Internet Journal of Airway Management

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Improvement of the Laryngeal View Using a New Levering Laryngoscope Blade 

 

 

Anita Moser, MD1, Ewa Leleno, MD1, Michaela Hermann, MD1, Ulrike Kirchtag, MD1, Christel Urban, MD1, and Ernst Zadrobilek, MD2 

 

 

1Staff Anesthetist and Intensive Care Physician, Empress Elisabeth Hospital of the City of Vienna

2Associate Professor of Anesthesia and Intensive Care, Empress Elisabeth Hospital of the City of Vienna

 

Address correspondence and comments to Dr. Ernst Zadrobilek.

Received from the Department of Anesthesia and Intensive Care, Empress Elisabeth Hospital of the City of Vienna, Vienna, Austria.

This clinical report will be soon updated with digital images.

Statements: Support was provided solely from departmental and institutional sources. None of the authors has any financial relationship with the manufacturer or the local distributor of the levering laryngoscope blade used in this study.

Key Words:

Tracheal intubation: McCoy levering laryngoscope blade.

Laryngoscopic view: external laryngeal pressure.

Improvement of the laryngeal view: external laryngeal pressure.

 

Published: April 10, 2000.

 

 


 

The correct citation of this clinical report for reference is:

Moser A, Leleno E, Hermann M, Kirchtag U, Urban C, Zadrobilek E. Improvement of the laryngeal view using a new levering laryngoscope blade. Internet Journal of Airway Management 1, 2000-2001.
Available from URL:
http://www.adair.at/ijam/volume01/clinicalreport1.htm
Date accessed: month day, year.

 


This clinical report will be supplemented with multimedia content, if there is material available.

Last updated: April 10, 2000.


 

Abstract

Objective: To evaluate the changes in laryngeal view by activation of a new levering laryngoscope blade (LLB) for fiberoptic battery handles in anesthetized patients requiring orotracheal intubation.
Design: Prospective, non-consecutive observational study.
Setting: Community hospital.
Patients: One hundred and forty patients undergoing elective thyroid surgery were investigated.
Interventions: In easy laryngoscopy (visualization of the entire laryngeal aperture) with the unactivated LLB, tracheal intubation was performed with no further manipulations. In all other laryngoscopic views, the LLB was activated before tracheal intubation was attempted. When tracheal intubation failed, an additional external backward, upward, and to the right pressure (BURP) on the larynx was applied before the tracheal intubation attempt was repeated.
Measurements and Main Results: The laryngeal view (divided into 5 grades) was evaluated before and after each manipulation. Easy laryngoscopy was observed in 58 patients. Activation of the LLB improved the laryngoscopic view in restricted laryngoscopy (visualization of just the posterior portion of the laryngeal aperture or of just the arytenoids) in 40 of 42 patients and in difficult laryngoscopy (visualization of only the epiglottis or of just the soft palate) in 21 of 40 patients, respectively. In 22 patients with difficult laryngoscopy and failed tracheal intubation with the activated LLB, applying a BURP maneuver improved the laryngeal view in all except one patient; only two patients required another technique (according to the protocol the use of a flexible fiberbronchoscope) to intubate the trachea.
Conclusions: Activation of the LLB reduced the incidence of restricted and difficult laryngoscopy; however, the LLB did not obviate the need of the BURP maneuver for improving the laryngeal view and the success rate of tracheal intubation.


 

Introduction

The levering laryngoscope blade (LLB) is a modification of the standard Macintosh laryngoscope blade designed to improve the laryngeal view (1). The LLB incorporates a levering tip controlled by a lever on the handle of the laryngoscope.

The objective of this observational study was to evaluate the changes in laryngeal view using a new LLB for fiberoptic battery handles in the Macintosh and activated configuration. In the situation of failed tracheal intubation despite the activation of the LLB, we investigated the effect of additional external laryngeal pressure on laryngeal view and definitive success rate of tracheal intubation. We applied a backward, upward, and to the right pressure (BURP) which may be more effective than a simple backward pressure on the larynx (2).

 

Materials and Methods

Legal and Ethical Considerations: The study was approved by the Institutional Review Board. Informed patient consent was obtained for anonymous use of patient data for scientific purposes.

