 4. 5.
lryyngosco~e: Roberts
Solution
Blow oxygen across lens, warm lens, use antifog solution Clean lens again Blow secretions away with oxygen Withdraw scope Back up 1 cm, Rotate tube counterclockwise, and try again Bend tip of scope in opposite direction. Add teaching or video attachment Coherent fibers are broken and need to be replaced.
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tion in which the tip of the fiberscope is pointing. Videotapes of fiber-optic intubations have shown the tip of the fiberscope to be moving laterally when the laryngoscopist was certain the tip was moving in a vertical plane. If these two maneuvers do not correct the situation, the fiberscope should be withdrawn until the obstacle can be identified. A fifth problem occurs very frequently. Once the fiberscope is inserted to the carina, the endotracheal tube advances only so far and then stops. In most cases, the center of the laryngeal opening is occupied by the fiberbundle, causing the tip of the endotracheal tube to be forced laterally and to catch on the patient’s right arytenoid (corniculate and cuneiform) cartilages. The author has confirmed this occurrence with videotapes. When this situation occurs, the endotracheal tube should be withdrawn 1 cm, rotated 90 degrees counterclockwise, and readvanced (Figure 12). This maneuver can be repeated as necessary. If the patient’s head is fixed in a flexed position, this maneuver may not work, since the endotracheal tube will approach the larynx from a difficult angle. The laryngoscopist can try using a guidable endotracheal tube over the fiberscope to direct the tip of the tube into the laryngeal opening. A sixth problem occurs when turbinates are in full view during an attempt at oral intubation. The solution to this problem is simple: since the fiberscope tip is bent acutely in the wrong direction, the bend of the tip should be reversed. A seventh problem occurs when the instructor teaching the fiber-optic technique cannot see what the student sees. A teaching adapter attached to the fiberscope (Figure 14) allows a second person to see the view through the fiberscope. A video adapter (Figure 15) not only allows additional individuals to view the process but also permits videotaping for future instruction or record keeping. A final problem is irreversible. Black dots in the field of view indicate fractured fibers in the coherent optical bundle. When these dots excessively interfere with the optics, the fiberbundle must be replaced.
Eighteen Common Mistakes A mistake is a wrong action or inaction resulting from faulty judgment, inadequate knowledge, or inattention. The first 13 mistakes result from a lack of correct action (acts of omission), while the last 5 are active mistakes (acts of commission). 1. The fiberscope is not kept extended during laryngoscopy. This situation commonly results in torquing of the fiberbundle and loss of orientation.
2. Oxygen is not directed through the fiberscope. Oxygen moves secretions away, defogs the lens, and oxygenates the patient. 3. The patient’s mouth is not suctioned prior to insertion of the fiberscope. Secretions commonly are stimulated as a result of succinylcholine. 4. The fiberscope is inadequately lubricated, preventing the endotracheal tube from sliding smoothly over the scope. .5. If flexible fiber-optic intubation is attempted orally without a bite block, pressure from the teeth may destroy the coherent optical bundle. 6. A second person is not on hand to monitor the patient and his or her vital signs while the laryngoscopist attempts the fiber-optic intubation. 7. The patient is inadequately prepared because of a lack of sedation or inadequate regional anesthesia to the airway. 8. ‘l‘he laryngoscopist has performed an insufficient number of routine cases. A minimum of 20 oral intubations is necessary to quicken oral intubation technique to less than 1 minute. 9. A sterile instrument is not ready for use. 10. Skill with the fiberscope is not maintained once it has been mastered. 11. The light source is not activated prior to paralyzing the patient. The most common time for a bulb to fail is with the initial power surge. If the bulb fails after the patient has been paralyzed, the fiber-optic technique should be abandoned and standard laryngoscopy performed. 12. A manikin is not used for practice prior to using the scope on patients. 13. ‘l‘he fiberscope is not focused prior to anesthetizing the patient, thus wasting critical time. 14. Movement of the fiberscope is too rapid and too extensive. 15. ‘I‘he fiberscope is inserted past the laryngeal opening. 16. The fiberscope is forcefully advanced against resistance. 17. The endotracheal tube is forcefully advanced against resistance. 18. The distal fiberbundle is torqued instead of being rotated by the handle of the fiberscope.
‘l’he availability of superb fiber-optic instruments has opened a door in patient care. It is now the anesthesiologist’s responsibility to master and maintain the skill of flexible fiber-optic laryngoscopy by repeatedly using the instrument for routine intubations. Then, when the physician is presented with a difficult airwav patient, he or she is prepared.
UGng
Further Reading 1. Roberts JT: Fundamentals of Tracheal Intubation. New York: Grune & Stratton, 1983. 2. Ovassapian A, Yelich SJ, Dykes MHM, Brunner EE: Fiberoptic nasotracheal intubation: incidence and causes of failure. Anesth Analg 1983;62:692-5. 3. Rogers SN, Benumof JF: New and easy techniques for fiberoptic endoscopy-aided tracheal intubation. Anesthesiology 1983;59:569-72.
the flexible fiber-optic
lq’ngoscope:
Roberts
4. Patil V, Stehling L, Zauder H: Fiberoptic Endosco$y in Anesthesia. Chicago: Year Book Medical Publishers, 1983. 5. Wangler MA, Weaver JM: A method to facilitate fiberoptic laryngoscopy. Anesthesiology 1984;61: 111. 6. Patil V, Stehhng LC, Zauder HL, Koch JP: Mechanical aids for fiberoptic endoscopy. Anesthesiology 1982;57:6970. 7. Baraka A: Transtracheal jet ventilation during fiberoptic intubation under general anesthesia. Anesth Analg 1986;65:1091-2.
