Abstract
Operative delivery requires the use of a vacuum extractor; obstetricians can choose the appropriate vacuum extractor to make the delivery process smoother and safer. However, there is no biomechanical literature focused on the imposed effects of a vacuum extractor prepared with different materials and vacuum pressure on the fetal head during the process of delivery. Therefore, we first established and performed the finite element analytical model to explore the influences of vacuum extractors manufactured from different materials on the fetal head under various extractive pressures. The model of the vacuum extractor was designed as a hemispherical shape, and the material of the vacuum extractor was composed of silicone rubber and stainless steel for comparison. Four different vacuum pressures (500 cm H2O, 600 cm H2O, 700 cm H2O, and 800 cm H2O) were applied as the factors for investigation. The reaction force on the fetal head, von Mises stress of vacuum extractor, and von Mises stress on the skull of fetal head were measured and analyzed to evaluate the effects. The results revealed that subtle divergent influences of different vacuum pressures were observed, and the stainless-steel vacuum extractor induced a larger reaction force (358.04–361.37 N), accompanied with stress (13.547–13.675 MPa), on the fetal head than non-metallic or relatively softer materials. The results provide a reliable basis for selecting proper vacuum extractor during operative delivery to avoid obstetrical complications, such as scalp scratch, cephalohematoma and even intracerebral hemorrhage.
Highlights
Operative delivery is an important lifesaving obstetric technique in clinical delivery units, wherein obstetrical physicians can perform a smoother and safer delivery with the help of a vacuum extractor and forceps [1]
On the whole, when silicone rubber was used as the material of vacuum extractor (12.229–15.064 N), the reaction force was smaller, compared with using stainless steel (358.04–361.37 N)
When the time t = 1 s, the results show that the von Mises stress in the area on the fetal head skull extracted by the vacuum extractor showed relatively greater stress with the increasing vacuum pressure when silicone rubber was used as the material of the vacuum extractor
Summary
Operative delivery is an important lifesaving obstetric technique in clinical delivery units, wherein obstetrical physicians can perform a smoother and safer delivery with the help of a vacuum extractor and forceps [1]. Using these tools for assistance in operative vaginal delivery still has related risks. Vacuum extractors are made of different materials, such as soft (e.g., silicone rubber) and hard (e.g., metals) materials [5]. According to the clinical experience of application, vacuum extractors made of soft materials are easy to use and infants are less likely to be injured, compared with vacuum extractors made of metal materials for extraction [6]. The above is known clinically, there is still no associated biomechanical research that can clearly monitor the stressed influences of vacuum extractors manufactured from diverse materials and at different vacuum pressures
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