In the Scandinavian and Swiss HEMS critical care teams, the prehospital tracheal intubations (TI) are performed by airway experts with high success rates and low rates of complications. Due to environmental conditions these are today frequently performed in-cabin before take-off. There are so far no published data on comparing outside and in-cabin TI under these circumstances.

This will therefore be the first prospective study comparing prehospital TIs outside or incabin, performed by airway experts.

Background Seriously ill or injured patients might require prehospital TI, which is a potentially lifesaving intervention. Performing TI in a prehospital context differ from the preconditions inhospital due to environmental and technical aspects and resources available (3). Today there is a consensus that prehospital critical care should at least be on the same standards as in-hospital care. The trend therefore has been towards more rigorous safety precautions introducing Standard Operating Procedures (SOP) including 360oaccess to patients with all equipment at close hand brought out from the helicopter or the ambulance and long challenge-response lists. This will shift focus towards adherence to SOPs instead of tailoring the sequence of procedures according to circumstances and patient needs. An experienced operator can plan and communicate appropriate actions from a risk-benefit perspective in a stressful situation. Prehospital interventions have to be time effective, especially where short on-scene times are preferable in time-critical conditions such as uncontrolled internal haemorrhage and traumatic brain injuries.

A recent Nordic multicentre study, PHAST, shows that emergency systems staffed with highly experienced anaesthetists can perform prehospital TI with high success rates, low incidence of complications and short on-scene times. Due to environmental factors, weather and light conditions in the Scandinavian countries, it is not always favourable to perform TI outside the helicopter or ambulance, with 360o -access. Technical aspects in-helicopter/in-ambulance such as access to better suctioning and stretcher positioning, can influence the operator's decision on where to perform the TI. Whether the location of the TI affects the outcome has not yet been studied. A recent experimental mannequin study, SPRINT, suggests that in-cabin intubations can offer equal to, or even better conditions than out of cabin and can shorten on-scene time. To investigate whether this applies to real life conditions, a prospective large-scale clinical study must be done.

Performing prehospital TI is dependent on a well-functioning team where the operator has an assistant backing up during the procedures. The assistants' level of airway experience and the teams' accumulated experience working together has not been studied earlier.

Inclusion Criteria:

• Patients in need of prehospital drug-assisted intubation.

Exclusion Criteria:

• All cases where prehospital TI is performed without the use of any drugs.

All drug-assisted intubations performed at the participating HEMSorganizations between 01/01/2020 and 01/09/2021.

All collected IPD

From 2022