Royal United Hospital, Combe Park, Bath BA1 3NG, UK*Corresponding author. E-mail: steve.twigg@lineone.net
Presented at 35th Annual Scientific Meeting of Group of Anaesthetists in Training (GAT), June 2002, as part of the registrars prize competition.
This article is accompanied by Editorial I.
Accepted for publication: June 26, 2002
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Methods. We compared six types of single-use laryngoscope with the standard Macintosh laryngoscope using the Laerdal SimManTM patient simulator. Twenty anaesthetists attempted to intubate the simulator with standardized airway settings allowing a full view of the vocal cords (easy intubation). The airway settings were then changed so that only the posterior part of the glottis was visible (difficult intubation) and the anaesthetists were asked to intubate the simulator again.
Results. The time to intubate with the standard laryngoscope was less in both easy (P<0.05) and difficult (P<0.01) intubations. The performance of five laryngoscopes during easy intubation (P<0.01) and four during difficult intubation (P<0.001) was significantly worse than that of the Macintosh. There was a significant difference in Cormack and Lehane grading between the laryngoscopes tested in both easy (P<0.05) and difficult (P<0.05) intubation. The percentage of glottic opening visible (POGO score) also differed between laryngoscopes in both the easy (P<0.01) and difficult (P<0.001) groups. The highest POGO scores were obtained with the Macintosh laryngoscope. During the difficult intubation simulation, the reusable Macintosh laryngoscope needed less use of a bougie and had fewer failed intubations than the single-use laryngoscopes, but these differences did not reach statistical significance.
Conclusions. Of the laryngoscopes tested, the standard reusable Macintosh laryngoscope performed best. The EuropaTM was the best single-use laryngoscope. Some single-use laryngoscopes tested were significantly inferior to the Macintosh. This raises concern over their use in clinical practice, particularly if intubation is difficult.
Br J Anaesth 2003; 90: 813
Keywords: complications, prion diseases, CreutzfeldtJakob disease; equipment, disposable; equipment, laryngoscopes; infection, cross infection; intubation, tracheal
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
Material and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Six size 3 Macintosh-type single-use laryngoscopes of different designs, a sheathed Macintosh laryngoscope and a standard Macintosh laryngoscope were tested. Details of the laryngoscopes are given in Table 1, and photographs are provided in Figures 1 and 2. A size 8 Portex cuffed tracheal tube was used for intubation and a gum elastic bougie was available.
|
|
|
The eight laryngoscopes studied were presented consecutively in a random order generated by picking numbered balls out of a bag. Initially the simulator was set to easy intubation. Time from picking up the laryngoscope to the second chest inflation was taken as the time to intubate. A maximum of 2 min was allowed, after which time the intubation was classed as failed. Outcome measures were time to complete intubation, grading of view obtained at laryngoscopy after Cormack and Lehane,4 POGO score,5 frequency of use of a gum elastic bougie and failed intubation. The set of eight intubations was then repeated in a new random order with the simulator set to difficult intubation.
Data were analysed using SPSS (SPSS, Chicago, IL, USA). The time to complete intubation for each laryngoscope was analysed with a KaplanMeier survival plot (graphs not shown). For each intubator, the time to complete intubation was ranked according to type of laryngoscope. This ranking was analysed by univariate analysis of variance. Comparison of each laryngoscope with the standard Macintosh laryngoscope was made by post hoc testing with Dunnetts two-sided t-test, which includes a correction for multiple testing. Cormack and Lehane grading of view at laryngoscopy, use of bougie and number of failed intubations per laryngoscope were analysed with the 2 test. POGO score was compared using the KruskalWallis test. Statistical significance was taken if P<0.05.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Time to complete intubation
The median time to complete intubation for each laryngoscope is given in Table 2. There was a significant difference between the laryngoscopes in both the easy (P<0.05) and the difficult airway setting (P<0.01). The single-use laryngoscopes were ranked for each intubator and the rankings were compared with those of the standard Macintosh (Table 3). The standard Macintosh laryngoscope was ranked above all others for both easy and difficult intubation. In the easy intubation group, the Lite-BladeTM, OptimaTM, OptiscopeTM, VenticaireTM and Vital ViewTM all performed significantly worse than the standard Macintosh. In the difficult intubation group, the Vital View, Optima, Venticaire and Optiscope performed significantly worse.
|
|
|
|
|
|
Grade of intubator
Anaesthetists ranged in experience from 1 to 30 yr practising anaesthesia. There was no correlation between time to intubate with the various laryngoscopes and years of anaesthetic experience (data not shown).
