Videolaryngoscopy is increasingly used for difficult airway management in anaesthesia,1–3 intensive care units4 and emergency departments.5 Recently, videolaryngoscopy has been incorporated into various difficult airway management algorithms,6,7 being recommended as one of the initial steps in the management of difficult airways. Videolaryngoscopes have reduced the incidence of emergency surgical airway management in the peri-operative setting.8 Until the introduction of videolaryngoscopy, intubation using flexible fibreoptic bronchoscopy was regarded as the gold standard of difficult airway management in anaesthesia.9–11 Studies have shown that videolaryngoscopy can replace flexible fibreoptic bronchoscopy for difficult airway management12,13 but the indications and pattern of using videolaryngoscopy in daily practice are currently unknown.14
The goal of this retrospective cohort study was to ascertain whether the introduction of the GlideScope AVL (Verathon Inc., Seattle, Washington, USA) in a tertiary academic referral centre led to changes in the frequency of use of flexible fibreoptic bronchoscopy or other methods of difficult airway management in adult patients undergoing general anaesthesia with tracheal intubation with expected or unexpected difficult intubation, a history of difficult intubation or with cervical disorder or limited mouth opening. Additionally, we investigated whether there was a change in frequency of cases with impossible intubation after the introduction of the GlideScope.
The Glidescope is a videolaryngoscope including a light source and video camera at the distal end of a laryngoscope blade transmitting a real-time picture to a separate screen. Similar types of videolaryngoscopes are available from several other manufacturers.
We hypothesised that the introduction of videolaryngoscopy reduced the use of flexible fibreoptic bronchoscopy and other methods of airway management and that cases of impossible tracheal intubation were markedly reduced.
Ethical approvals for this study with waiver for informed consent was provided by the Institutional Review Board of the Hadassah Medical Organisation, POB 12000, Jerusalem, 91120, Israel (Ref: HMO-13–0007, approval date 4 March 2013 and HMO-11–0316, approval date 30 November 2015, Chairperson Professor T. Chajek).
Initially, data on all techniques of tracheal intubation in adults (≥18 years of age) were retrieved from the anaesthesia information management system (Metavision, iMDsoft, Tel Aviv, Israel) for equal periods prior to introduction of the GlideScope (from 19 July 2009 until 27 April 2011) and thereafter (28 April 2011 to 3 February 2013, start of retrospective data collection). Each period was 647 days long. Patients having tracheal intubation performed with a nondirect laryngoscopic technique (see below) and patients with failed tracheal intubation were then identified in order to calculate the frequencies of each of these techniques as a proportion of all patients undergoing tracheal intubation.
The following data were retrieved from the anaesthesia information management system: age, sex, ASA physical status classification system, weight, intubation technique and whether tracheal intubation failed. For patients intubated employing a nondirect laryngoscopy technique, data on whether intubation was expected to be easy or difficult or unexpectedly difficult were retrieved.
From the Hadassah hospital information system, the following information was gathered: expected or known history of difficult intubation, past or current history of cervical disorder (such as cervical injuries, previous cervical surgery or other diseases), or limited mouth opening.
Finally, quarterly data on techniques used for all tracheal intubations during a 10-year period (from February 2007 to February 2017, 4 years before and 6 years after the introduction of the GlideScope) were retrieved from the anaesthesia information management system in order to analyse temporal changes.
Intubation techniques used for difficult airway management were divided into three groups: GlideScope, flexible fibreoptic bronchoscopy or other difficult airway management devices [including Truview evo2 laryngoscope blade (Truphatek, Israel), Airtraq (Prodol Meditec, Spain), LMA Fastrach Re-usable (Teleflex Incorporated, Ireland) (with subsequent blind intubation or with use of flexible fibreoptic bronchoscopy)].
The proportion of nondirect laryngoscopy intubations during the periods before and after the introduction of the GlideScope were compared. Among nondirect laryngoscopy techniques, patient characteristics were compared for the periods before and after the introduction of the GlideScope. Differences were sought between the two periods in the proportion of cases employing flexible fibreoptic bronchoscopy, both for awake and anaesthetised patients. Similarly, the use of difficult airway management techniques other than flexible fibreoptic bronchoscopy was compared. Quarterly use of the various techniques was analysed over a 10-year period.
