Device technique
The original IFU was developed prior to this study during the phase 1 clinical and simulation studies and included 22 operative steps. In this IFU, the AVB was divided into six domains according to purpose (Table 2). It was hypothesised that the steps may vary between cases, depending on factors such as station and position. Qualitative analysis provoked and encouraged operators to discuss cases between themselves, either through telephone calls or via a dedicated end-to-end encrypted messing service.
Principal adaptions to the original IFU included (i) device application during rather than between contractions, (ii) altering the application angle and (iii) deflating the air cuff as soon as any aspect of the blue deflation line became visible.