New tools for Difficult Airway Management
Technological innovations have played a vital role in development of specialty of anesthesia. From the time Robert Macintosh introduced the direct laryngoscope for endotracheal intubation, it has remained the gold standard, save for modifications in blade shape, size, or changes in handle and light source. It continues to be the integral part of training and practice of anesthesiology.
However, as every anesthesiologist will agree, there are many patients who present challenges to our ability to manage the airway with the direct laryngoscopy, however much experienced or experts we are. These patients have anticipated or unanticipated difficulty in laryngoscopy or intubation, with or without difficulty in mask ventilation. The underlying mechanisms leading to these clinical situations include inability to align the oral pharyngeal and laryngeal axes, restricted mobility of soft tissue, restricted mouth opening and infra glottic pathology. We always wished that we had equipment with which there would be hardly any difficult or failure to intubate situation.
Advent of video laryngoscopes (VL) represents a new milestone in airway management. VL is a modification of the laryngoscope where a video chip or camera is placed in the blade, in close proximity to the glottic opening the view of which is displayed in a monitor. Broadly, a VL enables the laryngoscopist to have a direct vision of the glottic opening and helps in guiding the endotracheal tube.
Features of an ideal Video laryngoscope
- Easy to assemble with minimal connections
- Fast access
- Different types and sizes of blades
- Easy to intubate
- Clear and bright images
- Record and store images and video
- Long battery life
- Easily sterilizable
- Provision for oxygen administration,suction
- Sharp learning curve
The devices and design
By design, a VL provides a view of the glottic opening on a dedicated monitor or screen which is either a part of the VL itself or attached to the VL, from a video chip or video camera placed on the tip of the blade.
The differences between the different VL are based on various functional and design aspects:a)position of the video chip or video camera b)type and shape of the blade c)presence of a channel d)position, size and brightness of the screen d)other unique features.
Different technologies used in development of VL include high resolution digital camera, direct couple interface(DCI),CMOS active pixel sensor, miniaturization of monitors, camera and anti fogging.
One of the earliest video laryngoscopes was Weiss video laryngoscope, a simple modification of a conventional Macintosh type laryngoscope made of plastic connected by a video cable to a monitor screen
A different but related group of intubation aids is video stylets like Bonfils, Shikani stylet etc
Commonly available VL
- Airway scope
- C MAC
- Glide scope
- King vision
- Kipler intubation systems
- Mc Grath video laryngoscope
Air Traq Optical Laryngoscope
It is a self- contained, lightweight, portable VL with a magnifying wide angle viewing mirror, LED light source and a tracheal tube guide channel. Airtraq is meant to be a single use device.
Airtraq is available in different sizes from neonates to adults and for oral and nasal intubation. It is become popular because of the simplicity of the design, portability and low cost.
The different sizes are color coded.
C-MAC Berci Kaplan Video Laryngoscope is an improvement over Karl Storz DCI video laryngoscope. Has detachable electronic module and a CMOIS chip which prevents fogging. Has size 2,3 and 4 Macintosh blades and a specially angulated D blade. Can be used as direct laryngoscope also. Insertion in midline or at the angle of the mouth. C MAC monitor is common interface for VL, Bonfills and intubation fiberscope
GlideScope(GS) was the first commercially available video laryngoscope. It comes with a blade with steep angulation of 60 degrees in the middle, where it houses a CMOIS APS digital camera. The camera is protected from contamination from patients blood or secretion. Also, there is a lens heating mechanism to prevent fogging. The monitor provides a wide viewing angle of 50degrees.A special stylet, Verathon stylet, facilitates intubation with glide scope. Blades are available in different sizes from preterm infant to morbidly obese patients.
Incorporation of newer technological innovations led to the development of different designs for wide range of airway management situations. These include
- GlideScope ranger, single use for military and air ambulance purposes
- GlideScope titanium with titanium thin blades with 4 different blade designs including Macintosh type ones.
- Glidescope AVL
- (Advanced Video laryngoscopy) and GVL
- Glidescope cobalt
King Vision video laryngoscope
It’s one of the earliest VL to be introduced. Has the monitor mounted on the handle. The blades are disposable and come in two designs; standard blades and the channeled blades. The former requires stylet to intubate.
McGrath Series 5 videolaryngoscope
It has an angulated disposable acrylic blade,requiring the endotracheal tube to be pre-curved with a stylet prior to insertion in midline.
It has the camera and light source at the tip of the camera Stick into which a disposable blade can be fitted and screen attached to the handle.
- Can be used both in adults and children.
- Portable and lightweight
In a study of comparison with C-MAC, it was found that McGrath had associated with more number of grade I laryngoscopic views but the intubation time was prolonged.
Pentax AW airway scope
- It is a channeled indirect fiberoptic VL
- No neck extension required
- Has a disposable P blade which has a channel for endotracheal tube and suction channel
- Multi positional monitor
- Target tracking system
- Portable and water resistant
Advantages, indications and limitations
Advantages of VL
- Clear and sharp image of laryngeal inlet with wider angle of view compared to direct laryngoscope
- Less displacement of tissues
- Reduced movement of cervical spine
- Less traumatic
- Ability to pass the endotracheal tube or boogie under vision
- Better external laryngeal manipulation under direct vision
- Recording of images and video
- Teaching and assessment of effectiveness of training
- Routine laryngoscopy as alternate to direct laryngoscope
- Anticipated difficult airway
- Unanticipated difficult intubation
- Failed intubation with other device
- Preoperative evaluation of airway
- Diagnostic laryngoscopy
- Preoperative intubation
- To aid fiberoptic intubation
- Teaching and training of laryngoscopy and intubation
Role in different clinical scenarios
- Routine airway management
- Video laryngoscopes can be used in all the patients where routinely direct laryngoscope is used. This helps in gaining the required skill which becomes useful when a difficult airway is encountered.
