A new swivel model for parenteral and enteral infusion in rats

In experimentation with rats submitted to enteral and parenteral infusions for medium to long periods it is necessary to use swivels. With the objective of developing a new biocompatible, safe, efficient, and low cost swivel, the medical and engineering teams of the University of São Paulo joined forces.

After defining the characteristics and criteria for the mechanical design, the new swivel was developed and bench tested for flow, rotation and sealing. Later it was evaluated on rats, after catheterization of jugular vein and stomach (by gastrostomy) for infusion of different solutions at certain concentrations and infusion rates (mean 6.73 days of infusion).

The new swivel consisted of two sections of common plastic syringes for injection, together with the rubber seals, a plunger, and a hypodermic needle. The syringe with a slightly smaller diameter rotates inside the larger diameter syringe interconnected with a needle sealed by their respective rubber rings. The bench and animal tests did not reveal any functional defects. There were no blockages or leaks in the swivel and it was reused three times without losing its mechanical properties, after being hygienized and sterilized with ethylene oxide. The cost of producing this swivel is estimated to be no more than $3 US.

The cooperation between the departments of medical research and mechanical engineering enabled the development of a swivel that is simple and inexpensive to make, yet fully meets the needs of parenteral and enteral infusion in rats. The authors present detailed instructions for the construction of this new swivel.