Proportions were compared using Fisher's exact or Pearson's χ2-square test, as appropriate. Means were compared with paired t-tests. P < 0.05 was considered statistically significant. Regression analyses evaluated changes in mean quarterly use over the 10-year period of each of the techniques for difficult intubation before and after the introduction of the GlideScope. Statistical analyses were performed with SAS Version 9.2 (SAS Institute, Cary, North Carolina, USA), WinPepi Version 11.6515 and Microsoft Excel 365 (Microsoft, Redmond, USA).
During the period before the introduction of the GlideScope 8306, patients underwent tracheal intubation, compared with 8517 during the period after the GlideScope introduction. Patients’ characteristics were very similar in both periods (Table 1). During the period before the introduction of the GlideScope, a difficult airway management technique was used for 235/8306 (2.8%) patients versus 480/8517 (5.6%) patients after its introduction (P < 0.0001). There were no differences in the percentage of patients in whom a difficult airway management method was used for expected or unexpected difficult intubation, for patients with limited mouth opening or for patients who had a previous history of difficult intubation (Table 2). After introduction of the GlideScope, a higher proportion of patients with cervical disorder and unknown or other indications (such as obstruction or deviation of the glottic or subglottic area because of a tumour or other disease) underwent intubation with a nondirect laryngoscopic technique than before the introduction of the GlideScope. There was no difference in the proportion of intubations performed with flexible fibreoptic bronchoscopy for cervical disorders and unknown/other reason between the two periods [cervical disorder: before GlideScope: 16/8306 (0.19%), after GlideScope: 12/8517 (0.14%), P = 0.410; unknown/other reasons: before GlideScope: 27/8306 (0.33%), after GlideScope 29/8517 (0.34%), P = 0.862]. The changes in use of flexible fibreoptic bronchoscopy, GlideScope and other devices for the different indications before and after the introduction of the GlideScope are summarised in Table 2.
The overall use of flexible fibreoptic bronchoscopy decreased by 44.4% after the introduction of the GlideScope [before GlideScope 149/8306 (1.8%); after GlideScope 85/8517 (1.0%), P < 0.0001) (Table 3)]. This reduction was found for both awake patients and patients under general anaesthesia [awake: before GlideScope 110/8306 (1.3%); after GlideScope 62/8517 (0.7%), a 43.8% reduction, P < 0.001; under general anaesthesia: before GlideScope 39/8306 (0.47%); after GlideScope 27/8517 (0.27%), a 42.6% reduction, P = 0.006). There was also a significant decrease in use of other nondirect laryngoscopy intubation equipment after the introduction of the GlideScope [before GlideScope 84/8306 (1.0%); after GlideScope 22/8517 (0.26%), a 70% decrease, P < 0.0001]. There was no difference in the number of impossible tracheal intubations between the two periods (before GlideScope 2/8306 (0.02%), after GlideScope 2/8517 (0.02%), P = 0.98).
After introducing the GlideScope, the use of flexible fibreoptic bronchoscopy in awake patients decreased significantly among patients with expected and unexpected difficult intubation and among patients with a history of difficult intubation (Table 3). The use of awake flexible fibreoptic bronchoscopy remained stable for patients with limited mouth opening, cervical disorder or with other and unknown reasons (Table 3). Use of flexible fibreoptic bronchoscopy under general anaesthesia was significantly reduced in patients with unexpected difficult intubation, but not in patients with expected difficult intubation, limited mouth opening and other and unknown reasons (Table 3).
After the GlideScope was introduced, the use of other difficult airway management techniques was significantly reduced in patients with expected or unexpected difficult intubation and unknown or other reasons (Table 3).
