Techniques in Airway Management

Educational Objectives

The goal of this program is to improve the management of airway assessment and maintenance, and to improve the preparation and performance of pediatric airway surgical procedures. After hearing and assimilating this program, the clinician will be better able to:

1.   Establish airway assessment protocols based on statistical evidence of expected difficulties.

2.   Evaluate newer technologies designed to improve airway assessment and management.

3.   Choose and organize tools for use in airway management procedures.

4.   Establish improved airway management procedural protocols involving the use of newer technologies.

5.   Perform safe and effective airway management techniques on children undergoing airway surgical procedures.

Acknowledgments

Dr. Walls was recorded at High Risk Emergency Medicine, held May 21-23, 2009, in San Francisco, CA, and sponsored by the Emergency Department at San Francisco General Hospital and the Department of Emergency Medicine, University of California, San Francisco, School of Medicine. Dr. Cable was recorded at UCSF Otolaryngology Update 2009, held in San Francisco, CA, and sponsored by the University of California, San Francisco, School of Medicine. The Audio-Digest Foun­dation thanks the speakers and the sponsors for their cooperation in the production of this program.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the plan­ning committee to disclose relevant financial relationships within the past 12 months that might create any personal con­flicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. The following has been disclosed: Dr Walls is a consultant on patent litigation for Black, Lowe and Graham, PLLC, acting for Varathon, Inc. Dr. Cable and the planning committee re­ported nothing to disclose.

Airway Management: Five Devices You Must Know About

Ron M. Walls, MD, Professor of Medicine, Harvard Medical School, and Chairman, Department of Emergency Medicine, Brigham and Women’s Hospital, Boston, MA

Prevalence of airway management difficulties: difficult intubations uncommon; relative ease of airway manage­ment causes slow technologic progress for management of difficult airways; moderately difficult intubations usu­ally manageable

Difficult direct laryngoscopy

Measurement of difficulty: Cormack-Lehane (CL) scoring system based on views obtained using direct laryngo­scope; views translatable into grades (1-4); grade occurrence frequencies have been evaluated

CL grading system: grade 1  —  perfect view of glottis; grade 2  —  partial view of glottis, arytenoids, some (vocal) cords; grade 3  —  view of epiglottis, no glottis; grade 4  —  no view of epiglottis

General intubation success rates based on CL scores: grades 1 and 2 (combined)  —  success rate high; grade 3  —  success rate low; grade 4  —  success rate zero

Prevalence of poor CL views in operating room (OR): combined CL grades 3 and 4 (resulting in <20% intubation success rate) observed in <5% of cases; grade 4 (predictor of impossible intubation) occurs in £1% of cases (»1 in 600 patients); “can’t intubate/can’t ventilate” (CICV) situation (with preintubation assessment for difficult air­way and patient selection) occurs 1 in 10,000 patients (data predates advent of laryngeal mask airway [LMA] and other extraglottic airways)

Prevalence in emergency department (ED): based on experience in OR, chance of unexpected CICV situation (with preintubation assessment for difficult airway) extremely low; extraglottic devices expected to further decrease failure rate; ED (unselected population) difficult airway rate higher than observed in OR (selected) population; with adoption of newer technologies, ED rates should approach OR rates

Difficult bag-mask ventilation (OR data): occurs in 3% to 5% of patients; impossible bag-mask ventilation occurs in 1 in 600 cases; hard-to-ventilate patients easily identifiable; difficult ventilation-intubation correlation  —diffi­cult bag-mask ventilation results in 4 times higher rate of difficult intubation, and 12 times higher rate of impos­sible intubation

New airway devices: not bag mask, not direct laryngoscope, not bougie; uncommonly used devices (eg, videolaryn­goscope) often considered “toys” to be reserved for difficult airways; speaker opines these devices should not be re­served for difficult or failed airways (exception being cricothyrotomy); modern treatment methodologies require adoption of newer (better) technologies; airway management paradigm shifting; speaker asserts that standard use of videolaryngoscopy in airway management increasing; learning curve shorter for videolaryngoscopy than for direct laryngoscopy

Videolaryngoscopy vs direct laryngoscopy: in speaker’s experience, once physician has done 3 to 5 intubations with videolaryngoscope, he or she abandons direct laryngoscopy; in literature, term “difficult intubation” histori­cally refers to direct laryngoscopy and views obtained using direct laryngoscope; incidence of poor visualization with videolaryngoscope so rare that prediction of patient attributes that correlate with poor visualization may be impossible; geometry of visualization in laryngoscopy  —  direct laryngoscopy requires manipulation of oropharyn­geal tissue to attain direct linear view; videolaryngoscopy does not require substantial manipulation to obtain ac­ceptable view of airway

