User Experience Network™ [Health Devices Feb 1993;22(2):97]

Hospital

We are currently looking at different suppliers from whom to obtain disposable blood pressure transducers. Several models that we are looking at do not have the back-side calibration feature that our current models have. Can you provide us with your opinion on those models that do not have the back-side calibration port?

In our previous evaluation of disposable blood pressure transducers (Health Devices 17[3], Mar 1988), we slightly preferred units that had a back-side calibration port over units that lacked this feature. The back-side calibration port simplifies both pre-use testing of the transducer and accuracy verification of transducers that are already connected to a patient. Units that have such a port often require a special pneumatic test device. Because this device costs about $500, hospitals should negotiate with vendors to minimize any additional cost when contracting for new transducers. Users should also check the pneumatic tester's accuracy at least twice a year.

Do not use a mercury or aneroid manometer to test the transducer after it is connected to the patient. Errors such as incorrect stopcock positioning can result in pumping air into the blood vessel. We have received reports of fatal cerebral air embolism immediately following routine recalibration of invasive arterial blood pressure monitoring systems while connected to a patient (see our Hazard Report in Health Devices 12[1], Nov 1982).

Problems with pressure monitoring accuracy are likely to be caused by blood clotting at the tip of the catheter or poor dynamic response of the pressure monitoring system. Questions also arise when noninvasive (cuff) and invasive (transducer) measurements do not agree; however, because of differences in the measurement method and location of the measurement within the circulatory system, these results will often differ.

Pre-use testing of transducers will virtually eliminate the possibility that a transducer failure will cause an erroneous measurement. In the few instances in which a concern exists about a transducer that is already in use, the transducer can simply be replaced (after checking zeroing) if it does not have a back-side calibration port. This would further minimize risks and eliminate the time expenditure needed to perform such calibration. If the unit has a back-side calibration port, the calibration procedure will be easier and more reliable.

UMDNS Term

Transducers, Pressure, Disposable [16-909]

Cause of Device-Related Incident

Device factor: Improper maintenance, testing, repair, or lack or failure of incoming inspection

Mechanism of Injury or Death

Embolism (gaseous); Monitoring failure