The quarterly use of flexible fibreoptic bronchoscopy and other techniques for tracheal intubation during a 10-year period is shown in Fig. 1 (including 4 years before and 6 years after the introduction of the GlideScope). The percentage of patients intubated with flexible fibreoptic bronchoscopy per quarter was higher before the introduction of the GlideScope than after its introduction [before: 1.9 ± 0.5 (95% CI, 1.7 to 2.1) patients per quarter versus after 1.0 ± 0.3 (95%, CI 0.8 to 1.1) (P < 0.0001)]. However, the absolute number of quarterly uses of flexible fibreoptic bronchoscopy was stable during each period (before P = 0.1646, after P = 0.3019); this was true also for awake patients (before P = 0.2132, after P = 0.9878) and patients under general anaesthesia (before P = 0.2985, after P = 0.1709). Quarterly proportional use of other devices increased over time before the introduction of the GlideScope (P < 0.0001) but there was no change (P = 0.2704) in the quarterly proportional use after its introduction. There was a steady and significant increase in quarterly use of the GlideScope over time in the 6 years after its introduction (P < 0.0001). The use of the GlideScope was disproportionately higher than the reduction in use of flexible fibreoptic bronchoscopy and other devices.
The results of this study supported our hypothesis that introducing videolaryngoscopy into the operating rooms of a tertiary care university hospital was associated with a 44% reduction in the use of flexible fibreoptic bronchoscopy and a 70% decrease in the use of other difficult airway management techniques. The diminished use of flexible fibreoptic bronchoscopy was especially marked in cases of unexpected difficult intubation and those with a history of difficult intubation. However, there was almost no change in the use of flexible fibreoptic bronchoscopy in cases of limited mouth opening and other or unknown reasons. This latter group of patients explained the reduced, but stable, quarterly use of fibreoptic intubations after the introduction of videolaryngoscopy (Fig. 1).
Notably, this study demonstrated that videolaryngoscopy use was disproportionately greater than the prior use of fibreoptic bronchoscopy and all other difficult airway techniques (Fig. 1). This might be because of cases in which the GlideScope was used for resident teaching and these cases can be attributed to situations where the indication for its use could not be determined (64% of all GlideScope uses). An alternate explanation is that this liberal use of videolaryngoscopy might be as it provided a feeling of security to anaesthesiologists managing suspected or anticipated difficult intubations,3 without having a real impact on outcome (the number of impossible intubations was equally low in both groups). Moreover, we assume that it is more comfortable for a patient with suspected difficult intubation to be intubated with a videolaryngoscope while under general anaesthesia than awake with flexible fibreoptic bronchoscopy.
Although there was a 26% reduction in the use of flexible fibreoptic bronchoscopy for patients with cervical disorders, the proportion of patients with reported cervical disorders was higher in the period before than after the introduction of the GlideScope. In more than two-thirds of the patients with cervical disorder in the period after the introduction of the GlideScope, videolaryngoscopy was used for tracheal intubation. However, there was no difference in the proportion of flexible fibreoptic bronchoscopy use among the patients before and after the introduction of GlideScope. This is probably attributable to the use of direct laryngoscopy with axial traction and manual inline stabilisation among patients prior to the introduction of the GlideScope with only suspected or minor cervical disorders.16 The number of such patients could not be identified as such cases were reported in the anaesthesia information management system as ‘direct laryngoscopy’ without any notation of cervical disorder or axial traction and inline stabilisation.
Liberal use of a videolaryngoscope with single-use disposable blades results in higher costs. The single-use metal Macintosh blade used in our department costs approximately €3.00 and the GlideScope single-use blade about €24.50. On the basis of the data from the anaesthesia information management system for 2017, this increased costs by about €8200/year (the GlideScope was used for 8% of tracheal intubations). In contrast, the annual costs of using reusable flexible fibreoptic bronchoscopes (including purchase, repairs and handling/cleaning per case) are high and estimated at €18200.17 The approximately 50% reduction in flexible fibreoptic bronchoscopy observed in our study would lead to a yearly saving of about €9100.
Although it is questioned whether flexible fibreoptic bronchoscopy is still considered the gold standard for managing difficult intubation,18 Popat and Woodall19 showed that awake fibreoptic intubation is underutilised and that the threshold for using this technique should be lowered. As this study showed, videolaryngoscopy replaced fibreoptic intubation in cases of expected and unexpected difficult intubation, but in patients with limited mouth opening, fibreoptic intubation was still the first choice. Law et al.20 reviewed 12 years of practice and showed no reduction in the incidence of awake fibreoptic intubations despite the introduction of videolaryngoscopes. Unfortunately, they did not study the indications for the use of awake intubation. Wanderer et al.21 found similar results (decreased fibreoptic intubations, a disproportionate increase in the use of videolaryngoscopy) but did neither report the reasons why videolaryngoscopy replaced fibreoptic intubation nor the indications for the continued use of fibreoptic intubation.
