Reported complications associated with the use of GlideScope ® video laryngoscope – How can they be prevented ?

Introduction The use of the GlideScope® video laryngoscope has increased tremendously since its release in 2001. Compared to the Macintosh laryngoscope, its unique design allows an improved view of the glottis. During intubation, it decreases the need to anteriorly displace the lower jaw or manipulate the cervical spine. As a result, there is lesser sympathetic response to intubation and possibly fewer traumas to the dentition. Intubation may be performed on an awake patient more easily. The GlideScope® video laryngoscope plays a significant role in the management of routine and difficult airways. Unfortunately, the same unique design also requires the use of a stylet and introduces blind spots in the oropharynx during intubation. As a result of this drawback, cases of airway trauma have been reported. We have aimed to write a critical review discussing the complications and precautions associated with the use of the GlideScope® video laryngoscope. Conclusion The GlideScope® video laryngoscope is an improvement over the Macintosh laryngoscope as it reduces airway manipulation, but further research must be conducted in order to increase our understanding of the potential pitfalls associated with it and to develop strategies to avoid them. Introduction GlideScope® was developed by the Canadian surgeon John Pacey and became commercially available in late 2001. It allows real-time viewing of the airway and tube placement, and it is one of the more widely used video laryngoscopes available, with more than 300 associated publications in Medline1. The purpose of this critical review is to provide a basic, concise overview of the GlideScope® video laryngoscope, with emphasis on the advantages and reported complications in literature, and to discuss strategies to optimise intubation technique. Discussion The authors have referenced some of their own studies in this review. These referenced studies have been conducted in accordance with the Declaration of Helsinki (1964) and the protocols of these studies have been approved by the relevant ethics committees related to the institution in which they were performed. All human subjects, in these referenced studies, gave informed consent to participate in these studies. battery, with an average battery life of 90 minutes and 500 charge cycles. Other GlideScope® models include the GlideScope® advanced video laryngoscope designed for difficult and unpredictable airways, and the GlideScope® Ranger, optimised for rugged conditions in pre-hospital settings. Table 1 summarises the GlideScope® product range. How GlideScope® works during intubation In conventional laryngoscopy with the Macintosh laryngoscope, the patient’s head is positioned by flexing the lower cervical spine and extending the atlanto-occipital joint, known as ‘sniff the morning air’ position2. It is believed that direct laryngoscopy aligns the oral, pharyngeal and laryngeal axes to aid in the direct visualisation of the glottis, as shown in Figure 13. In contrast, the camera is sited near the distal tip of the GlideScope® blade. When correctly positioned, the camera acts as the ‘eye’ of the operator and is situated in the pharynx of the patient. This enables the image of the glottis to be projected on the monitor, allowing the operator to see around the corner. The main advantage conferred by this technique includes an improved view of the glottis without the need to anteriorly displace the lower jaw and reduce cervical spine motion4. As a result, there is less sympathetic response to intubation and possibly less leverage force on the teeth5. Intubation may then be performed on an awake patient more easily6. Therefore, this technique has a significant role in the management of routine and difficult airways7. Eq ui pm en t * Corresponding author E-mail: thongszeying@gmail.com Department of Anaesthesia, Singapore General Hospital, Block 2, Level 2, Outram Road, Singapore 169608 Types of GlideScope® video laryngoscopes The reusable GlideScope® video laryngoscope has a 60-degree curve blade and comes in four sizes: 2, 3, 4 and 5, to facilitate intubations in infants weighing 1.8 kg to the morbidly obese. The unit consists of a portable colour video monitor which has a colour image of 320 × 240 pixels. Start-up is quick with a single button, and does not require any adjustment or white balance. It uses a 12V lithium rechargeable


Introduction
GlideScope ® was developed by the Canadian surgeon John Pacey and became commercially available in late 2001.It allows real-time viewing of the airway and tube placement, and it is one of the more widely used video laryngoscopes available, with more than 300 associated publications in Medline 1 .
The purpose of this critical review is to provide a basic, concise overview of the GlideScope ® video laryngoscope, with emphasis on the advantages and reported complications in literature, and to discuss strategies to optimise intubation technique.