Adoption of videolaryngoscopy: “standard of care” (SOC) defined as treatment protocol provided by reasonable person(s) performing similar tasks; speaker asserts that when 50% of practitioners perform task in same way, it be­comes SOC

Glidescope videolaryngoscope: specifications  —  1.7-cm (0.68-in) insertion profile vs >3-cm (1.2-in) profile for direct laryngoscope; high intubation success rate; full video observation makes it good teaching tool; handheld; uses blade similar to Macintosh laryngoscope blade (size 3); distal one-third of blade extended and inflected up­ward at 60°; attachment on wide-angle view of vocal cords; Glidescope —  true midline approach; minimal tongue manipulation required

Comparative study: Glidescope effectiveness assessed in study of 133 anesthesiology practitioners or students, in­volving 728 GlideScope laryngoscopies (133 also had direct laryngoscopy); results  —  Glidescope views (matched) always as good as or better than direct laryngoscopy; 35 grade 3 or grade 4 views with direct laryngos­copy; two-thirds of these (poor) views had lower than grade 3 (ie, better) views with the Glidescope; failure with Glidescope 3.6%; possible cause limited training; >50% of Glidescope failures had grade 1 views

Second comparative study: routine airway study involving 400 patients; all had direct laryngoscopy and videolar­yngoscopy; results with direct laryngoscopy    —  grade 1, 67%; grade 2, 26% ; grade 3, 6%; grade 4, 0.5%; results with Glidescope videolaryngoscopy  —  grade 1 89.5%; grade 2, 10.5%; grade 3, 0%; grade 4, 0%; overall success rate (£3 attempts) 99.9%; time requirement <40 sec (mean time 21 sec)

McGrath videolaryngoscope: video camera recessed in underside of sharply flexed tip; separate viewing system; one piece; results comparable to those with Glidescope; new device (no large-study data available)

Storz video laryngoscope: uses standard Macintosh blade with fiberoptic system; video camera snaps into handle; conventional blade helpful because of familiarity, and makes maneuver to larynx straighter; easier to obtain grade-1 view and intubate than with Glidescope

Storz C-MAC video laryngoscope: one-piece screen; one cable; one-piece handle; fewer parts and accessories (ease of simplicity); complementary metal oxide semiconductor (CMOS) video processing; non-fiberoptic; auto-heating lens eliminates fog; same price as Glidescope for basic system (»$9000)

Storz videolaryngoscope study: 54 patients tested with Storz and direct laryngoscopy by expert anesthesiologist; force on maxillary incisors 7 times greater with videolaryngoscopy than with direct laryngoscopy; grade 3 and 4 (combined) views 17% with direct laryngoscopy vs 0% with videolaryngoscopy

Pentax Airway Scope (AWS): videoscope; lenticle (small lens) aiming device; endotracheal tube (ET) preloaded in channel on blade; problem with lenticle not getting to cords; lenticle may be used to position bougie; ET may be placed over bougie; better than direct laryngoscopy

Conclusion: all videolaryngoscopes evaluated better than direct laryngoscope

Fiberoptic stylets: different technologic approach, ie, stylet visualizes cords; 4 main stylets being evaluated; AirRfl; Clarus Shikani Optical Stylet (SOS); Clarus Levitan stylet (uses direct laryngoscopy); Storz Bonfils stylet

General approach to use of stylet: insert stylet into ET; insert (both) to visualize cords; properly position tube past cords

Clarus Levitan stylet: designed to augment direct laryngoscopy; ET loaded onto stylet; direct laryngoscopy per­formed; bright light on stylet then used to insert tube; if difficulty encountered in placing tube, use eyepiece to vi­sualize end of tube

Clarus SOS: malleable; midline scope; inexpensive (»$2300); videoadaptable; highly portable; mannequin-model study  —SOS requires less manipulation of cervical spine than direct laryngoscope; longer intubation time than direct laryngoscopy; faster than direct laryngoscopy with bougie; 3-step intubation approach  —  insert partially; visualize; complete insertion

AirRfl Stylet: possibly difficult to clean; squeeze lever-flex-tip dynamic control; durability may be issue

Storz Bonfils Stylet: portable light source; not malleable; eyepiece; ET mount; not midline device; unique shape; retromolar insertion; useful for trauma (no open-mouth requirement)

Closing comments: videolaryngoscopy superior to direct laryngoscopy; shorter learning curve; better glottic views; equal or better by all measures (with possible exception of time; 35 sec for videolaryngoscopy vs 26 seconds for di­rect); direct laryngoscopy introduced in 1940s; exploration of new technology beneficial; once adopted, use new technology for all cases; direct laryngoscopy potentially dangerous; achievable proficiency with videolaryngoscopy superior to that of direct laryngoscopy