J. Clin. Anesth., vol. 3, January/February
1991
75
Preparing to Use the Flexible Fiber-optic Laryngoscope
James T. Roberts, MD* Departments Hospital
Study
Objective:
of Anaesthesia,
To describe a current method of teaching
Harvard
Medical School and Massachusetts
General
tubation may be taught safely using thiopental sodium and
jlexible fiber-optic lalyngosco$y.
succinylcholine by adhering to the guidelines outlined in this
Design: Review of a current technique. Setting: Inpatient surgery area at a university medical center. Patients: More than 1,000 ASA physical status I and II
paper.
patients requiring general endotracheal anesthesia for renal lithotripsy were intubated orally using a jlexible fiber-optic
Keywords: Flexible fiber-optic laryngoscope; laryngoscopy; intubation; anesthesia; airway; teaching; safety.
laryngoscope. Patients were given a sleep dose of thio-
Interventions:
pental sodium (4 mglkg) and paralyzed with a bolus of suc-
Introduction
cinylcholine (1 mglkg).
Measurements saturation,
and Main Results:
capnography,
Peri@eral
electrocardiography
tomated blood pressure (BP) measurements,
oqgen
(OJ
(EKG),
au-
and clinical re-
sponse of the patients were closely monitored by the attending anesthesiologist.
Three obese patients rapidly desaturated,
leading to abandonment
of the technique for teaching pur-
poses. After ventilation with 100%
02, all 3 patients were
rapidly intubated orally by the instructor using the flexible ,fiber-optic technique.
Conclusions:
Oral flexible fiber-optic laryngoscopy and in-
*Assistant Professor of. Anaesthesia, Harvard Medical School; Associate Anesthetist, Massachusetts General Hospital Address reprint requests to Dr. Roberts at the Department of Anesthesia, Massachusetts General Hospital, 32 Fruit Street, Boston, MA 02114, USA. Received for publication February 13, 1990; revised manuscript accepted for publication April 9, 1990. 0 1991 Butterworth-Heinemann
64
J. Clin. Anesth.,
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1991
The technique of flexible fiber-optic laryngoscopy is stirring the interest of anesthesiologists across the country. In the past 3 years, there has been a great response to the workshop on this technique offered at the annual meeting of the American Society of Anesthesiologists (ASA). Greater numbers of anesthesiologists are now developing and maintaining their skills with fiber optics by using this technique for routine intubations. In the author’s hands, the thiopental sodium-succinylcholine induction routine works as well for a fiber-optic intubation as it does for an intubation using a standard laryngoscope with a No. 3 Macintosh blade. After 20 intubations, the average resident can easily intubate a patient in less than a minute (Fi
Using the flexible fiber-optic
laygoscope:
Roberts
TIME (MINUTES] 71--------
0
L__-_ 0
I
._~, 5
10
15
20
INTUBATION Paw Ttmes
-
25
30
35
NUMBER RegressIon
Curve
Figure 1. Resident learning curve--times
of the first 30 intubation attempts. After 10 intubations, intubation time averages less than 2 minutes, and after 20 intubations, it averages less than 1 minute.
Figure 2. LF-1 laryngoscope. The important features include (A) the focusing ring on the eyepiece; (B) the thumb control lever; (C) the channel control valve; and (D) the oxygen connector.
the author chaired a workshop titled “Details That Make Fiberoptic Laryngoscopy Successful” in which he approached teaching fiber-optic laryngoscopy from three perspectives: preparation, equipment, and the patient. This article is organized in a similar fashion, not as a review of the history or development of flexible fiberoscopy in anesthesia but with a focus on the clinical use and appropriateness of the technique. The author has included a suggested reading list for those interested in the historical development of fiber-optic laryngoscopy.
Preparation Preparation means understanding the functioning parts of the fiber-optic laryngoscope (fiberscope), exploiting the features of the fiberscope to the patient’s advantage, knowing when (and when not) to use the scope, refreshing understanding of airway anatomy, practicing on a manikin prior to using the instrument on a patient, recognizing potential problems while anticipating their solutions, and avoiding common mistakes.
