A comparison of 20 laryngoscope blades using an intubating manikin: visual analogue scores and forces exerted during laryngoscopy*

Abstract

SummaryFifty anaesthetists were recruited to use 20 different laryngoscope blades (one metal re-usable blade, five metal single-use blades and 14 plastic single-use blades, of which eight were bulbtype and 12 were fibreoptic-type) in a manikin to achieve a grade I Cormack and Lehane view. The anaesthetists were asked to provide visual analogue scores (VAS) for: ease of attachment of the blade to the handle; illumination; view of the larynx; and satisfaction for clinical use. The peak force applied and time to achieve the grade I Cormack and Lehane view were also measured. A cluster analysis method was used to group together blades with similar scores or measures.Ease of attachment, illumination, view, clinical use, force and duration were all significantly affected by the blade used (p < 0.0001 for all six). The mean peak force applied and mean duration for the 20 blades were 32-39 N and 4.4-9.5 s, respectively. All five metal single-use and four plastic single-use blades were always placed in the 'best' group in the cluster analysis. Two plastic blades provided a poor view and increased the duration of laryngoscopy.

Flexibility and light emission of disposable paediatric Miller 1 laryngoscope blades*

“…The blade has the advantage that it may be used to lift the floppy epiglottis of an infant. With the discovery of variant Creutzfeldt-Jakob disease in tonsillar material [3], there has recently been an increase in the number of disposable blades on the market [4], including many describing themselves as 'Miller 1', their manufacturers having made alterations to the original design ( Fig. 1).…”

“…Blade design often changes during the manufacturing process [8,9], and therefore blades from different manufacturers may have different characteristics. Disposable blades have been manufactured from both plastic and metal [4], and their flexibility appears to vary. In the first part of this laboratory-based study, we investigated the flexibility of 11 different disposable Miller 1 blades when tested in three different directions of force.…”

“…Disposable adult laryngoscopes have been investigated both in patients [5] and in the laboratory [4,6,7] with varying results. Blade design often changes during the manufacturing process [8,9], and therefore blades from different manufacturers may have different characteristics.…”

The use of single‐use devices in anaesthesia: balancing the risks to patient safety*

“…[25]. Anaesthetists were asked about the quality of illumination given by each blade, their satisfaction with the resulting view and their perception of its clinical appropriateness.…”

Use of manikins in airway equipment development

“…Of course, researchers should apply the same rigorous research design criteria to manikin-based as they do to patient-based studies. We are aware of at least two examples where manikin-based studies exposed a badly designed and inefficient piece of equipment [7,8]. The recently published 4th National Audit Project (NAP4) [9] reported significant patient harm from devices for which the potential for harm was established in previously published manikin studies of those devices [7,10].…”