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This systematic review of patients with a serious head injury found that prehospital intubation by undertrained or inexperienced staff was linked to an increased risk of death when compared to no intubation or intubation after arrival in the hospital. Restoring an individual’s airway is a priority because lack of oxygen can cause death, brain damage and other negative outcomes, but prehospital intubation was not linked with a change in mortality generally.

Staff need to be trained in intubation and have regular refreshers to maintain their skills. It is not clear what proportion of emergency service personnel in the UK have such specialist training and therefore what, if any, additional resource would be required to ensure this level of experience was present across the workforce.

Why was this study needed?

People with traumatic brain injury caused by a serious head injury can have a reduced level of consciousness, leading to their airway becoming blocked as muscles in the airway relax. Restoring the airway is a treatment priority because lack of oxygen can cause death, brain damage and other negative outcomes. The airway may be opened by simple techniques such as tilting the head back or removing obstructions manually. However, this is not always effective in people with serious head injuries.  In such cases a tube may be inserted through the mouth and into the windpipe to provide a clear airway before the person is taken to hospital. In the UK paramedics may have variable experience in performing intubation. As such the expertise of the practitioner could have an influence on the risk of adverse outcomes.

This systematic review aimed to look at the effects of intubation before hospital on mortality and whether the level of experience of the person performing the procedure had an effect on outcomes.

What did this study do?

This systematic review identified 24 trials (a total of over 30 000 patients); one randomised controlled trial, one secondary analysis of a randomised controlled trial and 22 cohort studies. In seven of the studies intubation was performed by an experienced provider, in five studies the provider’s experience was limited, and in 12 studies their level of experience was unclear.

The results of six of the studies (including a total of 4772 participants), where experience of the person intubating was clear and which also had a low risk of bias, were pooled in a meta-analysis.

The review looked only at “severe” traumatic brain injury, defined as a score of nine or less on the 15-point scale Glasgow Coma Scale accompanied by evidence of head injury. The age of participants in the included studies was 14 years or more; trials looking specifically at children were excluded. This review followed good practice for conducting systematic reviews, but many studies underlying the review were conducted in the US where paramedic standards and training may differ from the UK.

What did it find?

  • Overall there was no significant association between pre-hospital intubation and mortality (odds ratio [OR] 1.35, 95% confidence interval [CI] 0.78 to 2.33) when compared to no intubation or intubation on arrival in hospital.
  • Pre-hospital intubation by providers with limited experience was associated with significantly higher risk of mortality (OR 2.33, 95% CI 1.61 to 3.38). When it was performed by an experienced provider it was not associated with increased mortality (OR 0.75, 95% CI 0.52 to 1.08).

What does current guidance say on this issue?

NICE recommends that pre-hospital management of serious head injuries treats the greatest threat to life first. The guidance gives specific recommendations for when intubation should be performed immediately and before transfer, including when the person has a Glasgow Coma Scale of less than nine. NICE also recommends that initial assessment and care is in line with principles of best practice such as the Pre-hospital Trauma Life Support course and the Joint Royal Colleges Ambulance Service Liaison Committee Guidelines for Head Trauma. Guidelines produced by the Resuscitation Council recommend that pre-hospital intubation is only carried out by appropriately trained staff who undergo regular refreshers and suggest that another airway device (such as a laryngeal mask airway) may be preferable as it is easier to use.

What are the implications?

Compared to no intubation or intubation after arrival in hospital, pre-hospital intubation carried out by undertrained or inexperienced staff is associated with an increased risk of death. Even when performed by experienced staff it has no effect on mortality. The failure of intubation, even in experienced hands, to reduce mortality is an important finding. Current UK guidelines reflect the importance of a stepped approach to airway management with intubation reserved for those unable to maintain oxygenation by other means.

It is clear that this review may have training implications for the UK emergency response workforce, however the fact that most studies were conducted in the US, which has a different health system means that local information applicable to the NHS is required. This could include an assessment of the proportion of paramedics in the UK who have the required extensive experience and the potential costs of training more.


Bossers SM, Schwarte LA, Loer SA, et al. Experience in Prehospital Endotracheal Intubation Significantly Influences Mortality of Patients with Severe Traumatic Brain Injury: A Systematic Review and Meta-Analysis. PLoS One. 2015;10(10):e0141034.


NICE. Head injury: Assessment and early management. CG176. London: National Institute for Health and Care Excellence; 2014.

RSUK. Adult advanced life support. London: Resuscitation Council (UK).

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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