Vacuum extraction failure or lack of skill



I refer to ‘Randomised controlled trial of a new handheld vacuum extraction device’, by Attilakos et al.1

This randomised controlled trial (RCT) purports to show that in a population of 194 women requiring vacuum extraction, the single-use Kiwi Omnicup was associated with a significantly higher failure rate than standard (metal or silicone) cups.

I would suggest that the paper demonstrates no such thing.

The fact that the background rate of failure to achieve delivery with vacuum extraction at the institution where the study was performed (Southmead Hospital, Bristol) was ‘approximately 25%’ in the several years prior to the study being performed seems to indicate that the accoucheurs at Southmead are not sufficiently skilled in vacuum extraction. I believe that if a service is having more than 10% failure with whatever assisted delivery device that they are using, it is a very strong reason to look to in-service training rather than setting themselves up as a centre for the purpose of testing a new device.

Attilakos et al. state that when the Omnicup was introduced into their unit, all obstetricians had the opportunity to watch a training video supplied by the company marketing the device. I would suggest that not much notice was taken of this training video. In the section of this video on minimising failure, the importance of placement of the vacuum cup over the ‘flexion point’ is made very clearly and, indeed, repeatedly. In the analysis of the factors associated with failure, Attilakos et al. do not even mention where their cups were placed on the baby's head.

Another comment in the discussion section of this paper also would indicate a lack of understanding of the principles of vacuum extraction. Transverse and posterior positions of the occiput should not be associated with a higher incidence of failure to achieve delivery with a manoeuvrable vacuum cup, i.e. one that is possible to place over the flexion point. This is because when one places the vacuum cup over the flexion point in posterior and transverse positions, the first ‘pull’ produces increased flexion of the fetal head attitude thereby facilitating descent and rotation. In anterior positions, the first flexing pull may serve to reduce presenting diameters a little, but after that all the vacuum offers is traction to augment the mother's expulsive efforts.

If one places any cup at all in a deflexing or paramedian application on the fetal head, then there will be more fetal scalp trauma and a higher risk of delivery failure with standard guidelines of traction time and number of pulls.

I think the definitive RCT on this issue needs to be done in a unit where the background vacuum failure rate is at least not more than 10%.