Structure and Function of a Fiberscope Because the author regularly uses the Olympus LF-1 fiberscope (Olympus Corporation, Tokyo, Japan), it will be used as an example to discuss the functional components of a fiberscope (Figure 2). A convex glass
Figure 3. A close-up of the fiberbundle tip demonstrates one noncoherent light-carrying bundle, one coherent image-transmitting bundle, and a channel for administration of oxygen or drugs.
lens having a 60-degree angle of view and a composition that is unaffected by repeated cleaning and sterilization in a glutaraldehyde solution is fused to the distal end of a coherent fiber-optic bundle, (Figure 3). The coherent fiber-optic bundle transmits an image from the distal lens to the proximal eyepiece. Individual fibers occupy similar positions at the distal and proximal ends of the bundle. Use of glass fibers accounts for the exceptional clarity of the image from the tiny bundle. The entire length of the fiber-optic bundle is passively flexible except for the distal 2 cm, J. Clin. Anesth., vol. 3, January/February
1991
65
which may be moved within a vertical plane through the long axis. Rotating the eyepiece focuses the scope with the normal focusing depth indicated by a white line on the band (Figure 2A). The flange of the eyepiece helps keep extraneous light from entering the image path and is designed so that a teaching adapter or a television camera may be attached for additional monitoring capability. Movement of the distal tip is controlled by two wires in the fiber-optic bundle. Moving the thumb level forward, away from the laryngoscopist, moves the tip vertically by actuating a cam that places tension on the upper wire while at the same time releasing tension on the lower wire. Moving the thumb lever toward the laryngoscopist reverses the tension and (Figure 28). To ensure that bends the tip downward the plane of movement is truly in a vertical and not a diagonal plane, the bundle must be kept fully extended while in use (Figuw 4). A handle encases the cam mechanism, protects the junction of the fiberbundle with the eyepiece, and aligns concentrically with the axis of the fiber-optic bundle, making it easy to rotate the scope around its long axis. A separate, noncoherent fiber-optic bundle transmits light from the light source through a side extension, permitting use of the fiberscope at some distance from the light source. Oxygen (0,) may be directed through the open
channel in the fiber-optic bundle sheath. ‘I’he chamlel also may be used to guide drugs or a biopsy wire to the tip of the bundle or permit suctioning of secretions from the area in front of the lens. The control valve of the open channel resides in the upper part of the 2C). 0, is directed through the scope handle (F&w channel by occluding the openings of the control valve with the index finger (Figure 2B). A rigid metal connector for 0, or suction tubing projects from the left side of the scope (Figure 20). A smooth covering protects the instrument during repeated sterilizations and enhances movement oft he endotracheal tube along the scope. Circular- white markings 5 cm apart indicate depth of insertion in the nose or mouth (Figure 4).
Manipulating
the Fiberscope
Four manipulations of the fiberscope facilitate intubation. The laryngoscopist may (1) bend the tip up or down, (2) rotate the entire instrument (clockwise or counterclockwise) along its extended axis, (3) advance or withdraw the scope, or (4) put the channel to use. Tip flexion and bundle rotation interact to change the field of view through the fiberscope. ‘l’he field of (Figure 5). view may be divided into four quadrants If the bundle is rotated without bending the tip, the fiberscope acts exactly like a rotating telescope--i.e., there is no change in the field of view. To change the field of view from one quadrant to another, the tip must be bent while the fiberscope is rotated. For example, if the laryngoscopist wishes to direct the tip of the scope, and consequently the field of (ix., center the left view, to the left upper quadrant
UP CLOCKWISE
C-CLOCKWISE
Figure 4. Fully extended fiberscope. When the fiberscope is not kept fully extended, the fiberbundle torques, possibly confusing orientation. The white circular lines mark 5 cm increments from the tip. The fiberbundle is initially held at the second (10 cm) white ring as it is inserted into the mouth. 66
,J. Clin. Anesth., vol. 3, JanuaryiFebruarv
1991
CLOCKWISE
DOWN
C-CLOCK WISE d
Figure 5. Four-quadrant field of view. ‘l&e figure demonstrates how to manipulate the fiberscope to change the field of view to a new location.
upper quadrant in the field of view), he or she should first bend the tip of the scope slightly upward, then rotate the scope counterclockwise. If the laryngoscopist wishes to direct the scope to the lower left quadrant, he or she bends the tip downward and rotates the instrument clockwise. This process is simplified once the user develops a mental image of the tip motion. Frequently, the author observes residents moving from side to side, lifting and twisting their shoulders as they manipulate the scope. This body movement does nothing to improve control of the scope; in fact, it destroys the laryngoscopist’s optimal alignment with the patient. The user is cautioned not to advance the scope against resistance. This approach may result in breaking of fibers (seen as black dots), which leads to costly repairs. The instrument should be guided to the center of the base of the patient’s tongue under direct vision; the user should not look through the scope while initially inserting it through the bite block. New laryngoscopists commonly advance the fiberscope too far into the mouth, past the laryngeal opening, and then wonder why they cannot identify laryngeal structures. A general rule for oral intubation is to advance the scope through a bite block, aligning the fiber-optic bundle with the center of the tongue. The scope should be advanced until the second white line ( 10 cm) is level with the upper lip. The user may then begin to look through the scope. When one sees nothing but pink through the scope, its tip usually is against the tongue, the posterior oral pharynx, or the piriform fossa or is in the upper portion of the esophagus. A solution to this problem may be to lift the mandible, bend the tip of the scope, and/ or rotate or straighten the fiber-optic bundle. If the user still cannot identify structures, he or she should slowly and gently withdraw the scope until he or she can do so. The fourth manipulation uses the scope’s channel. A connector to the channel is located on the side of the fiberscope ~Fig~re 2). 0, should be introduced through this port; suction should not be applied. It is important to remember that control of 0, flow through the channel is achieved by occluding both holes on the 0, control valve on the upper aspect of the scope cF@ure 2A). Directing O:, into the channel has more advantages than suctioning secretions through it. As a dry gas, 0, defogs and blows secretions away from the distal lens. Directing 0, into the channel helps oxygenate the patient, as opposed to sucking secretions toward the lens and thus obstructing the field of view. Occasionally, the laryngoscopist may wish to use the channel to administer a drug such as lidocaine.
