Comparison of a new vacuum extractor with the Malmstrom system - in vitro experiments and clinical application

Background: The vacuum extractor is used in about 5% of deliveries. It is a ssociated with a lower maternal morbidity than is forceps extraction. On th e other hand, cephalhematomas, hyperbilirubinemia and cerebral hemorrhages in the baby are observed more frequently. The sudden detachment of the vacu um extractor with appreciable fluctuations in intracranial pressure in the baby is especially dangerous. In order to improve the conventional Malmstro m system, we have developed a new vacuum extractor and investigated its han dling in vitro and in clinical application. Patients and Methods: The essential constructional principle of the new vac uum extractor consists in a pivot lowered by ball bearings and a volume red uction of one third. Moreover, in two-chamber vacuum it is possible to give a warning of sudden detachment. The possible tractional force in kiloponds was determined at various angles (0 degrees, 15 degrees, 30 degrees und 45 degrees) comparing the Malmstrom extractor with the new one and two-chambe r system in a standardized apparatus. In addition, the new vacuum extractor was also used clinically in 43 women; besides the obstetric parameters, th e handling was also appraised. Results: In the in-vitro experiments, a distinct decrease of the possible t ractional force with increasing angles was shown for the Malmstrom extracto r (0 degrees - 15.7 kp, 15 degrees - 12.7 kp, 30 degrees 8.6 kp, 45 degrees - 7.3 kp). The values for the new one-chamber system were significantly gr eater from a tractional angle of 15 degrees (0 degrees -15.6 kp, 15 degrees - 14.4 kp, 30 degrees - 14.0 kp, 45 degrees - 13.8). The clinical applicat ion of the new vacuum system was unproblematic and confirmed the feasibilit y of good traction. A very much smaller caput succedaneum was found in the baby. Especially in the training situation, the warning system enables a go od surveillance before sudden detachment, but reduces the possible traction al force. Conclusions: The new vacuum system appears to enable the vaginal surgical d elivery to be improved compared to the conventional Malmstrom extractor. Af ter these promising appreaches, a multicenter study was commenced in order to enable better evaluation of their clinical significance.