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INTRODUCTION: Leaching of plasticizers, especially the phthalate DEHP (diethylhexyl phthalate), from PVC materials is well-known, and health-concerns are raised with regards to human exposure to DEHP leached from the materials [1]. Still, PVC tubes are used as feeding tubes, also for neonates and prematures. At Haukeland University Hospital (Bergen, Norway), the use of PVC feeding tubes was questioned after observing property changes (stiffening) of the tubes upon use for some days. Recently, the DEHP plasticizer was exchanged with TOTM (trioctyl trimellitate) in some tubing materials. The aim of this study was to analyse the leaching of plasticizers from feeding tubes in combination with the evaluation of changes in mechanical properties as measured by tensile testing.

METHODS: Feeding tubes made from silicone, polyurethane or PVC were tested. The leaching of plasticizers from different tubes was measured (chromatographic analysis, GC/MS and LC/MS) in hydrophilic and lipophilic solutions to simulate gastric fluid and feeding solutions, respectively. The property changes of the feeding tubes were investigated using a tensile test (Fig. 1) measuring the relative elongation and the elastic modulus of the feeding tubes as delivered, and after soaking in simulated feeding solution for 48 h.

RESULTS: Only minor amounts of plasticizer were found to leach into the hydrophilic solutions after 48 h. The amounts were estimated to be in the range 50-100 ng DEHP per ml solution for the PVC materials, corresponding to app. 15-30 ng/cm of tubing material. However, larger amounts of phthalates were found when soaking the tubes for 48 h in the lipophilic solutions: 833-2344 µg/ml DEHP was detected, corresponding to 1.7-4.7 mg/cm of tubing material. Feeding tubes of alternative materials (silicone and polyurethane) did not contain DEHP or TOTM. The elastic moduli of the PVC-tubes increased with up to 80% after the tubes were soaked in lipophilic solution for 48 h. The elastic property of the other tested tubes of alternative materials (silicone and polyurethane) did not show such pronounced changes.

DISCUSSION & CONCLUSIONS: The low water solubility of DEHP (reported between 1 and 1200 ng/ml) limits its migration into aqueous solutions. However, the solubility and migration into lipophilic solutions is much higher. Similar behaviour may be suggested for the alternative plasticizer TOTM. PVC tubes may thus still have unwanted property changes upon use with lipophilic solutions. Tubing materials of polyurethane or silicone seem to keep their properties after soaking in simulated feeding solutions

REFERENCES: 1 SCENIHR (Scientific Committee on Emerging and Newly-Identified Health Risks), Scientific opinion on the safety of medical devices containing DEHP-plasticized PVC or other plasticizers on neonates and other groups possibly at risk, 6 February 2008.

ACKNOWLEDGEMENTS: The support from Haukeland University Hospital and Norwegian suppliers of feeding tubes is appreciated.


Reference
Feeding tubes for neonates – leaching of plasticizers in food simulating solutions and resulting changes in mechanical properties.
Kopperud HM, Gjerdet NR.
European Cells and Materials Vol. 23. Suppl. 5, 2012 (page 20). ISSN 1473-2262