Topicalizing the larynx via this route is particularly useful for performing an awake intubation on a patient with a cervical collar, since the collar prevents cutaneous access to the superior laryngeal nerves (see the section on anatomy for substitute methods of blocking the superior laryngeal nerves). Although the channel was originally designed for suctioning, this should not be its primary use. Secretions should be aspirated with a suction separate from the fiberscope. Rarely should the channel be used for a biopsy wire or to retrieve a foreign body such as a chip from a tooth.
Indications for Using the Fiberscope The original indication for using the flexible fiberoptic laryngoscope was a difficult airway problem, which may be identified in the patient’s history or by physical examination of the patient. Physical attributes suggesting a difficult airway problem include temporal mandibular arthritis, an anterior larynx, inability to open the mouth, cervical injury, or blood in the oral cavity. Patients with an unsuspected difficult airway are the most disconcerting. Having the necessary fiberscope immediately available and sterile is imperative for proper management of these patients. It is gratifying to hear former residents cite specific instances in which the flexible fiber-optic laryngoscope bailed them out. It is not a good idea to teach the technique on a patient who is known to have a difficult intubation problem. In the author’s teaching program, oral flexible fiber-optic intubation is used on almost every ASA physical status I and II patient requiring endotracheal intubation. This approach gives the residents experience under controlled conditions that are safe for the patient. During his or her month in the author’s service, a resident can expect to perform up to 30 oral intubations. The author emphasizes the oral endotracheal route because it is more difficult than the nasal approach. Once a resident masters oral fiber-optic intubation, he or she can easily manage a nasal intubation, since the nasal passages tend to guide the fiberscope to the laryngeal opening.
Contraindications
to Using the Fiberscope
Although rare in occurrence, patient refusal constitutes an absolute contraindication to oral or nasal intubation. Hemorrhage in the oral cavity is a relative contraindication to fiber-optic intubation because J. Clin. Anesth.,
vol. 3, January/February
1991
67
Special Article
blood may obliterate the field of view through the instrument. Obesity is a relative contraindication to teaching the elective oral flexible fiber-optic approach because obese patients develop 0, desaturation faster than nonobese patients, and they also are anatomically more difficult to intubate. Agitated awake patients must be appropriately sedated and the oral cavity and larynx properly anesthetized. In general, patients requiring rapid-sequence intubation should not be intubated with the fiberscope except following failed attempts at standard laryngoscopy. A fungating laryngeal tumor may be a contraindication to oral or nasal intubation, with the preferred technique being early elective tracheostomy.
should increase the bulk of the sterile cotton (Figure the local anesthetic and/or 8) to facilitate spreading astringent over a wide area in the nasal passage. The posterior oropharynx is innervated by the glossopharyngeal nerves. A glossopharyngeal nerve block at the styloid process almost always affects the spinal accessory nerve. It is, therefore, easier to topicalize locally, either with a spray or by allowing 5% lidocaine ointment to melt in the patient’s mouth while in the supine position. Gargling a 4% lidocaine solution achieves a similar result. The base of the tongue, epiglottis, piriform fossa,
Airway Anatomy To anesthetize the airway for an awake fiber-optic intubation, the laryngoscopist should know the distribution (sensory and motor) of the nasopharyngeal, oropharyngeal, laryngeal, and tracheal nerves. Sensory innervation of the nasal passages is provided by the following nerves: anterior superior alveolar, olfactory, anterior ethmoid, sphenopalatine, and infraorbital (Figures 6 and 7). Multiple nerves necessitate distributing the topical anesthetic over the entire nasal passage. This action may be accomplished by spraying or application with a cotton applicator stick. The user
6. Sensory distribution of’ the nasal passage. Multiple nerves must be anesthetized to achieve total topical anesthesia. The lateral wall is innervated primarily by the (A) anterior ethmoid, (B) infraorbital, (C) anterior superior alveolar, (D) olfactory, (E) maxillary and sphenopalatine ganglion, and (F) middle and inferior turbinates. (Reproduced with permission from Fundamentals of Tracheal Intubation by James T. Roberts, published by Grune and Stratton, New York, 1983.)
7. Sensory innervation of the nasal septum: (A) anterior ethmoid, (B) infraorbital, (C) olfactory, (D) nasopalatine, and (E) nasopharynx (glossopharyngeal). (Repro duced with permission from Fundamentals of Tracheae/ Intubation by James T. Roberts, published by Grune and Stratton, New York, 1983.) Figure
Figure
68
J. Clin. Anesth., vol. 3, January/February
1991
Figure 8. Large cotton swabs are not commercially available but can be made from a cotton swab and the center of a Topper gauze pad.
