1Associate Professor of Anesthesia and Intensive Care, Chairman of the Austrian Working Group for Airway Management and Director of the Department of Anesthesia and Intensive Care, Empress Elisabeth Hospital of the City of Vienna, Vienna, Austria.
Address correspondence and comments to Ernst Zadrobilek.
December 31, 2007.
Published: December 31, 2007.
The correct citation of this editorial view is:
Videolaryngoscopy: should we change our current practice of
laryngoscopy and tracheal intubation? Internet Journal of Airway Management
Date accessed: month day, year.
Last updated: December 31, 2007.
In this and in the previous volume of the Internet Journal of Airway Management, members of the Austrian Working Group for Airway Management published their favorable experiences with the use of various video laryngoscopes (VLs) for orotracheal intubation in adult patients (16-18, 27); only patients presented for thyroid surgery were selected in order to recruit a sufficient number of patients with variable degrees of airway difficulties and conventional laryngeal views (evaluated using only gentle lifting force on the laryngoscope blades without applying external laryngeal manipulation).
VLs allow for the transmission of a video image to a monitor, enabling the operator to visualize anatomical structures of the laryngeal aperture not necessarily in the line-of-sight with conventional laryngoscopy (CL). The various models of the GlideScope Video Laryngoscope (GVL) are used with separate monitors; the McGrath Portable Video Laryngoscope (MVL) has a minituarized video screen mounted on the proximal end of the laryngoscope handle. The Airtraq Optical Laryngoscope (AOL) can be also used as VL with a dedicated, clip-on video camera system instead of the removable rubber coat of the view finder with viewing of laryngoscopy and the tracheal intubation process on a compatible medical monitor or on a suitable laptop computer (14).
The handling of VLs and optical laryngoscopes is similar to CL with the Macintosh laryngoscope and may be easily adopted by novice users. Because of primary problems with viewing the intubation process on a monitor or screen and difficulties in manipulating the tracheal tube (TT) through the laryngeal aperture into a midtracheal position, novice users should first receive formal hands-on training on a suitable airway model [favorably on the AirSim Multi (20)] and then instruction during the early series of performance on patients.
GlideScope Video Laryngoscopes
Laryngoscopy and orotracheal intubation with the use of variable models and systems of the GVL (including the Standard Adult GlideScope Video Laryngoscope, the Lo Pro Adult GlideScope Video Laryngoscope, and the battery-powered, portable GlideScope Ranger Video Laryngoscope System) and the Schroeder directional tracheal tube stylet (DS) was successful at the first attempt in 98 percent (869/884 patients) (16-18); only 15 patients required a second attempt for successful tracheal intubation. It should be noted, that these favorable results may not be obtained when GVL-assisted tracheal intubation is attempted by uninstructed or less experienced operators using these devices for routine and difficult airway (DA) management (6). The primary failures of GVL-assisted tracheal intubation were failed identification of laryngeal structures, malfunction of the DS, and failed TT advancement during oropharyngeal, laryngeal, or tracheal passage in 2, 2, and 11 patients, respectively.
In all GVL studies, the DS was used for adjusting the curvature of the TT as needed during the tracheal intubation process; the shape of the TT is an important part of tracheal intubation with GVLs, determining the sussess or failure. Using TTs with prebended malleable stylets, the 60-degree curvature recommended by the manufacturer must often be increased; inappropriate preshapening of the TT was the most frequent cause of difficulties with laryngeal TT passage in a study evaluating evaluating the GVL on an airway model simulating easy and difficult laryngoscopy (12).
The operators were very successful at visualizing laryngeal structures with the various GVL models despite the high incidence of difficult CL. Conventional laryngoscopic view grading (CLV) was performed using a standard Macintosh laryngoscope. The 5-grade modification of the original classification of laryngoscopic views by Cormack and Lehane was used for CLV (22): grade 1, visualization of the entire laryngeal aperture; grade 2, visualization of just the posterior portion of the laryngeal aperture; grade 3, visualization of only the arytenoids; grade 4, visualization of only the epiglottis; and grade 5, visualization of just the soft palate. Laryngeal views of grade 1 to 5 at CL were obtained in 287, 224, 172, 181, 20 patients, respectively; the GVL views (also obtained without external laryngeal manipulation) were always comparable or superior than those provided by CL. In 201 patients with difficult CL (grade 4 or 5), GVL laryngeal views of grade 1 to 3 were obtained in 97, 94, and 10 patients, respectively, with the worsest view of at least the arytenoids in only 5 percent.