Over a study period of 6 months, patients with ASA physical status classification 1, 2, or 3 requiring orotracheal intubation for elective thyroid surgery were investigated when the set of the LLB (with both sizes for small and large adults) was available. Patients with gastroesophageal reflux disease and other risk factors for pulmonary aspiration of gastric contents were excluded from the study. Patients with anatomic anomalies predictive for difficult laryngoscopy and tracheal intubation were given preferential enrollment into the study. Therefore, this clinical report represents data of a prospective, but non-consecutive observational study.

Five experienced anesthetists using the Macintosh blade as the first choice laryngoscope in routine anesthetic practice participated in the study. All had performed a minimum of 10 tracheal intubations with the LLB prior to the study; this number was judged by the attending anesthetists as sufficient for acquisition of the skill in handling with this new device.

Patient monitoring was provided by non-invasive techniques (Datex-Ohmeda AS/3 Anesthesia System, Instrumentarium Corporation, Helsinki, Finland). General anesthesia was induced with 2.5 to 3.5 mg.kg-1 propofol supplemented by 1.5 to 3.0 µg.kg-1 fentanyl. After confirmation of effective mask ventilation with oxygen, muscle relaxation was achieved using 0.6 mg.kg-1 atracurium. Three minutes after receiving the muscle relaxant, laryngoscopy was performed with a size 3 or 4 LLB for fiberoptic battery handles (Flexible Tip Laryngoscope, Heine Optotechnik, Herrsching, Germany) after checking the proper function of the levering mechanism (see Figure 1). As with the standard Macintosh laryngoscope blade, the LLB was inserted from the right side lateral to the tongue, the tongue was moved to the left, and the LLB was advanced in the midline; optimum depth of insertion was determined by the vallecula. Positioning of the head, including elevation of the head and extension of the neck, selection of the size of the LLB, lifting force for elevation of the LLB, extend of activation of the LLB, and use of a malleable tube stylet depended on the discretion of the attending anesthetist. A standard tracheal tube (Mallinckrodt Medical, Athlone, Ireland) with an inner diameter of 7.5 mm was used in all patients.

 

 

 

 

 

 

 

 

 

 

 

Figure 1. Lateral view of the levering laryngoscope blade (size 4) in the unactivated Macintosh configuration, in the gently and fully activated position, and after return from the activated to the Macintosh configuration.

 

The attending anesthetist evaluated the laryngoscopic view with the LLB in the unactivated position and after each manipulation. A modification of the original classification of laryngoscopic views by Cormack and Lehane (3) was used: grade 1, visualization of the entire laryngeal aperture; grade 2, visualization of just the posterior portion of the laryngeal aperture; grade 3, visualization of only the arytenoids; grade 4, visualization of only the epiglottis; and grade 5, visualization of just the soft palate.

When a grade 1 view at laryngoscopy was obtained with the LLB in the unactivated position, tracheal intubation was performed with no further manipulations. In patients with a laryngoscopic view grade 2 or higher, the LLB was gently activated (until the best laryngeal view was obtained) before tracheal intubation was attempted. When tracheal intubation failed with the activated LLB, an additional BURP was applied by an assistant with direction from the attending anesthetetist and the tracheal intubation attempt was repeated. Only one attempt of tracheal intubation using the LLB was allowed at each step; when conventional tracheal intubation failed, the protocol provided tracheal intubation using a flexible fiberbronchoscope.

 

Results

One hundred and forty patients requiring tracheal intubation for elective thyroid surgery were enrolled into the study. The demographic data of the patients according to laryngoscopic view grading obtained with the unactivated LLB are summarized in Table 1. The majority of the study patients were female.


Table 1. Demographic data of the patients according to laryngoscopic view grading obtained with the unactivated levering laryngoscope blade.


