Kinetics of the aeration of ethylene-oxide sterilized plastics.
The aeration of ethylene-oxide (EO) sterilized medical plastic materials is dealth with mathematically, and subsequently the model found is used for calculation of the EO diffusion coefficient in various plastics with the composition and temperature as variables. Absorption and dissolution of EO in various plastic materials are measured at varying concentrations of EO, temperatures and compositions of plastics. The mathematical model is used to evaluate the EO desorption from medical devices under different physico-chemical conditions as well as in vivo. EO analysis methods are evaluated on the basis of the model and are compared with experimental results.
Technical aspects of gaseous formaldehyde as a sterilant.
The design of a sterilizer for sterilization of heat sensitive items using gaseous formaldehyde and steam is described. The sterilizer is able to create a constant formaldehyde-steam concentration over a period of at least one hour. It is further able to operate at formaldehyde concentrations close to saturation with only small residues on sterilized plastic materials. The autoclave is used for measurement of formaldehyde solubility in polyolefines and poly(vinyl chloride) being approx. 15 and 250 ppm, respectively, at 70 degrees C and 30 mg HCHO I-1. The diffusion coefficient of formaldehyde in poly(vinyl chloride) is measured and is in the same order of magnitude as for ethylene oxide in poly(methyl methacrylate) i.e. 10(-10) cm2 s-1. Measurements of airborne formaldehyde in front of different sterilizers show that it is possible to design facilities meeting occupational exposure limits.
Causes of Damage to Tissues by Polymers and Elastomers Used in the Fabrication of Tracheal Devices
Prolonged exposure of body tissues to tracheal devices has demonstrated that some devices injure tissues. Techniques for safety–testing of polymers (plastic) and elastomers (rubber) by implantation in rabbit muscle and by cell culture are described. Use of these tests should prevent distribution of toxic devices. Products safety–tested by the manufacturers are marked “IT” or “Z-79.” Sterilization of a tracheal device may change it from nontoxic to toxic. The compositions of polymeric and elastomeric devices and problems of sterilization are described.