Design and Development of Atraumatic Vacuum Assisted Delivery Devices

Vacuum-Assisted Delivery (VAD) is an obstetric practice used to assist child delivery during the second stage of labour. During the procedure, the obstetric professional attaches the VAD device to the scalp of the foetus through suction and tractive force is then applied alongside maternal contractions to assist the baby’s passage through the delivery channel. VAD is more prevalent than obstetric forceps due to its ease of use, lower maternal morbidity and improved cosmetic outcome for the mother and her baby. However, safety concerns such as unintentional cup detachment or high vacuum, can lead to induced trauma to the foetus. Since its original inception, there have been limited efforts to evaluate the safety of VAD devices or optimise their design and operation. Here, an engineering approach to assess the devices’ failure modes is proposed to inform training, best obstetric practice and improved VAD design. An instrumented experimental recreation of VAD has been developed to achieve a comprehensive understanding of the mechanics of VAD devices and the associated trauma. It features an instrumented adaptation of a commercially available VAD device (the Kiwi® Omnicup™) connected to a tensile testing machine to simulate obstetric traction onto a head scalp model (fabricated using textile reinforced silicone). A pneumatic control system provides an actively controlled vacuum to the instrumented device. Optical markers, placed onto the scalp model, combined with a high-speed camera system provide tracking of scalp deformation during the mechanical simulation of an obstetric traction. Experimental factors such as traction speed, magnitude of vacuum imposed & changes to the design geometry of the VAD cup and pneumatic architecture including the consideration of frictional attributes of the maternal environment, were investigated. The results from the experimental studies show that a simulated obstetric VAD traction produces a characteristic response from which a number of key clinically relevant metrics can be determined and highlight the association of clinical factors and mechanical factors to device performance. The research informed on the conception of an atraumatic concept to prevent cup detachment. Upon evaluation of the technical and commercial feasibility of the concept, commercial and research opportunities were identified, which could help improve the performance of VAD devices, in the future.