Determination of the utility of the Intubation Difficulty Scale for use with indirect laryngoscopes

Abstract

SummaryThe purpose of this study was to determine whether the Intubation Difficulty Scale is meaningful when used with indirect laryngoscopes. Data were analysed from previously published clinical trials from our group that compared the indirect laryngoscopes with the Macintosh laryngoscope. For each laryngoscope type, the Intubation Difficulty Scale score obtained for each tracheal intubation was correlated with data for duration of the intubation attempt and with the user rated difficulty of the intubation attempt. The strengths of the correlations between these indices were then compared for tracheas intubated with the Macintosh vs the indirect laryngoscopes. The Intubation Difficulty Scale performed well when compared with data for duration and user rated difficulty of the intubation attempts for the both direct and indirect laryngoscopy. However, the correlation between the Intubation Difficulty Scale score and both user rated difficulty (p = 0.001) and the duration of tracheal intubation (p = 0.003) were significantly stronger for the Macintosh laryngoscope compared with the indirect laryngoscopes. In contrast, the correlation between user rated difficulty scores and the data for duration of tracheal intubation was not different between the device types. The Intubation Difficulty Scale performs less well with indirect laryngoscopes than with the Macintosh laryngoscope. These findings suggest the need for caution with the use of this score with indirect laryngoscopes. Difficult tracheal intubation remains a major source of morbidity and mortality, in the operating theatre [1][2][3] and in the emergency setting [4,5]. Difficult or failed tracheal intubation is an important cause of anaesthetic death and brain damage [6][7][8][9][10][11]. These issues have stimulated the development of 'indirect' laryngoscopes, with the aim of reducing the difficulty obtaining a laryngeal view. Many such devices now exist on the market, including the Glidescope [12, 13], Airtraq [14], Pentax Airway Scope (AWS) [12,15,16], TruView [12,16], and LMA C-Trach [17]. One difficulty encountered investigating the utility of these devices is the lack of a gold standard descriptor for intubation difficulty. While indices such as the duration of tracheal intubation attempts and user rated scores of the difficulty of laryngoscopy and intubation are useful, they do not provide a complete picture. A more objective scoring system might serve as a reproducible quantitative means of overcoming some of these limitations.Adnet et al. proposed the Intubation Difficulty Scale (IDS), which incorporates seven parameters (see Appendix 1) [18], for use when describing direct laryngoscopy and intubation. More recently, the IDS has been used to describe difficulty of laryngoscopy and tracheal intubation with indirect laryngoscopes in multiple studies by our group [13,16,17] and others [15,19]. However, the validity of the IDS when used with indirect laryngoscopes has not been evaluated.

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“…Comme critère de jugement secondaire, nous avons utilisé une échelle de difficulté d'intubation, qui est largement utilisée et qui a été validée pour les laryngoscopies directes. Son utilité pour l'évaluation des laryngoscopes indirects n'est pas encore établie, 36 toutefois une corrélation positive est retrouvée entre l'échelle de difficulté d'intubation et un score subjectif (échelle visuelle analogique) dans la plupart des études. 27,36 Dans notre étude l'Airtraq et le X-Lite ont permis de réduire le temps d'intubation par rapport au laryngoscope standard dans la chirurgie thyroïdienne.…”

The GlideScope Video Laryngoscope: A Narrative Review

“…However, a study by McElwain et al [47] found that the correlation between the IDS score and both user rated difficulty and the time needed for tracheal intubation was significantly stronger for the Macintosh laryngoscope than for the indirect laryngoscopes studied (GlideScope, Pentax AWS, Airtraq). These findings led the authors to conclude that the IDS "performs less well with indirect laryngoscopes than with the Macintosh laryngoscope" and that clinicians should use "caution with the use of this score with indirect laryngoscopes.…”

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“…However, a retrospective study by McElwain has raised concerns about the validity of the IDS with VLS [13]. The most important outcome parameter for VLS or any guided intubation devices is the success rate.…”