Grade 1 Grade 2 Grade 3 Grade 4 Grade 5

Number of patients

58 23 19 35 5
Age (years) 54 (23-79) 52 (26-78) 56 (31-77) 56 (18-86) 61 (53-67)
Height (cm)

170 (153-189)

166 (156-181) 167 (153-176) 171 (154-189) 170 (164-175)
Weight (kg) 78 (45-112) 72 (53-100) 74 (54-108) 75 (50-95) 83 (76-95)

Male/female ratio

17/41 0/23 4/15 7/28 1/4

ASA physical status (1/2/3)

15/34/9 9/14/0 4/13/2 9/21/5 1/4/0

Values for age, height, and weight are expressed as median (range).


In 58 patients (41 percent), a grade 1 view at laryngoscopy was obtained with the unactivated LLB and the trachea was intubated with no further manipulations. In 23 patients (16 percent), a grade 2 view at laryngoscopy was obtained with the unactivated LLB; the laryngeal view with the activated LLB was improved to grade 1 in 22 patients and remained unchanged a grade 2 view in one patient. In 19 patients (14 percent), a grade 3 view at laryngoscopy was obtained; the laryngeal view with the activated LLB was improved to grade 1 in 4 patients and to grade 2 in 14 patients, and remained unchanged in one patient. In all patients with initial laryngoscopic view grade 2 or 3, the trachea was intubated without additional BURP.

In 35 patients (25 percent), a grade 4 view at laryngoscopy was obtained with the unactivated LLB; the laryngeal view with the activated LLB was improved to grade 1 in 3 patients (all tracheal intubations successful), to grade 2 in 8 patients (all tracheal intubations successful) and to grade 3 in 7 patients (3 failed tracheal intubations), and remained unchanged in 17 patients (14 failed tracheal intubations). In the patients with failed tracheal intubation, the laryngeal view with additional BURP (compared to the laryngeal view with the activated LLB alone) was improved by two grades in 7 patients and by one grade in 9 patients, and remained unchanged in one patient; this resulted in a laryngeal view grade 1 in 2 patients, a grade 2 in 6 patients, a grade 3 in 8 patients, and a grade 4 in one patient. The trachea was then intubated in all except one patient with a final grade 4 view; in this patient orotracheal intubation was performed by using a flexible fiberbronchoscope.

In 5 patients (4 percent), a grade 5 view at laryngoscopy was obtained with the unactivated LLB; the laryngeal view with the activated LLB was improved to grade 4 in 3 patients and remained unchanged in 2 patients (all tracheal intubations failed). The laryngeal view with additional BURP (compared to the laryngeal view with the activated LLB alone) was improved by one grade in all patients. The trachea was then intubated in all except one patient with a final grade 4 view; in this patient orotracheal intubation was performed by using a flexible fiberbronchoscope.

The laryngeal views in 82 patients with restricted (grade 2 and 3) or difficult (grade 4 and 5) laryngoscopy before and after activation of the LLB and the laryngeal views of 22 patients with difficult laryngoscopy and failed tracheal intubation with the activated LLB before and after applying an additional BURP are summarized in Table 2 and 3, respectively.


Table 2. Laryngeal views in 82 patients with restricted or difficult laryngoscopy before and after activation of the levering laryngoscope blade.


Grade 1 0 29
Grade 2 23 23
Grade 3 19 8
Grade 4 35 20
Grade 5 5 2

 


Table 3. Laryngeal views in 22 patients with difficult laryngoscopy and failed tracheal intubation with the activated levering laryngoscope blade before and after applying an additional backward, upward, and to the right pressure.


Grade 1 0 2
Grade 2 0 6
Grade 3 3 11
Grade 4 17 3
Grade 5 2 0

During airway management, heart rate and systemic arterial pressure varied within 25 percent of the baseline values in the awake state; oxygen saturation by pulse oximetry was maintained above 95 percent in all patients. Injuries to oropharyngeal structures attributable to the use of the LLB were not observed immediately after tracheal intubation and at the postanesthesia care unit.

 

Discussion

In this prospective, but non-consecutive observational study, activation of the LLB improved the laryngoscopic view in restricted laryngoscopy (grade 2 and 3) in 40 of 42 patients and in difficult laryngoscopy (grade 4 and 5) in 21 of 40 patients, respectively. In 22 patients with difficult laryngoscopy and failed tracheal intubation with the activated LLB, displacement of the larynx by applying a BURP maneuver improved the laryngeal view in all except one patient; only two patients required another technique (according to the protocol the use of a flexible fiberbronchoscope) to intubate the trachea.

