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Applied forces with direct versus indirect laryngoscopy in neonatal intubation

A randomized crossover mannequin study

Canadian Journal of Anaesthesia

Submitted August 2023 by Dr Caroline Mann

Read by 231 Journal Watch subscribers

This is a single centre randomized crossover trial comparing applied oropharyngeal forces of tracheal intubation of direct laryngoscopy versus video laryngoscopy in a neonatal manikin.

Manikin intubation was demonstrated. Oropharyngeal forces were then compared during intubation using a straight blade direct laryngoscope (Miller 1), straight blade video laryngoscope (Glidescope Miller 1) and hyperangulated videolaryngoscope (Glidescope LoPro S1). Pressure sensors were attached to the laryngoscope blades. The manikin was a Laerdal Newborn Anne. A 3mm ETT and stylet were used.

Participants were 30 neonatal/anaesthetic/paediatric specialists and trainees.

Primary objective: comparison of maximum peak oropharyngeal force

Secondary objectives included comparison of average peak force, time to intubate and subjective workload (using the NASA Task Load Index).

Key Findings

• Less force was required for videolaryngoscopic intubation with straight or hyperangulated laryngoscope blades compared with direct laryngoscopy

• When comparing direct laryngoscopy vs hyperangulated videolaryngoscopy, median differences between maximum peak forces were 5.3N (99%CI 3.9-7.2). Median difference between average peak was 7.3N (99% CI 4.1-8.8N)

• When comparing direct laryngoscopy vs straight blade videolaryngoscopy there was no detectable median difference in peak pressures

• No differences were found for time to intubation or subjective workload


This study addresses the issue of force required for neonatal intubation, which is clinically relevant to this vulnerable population. This is especially important for premature neonates at higher risk of intraventricular haemorrhage and oropharyngeal trauma. Recent research in this area has mainly focused on adult studies, which show similar results of reduced force for intubation using videolaryngoscopy vs direct laryngoscopy.

This is a reasonably well designed study using appropriate equipment and a simple crossover design.

The main study limitation acknowledged by the authors was that manikins were used. The authors recommend further clinical studies before drawing significant conclusions.

Intubation is very different in actual neonates. Techniques to optimise neonatal intubation including patient positioning and laryngeal manipulation to bring the vocal cords into view, which are often used in vivo as neonatal tissues are soft and malleable, therefore laryngoscopic forces used may be much lower.

Intubation experience of the participants was wide ranging, from senior neonatal anaesthetists to junior trainees, which may have led to wide ranging results, but also reflect the intubators in clinical practice.

Laryngoscopic technique may have varied, despite demonstration. Successful neonatal intubation with minimal force is usually dependent upon the operator’s technical skill, including placing the laryngoscope blade tip in the correct area, the ability to swiftly adjust tip position and laryngeal manipulation to bring the cords into view without repeat laryngoscopy.

In vivo other outcome measures indicating pressure and stimulation such as heart rate and arterial pressure changes may also be monitored. Other factors potentially causing trauma clinically include oropharyngeal trauma from intubators inadvertently blindly advancing the stylet/endotracheal tube during videolaryngoscopy, which may be a relatively common issue in inexperienced videolaryngoscope users.

Despite these limitations, the findings fit anecdotally with that of experienced neonatal intubators. That is that less force is required during videolaryngoscopy of neonates especially when using hyperangulated blades. This is relevant to all neonatal intubators.

Take Home Message
Less force may be required for neonatal intubation using videolaryngoscopy vs direct laryngoscopy

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