EBME Forums Forums Maintenance Technical Assistance Occlusion Pressure Setting in Syringe Pumps

We have 3300's using a stat of 200ml/hr and using the free flow device with no probs. It just sem to be a problem with the 3200's. Units are adjusted to the factory set value.

There seems to be a bit of ambiguity regarding occlusion levels and apporpriately set prssure alarm levels. Some pundits seem to advocate setting pressure levels just above line pressure in order to have an rapid time to occlusion, others seem to advocate that it doesn't matter. Am I missing something?

Richard, Can you give me the references you are referring to. We to have a similar issue with 3200's.

Sure - I will dig them out of the in-tray on my bench.

Yes Joe - the point I made was that the 3200 occlusion specification, if the same as the 3100 (3.5Kgf- 4.2Kgf from memory), may be lower than the 3300 occlusion specification.

Unfortunately I haven't looked at a 3200 manual for years so I'm only guessing (perhaps you could tell me what the specification is and how you check compliance with it).

Anyhow what I was getting at is that if we (and others) have had problems with a similar line/syringe setup using the 3300 (200ml/hr stat rate) then problems with a 3200 at 200ml/hr using manufacturers specifications, for the occlusion threshold, are likely.

I was interested in the comments regarding tissuing and occlusion pressures.

I am sure in my own mind that tissuing will occur regardless of occlusion pressure setting if the clinical conditions exist, i.e. cannula movement, fragile vein, poor positioning etc. There are examples of tissuing occuring with gravity infusions where the in line pressures are marginally above the venous pressure to ensure positive infusate flow.

The purpose of occlusion limits as has been well descibed earlier it to prevent bolus delivery and indeed pump or disposable damage, not tissuing. The idea of trending is Ok so long as someone is there to view and interpret the data.

I know many a sales pitch has been built up on the benefits of pressure monitoring and tissuing incident reduction but I remain sceptical. I am firmly in the camp of "routine observation of the IV site" as a method of prevention. If the reply comes back that there arn't enough staff to undertake the observations, then there arn't enough staff to interpret pressure trend data either!

We have remained with the manufacturer's default setting for all infusion devices apart from those for neonates for whom we reduce the setting by 50%. Tissuing events as reported to me have been low to non existant.

Lucky? - possibly but I wait to be convinced.


Brian

I do prefer calibration of occlusion alarm thresholds, externally, rather than the tedious internal, mechanical, adjustments necessary on older generations of syringe drivers - whatever the source of alarms.

The other potential benefit of pressure monitoring/trending is that some syringe drivers use "fast start" and "backoff" features that remove actuator backlash (which causes initial loss of delivery at startup) by monitoring syringe actuator/line back-pressure and can actually remove the bolus, due to occlusion or excessive pressures in the distended line, by withdrawing ("backoff") the syringe plunger until pressures are in the normal range i.e. on alarm excessive pressure is removed from the system and bolus prevented from being delivered (if the occlusion is subsequently cleared under pressure). The pressure monitoring effectively completes a control-loop.

Brian correctly points out that there should be regular monitoring of infusion sites. However, once the operator observes colour change and swelling, damage has already occurred. In neonates particularly it is important to use devices that can measure small changes in pressure. The line pressure will vary depending on syringe size, flowrate and drug viscosity. It is therefore important to measure the line pressure for a few minutes post setup and then set a pressure window on top of that. Should a pressure increase occur, then it will be detected early before there is visible signs of tissue damage. Some syringe drivers allow this accuracy by using pressure monitoring sets. Some users choose to follow this procedure - some do not. If there is an incident and the technology was available and not used, would this be criticised? Is it not true that in the best interests of patient safety particularly in our most vulnerable patients (neonates) that pressure monitoring be carefully applied.