The outstanding feature of all GVL models is that the camera systems are resistant to fogging (by warming-up the systems slightly above normal body temperature); frequent problems with fogging of the optical system usually enountered with rigid fiberoptic laryngoscopes (the Bullard or the Upsher laryngoscope) were not evident. Excessive secretions in the hypopharynx (also a major problem with the use of rigid fiberoptic laryngoscopes) may obscure the laryngeal view with GVLs but did not reduce the success rate of tracheal intubation as the video cameras are protected and remote from the tip of the blades.
McGrath Portable Video Laryngoscope
Laryngoscopy and orotracheal intubation using the MVL and the DS (performed by experienced GVL and DS users) was successful at the first attempt in 95 percent (76/80 patients) with laryngeal views of grade 1 in all of these patients (27); only 4 patients required second attempt for successful tracheal intubation despite the high incidence of difficult CL (grade 4 in 10 patients). The primary failures of MVL-assisted tracheal intubation were acute loss of battery power in one patient and failed TT advancement during laryngeal passage in 3 patients (partly due to the unfavorably modified DS with a locking mechanism used in this study).
The MVL is a battery-powered, portable VL with a miniaturized video screen mounted on the proximal end of the laryngoscope handle and a disposable laryngoscope blade (DLB) entirely covering the adjustable camera stick. The low profile of the DBL makes blade insertion easy and provides much space for oropharyngeal TT passage; unfortunately, the camera system of the MVL is not resistant to fogging.
Airtraq Optical Laryngoscope
Laryngoscopy and orotracheal intubation with the standard AOL (performed by instructed operators) was successful at the first attempt in 97 percent (207/214 patients) (14); only 7 patients required second attempt for successful tracheal intubation despite the high incidence of difficult CL (grade 4 and 5 in 32 and 2 patients, respectively). The primary failures of AOL-assisted tracheal intubation were failed identification of anatomical structures, failed TT advancement during laryngeal passage, and requirement of downsizing the TT for unimpeded and atraumatic laryngeal passage in one, 4, and 2 patients, respectively. It should be noted, that successful AOL-assisted tracheal intubation requires laryngeal views of the entire laryngeal aperture finally provided in all patients.
The standard AOL is a battery-powered, portable, and disposable device for orotracheal intubation, currently available in two sizes for adult patients. The AOL allows for the transmission of an adequate color video image to the view finder at the proximal end of the laryngoscope handle (by internal arrangements of optical components), usually providing the operator a panoramic view of the laryngeal aperture with adequate image quality when properly inserted. There were no problems with poor visibility due to fogging of the optical system (by warming-up the system slightly above normal body temperature within a short period of time) and the presence of secretions. However, the tube-guide channel on the right side of the AOL blade (to guide the TT into the correct position) may incorporate some problems with deflection and impingement of the TT on surounding laryngeal structures; a backward, upward, and to the left or right movement of the AOL blade regularly solved this problem. The relatively bulky AOL blade may impede blade insertion but it incorporates the TT already in the tube-guide channel, eliminating the need for additional space passing the TT through the oral cavity.
The reasonable costs of the AOL allows for this disposable device to be provided at multiple locations within the hospital (at all anesthesia working stations, positions at the intensive care unit, emergency admission areas, and normal wards) as backup for difficult CL and tracheal intubation situations. Hygienic reprocessing of reusable AM devices may be problematic, particularly in patients with transferable diseases. The routine use of the disposable AOL in this patient population may further reduce possible cross contamination associated with airway management devices (13).
Hygienic reprocessing of the former GVL models may be simplified with the recently released GVL (the GlideScope Cobalt Video Laryngoscope) with a video baton and dedicated DLBs, currently provided in two sizes for adults (24). The DLBs entirely cover the video baton and the handle of this new GVL eliminating time-consuming cleaning and disinfection; this means that the device is always ready for use in other patients. Because of the thickness and design of the DBLs, ease and performance of laryngoscopy and tracheal intubation may be located between those with the former standard and the more favorable lower-profile GVL (preliminary personal experiences on patients).
The Airway Scope (AWS) is a new battery-powered, portable VL with a miniaturized video screen mounted on the proximal end of the laryngoscope handle and a dedicated DLB (available in one size for adults) entirely covering the flexible camera unit (23). The DBL incorporates a tube-guide channel on the right side (similarly to the standard AOL) to guide the TT through the laryngeal aperture. There is currently only one clinical study evaluating the AWS on patients with apparently normal airway anatomy (3); as the camera unit of AWS is not resistant to fogging, there may be some problems with obscuring the view.
The manufacturer of the standard AOL recently released a modified AOL specifically designed for nasotracheal intubation, currently available in only one size for adults (25). The tube-guide channel at the right side of the standard AOL was removed and the remaining flange of the blade serves as guide for the nasally introduced TT. In addition, an AOL suitable for bronchial intubation with double-lumen tubes was simultaneously launched (26). Both new AOLs perform well on a suitable AM model (personal experiences); unfortunately, there are currently no studies available to support these experiences in clinical practice.