- As a tool to teach and impart training in laryngoscopy and intubation
- Difficult airway management
Difficult airway is not a single entity but a common terminology for various abnormalities of the airway which affect different aspects of management; mask ventilation, intubation and oxygenation.
A VL is useful in following situations in difficult airway management
- Assessment of the airway during preoperative evaluation, under topical or local anesthesia
- Assessment of airway after induction of anesthesia, before intubation.
- Intubation in patients with modified Mallampati score 3 or 4
- Obese patients
- Initial failure with direct laryngoscopy
- Reduced mouth opening
- Restricted neck movement as in disease and trauma
- Unanticipated difficult airway
- To aid nasal intubation
VL in children
At present,several VL are available with blades appropriate to small children, even for neonates.They have proved invaluable in both anticipated and unanticipated difficult airways situations.
VL can be used for airway management in prehospital set up, emergency department and intensive care ass well.
- Tube exchange in ICU
- Insertion of Double Lumen Tube
- Removal of foreign Body
- Insertion of TEE probe
Techniques of videolaryngoscopy
- Know your equipment
- Preparation of the equipment
- Patient preparation
- Insertion of the VL and obtaining glottic view
- Removal of the VL
Know your equipment
It is absolutely essential that one acquires a sound knowledge of the equipment, in terms of its basic design, operations, light source, sterilization and special requirements, if any.
Preparation is similar to other airway management techniques as appropriate to different clinical scenarios. The need for alignment of the oral, pharyngeal and laryngeal axes, which may not be possible in various situations, is not a prerequisite for VL.
Preparation of the equipment
- The VL is turned on before the patient arrives and tested for working and a good image
- Adequate battery life should be ensured
- Sterilization of the blade is ensured
- A proper sized endotracheal tube is selected, tested and pre shaped with a stylet, if recommended by the manufacturer
Steps of Videolaryngoscopy
- Insertion of the VL – Look at the mouth
Inserted in midline or in a manner similar to the direct laryngoscope depending on the particular VL’s. There is usually no need for displacement of the tongue.
- Obtain the best view of the glottis – Look at the video
when the tip of the VL blade is beyond the tongue, the focus is shifted to the screen and it is moved forward and backward to position the tip at the valleculum. Sometimes, external laryngeal manipulation may be required to obtain the best view.
Videolaryngoscopy provides consistently better view of glottis than direct laryngoscopy.
- Introduce the endotracheal tube – look at the mouth
Introduce the prepared tube,with or without preshaping with stylet as required,and pass the tip beyond the tip of the VL blade
- Intubate the trachea – Look at the video
Smooth passage of the ET Tube is performed under direct view, if requiring using gentle manipulations such as rotation or external manipulation.
- Not able to get a full glottis view
- More forward thrust of the blade
- External laryngeal manipulation
- Consider use of bougie
- Seeing the glottis, not able to pass the tube
- Consider using stylet
- Partial withdrawal of the stylet after introduction of the tip of tube into the larynx
- Clockwise rotation of the tube
- Consider use of bougie
Limitations of the VL
A Video laryngoscope is not a “one size fits all” solution for difficult airway management.it has limited applications or not applicable in following clinical situations
- Severe limitation or absence of mouth opening
- Infra glottic pathology preventing intubation
Many of the VL have reusable blades. They can be safely disinfected or sterilized by chemical methods or ethylene oxide.
Current status in different algorithms
- ASA Difficult Airway Management Revised Guidelines (2013)
Use of VL is recommended for initial attempt of intubation as it is shown to improve the overall success and first attempt succes rate.
- Canadian Airway Focus Group( CAFG)
CAFG included predictors of difficulty in use of GlideScope VL and also use VL in management of unanticipated difficult airway after induction of anesthesia.
Overall,VL is advocated both as initial choice of intubation and also for the second attempt of intubation if direct laryngoscopic first attempt fails.
Application of technology has resulted in development of better design, quality of image, prevention of fogging, rapid “booting”, portability, working under extreme conditions, improved sturdiness and overall performance.
Enhanced Direct laryngoscopy (EDL) is a newer approach where in the techniques of direct and videolaryngoscopy can be combined with a single equpment, McGRATH MAC EDL
Kepler Robotic Intubation system
After successful trials on mannequins,first series of robotic tracheal intubation was performed in Montreal,Canada,using Kepler system.The system uses Pentax AWS videolaryngoscope for performing the intubation.
In comparison with direct laryngoscopy,
- Video laryngoscopes in general improve the glottic opening, overall success rate and improved first attempt success.
- VL require similar or slightly more time for intubation
- VL is associated with comparable incidence of complications
- There are inter device variations in success rates.
- VL has changed the way intubation is performed in various airway settings. It has dramatically reduced incidence of difficult intubation.
- Different devices have different disgns in terms of the type and design and angulation of blades, location of the camera, light source and screen. Blade may be Macintosh type or angulated, channeled or without channel.
- Familiarity with a particular VL, preparation of the equipment and patient are prerequisites before performing VL
- VL is introduced in midline or at the angle of mouth depending on the device.
- Obtaining a good glottic view doesn’t guarantee easy intubation or successful, intubation.
- VL has wide range of applications in airway management
- VL are available for pediatric use.
- Familiarity with at least one device is desirable
- VL is accepted to be a part of different difficult airway management.
- Use of Intlock in Airway Scope(AWS), Pentax,in pediatric sizes
- Broken glide scope blade
- NG,AL Hill,et al British Journal of Anaesthesia 109 (3):439-43(2012)