Using the flexible fiber--optic laqngoscope: Roberts
and vallecula receive sensory innervation from the superior laryngeal nerves (Figure 9). These nerves are easily blocked by any of three approaches: percutaneously, just anterior to the superior horn of the thyroid cartilage, anteriorly, through the notch of the thyroid cartilage; or intraorally, in the piriform recess. A special needle with a 45-degree bend facilitates intraoral injection. The laryngoscopist should avoid injecting the carotid artery, since as little as 1 ml of 1% lidocaine can increase the arterial lidocaine concentration above 5 pg/ml and induce a grand ma1 seizure. The sensory mucosa supplied by the superior laryngeal nerves also can be anesthetized by simply spraying the oral mucosa with 4% lidocaine. Bilateral recurrent laryngeal nerves innervate the trachea (Figure 10). Blocking these nerves, or inadvertently cutting both nerves during thyroid surgery, results in obstruction of the airway by unopposed activity of the motor division of the superior laryngeal nerve. The superior laryngeal nerve innervates only one muscle, the cricothyroid, which is a tensor of the cords (Figure IO). All other intrinsic muscles of the larynx are supplied by the recurrent laryngeal nerves. The trachea may be topically anesthetized by spraying via the oral cavity, by a midline percutaneous injection, or by inhalation of a vaporized lidocaine solution. Each of these approaches produces satisfactory local anesthesia of the trachea.
Airway Physiology Reflex constriction of the bronchial smooth muscles is of concern whenever a foreign body is purposely or accidentally introduced into the trachea. The laryngoscopist should be prepared to administer a bronchodilator, an intravenous (IV) narcotic to suppress reflex coughing, or an agent such as atropine to suppress secretions.
Manikin Practice An excellent anatomical model suitable for either oral or nasal intubation training is available through the
lnterna I Laryngeal Nerve /
Recurrent Laryngeal Nerve
10. The superior laryngeal nerves supply motor innervation of the cricothyroid muscle by its external branch and sensory innervation by its internal branch. Note the recurrent laryngeal nerves lying posteriorly lateral to the trachea. These nerves supply sensory innervation to the trachea and motor innervation to all intrinsic muscles of the trachea except the cricothyroid.
Figure
distribution of the superior laryngeal nerves supplying the base of the tongue, epiglottis, vallecula, and piriform recesses down to the vocal cords. (Reproduced Figure
9. Sensory
with permission from Fundamentals of Tracheal Intubation by James T. Roberts, published by Grune & Stratton, New York, 1983.)
J. Clin. Anesth., vol. 3, January/February
1991
69
Special Article
Olympus Corporation (Lake Success, NY). An acceptable routine for manikin practice is as follows. The adapter from an appropriate endotracheal tube is removed, and the lubricated fiberscope is threaded through the endotracheal tube. The adapter is too large to fit through the Olympus mouthpiece. The laryngoscopist positions himself or herself at the head of the patient and places one of the many available mouth bites between the teeth to protect the fiberscope. The fiberscope is inserted through the mouth bite, following the center of the tongue. The tip of the scope is flexed, then guided past the base of the tongue. The scope is inserted until the 10 cm white ring is adjacent to the upper lip, then the tip is straightened. The laryngoscopist should now begin looking through the scope to guide it to the laryngeal opening. When the laryngeal opening is immediately in front of the scope tip, the tip is guided into the trachea by bending it slightly downward, or posteriorly (FZgure 11). The center of the trachea is kept in the center of the field of view as the scope is advanced. The scope should be advanced until the carina is clearly in view. At this point, the handle of the fiberscope is turned 180 degrees and placed above the umbilicus (Figure 12). With the fiberscope still in place, the endotracheal tube is advanced over the scope, which now acts as a stylet. In a patient, the laryngoscopist may encounter resistance to advancing the endotracheal tube. This resistance is usually due to the Murphy tip of the endotracheal tube hanging up on the right arytenoid
Figure 12. After the fiberscope tip is inserted to the level of the carina, rotating the scope 180 degrees places the handle above the patient’s umbilicus and allows the natural curve of the endotracheal tube to match the natural curve of the oropharynx.
(corniculate) cartilage (Figure 13). To pass the tube beyond this point, the tube is withdrawn 1 cm or so, rotated exactly 90 degrees counterclockwise, and advanced again. The tube now will pass easily into the trachea. The tube should be positioned so that the 22 cm mark is at the upper teeth, then the fiberscope is withdrawn without moving the endotracheal tube. The mouth bite is removed, and the endotracheal tube adapter that was previously removed is inserted and connected to the anesthesia circuit. The cuff is inflated and positioned just distal to the vocal folds, then taped securely in place. Both oral and nasal approaches are repeated during the manikin practice becomes second until manipulation of the fiberscope nature.
