Sooner or later we all get lucky and find ourselves able to replace older equipment. When you have equipment that’s so old it can’t be repaired (either because the manufacturer no longer supports it or because the manufacturer no longer exists), you’d think this would be a no-brainer but money is always in short supply. I’ve often had to try to keep equipment running long past its expected life time and was only allowed to replace it when it finally broke beyond all hope of repair.
One of the reasons to perform biological QC is so that you can recognize changes in the equipment that don’t appear during a calibration. It also a useful (and recommended) way to assess new test equipment. So what happens when you finally get that new test system and your results are substantially different from what they were before?
I was recently contacted by the manager of an employee health service that had replaced their 18 year old spirometer with a brand-new one. When using their new spirometer they had found their biological QC results coming out noticeably lower (-9%) than they had gotten from their old spirometer and I was asked if I could help them determine why.
My first question was whether or not they were using the same 3 liter syringe to calibrate the different spirometers. Once I found out this was the case I then asked them to use the 3 liter syringe in test mode. The results from this were actually very informative. The old spirometer showed an average FVC of 3.24 liters and the new spirometer showed an average FVC of 3.06 liters.