Augmented reality laryngoscopy and ergonomics: a different stance

Abstract

We read with interest the study by Ding et al. into the use of augmented reality technology to improve operator ergonomics during laryngoscopy [1]. Musculoskeletal injuries of the upper limb and cervical spine are common in anaesthesia, and laryngoscopy is considered an especially hazardous activity. This study is useful in prompting clinicians to reflect on their practice and the optimal position for laryngoscopy, whatever the method. However, several limitations of this study should be noted: the operators could not be blinded to the device, which may affect the reliability of their assessments; there is inherent bias in the provided images; the use of an industrial rather than clinical endoscope raises concerns; and the imperfect laryngoscopy technique and manikin positioning likely influenced operator posture.

In our opinion, direct laryngoscopy is best performed when the lifting force applied through the blade (upwards and forwards) is generated predominantly from the shoulder/upper back rather than the forearm, facilitated by a minimally flexed arm (at the elbow), with the operator standing upright and leaning very slightly backwards away from the patient. Figure 1a [1] appears to be inconsistent with this.

The manikin is lying supine, which may affect airway management. The head-up (semi-Fowler's) position optimises patients' respiratory mechanics, the efficacy of pre-oxygenation and apnoeic oxygenation, and other aspects of airway management such as glottic views at laryngoscopy [2]. Additionally, it improves operators' posture and access to the airway.

It appears that a pillow/neck roll was not used to achieve optimal flexion/extension of the cervical spine during laryngoscopy, such that the operator was required to adjust their stance to compensate. The operating table was set at the level of the operator's upper thigh; insufficient vertical table height likely impaired posture most during direct laryngoscopy, since this has been shown to be best performed at close to nipple height [3], accounting for the greatest angle of deviation from the vertical (Fig. 1a [1]). Videolaryngoscopy with a hyperangulated blade, like the UEScope® (Newton Centre, MA, USA), which has more curvature than a Macintosh blade but less than other hyperangulated blades, is often done at a lower table height which explains the smaller angle of deviation (Fig. 1b [1]). In the augmented reality technology video ([1]), the operator still had to lean while inserting the tracheal tube, deviating from their usual upright posture (Fig. 1c [1]).

The authors state that bending down/lowering the head is required to view handle-integrated videolaryngoscope screens. This is debatable, as most devices have screens that can tilt vertically and rotate horizontally for optimal viewing (including the ‘all-angles’ UEScope monitor). It appears that neither of these functions was utilised (Fig. 1b [1]).

The limitations of manikins in airway studies are well described [4]; in particular, lack of tissue pliability can impair blade lifting, causing the operator to lower themselves closer to the manikin to achieve an adequate glottic view. This issue is likely to be most apparent during direct laryngoscopy, since it requires the most blade lifting, influencing the study findings.

Poor manikin positioning and technique in this study hinder the interpretation of the results; such errors in real life could have serious consequences. Technological advancements should not compensate for suboptimal preparation or technique, nor should they negate the need for high-quality training. Airway managers must maintain basic airway management skills to fully benefit from advanced technology.