Preparing
the Appropriate Equipment
Sterile Fiberscope. A common routine for sterilizing the fiberscope is to soak it in a glutaraldehyde solution for at least 10 minutes, then wash it with sterile water and store it in a sterile environment. Figure 11. Sagittal section of cadaver showing oropharynx and upper trachea. Arrow indicate the fiberscope path curving around the tongue and then angling posteriorly into the trachea. (Photo modified from one appearing in Emergency Airway Management by Michael Gorback, M.D., published by B.C. Decker, Philadelphia, 1990.) 70
J. Clin. Anesth., vol. 3, January/February
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Oxygen to the Scope. O2 is connected directly to the scope through the side port. Seven liters per minute has been ideal for directing secretions away, helping defog the lens, and oxygenating the patient.
Using the flexible Jibrr-optic la~yngoscofw:Robert>
Williams bite block (Anesthesia Associates, San Marcos, CA) surrounds the endotracheal tube.
A second light source should be available as a backup to a lamp that burns out at a critical moment. Dual light sources are available through Applied Fiberoptics (Southbridge, MA).
Backup Light Source.
Second Suction.
thesia machine,
In addition to the suction to the anesan oral suction is mandatory.
The pulse oximeter allows for the safe teaching of oral fiber-optic laryngoscopy by the thiopental sodium-succinylcholine method. With 5 minutes of preoxygenation and hyperventilation, the ASA physical status I and II patients who tend to desaturate are the obese patients. Obese patients are not, therefore, selected for routine fiber-optic intubation.
Pulse Oximeter.
When the author first began performing routine oral intubations by the fiber-optic method, he found increases in arterial blood pressure (BP) after intubation. Upon measuring the expired carbon dioxide (CO,) by capnometry, he discovered that arterial CO, tension (PaCO,) increased at an average rate of approximately 4 mmHg/min. With an initial value of 30 mmHg, 3 minutes of complete apnea gives a final value of 42 mmHg, hardly enough to explain the increase in BP. These BP increases were easily controlled by adding a volatile anesthetic immediately after paralysis with succinylcholine and before the intubation attempt. A paper record from the CO, analyzer allows accurate timing of the intubation process from last mask breath to first intubated breath.
Carbon Dioxide Analyzer.
13. Since the fiberscope occupies the center of the laryngeal opening, advancement of the concentrically placed endotracheal tube is frequently interrupted by the right corniculate cartilage. This problem may be overcome by (1) withdrawing the endotracheal tube 1 cm to free it from the corniculate cartilage but not removing it from under the epiglottis, then (2) rotating the endotracheal tube 90 Figure
degrees counterclockwise past the vocal cords.
before (3) advancing the tube tip
Dinamap,
Several oral bite blocks are available. The Olympus bite block (Olympus Corporation, Lake Success, NY) is designed primarily to protect the fiberscope from the patient’s teeth. The Patil airway (Anesthesia Associates, San Marcos, CA) is a metal airway designed not only to protect the fiberscope from the teeth but also to guide the tip of the scope toward the laryngeal opening. The Ovassapian airway (The Kendall Company, Boston, MA) is a disposable plastic airway designed to protect the fiberscope, guide the tip of the fiberscope toward the laryngeal opening, and allow easy removal of the endotracheal tube. The Oral Bite Blocks.
EKG,
IV,
Drugs,
and
Anesthesia
Ma-
The author has grouped these items together because they are standard equipment for all intubation attempts. An automated BP apparatus frees one’s hands for the intubation process. The author has no specific drug preference suggestions. A variety of sedatives and narcotics are satisfactory, and the author leaves the nuances of drug interaction to be argued by others. chine.
Accessories. Teaching scopes that attach to the head of the fiberscope are available to allow the
Teaching
.J. Clin. Anesth., vol. 3, January/February
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71
Figure 14. A teaching fiberbundle is easily attached to the eyepiece, allowing an additional person to view the
image through the fiberscope.
Figure 15. A video camera attachment allows simultaneous viewing and videotaping of fiber-optic laryngoscopy. The videotape provides legal proof of intubation.
attending physician to view the intubation and guide it if necessary (Figure 14). A video camera also may be attached to the fiberscope to permit video monitoring of the intubation and a permanent record to be made (Figure 15). To improve teaching of flexible fiber-optic laryngoscopy, it is possible to expose the larynx with a new monitoring laryngoscope that lifts the tongue. This also allows the attending physician to observe and comment on the resident’s manipulations of the tip of the flexible fiberscope (Figure 16).
Preparing the Patient A preoperative interview and physical examination help to answer three basic questions prior to selection of fiber-optic intubation for a patient. First, is the patient to be intubated orally or nasally? Second, is the patient to be asleep under general anesthesia or awake with sedation and regional anesthesia to the airway? Third, if the patient is to be operated on under general anesthesia, is it reasonable to use muscle relaxants? Fiber-optic intubations are commonly done under all of the above conditions.
For teaching purposes, the nasal approach has been traditional. While there are definite advantages to this approach, the author has chosen to teach flexible fiber optics by the oral route for the following reason: since the oral approach is more difficult, once his residents learn to intubate by this method, nasal intubations are effortless. This finding is borne out by resident learning curves. One may consider using the endotracheal tube as Oral or Nasal Intubation?
