Balloon laryngoscopy reduces head extension and blade leverage in patients with potential cervical spine injury

Abstract

Head extension and excessive laryngoscope blade levering motion (LBLM) are undesirable during airway management of trauma patients. We hypothesized that laryngoscopy with a modified blade facilitating glottic exposure by balloon inflation would reduce head extension and LBLM. -tests. Laryngoscopic view grade and oxygen saturation were also determined. <0.001). Laryngoscopic view was approximately identical with both blades, and oxygen saturation was always above 97%. Balloon laryngoscopy reduces head extension and LBLM under simulated cervical spine precautions.

Background:

Head extension and excessive laryngoscope blade levering motion (LBLM) are undesirable during airway management of trauma patients. We hypothesized that laryngoscopy with a modified blade facilitating glottic exposure by balloon inflation would reduce head extension and LBLM.

Patients and methods:

-tests. Laryngoscopic view grade and oxygen saturation were also determined.

Results:

<0.001). Laryngoscopic view was approximately identical with both blades, and oxygen saturation was always above 97%.

Conclusions:

Balloon laryngoscopy reduces head extension and LBLM under simulated cervical spine precautions.

Introduction

].

].

We hypothesized that balloon laryngoscopy might result in less head extension and LBLM, because balloon inflation and subsequent blade elevation should facilitate laryngeal exposure and reduce the extent of the necessary laryngoscopic manoeuvres.

We determined the head extension and LBLM needed for maximal glottic exposure with both blades, the laryngoscopic view grade during each laryngoscopy and oxygen saturation. The present results showed significant reduction in the head extension and LBLM angles during balloon laryngoscopy.

Modified Macintosh Blade with right catheter balloon inflated with 2 ml air and automatic angle finder. MR, angle finder's metallic ruler; VA, angle finder's vertical arm.

Patients and methods

].

), was sequentially placed on the right-long and cephalad-short sides of the table's metallic frame; and each time the table's inclination was adjusted until the angle finder read 0°.

). Standard monitoring (including pulse oximetry) was used.

), and the head was manipulated until the angle finder read 0°. Subsequently, laryngoscopy was performed with both standard and modified blades in randomized order. In between laryngoscopies, neutral head position was resumed.

, respectively) were measured with the angle finder upon maximal glottic exposure with each blade. To measure the angle of the handle relative to horizontal, the angle finder's metallic ruler was placed on the median longitudinal axis of the handle's posterior aspect. All patients were intubated during the second laryngoscopy immediately after measurements were taken.

) proposed by SDM and MJJ.

; point E).

The maximal acceptable laryngoscopy duration and time between the two laryngoscopies were 30s, and the maximal allowable study procedure duration was 180s. Procedure timing began upon succinylcholine administration.

< 0.05 was considered statistically significant.

An adhesive tape is placed on the right cheek of an assistant. The tape's median longitudinal axis (AB) is parallel to the occlusal surface of the maxillary molars.

, angle of laryngoscope blade levering motion; AH, axis of handle; CH, chord corresponding to the radian formed by the proximal third of the laryngoscope blade convex surface; E, distal end point of said radian; OS, axis of occlusal surface of maxillary molars or gums.

The modified Cormack-Lehane grading scale used to evaluate the laryngoscopic findings obtained in the present study

Results

< 0.001).

Patient-by-patient values of the determined head extension and laryngoscope blade levering motion angles. CMB, conventional Macintosh blade; MMB, modified Macintosh blade.

Values of the head extension and laryngoscope blade levering motion angles during conventional and balloon laryngoscopy

-test.

Discussion

). This might be due to reduced need to manoeuvre the modified blade while exposing the glottis.

].

) and similar laryngoscopic views with both blades.

].

]. The maximum allowable head extension during airway management of trauma victims and the actual risk of neurological deterioration associated with conventional airway management techniques applied in cervical spine-injured patients still remain to be determined, however.

). This chord is the best straight-line approximation to the geometrical shape of the proximal one-third of the blade's convex surface. This portion of the no. 4 blade is most frequently in close proximity with the upper teeth of adult males during laryngoscopy, and may traumatize them if excessive LBLM is employed. Upper incisor trauma and/or dislodgment may then result in aspiration of tooth fragments into the trachea.

In our opinion, the potential risks of spinal cord injury and of maxillary teeth dislodgement during laryngoscopy performed in trauma patients under cervical spine precautions should not be underestimated (especially in the presence of unstable cervical spine injuries and/or maxillary trauma), despite the fact that they have not yet been accurately determined.

In summary, we demonstrated that the head extension and LBLM angles are significantly reduced when balloon laryngoscopy is performed under simulated cervical spine precautions in carefully preselected and adequately anaesthetized and paralyzed elective surgery patients. Such 'ideal' conditions may not be achievable in the emergency setting, however. Thus, further investigation is required to prove the usefulness of balloon laryngoscopy in the emergency airway management of cervical spine-injured patients.

Keywords

• balloon laryngoscopy
• blade
• extension
• head
• leverage
• spine