Ease of intubation and incidence of dental injury during direct laryngoscopy: A randomized controlled trial comparing five different laryngoscope blades (Macintosh, Miller, Reduce flange, Blechman and Flangeless)

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Highlights

  • Direct laryngoscopy still remains an invaluable tool in limited resource scenarios.

  • First attempt rates of Macintosh are similar to Reduced flange and Blechman blade.

  • Force during laryngoscopy is a major determinant of overall success and risk of injury.

  • Reduced flange and Blechman blade have lower incidence of dental contact and injury.

  • Flangeless blade required higher force which results in difficult intubation and injury.

Abstract

Background

Direct laryngoscopy remains an invaluable and readily available option despite the increasing use of video laryngoscope for securing the airway in different situations, particularly in limited resource and unanticipated difficult airway scenarios. Several variations of the laryngoscope blades are available for various purposes. However, knowledge of the functioning of different blades in a similar controlled environment is required because of the unavailability of all blades in a given setting.

Aim

This study assessed the ease of intubation and the degree of dental injury with five types of laryngoscope blades (Macintosh, Miller, Reduced flange, Blechman, and Flangeless blade).

Methods

This prospective randomized controlled study was conducted in patients undergoing tracheal intubation with direct laryngoscopy using five different blades posted for elective surgery under general anesthesia in a single center.

The primary outcome parameters were Cormack–Lehane grade and intubation difficulty score, whereas secondary outcome measures were the proportion and grades of dental injury.

Results

A Cormack–Lehane grade 3 view was observed more often with flangeless blades 7 (22.5%) than others, with the lowest incidence for the Macintosh blade 1 (3%) (p = 0.228). The first pass success rate was highest in Macintosh (94%), similar in reduced flange Macintosh and Blechman blades (90% each) and least in the flangeless blade (77%). The force required for laryngoscopy varied significantly between the blades (p < 0.001). The median interquartile range intubation difficulty score was the highest with flangeless blades [2 (2–3)] among all the groups (p = 0.048). The dental contact during laryngoscopy varied significantly between the groups (p < 0.001). The incidence of dental injury was the highest in flangeless (13%) among all the blades (p = 0.526).

Conclusions

Reduced flange Macintosh and Blechman blade had ease of intubation similar to standard Macintosh blade, where as flangeless blade is associated with more difficult intubations. Reduced flange Macintosh, and Blechman blades were associated with a lower incidence of dental contact and injury than other three study blades.

Introduction

Direct laryngoscopy and tracheal intubation remain the fundamental skills for definitive control of the airway by anesthesiologists and emergency physicians [1,2]. Despite the increasing use of video laryngoscopy for securing the airway in different situations, direct laryngoscopy remains an invaluable and readily available option, particularly in limited resource and unanticipated difficult airway scenarios [3]. Several variations of the laryngoscope blades for various purposes are available in the market [4,5], with each blade having its own advantages, disadvantages [5,6], and purpose. Some blades are designed for special conditions such as buck teeth, receding jaw, and bull neck, whereas some are designed to decrease dental injury even with limited mouth opening [4]. Although a few blades have been studied in different clinical scenarios, other blades have not been studied [4].

Dental trauma is a known complication of airway management during general anesthesia and associated with largest number of malpractice claims against anaesthesiologists [7,8]. It is more likely in patients with difficult tracheal intubation because anesthesiologists use the upper maxillary teeth as a fulcrum to obtain an optimal view of the glottis [7,9,10]. Studies on some blades have exhibited improved performance and reduced incidence of dental damage with various modifications of curved and straight blades [8,[10], [11], [12]]. However, results of studies on the flangeless (Bizzarri–Giuffrida) blade have been controversial [13,14], whereas the efficacy of the Blechman blade has not been studied yet [4]. Additionally, all types of blades are often unavailable in a scenario where maintenance of the airway demands an immediate and prompt action. Hence, knowledge of the functioning of different blades in a similar controlled environment is required. Therefore, the present study assessed the ease of intubation and the degree of dental injury associated with five types of laryngoscope blades during direct laryngoscopy in patients undergoing elective surgery under general anesthesia.

Section snippets

Study design and setting

This prospective, randomized, controlled, single-center study was conducted from November 2018 to June 2019 in the operation theater complex of All India Institute of Medical Sciences, Bhubaneswar, India, after obtaining institutional ethics clearance (IEC-T/IM-NF/T&EM/18/27). The study was prospectively registered in the clinical trial registry of India (CTRI/2018/10/016033).

Study population

A CONSORT checklist was prepared for enrollment and allocation of patients. American society of anesthesiologists (ASA)

Results

A consort flow chart of study participants is illustrated in Fig. 2. The baseline demographic variables were comparable in all the groups (Table 1a). The preoperative baseline airway assessment values were comparable in all the groups (Table 1b). The Blechman blade exhibited a greater number of patients with Mallampatti grade 3; however, this difference was statistically nonsignificant (p = 0.07). Outcome variables during laryngoscopy and IDS score between the different blades are illustrated

Discussion

The present study exhibited a Cormack–Lehane grade of 3 more often with the flangeless blades than with others, with the lowest incidence observed in the Macintosh blade. The flangeless blade was associated with highest percentage of moderate to major intubation difficulty (IDS score >5). Similarly, the requirement for a higher than usual force was more often observed in the flangeless blade than in others, and it was found to be the lowest in the Macintosh blade. Macintosh blade had the

Conclusion

In our study Machintosh blade had highest first attempt success rate, followed by equal rates in reduced flange Macintosh and Blechman blades. The flangeless blade had least first attempt success rate. The overall intubation success rates with all blades was 100%. The force during laryngoscopy increases with reduction of flange. The complete removal of the flange in case of the flangeless blade results in higher intubation difficulty score (difficult intubation), dental contact, and dental

Author statement

We are grateful and obliged to the esteemed reviewer for a detailed assessment and useful comments/remarks for the betterment of the work.

Source(s) of support

Nil.

Declaration of competing interest

Nil.

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