Experience with the McCoy laryngoscope in difficult laryngoscopy

Abstract

SummaryFifty female patients were studied to compare the view of the larynx at direct laryngoscopy under general anaesthesia with and without cricoid pressure applied. We also compared the view using the standard technique of cricoid pressure with that using cricoid pressure in an upward and backward direction and further investigated whether these views were improved with a firm foam rubber neck support. The order in which the types of cricoid pressure were applied was randomised and also blinded with a drape over the neck. Cricoid pressure was simulated on weighing scales after each case and a mean force of 3.2 kg was applied. The majority of views at laryngoscopy (95%) were grade 1, with too few grade 2 and 3 views for statistical comparison. Both types of cricoid pressure applied without neck support were more likely to give a better view than no cricoid pressure (p < 0.01) and cricoid pressure in an upward and backward direction was more likely to give a better view at laryngoscopy than the standard technique (p < 0.01). Neck support during the standard technique of cricoid pressure did not improve the view of the larynx at laryngoscopy. Cricoid pressure is likely to improve the view at laryngoscopy which may be further improved by applying it in an upward and backward direction.Keywords Larynx; cricoid pressure. Intubation; tracheal. ...................................................................................... Correspondence to: R. G. Vanner Accepted: 17 February 1997 Cricoid pressure is routinely used to prevent regurgitation of gastric contents into the pharynx during the induction of general anaesthesia in all the Maternity Units recently surveyed in the UK [1]. However, it has been suggested that the use of cricoid pressure may make tracheal intubation more difficult [2, 3]. It is not clear whether poor technique alone is responsible or whether correctly applied cricoid pressure may also cause difficulty with intubation. Although it is well known that a degree of pressure on the front of the larynx can improve the view at laryngoscopy [4] it is not known whether correctly applied cricoid pressure, at a force that would prevent regurgitation, alters the view at laryngoscopy.Neck support has been recommended to improve the view at laryngoscopy during the application of cricoid pressure by preventing the head flexing on the neck, either with a bimanual technique [5] or with a cuboid of foam rubber [6]. Bimanual cricoid pressure has been adopted widely [1, 7] despite the lack of evidence supporting this hypothesis; indeed one recent study showed no improvement in the view at laryngoscopy when comparing bimanual with single handed cricoid pressure [8].If the arch of the cricoid cartilage is pushed in an upward (cephalad) direction [9], or the whole larynx is moved in an upward direction [10, 11], the view at laryngoscopy is improved compared with the view with no external manipulation. Therefore, cricoid pressure applied in an upward and backward direction with enough force to prevent reg...

A quantitative review and meta‐analysis of performance of non‐standard laryngoscopes and rigid fibreoptic intubation aids

“…In studies of the McCoy laryngoscope, three studies used the device with its tip in the neutral position as if it were a Macintosh 3 blade [14][15][16] and compared this to the device with the tip elevated. There is some question whether this is entirely valid, but the evidence suggests that if the McCoy laryngoscope (in the neutral position) performs less well than the Macintosh 3 blade, this affects grade 1 and 2 views and the magnitude of this effect is small [17].…”

Straight blades improve visualization of the larynx while curved blades increase ease of intubation: a comparison of the Macintosh, Miller, McCoy, Belscope and Lee-Fiberview blades

“…Chisholm et al 12 report that the MC blade is unlikely to improve a Cormack IV laryngoscopy. Tuckey et al 13 report impaired vision when the tip was levered in patients with Grades 1 and 2.…”

The McCoy straight blade does not improve laryngoscopy and intubation in normal infants

“…12 More recently, the McCoy laryngoscope proved useful to aid intubation in about half of the patients with a grade III view at laryngoscopy but unlikely to improve a grade IV view. 13 The usefulness of the straight McCoy blade in the neonatal setting remains unclear. There are no pointers from our present study to suggest that the neonatal McCoy laryngoscope would be a useful addition to our intubating armamentarium.…”