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Figure 16. The Roberts adjustable, monitoring, and recording (AMR) laryngoscope has a pivoting handle, a blade that may be lengthened or shortened while in the mouth, a coherent fiber-optic bundle for imaging, and a noncoherent fiber-optic bundle for light transmission. By adding a video camera, the attending physician can view as well as videotape exactly where the laryngoscopist places the endotracheal tube.
a guide to advancing the fiberscope through the nose. There are advantages and disadvantages to this method. One advantage is that prior insertion of the endotracheal tube guides the fiberscope to the glottic opening. Disadvantages include greater duration of patient discomfort during awake intubations, since the endotracheal tube remains in the nasal passage while the laryngoscopist searches for the glottic opening with the fiberscope. Preinsertion of the endotracheal tube increases the chance of inducing bleeding and thus the chance of obstructing the laryngoscopist’s view. There is also a greater chance of inhibiting the passage of the fiberscope through the endotracheal tube once the tube is bent into position in the nasal passage. If it is necessary to move the fiberscope back and forth inside the endotracheal tube to effect passage, there is a greater chance of smearing some of the lubricant on the lens tip and obstructing one’s view. If the fiberscope is initially passed into the trachea, the endotracheal tube is introduced over the fiberscope, and discomfort to an awake patient is only momentary until the thiopental sodium takes effect. Another consideration is whether the patient should be awake or asleep. Intubation of an awake patient has the advantage that the patient is breathing spontaneously and is comfortable with proper topical anesthesia and/or nerve blocks and sedation. (Topical anesthesia and nerve blocks are dis-
Awake or Asleep?
Using the /lexible fiber-@tic
cussed under anatomy.) The awake intubation legitimately conjures up fear in most patients, so the physician must use his or her own judgment in deciding whether to use it. Awake intubation enables orthopedic patients to help situate themselves in difficult positions, such as the knee-chest position with the Tarlov frame. The anesthetized patient may be intubated while breathing spontaneously or while paralyzed. Spontaneous ventilation is helpful but requires a longer induction time prior to intubation.
By learning to use the thiopental sodium-succinylcholine oral fiber-optic tube, one can easily and safely use the flexible fiberscope without delaying a busy operating room schedule. Paralyzed muscles of the mandible and larynx relax their tone and tend to collapse inward. It is mandatory to have
Relaxation.
another person closely observing and recording the monitoring values while the laryngoscopist’s attention is focused on the eyepiece. This
person also may help by lifting the patient’s mandible, although this action is easily accomplished by the laryngoscopist. Reflex cord closure often occurs under general anesthesia as the fiberscope bundle approaches the laryngeal opening. Once the fiberscope induces reflex cord closure, a judicious amount of succinylcholine (20 mg) should be administered. This action will relax the laryngeal muscles and allow the fiberscope to pass through the cords and into the trachea.
Eight Potential Problems A problem is defined as a source of perplexity, distress, or vexation. Eight problems are discussed here and listed in Table 1. Perhaps the most common prob-
Table
1.
lem in using the flexible fiber-optic laryngoscope is fogging of the lens caused by the warm, humid air in the oral cavity condensing on the cooler fiberscope. This fogging is prevented by inserting the fiberscope tip into warm sterile saline to warm the lens prior to insertion in the patient’s mouth. Sterile defogging solution also may be applied to the distal lens. The author’s method is to direct 100% 0, through the scope channel at a rate of 7 L/min. The dry gas nicely dehumidifies the lens. Another problem is the presence of blood secondary to oral trauma or because of preexisting blood in the nasal passages, possibly from the laryngoscopist’s trying a blind nasal intubation before attempting it with the fiberscope. If blood blocks the field of view, the fiberscope must be removed and cleaned. If blood is present but not on the lens, a separate suction can be used to remove it (suction should not occur through the fiberscope). Suctioning through the fiberscope brings blood to the lens. A third and more common problem occurs when a patient’s secretions obstruct the view through the fiberscope. Secretions are removed by suctioning the oral cavity before inserting the fiberscope, pretreating with an anticholinergic, and/or directing them away with 0, channeled through the fiberscope. In the author’s experience, the last method is most useful. Another indication of trouble is when one sees only pink through the fiberscope. When this situation occurs, the liberscope should be c ecked to see that it follows the midline of the tongu t exactly. The fiberscope often tracks along the side of the tongue into the piriform recess. The fiberscope also should be fully extended. When it is not, the fiberbundle may be torqued. When torquing occurs, orientation through the scope is distorted, since the mark seen at 12 o’clock remains at 12 o’clock in spite of the direc-
Summary of Eight Potential Problems and Their Solutions Problem
1. Lens fogs Blood blinds view Secretions blind view Unrecognized view Endotracheal tube cannot be advanced 6. Turbinates visible in oral approach 7. Instructor cannot see 8. Black dots appear in field of view 2. 3. 4. 5.
lryyngosco~e: Roberts
Solution
Blow oxygen across lens, warm lens, use antifog solution Clean lens again Blow secretions away with oxygen Withdraw scope Back up 1 cm, Rotate tube counterclockwise, and try again Bend tip of scope in opposite direction. Add teaching or video attachment Coherent fibers are broken and need to be replaced.