Questions and answers: bougie  —  cannot be used with Glidescope; used with Pentax Airway scope by sliding bou­gie through mounted tube, then manipulating bougie through cords; trauma patients  —  videolaryngoscope easily and quickly removed, wiped clean of blood or vomit, and reinserted; comparable to direct laryngoscope

Evaluation of the Pediatric Airway

Benjamin Cable, MD, Associate Professor of Surgery, Uniformed Services University of the Health Sciences, Honolulu, HI

Airway cart: 2 standard options for storage and organization of airway instruments are trays and carts; cart superior choice; challenge  —  flimsy metal carts (made for anesthesia drugs); wrong size and layout; suggestion  —  talk to “tool person”; stainless steel carts available at standard retail outlets; good base cart  —  noncorroding, nonmagnetic (test with permanent magnet), with high nickel-content stainless steel; shelf sizes fit tools well; line shelves  —purchase multidensity foam (eg, Pick and Pluck; available from many manufacturers; similar to foam used in cam­era case); laser-cut cubes removable; benefits  —  instruments maintained in specific locations; durable; inexpensive; helps to organize small multipart instruments; no parts misplaced, lost, or forgotten

Three approaches to pediatric anesthesia: bronchoscope-assisted laryngoscopy; apneic anesthesia; spontaneous anesthesia

Bronchoscope-assisted laryngoscopy: involves intubating child with metal bronchoscope and introducing cameras, tools, and instruments; drawbacks  —  requires positive-pressure ventilation (not normal for child); may lead to failure to detect laryngomalacia or external compression on trachea; bronchoscope confines motion

Apneic technique: anesthesiologist induces significant respiratory depression; physician makes quick observations (with constant pulse oximetry monitoring), then switches back to mask; risky procedure

Spontaneous anesthesia: most common technique; requires skilled anesthesiologist to administer intravenous pro­pofol while patient breathing spontaneously; subsequent observation and exploration reveals features not seen with positive-pressure techniques; standard procedure  —  apply lidocaine to vocal cords (to prevent laryngospasm and bronchospasm) using intubating laryngoscope (speaker prefers Parsons videolaryngoscope); ventilate with mask for 2 min; establish and maintain airway conduit using jet cannula; may bypass jet and introduce oxygen via 3-mm connector to ET tube (helpful for high oxygen requirements); optional use of sevoflurane (use with caution); use of Lintome videolaryngoscope  —  provides panoramic view; excellent linear view, plus bidirectional lateral freedom for visualization and manipulation

Recommendations for management of difficult airways

Seldinger technique: problem  —  when intubating small children, even with good videolaryngoscope, view impaired by ET; solution  —  obtain endoscope used in sinus surgery and insert into ET; advance endoscope and ET into tra­chea without loss of visualization; withdraw endoscope; ideal for epiglottitis

Videolaryngoscope: use now common; allows visualization of posterior airway with light and camera; ideal for pa­tients with microgenia or sleep apnea; learning curve  must watch monitor instead of patient; benefit  —  view of airway superior to that seen with direct laryngoscope; speaker prefers Glidescope; highly portable; intubations performed with stylet (large curve required); good tool for resident training programs

Specialized instruments for airway cart

Vocal cord spreader: looks like surgical instrument for sinuses; equipped with paddles for gently spreading vocal cords; affords better exploration and visualization of larynx; useful for  —  subglottic stenosis; emergency explora­tions; procedures for congenital web; removal of masses from brachial cleft sinus or piriform fossa

Fiberoptic laser: differs from typical CO₂  laser in that it can be introduced farther down airway; problem with exist­ing fiberoptic lasers  —  limited motion; new Storz design  —  laser tip allows motion and angulation; instrument has smoke evacuation ports (field of view always clear)

Suggested Reading

Cattano D et al: Risk factors in the assessment of the difficult airway: an Italian survey of 1956 patients. Anesth Analg 99:1774, 2004; Mateer J et al: Continuous pulse oximetry during emergency endotracheal intubation. Ann Emerg Med, 22:675,1993; Nayyar P et al: Nonoperating room emergency airway management and endotracheal intubation practices: a survey of anesthesiology program directors. Anesth Analg 85:62, 1997; Maxwell B et al: Management of the Difficult and Failed Airway. JAMA ; 300:850, 2008; Doyle D et al: Upper airway diseases and airway management: a synopsis. Anesthesiol Clin North America, 20: 767, 2002; Sun D et al: The GlideScope Video Laryngoscope: randomized clinical trial in 200 pa­tients. Br J of Anaesth  94:381, 2005; Ovassapian A: Manual of Emergency Airway Management. JAMA 302:800 2009; Har­ries M: Laryngeal framework surgery (thyroplasty). J Laryngol Otol 111:103, 1997; Boyd S: Changing indications for tracheostomy in maxillofacial trauma. J Oral and Maxillofac Surgery 54:295, 1996.