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
During the same time, the use of single-use anaesthetic equipment was also mandatory, thereby stopping the use of reinforced laryngeal masks and necessitating the routine use of tracheal tubes and single-use laryngoscopes.8 When the directive on surgical equipment was reversed, restrictions on the reuse of anaesthetic equipment were initially lifted and then re-imposed in March 2002. The subject is controversial and opposing views have been expressed.914 The role of single-use laryngoscopes in future anaesthetic practice remains uncertain.
Equipment such as laryngoscopes can at present be introduced into practice without the stringent testing of performance that new drugs have to undergo. It is possible that equipment with worse performance than existing devices could be marketed. Many types of single-use blades are manufactured, with different designs and materials. There have been several reports of difficulty obtaining a view of the glottis with single-use laryngoscopes,3 12 but this equipment has not been evaluated formally, apart from a randomized study of one single-use laryngoscope in 100 patients.15 There was no difference between the Vital View and the standard Macintosh laryngoscope in the view that was obtained, but the study was of patients who were almost all easy to intubate. The study could not distinguish performance in cases of difficult intubation.
We compared different designs of single-use laryngoscopes in both easy and difficult intubation. The study was not masked and we used an intubation simulator rather than patients. However, masking in studies of direct laryngoscopy is practically impossible. A clinical study comparing several laryngoscopes, requiring multiple laryngoscopy and studying patients with known difficulty in intubation would be difficult and, in our view, unethical. A high fidelity airway simulator overcomes these problems and allows standardized reproducible intubation conditions of varying difficulty. We see no reason why the relative performance of the laryngoscopes on a simulator should not be the same in a clinical study.
Measuring ease of intubation is difficult. The Cormack and Lehane grade is an insensitive measure because different views of the larynx fall within the same grade. Our measures therefore included a more discriminating measure of laryngeal view, the POGO score,5 and other measures of difficulty (time taken and use of a bougie). The study used a difficult intubation setting that allowed intubation by most anaesthetists to be possible with difficulty when standard equipment was used. This made failed intubation with other laryngoscopes unlikely unless they performed very badly.
The best laryngoscopes were the reusable Macintosh and the Europa. The Europa laryngoscope has a metal blade, which, though slightly less robust than the reusable one, is otherwise almost indistinguishable from it. The best laryngoscope with a plastic blade was the Lite-Blade. The other plastic-bladed laryngoscopes and the reusable blade with a sheath were less adequate.
We believe our results are clinically important. Some of the single-use laryngoscopes tested were significantly worse than conventional equipment. If these results were the same in clinical practice, there would be more difficulty during intubation and more failed intubations. Considerable effort is made routinely to achieve the best conditions for intubation and avoid unnecessary difficulty. A difficult view of the larynx is associated with increased morbidity.16 We believe that intubation equipment that fails to match standard equipment should be avoided and is clinically unsafe. The unregulated use of single-use laryngoscopes must be questioned.
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
2 Laurenson IF, Whyte AS, Fox C, Babb JR. Contaminated surgical instruments and variant CreutzfeldtJakob disease. Lancet 1999; 354: 1823
3 Babb S, Mann S. Disposable laryngoscope blades. Anaesthesia 2002; 57: 2868[ISI][Medline]
4 Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 110511[ISI][Medline]
5 Levitan RM, Hollander JE, Ochroch EA. A grading system for direct laryngoscopy. Anaesthesia 1999; 54: 100910
6 Miller DM, Youkhana I, Karunaratne WU, Pearce A. Presence of protein deposits on cleaned re-usable anaesthetic equipment. Anaesthesia 2001; 56: 106972[CrossRef][ISI][Medline]
7 Balin MS, McClusky A, Maxwell S, Spilsbury S. Contamination of laryngoscopes. Anaesthesia 1999; 54: 111516
8 Martin F, Wilde A. Tonsillectomyanaesthetic technique and the new disposable surgical equipment. Anaesthesia 2001; 56: 90624[ISI]
9 Arnstein F. New variant CreutzfeldtJakob diseaseis our practice safe? Anaesthesia 2001; 56: 585
10 Gordon HL. R Coll Anaesth Bull 2001; No. 9: 433
11 Scott SH. R Coll Anaesth Bull 2002; No. 12: 5989
12 Matt CM. R Coll Anaesth Bull 2002; No. 12: 599
13 Smith G. R Coll Anaesth Bull 2002; No. 12: 59960
14 Lowe PR, Engelhardt T. Prion-related diseases and anaesthesia. Anaesthesia 2001; 56: 485
15 Asai T, Urchiyama Y, Yamamoto K, Johmura S, Shingu K. Evaluation of the disposable Vital View laryngoscope apparatus. Anaesthesia 2001; 56: 3425[CrossRef][ISI][Medline]
16 Rose K, Cohen MM. The airway: problems and predictions in 18,500 patients. Can J Anaesth 1994; 41: 37283[Abstract]