Critical Comments and Recommendations
CL and tracheal intubation may be difficult in up to 8.5 percent (21); problems with airway management (AM) may cause injuries (8, 9) and severe morbidity and mortality (19). Many of these adverse events are preventable, provided there are adequate equipment availability, familiarity with the devices and techniques, and formulated strategies for DA management (10). Multiple and prolonged conventional tracheal intubation attempts frequently lead to the development of progressive difficulties with face-mask ventilation; the maximum risk may then be represented by with the association of impossible ventilation and tracheal intubation. Therefore, the number of conventional tracheal intubation attempts (and the time required) should be limited.
Expert working groups developed guidelines and recommendations for the management of the (un)anticipated DA in order to assist the anesthesia community in decision-making and formulating departmental strategies, beginning with the landmark publication of the guidelines by the American Society of Anesthesiology task force (1) in 1993, followed by the Canadian recommendations (7) in 1998. For situations, where optimum positioning of the patient, appropriate selection of the type and size of the laryngoscope blade, and external laryngeal manipulation provide only a poor laryngeal view, early considerations either for choosing an alternative to CL, proceeding with a laryngeal mask airway, or awakening the patient (when possible) are strongly recommended (2, 7). The first prospectively evaluated and successful DA management algorithm (11) provided a limitation of CL to a maximum of two attempts.
For routine tracheal intubation in patients with apparently normal airway evaluation, CL will be still the method of choice unless difficulties with viewing the laryngeal aperture are encountered. Particularly in unanticipated difficult CL and tracheal intubation situations, alternative techniques are needed and adequate equipment should be immediately available to complete the procedure and solve the problem without failure and endangering patient safety in a timely fashion. Optimum preparation for CL and tracheal intubation should be already provided for the first attempt. Poor laryngeal views at this early stage of AM (indicating a difficult conventional tracheal intubation situation even for an experienced operator) should give rise to initiate rational decisions and strategies, for example, to use a VL for the second attempt as claimed by Cooper (4).
Although flexible bronchoscopes (FBs) are essential in DA management, they require different skills and an experienced assistance and do not prove to be the ultimative solution to the management of a DA (4, 5); flexible bronchoscopy-assisted (FBA) tracheal intubation is feasable in a variety of DA situations but may be difficult or impossible in others. A prerequisite for successul performance of FBA tracheal intubation in DA situations is continued training in routine practice (11); unfortunately, FBs require special maintenance and are easily damaged. Furthermore, TT advancement over a tracheally placed FB is finally a blind procedure; in this setting, the FB only functions analogically to a TT introducer. VLs and optical laryngoscopes (when properly inserted, probably with far less lifting fting force than applied with CL) usually provide an unobstructed view of laryngeal structures and offer visual control of TT advancement through the laryngeal aperture into the trachea. Rigid fiberoptic laryngoscopes (such as the Bullard or the Upsher laryngoscope) were successfully used by a few AM enthusiasts in DA management (4, 5), but these devices did not really survive the market (particularly due to less interests of promoting them by the manufacturers).
It should be noted that with VLs, the initial oropharyngeal passage of the styletted TT is usually blind (by diverting the visual attention of the operator from the patient to the monitor or screen) until the tip of the TT comes into view; pharyngeal injuries may be the result of uncontrolled TT advancement as observed with GVL-assisted orotracheal intubation (15). The styletted TT (especially with a conventional malleable stylet in place or the rigid stylet provided by the manufacturer of the GVLs) should be introduced and advanced through the oral cavity with special caution.
GVLs and AOLs are easy to use and the obscured view by soft tissues frequently seen during FBA tracheal intubation is usually controlled by the operator due to the blade designs; as a special feature, they are resistant to fogging. The favorable results with these devices should be taken into consideration when planning future equipment availability and updating formulated departmental strategies for (un)anticipated difficult CL and tracheal intubation situations. Videolaryngoscopy may significantly change our current practice of laryngoscopy and tracheal intubation. The extremly high acquisition costs of the various models and systems of the GVL may protract their availability in clinical practice; economic considerations will probably favor the disposable AOL models in the future. Transparent comparisons between these devices are needed; these studies should include acquisition and maintenance costs (including the expense of hygienic reprocessing of the former GVL models), the costs of the DBLs neessary for the newest GVL model, and the durability of the different GVL models (considering the replacement costs).
It is time to change our current practice of laryngoscopy and tracheal intubation. We should not reserve valuable techniques only for patients with DAs; these techniques should be also offered to all of our patients. They may probably povide our patients with the best medical care.
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