Bowie Dick results with new sterilizer...am I being too critical?

[harvj]

The good news is our department finally has a new autoclave!
The bad news is our department finally has a new autoclave!
We ran the bowie dicks and noticed the color change is not as uniform or dramatic (dark) as our other 5 year old machine (same manufacturer) and the card has splotchy, wet looking streaks from the upper edge of the card down to the lower edge.
Service people installing the machine suspected steam quality, so they sold us two new steam separators for both (even though the older machine didn't have the same problem).
Same splotchy results.....
They have replaced almost every mechanical component of the new machine, but have yet to achieve a quality dart test.
Now they are blaming our test packs because they aren't the same brand name as the machine!
Am I being too critical with the dart tests?
Anyone else seeing this situation out there?

[HRJohn]

That sounds kinda fishy to me.

I bet the manufacturer of your bowie dick test pack would be willing to help you with a specific interpretation of those results.

Is the manufacturer able to get a satisfactory result with their own test packs?

Also, what kind of result do they get when they run a leak test on the machine. Maybe you should run one independently and see what you get.

[doc7592]

what is a leak test and how do you run it?

[HRJohn]

Doc writes:

"...what is a leak test and how do you run it?..."


-A leak test pulls a vacuum inside the chamber, then lets the machine sit idle for about 10 minutes to measure how much outside air 'leaks' into the autoclave.

On an AMSCO 3000 series, you simply switch the power button from "on" to "standby", then back to "on" again.

The digital display will ask you if you want to run a leak test, and you press "1", I believe, for "yes".

The leak test then runs automatically, and will measure the inches of vacuum at the beginning of the cycle, and compare it to the end of the cycle.

I checked with my Steris tech., who said the acceptable amount of leakage is around 1.0 mmHg per minute. If you have something significantly higher than that, it's indicative of a problem.

If you have a different type of autoclave, your service rep should be able to show you how to run the leak test. It's usually the first thing I check if I suspect a problem.

[sonny1388]

I don't suppose you have some pictures of the test results? Generally speaking, the biggest concern with these tests are if there is a circle in the middle that is lighter than the outer edges. There are some conditions in the sterilizer that will cause splotchiness/spots/running of the chemical indicator. The way that these tests are made, the outside will turn before the inside, so as long as the center is as dark as the outside, it's an okay test. I'm not saying that there isn't a problem, just not with what the bowie dick's test for (the ability of the machine to produce sufficient vaccuum). Sounds like there might be an excess of condensation getting onto the test card. Is it still hot when you take it out? The temperature difference between inside the sterilizer and room temp could be condensating moisture onto the card, causing the spots. Are the tests being run on the bottom shelf, directly above the exhaust, laying flat? Just trying to get a feel for the conditions...

[harvj]

The test packs felt damp upon removal, with the wet streaks appearing in a top to bottom pattern. This blurred the ability to determine if the results were uniform.
The packs are on a rack, horizontal directly over the drain.
We have people from the test pack company coming Monday to meet with the sterilizer folks (I can probably sell spectator tickets!) to try to interpret the results.
Maybe it's from me posting here, maybe Karma or maybe the machine just sensed the big guns are coming, as during one of the ongoing dart tests yesterday, it sounded an abort signal, the tape printed "failed to reach temp" and continued with the dart test. This "burped cycle" produced the first streak free dart sheet in the four weeks since install!
I ran three more dart tests, time and temps reached with successful streak free results, then ran the three BI cycles.
With the negative BI's, we are now processing instruments!
In the future be assured if I have a process issue, I will quickly post here to see if the vibes from the "magic discussion board" proves the solution!
Thanks!

[autoclave1]

Service sold you a steam seperator that does nothing. As an ISO, 18 years of experience in service, a steam seperator has NO significant results on steam quality. I would like you to try this resolve for your problem: Go thru your normal warm-up cycle, but this time place a loading car inside and watch the temperature-pressure corrolation. An empty chamber has a tendency to superheat. This means that there is no mass to absorbe the steam to simulate a load-lag. Pressure/temperature corrolation shold be within the following window: 270-273--28-32psi. When you run your bowie-dick, do the same thing with a loading car,(just not the same one or let it cool to room temperature first) and compare results.

[autoclave1]

While a machine diagnostic leak rate will tell you something, it is not 100% accurate. It uses the electronic pressure transducer to compare results over time. The software was writted to detect 1mm in 1 min. The actual standard is 5mm in 5 min. This test can only be performed with a calibrated absolute gauge. With the incorporation of new software, service technicians have become lazy and do not typically use this tool any more, but it is part of their tol kit. A leak test is a good indication that there is something possibly wrong, but not necessarly. A machine will fail a leak test but still pass a bowie-dick. If you do a leak test on a regular basis, record the results to track any changes. Most of all, remember that a "leak test" is by no means a replacement for using a bowie-dick test pack.

[chipmoore]

Every B-D test has a designed pass/fail point and meets certain AAMI standards for the 510k clearance. Processing the B-D test on a Load Car is good, empty chamber not good. The Sterilizer Mfg design criteria is 1 mm/hg rate per minute measured over time (ST8-2001). The Dart Test is probably the toughest B-D test.
The Sterilizer that has an automated Leak Test feature, it's results should correlate with B-D test Pass/Fail results. If the sterilizer has properly calibrated Temp probes and Xducer, results should be as accurate as using an independent Heist Guage to measure absolute pressures.
The connected steam supply does need to be properly trapped, a steam separator works as does thermodynamic traps. Steam filters are good. I would tend to believe the service rep.
Here's an interesting story: hospital had failed B-D results but passed the BI's. The source of the B-D problem turned out to be a leaking air accutated valve on the steam supply line. The B-D results were irregulate shapes rather than circular. So, a failed B-D test is meaningful.
Chip Moore
Getinge
Rochester, NY