Background: 
Ensuring adequate bag-and-mask ventilation before the administration of a neuromuscular blocking (NMB) agent has become a generally accepted practice among many anaesthetists, in order to avoid a Can’t Intubate, Can’t Oxygenate situation, despite lack of evidence of any benefits for patient safety.  In contrast, the recently published DAS guideline for the management of the difficult airway promotes the use of NMB to resolve difficult mask ventilation.This study aimed to investigate the implementation, rationale for and effects of a mandatory mask ventilation trial before routine intubation.

Methods:
Adult patients of ASA class I-II scheduled for elective surgery under general anaesthesia with intubation were recruited. The anaesthetic team consisted of an anaesthetist (<10 years of experience), a nurse anaesthetist, and a nurse assistant. Video-assisted observations were made by an observer alongside one of two senior consultants taking detailed notes. Subsequently, participating anaesthetists were interviewed concerning their practice as well as the perceived departmental policy and the teaching of testing mask ventilation before NMB.

Results:
Preliminary data from 29 patients showed that, a test of mask ventilation was performed before the administration of NMB in 21 cases. In eight cases the anaesthetist was not satisfied with initial ventilation, in four of these eight cases the first response was to administer NMB, while in three cases mask ventilation was improved before administering NMB. In one case improvement was attempted but proved impossible, leading to decreasing SpO2. During the interviews the concept of testing mask ventilation before NMB was known to all 13 anaesthetists and was regularly used by ten. All 13 agreed that chest movements and/or CO2-wave formation was required for the test to be satisfactory. However, the perceived next step in case of a failed test varied. So did their understanding of the policy held by the department.

Conclusions: 
Mask ventilation before NMB is a prevalent practice of varying importance for the junior anaesthetist in our centre. Cases where the test was successful, partially successful, futile, or even potentially harmful were observed. The method of video recording real live anaesthetic team performance combined with observation notes and interviews may be useful for understanding mental models of best practice in anaesthesia. The concept of mandatory mask ventilation before NMB administration needs further study.

A mandatory mask ventilation trial before neuromuscular block: a qualitative study of its conceptual and practical significance for registrars and junior anaesthetists