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tion in which the tip of the fiberscope is pointing. Videotapes of fiber-optic intubations have shown the tip of the fiberscope to be moving laterally when the laryngoscopist was certain the tip was moving in a vertical plane. If these two maneuvers do not correct the situation, the fiberscope should be withdrawn until the obstacle can be identified. A fifth problem occurs very frequently. Once the fiberscope is inserted to the carina, the endotracheal tube advances only so far and then stops. In most cases, the center of the laryngeal opening is occupied by the fiberbundle, causing the tip of the endotracheal tube to be forced laterally and to catch on the patient’s right arytenoid (corniculate and cuneiform) cartilages. The author has confirmed this occurrence with videotapes. When this situation occurs, the endotracheal tube should be withdrawn 1 cm, rotated 90 degrees counterclockwise, and readvanced (Figure 12). This maneuver can be repeated as necessary. If the patient’s head is fixed in a flexed position, this maneuver may not work, since the endotracheal tube will approach the larynx from a difficult angle. The laryngoscopist can try using a guidable endotracheal tube over the fiberscope to direct the tip of the tube into the laryngeal opening. A sixth problem occurs when turbinates are in full view during an attempt at oral intubation. The solution to this problem is simple: since the fiberscope tip is bent acutely in the wrong direction, the bend of the tip should be reversed. A seventh problem occurs when the instructor teaching the fiber-optic technique cannot see what the student sees. A teaching adapter attached to the fiberscope (Figure 14) allows a second person to see the view through the fiberscope. A video adapter (Figure 15) not only allows additional individuals to view the process but also permits videotaping for future instruction or record keeping. A final problem is irreversible. Black dots in the field of view indicate fractured fibers in the coherent optical bundle. When these dots excessively interfere with the optics, the fiberbundle must be replaced.
Eighteen Common Mistakes A mistake is a wrong action or inaction resulting from faulty judgment, inadequate knowledge, or inattention. The first 13 mistakes result from a lack of correct action (acts of omission), while the last 5 are active mistakes (acts of commission). 1. The fiberscope is not kept extended during laryngoscopy. This situation commonly results in torquing of the fiberbundle and loss of orientation.
2. Oxygen is not directed through the fiberscope. Oxygen moves secretions away, defogs the lens, and oxygenates the patient. 3. The patient’s mouth is not suctioned prior to insertion of the fiberscope. Secretions commonly are stimulated as a result of succinylcholine. 4. The fiberscope is inadequately lubricated, preventing the endotracheal tube from sliding smoothly over the scope. .5. If flexible fiber-optic intubation is attempted orally without a bite block, pressure from the teeth may destroy the coherent optical bundle. 6. A second person is not on hand to monitor the patient and his or her vital signs while the laryngoscopist attempts the fiber-optic intubation. 7. The patient is inadequately prepared because of a lack of sedation or inadequate regional anesthesia to the airway. 8. ‘l‘he laryngoscopist has performed an insufficient number of routine cases. A minimum of 20 oral intubations is necessary to quicken oral intubation technique to less than 1 minute. 9. A sterile instrument is not ready for use. 10. Skill with the fiberscope is not maintained once it has been mastered. 11. The light source is not activated prior to paralyzing the patient. The most common time for a bulb to fail is with the initial power surge. If the bulb fails after the patient has been paralyzed, the fiber-optic technique should be abandoned and standard laryngoscopy performed. 12. A manikin is not used for practice prior to using the scope on patients. 13. ‘l‘he fiberscope is not focused prior to anesthetizing the patient, thus wasting critical time. 14. Movement of the fiberscope is too rapid and too extensive. 15. ‘I‘he fiberscope is inserted past the laryngeal opening. 16. The fiberscope is forcefully advanced against resistance. 17. The endotracheal tube is forcefully advanced against resistance. 18. The distal fiberbundle is torqued instead of being rotated by the handle of the fiberscope.
‘l’he availability of superb fiber-optic instruments has opened a door in patient care. It is now the anesthesiologist’s responsibility to master and maintain the skill of flexible fiber-optic laryngoscopy by repeatedly using the instrument for routine intubations. Then, when the physician is presented with a difficult airwav patient, he or she is prepared.
UGng
Further Reading 1. Roberts JT: Fundamentals of Tracheal Intubation. New York: Grune & Stratton, 1983. 2. Ovassapian A, Yelich SJ, Dykes MHM, Brunner EE: Fiberoptic nasotracheal intubation: incidence and causes of failure. Anesth Analg 1983;62:692-5. 3. Rogers SN, Benumof JF: New and easy techniques for fiberoptic endoscopy-aided tracheal intubation. Anesthesiology 1983;59:569-72.
the flexible fiber-optic
lq’ngoscope:
Roberts
4. Patil V, Stehling L, Zauder H: Fiberoptic Endosco$y in Anesthesia. Chicago: Year Book Medical Publishers, 1983. 5. Wangler MA, Weaver JM: A method to facilitate fiberoptic laryngoscopy. Anesthesiology 1984;61: 111. 6. Patil V, Stehhng LC, Zauder HL, Koch JP: Mechanical aids for fiberoptic endoscopy. Anesthesiology 1982;57:6970. 7. Baraka A: Transtracheal jet ventilation during fiberoptic intubation under general anesthesia. Anesth Analg 1986;65:1091-2.
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