In patients undergoing thyroid surgery, the larynx and its laryngeal aperture may be distorted by an (unilateral or bilateral) enlarged thyroid gland. In addition, anatomic anomalies such as limitations in mouth opening, forward movement of the jaw, and/or head and neck movement may have further contributed to the high incidence of restricted and difficult laryngoscopy (intended by the study design). When the laryngeal view was obscured with the blade in the Macintosh configuration, anterior displacement of the base of the tongue and elevation of the epiglottis by activation of the LLB improved the view particularly in patients with restricted laryngoscopy. In patient with difficult laryngoscopy and failed tracheal intubation with the activated LLB, the rightward displacement produced by the BURP maneuver usually improved the laryngeal view then by moving the larynx more into the line of vision (2).

In a previous clinical report with a similar study design, the original LLB for standard battery handles (McCoy Laryngoscope, manufactured by Penlon, Abingdon, England, UK) was used. Randell and co-workers (4) observed that in patients with restricted and difficult laryngoscopy, both the activation of the McCoy blade and BURP improved the laryngoscopic view, but BURP (with or without activation of the McCoy blade) was more effective. Difficult laryngoscopy was found in 20 of 100 patients at initial laryngoscopy without any manipulation; activation of the McCoy blade improved the laryngeal view in 11 patients, BURP in 14 patients, and the combination of both in 16 patients. We could largely confirm these observations by using a new LLB for fiberoptic battery handles.

Chisholm and Calder (5) as well as Tuckey and co-workers (6) reported improvements, but also deteriorations of the laryngeal view with activation of the levering mechanism of the McCoy blade. We did not observe this variable effect on laryngeal view with the activated LLB. Possible explanations for these conflicting results may be that in our study two sizes of the LLB (for small and large adults) were available, the optimum depth of insertion was determined by the vallecula, the levering mechanism was gently activated until the best laryngeal view was obtained, and an external pressure on the larynx was not applied before activation of the LLB.

In conclusion, activation of the new LLB reduced the incidence of restricted and difficult laryngoscopy in our selected study population of patients undergoing elective thyroid surgery; however, the LLB did not obviate the need of the BURP maneuver for improving the laryngeal view and the success rate of tracheal intubation.

 

References

  1. McCoy EP, Mirakhur RK. The levering laryngoscope. Anaesthesia 48:516-519, 1993.

  2. Takahata O, Kubota M, Mamiya K, Akama Y, Nozaka T, Matsumoto H, Ogawa H. The efficacy of the “BURP” maneuver during a difficult laryngoscopy. Anesth Analg 84:419-421, 1997.

  3. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 39:1105-1111, 1984.

  4. Randell T, Määttänen M, Kyttä J. The best view at laryngoscopy using the McCoy laryngoscope with and without cricoid pressure. Anaesthesia 53:536-539, 1998.

  5. Chisholm DG, Calder I. Experience with the McCoy laryngoscope in difficult laryngoscopy. Anaesthesia 52:906-908, 1997.

  6. Tuckey JP, Cook TM, Render CA. An evaluation of the levering laryngoscope. Anaesthesia 51:71-73, 1996.

 

Implications for Clinical Practice (Personal Views of the Authors)

The new LLB for fiberoptic battery handles should be available in both sizes at any anesthesia working station where anesthetists are assigned using the Macintosh blade as the first choice laryngoscope in routine practice. This device may improve the laryngeal view, particularly in combination with the BURP maneuver, and may increase the success rate of tracheal intubation in difficult laryngoscopy. We recommend that the LLB should be used in preference to the Macintosh blade when difficult laryngoscopy and tracheal intubation are anticipated.

During testing of the LLB prior to the study, we observed a temporary injury to the base of the tongue due to a malfunctioning levering mechanism. Therefore, the authors emphasize that the proper function of the levering mechanism should be checked before use of the LLB; failure to return from the activated to the Macintosh configuration during removal of the blade may cause injuries to oropharyngeal structures.


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