Discussion
The authors have referenced some of their own studies in this review.These referenced studies have been conducted in accordance with the Declaration of Helsinki (1964) and the protocols of these studies have been approved by the relevant ethics committees related to the institution in which they were performed.All human subjects, in these referenced studies, gave informed consent to participate in these studies.battery, with an average battery life of 90 minutes and 500 charge cycles.Other GlideScope® models include the GlideScope® advanced video laryngoscope designed for difficult and unpredictable airways, and the GlideScope® Ranger, optimised for rugged conditions in pre-hospital settings.Table 1 summarises the GlideScope ® product range.

How GlideScope ® works during intubation
In conventional laryngoscopy with the Macintosh laryngoscope, the patient's head is positioned by flexing the lower cervical spine and extending the atlanto-occipital joint, known as 'sniff the morning air' position 2 .
It is believed that direct laryngoscopy aligns the oral, pharyngeal and laryngeal axes to aid in the direct visualisation of the glottis, as shown in Figure 1 3 .In contrast, the camera is sited near the distal tip of the GlideScope ® blade.When correctly positioned, the camera acts as the 'eye' of the operator and is situated in the pharynx of the patient.This enables the image of the glottis to be projected on the monitor, allowing the operator to see around the corner.The main advantage conferred by this technique includes an improved view of the glottis without the need to anteriorly displace the lower jaw and reduce cervical spine motion 4 .As a result, there is less sympathetic response to intubation and possibly less leverage force on the teeth 5 .Intubation may then be performed on an awake patient more easily 6 .Therefore, this technique has a significant role in the management of routine and difficult airways 7 .

F
: Thong SY, Goh SY.Reported complications associated with the use of GlideScope ® video laryngoscope-How can they be prevented?OA Anaesthetics 2013 Mar 01;1(1):1.CMOS, complementary metal-oxide semiconductor; GVL, GlideScope ® reusable video laryngoscope; Li, lithium; SD, secure digital; TFT, thin film transistor; VGA, video graphics array.Its similarities to the Macintosh laryngoscope, as compared with other video laryngoscopes like the Pentax, may contribute to greater user acceptability for most operators experienced with the Macintosh.For both the novice and experienced anaesthetists, it is easier to achieve successful intubation with the GlideScope ® as compared with the Macintosh 8,9 .Direct laryngoscopy generally requires a steeper learning curve and a longer duration to master the technique as compared with the GlideScope ®10,11 .

Problems encountered during the use of GlideScope®
An interesting paradox is seen with the use of GlideScope ® .Even though Compe ng interests: none declared.Confl ict of Interests: none declared.
All authors contributed to the concep on, design, and prepara on of the manuscript, as well as read and approved the fi nal manuscript.
All authors abide by the Associa on for Medical Ethics (AME) ethical rules of disclosure.

Table 2. Clinical pearls for intuba on success and injury avoidance.
-Verathon recommends the inserti on of the GlideScope® blade via the midline of the tongue to the epiglotti s.This should be done under vision control 14 .
-The GlideScope® may be used like a Macintosh laryngoscope to indirectly lift the epiglotti s or produce a Miller's lift .
-The use of the ETT stylet is recommended.A malleable stylet with a 60-90 degree curvature may be used.GlideRite® Rigid Stylet produced by Verathon is also available.
-Introducing the ETT close to the side of the blade helps to avoid blind, traumati c inserti ons as the space created by the presence of the blade allows direct visualisati on of the stylett ed ETT, unti l its ti p is seen on the monitor 14 .
-To aid the passage of the ETT, once the ti p is at the vocal cords, withdraw the stylet slightly, about 2-3 cm, before further ETT advancement.This avoids trauma to the vocal cords by the rigid stylet.Withdrawal of the laryngoscope or reducti on of the lift ing force allows the glotti s to drop, which may also aid the passage of ETT.
-Always ensure that the ti p of the ETT is observed during advancement-initi ally via direct vision, and then via the monitor when the ti p disappears from direct view aft er further advancement.Avoid blind advancement of the ETT.This will reduce the risk of injury in the oral structures caused by the rigid stylet 17 .
-Aft er intubati on, as the GlideScope® is withdrawn, att enti on should be paid to the path of the ETT and possible injury to the oral cavity 18 .
-The use of soft -edge ETT (such as the Parker Flex-Tip ™ ) may avoid trauma to the pharynx 17 .
-Insert the ETT with the bevelled ti p facing against the blade of the GlideScope® 15 .

