Why you should not use PVC tubing in the O2/aircircuit if you are using Forane (or any anaesthetic gases)

Because the anaesthetic gases can react with PVC tubing to break it down and produce substances that can then get to the patient and/or other equipment in the line.  All tubing used in line with anaesthetic gases should be of a type that is inert to the gases.

The Perfusionists at a hospital had been using standard 1 / 4" clear green PVC tubing for carrying the O2/air mix to the Oxygenenator.  They had been using this tubing for years for this purpose.  In the last year or so they had been using Forane more and more routinely.  The forane comes from a vaporizer mounted on the pump assembly mast.  Recently they noticed some moisture appearing in the tubing on both sides of the vaporizer, with the majority of it on the oxygenator side of the tubing.  Upon further investigation, it was discovered that this moisture was very oily to the touch.  After considerable investigation it became apparent that the oily-type substance was being produced by a reaction between the Forane and the PVC tubing, and this subsequently was supported by information from the manufacturer of the tubing.  It is quite easy to reproduce.  Pour a small amount into a small piece of tubing and wait 5-10 minutes for it to evaporate.  You should be appalled at what is remaining.

The manufacturer subsequently offered an alternative and better product, a Teflon lined tubing.

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Why I.V. Administration Sets require In-line Filters?

Recent events in the UK have highlighted the fact that under some circumstances, users injecting drugs and additives into IV fluid bags sometimes scrape the needle along the plastic tube, resulting in strips of plastic (frequently spirals of plastic) peeling off the walls and ending up in the IV fluid.  This problem can usually be avoided by ensuring that the needle penetrates the injection port at 90o and not at an angle.

Particles may also be produced whenever membranes are pierced on entry into bags, vials, injection ports and whenever glass ampoules are opened.  Sets conforming to British Standard BS 2463, Part 2, are required to incorporate a filter.  If the set is a solution set, the filter must be a 40u filter or smaller and for blood sets, the filters may be of any size providing the filter blood to the same extent as a reference 200u filter.  Also, note that whilst solution sets conforming to the British Standard have filter pore size of 40u or less, these are not bacterial retention filters.  Pore sizes of around 0.22u are required for bacterial retention.

For further information please contact Pete Phillips, Deputy Director, The Surgical Materials Testing Laboratory.

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