Our study showed that in cases of limited mouth opening and cervical spine injuries, awake fibreoptic intubation can still be regarded as the gold standard, as emphasised by Benumof.22 In contrast, Lee et al.23 reported that the Trachway video stilette (Biotronic Instrument Enterprise Ltd., Tai-Chung, Taiwan), which more resembles a rigid fibreoptic bronchoscope than a classical videolaryngoscope, could replace fibreoptic intubation in cases of awake intubation in patients with limited mouth opening.
Trainees should acquire sufficient experience to ensure proficiency in the various difficult airway management techniques. Learning to use the flexible fibreoptic bronchoscope for intubation is a cornerstone of resident training in anaesthesia.24 However, teaching difficult airway management raises challenging ethical issues.25 The patient's right to receive the best treatment available and the right of informed consent must be weighed against the need to train residents and having attending anaesthesiologists maintain high levels of professional skill. The replacement of flexible fibreoptic bronchoscopy by videolaryngoscopy in half of the cases with expected or unexpected difficult intubation substantially reduces the training opportunities for residents.26 Although there is a high success rate in awake fibreoptic intubation during the first experience of supervised trainees,27 many attempts in a simulator are necessary to gain proficiency in fibreoptic intubation.28 Fibreoptic intubation simulators are available and recommended for training,29–32 but transfer of skills acquired with such simulators into clinical practice is questioned.33
The strength of this study is that it used a large database to examine the effects of adding videolaryngoscopy to the anaesthesia activities of a large tertiary care medical centre. It clearly demonstrates that, unlike other difficult intubation methods, this technology had major effects on daily practice. However, the study, being retrospective, was not designed to examine outcomes (reduced morbidity and mortality) or cost-effectiveness.
Both before and after the introduction of the GlideScope, there were only two cases of impossible intubation. It seems that even with the addition of videolaryngoscopy to the difficult intubation armamentarium, there are situations in which tracheal intubation was still impossible. However, in the anaesthesia information management system, only the final airway management technique was noted so that it likely that there were more patients with failed tracheal intubation who were ventilated with a laryngeal mask airway as a rescue technique. In such cases, the laryngeal mask airway would have been marked in the anaesthesia information management system as the airway management technique, and thus not included in the number of cases of impossible tracheal intubation. However, in our experience, the number of such cases is very low. Additionally, we do not know in how many cases flexible fibreoptic bronchoscopy was used after failed intubation with the GlideScope or vice versa.
Another limitation of this study is that it is retrospective, so that the choice of a specific technique for difficult intubation could not always be established because of missing or difficult-to-interpret data. A patient may have been assessed preoperatively as a potential difficult intubation, but the anaesthesiologists performing the intubation may have estimated the patient as being an easy intubation or vice versa. Another limitation is that this was a single-centre study and it is possible that in hospitals with different case mixes and departmental approaches or policies for managing difficult airway situations, the selection of equipment and the introduction of videolaryngoscopy may have a greater or lesser influence on the use of other intubation techniques.
The introduction of the GlideScope videolaryngoscope for difficult airway management led to a substantial change in difficult airway management, occasioned by a marked reduction in the use of flexible fibreoptic bronchoscopy and almost complete elimination of other difficult airway management techniques.
The widespread use of videolaryngoscopy for airway management has brought up the question of whether it will become the new standard for tracheal intubation, replacing conventional direct laryngoscopy. Therefore, there is a need for prospective studies on the indications, outcomes, safety and cost-effectiveness of videolaryngoscopy to determine whether videolaryngoscopy is a revolutionary, disruptive technology that will eventually replace traditional laryngoscopy or rather an evolutionary development used for difficult airways or suspected difficult airways only.
Acknowledgements relating to this article
Assistance with the study: none.
Financial support and sponsorship: none.
Conflicts of interest: none.
Presentation: preliminary data for this study were presented as a poster presentation at the 23rd International Congress of the Israel Society of Anesthesiologists and Critical Care, Tel-Aviv (Israel), 16 to 18 September 2014.
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