Pressure measurement evaluation and accuracy validation: the Gabarith test

Objective:The dynamic distortion introduced by manometric systems has been known for many years, with several methods developed to describe and quanti fy the degree of distortion. We developed the Gabarith as a technique to de scribe more accurately, and yet more simply, the dynamic accuracy of the ch ain of monitoring. Setting: A pressure monitoring system transforms some input signal, i. e. t he actual pressure waveform present in the artery, into some other shape of waveform, i. e. the waveform displayed on the patient monitor. This transf ormation is characterized by the transfer function of the total system. A c omplete technique to define the transfer function is to measure the respons e directly at many different frequencies and combine them to produce the dy namic response plot. Method: We described the dynamic response of a monitoring chain and we simp lified the communication of this dynamic response to users by developing th e Gabarith, as a tolerance envelope based on the frequency content of typic al pressure waveforms. If a given monitoring chain's dynamic response (incl uding a catheter, a pressure kit and a monitor) can be shown to fall within that tolerance envelope, the chain will provide adequate dynamic accuracy. Conclusion: "Gabarith tested" means that a pressure kit, in combination wit h a catheter and a monitor, has had its frequency response function measure d and that the function falls within a tolerance band for dynamic accuracy. Passing a Gabarith means that a given level of accuracy will be reached wh en using the sets which have passed the corresponding test.