Journal Pa ent characteris cs Complica ons Outcome Comments
Choo MK et al. 15 Can J Anaesth, 2007.
65-year-old female who was scheduled for urological surgery #7.5 ETT, preformed with stylet, was used for intubati on.At the end of the case, it was noti ced that he ETT had perforated the right palatopharyngeal fold.
Surgical consult was required for haemostasis with electrocautery.Pati ent was subsequently extubated aft er bleeding stopped.Pati ent required overnight hospitalisati on for observati on.Followup 6 weeks later showed good wound healing.
No resistance was encountered while passing the ETT into the oropharynx, but slight resistance was encountered as the ETT passed the laryngeal inlet.Examinati on of the oropharynx with direct laryngoscopy showed that the ETT had perforated the right palatoglossal arch.
The ETT was removed and reinserted under direct laryngoscopy aft er surgical consult.There was no acti ve bleeding and the pati ent remained mechanically venti lated.
An experienced operator performed the intubati on.Cormack-Lehane grade 2 view of the vocal cords was obtained with the GlideScope®.A contributory factor to the injury was the small oral cavity which contained a nasogastric tube, duodenal tube and an existi ng ETT.
Compe ng interests: none declared.Confl ict of Interests: none declared.
All authors contributed to the concep on, design, and prepara on of the manuscript, as well as read and approved the fi nal manuscript.All authors abide by the Associa on for Medical Ethics (AME) ethical rules of disclosure.

Journal Pa ent characteris cs Complica ons Outcome Comments
Magboul MM et al. 18 Middle East J Anesthesiol, 2010. it provides an improved view when compared with direct laryngoscopy, that does not necessarily translate to better intubation success 12 .Due to the line of sight created by direct laryngoscopy, even in poor views, intubation may be possible with adjuncts like the bougie and stylet 13 .In contrast, even when a grade 1 or 2 Cormack and Lehane view is obtained with the GlideScope ® , intubation may not be possible in the first attempt.
The manufacturer recommends a four-step technique when using the GlideScope ® : 1.The GlideScope ® is first introduced into the midline of the oral pharynx with the left hand.2. The epiglottis is identified on the screen and the scope is manipulated to obtain the best glottic view.3. The endotracheal tube is then guided into position near the tip of the laryngoscope by direct vision.4. When the distal tip of the endotracheal tube disappears from direct view, it should be viewed on the monitor.Gently rotate or angle the tube to redirect as needed.
Clinical pearls for intubation success and injury avoidance are summarised in Table 2.
The common factor associated with intraoral injuries such as palatopharyngeal, anterior tonsillar pillar or soft palate perforations, is blind advancement of the endotracheal tube.Injuries have occurred despite apparent gentle technique and the lack of resistance encountered by the operator.When upward force is applied to the GlideScope ® to achieve better laryngeal visualisation, the tonsillar pillars and related structures may be stretched taut and become susceptible to perforation 14 .
This highlights the need for constant visual assessment of the tip of the endotracheal tube under direct vision during the initial oralpharyngeal insertion, as well as during subsequent advancement of the tube on the GlideScope ® monitor.In the interim, there may be a blind spot, depending on the patient's oral anatomy 15 .A strategy to overcome such problems is to advance the endotracheal tube right next to the GlideScope ® blade, near the midline.This provides maximal space for endotracheal tube advancement.The anatomy of the oral structures is demonstrated in Figure 2.There was one report of a palate injury caused by the leading edge of the GlideScope ® video laryngoscope 16 .At all times, the advancement of the blade should be midline, gentle and under vision if possible.After intubation, the oral airway should be examined during laryngoscope withdrawal.Details of reported complications associated with the use of GlideScope ® are summarised in Table 3.

Conclusion
The GlideScope ® video laryngoscope is a useful tool for intubation.It improves glottic view and reduces the need for airway manipulation.Despite its ease of use, thorough understanding of its unique characteristics is important in avoiding potential intubation injuries.

Figure 2 :
Figure 2: Picture of the oral cavity.

Table 3 . Clinical reports of complica ons associated with the use of GlideScope ® .
F: Thong SY, Goh SY.Reported complications associated with the use of GlideScope ® video laryngoscope-How can they be prevented?OA Anaesthetics 2013 Mar 01;1(1):1.