How does a Piezo respiratory effort sensor work?
Ambu Sleepmate introduced the first piezo respiratory effort sensor the “Resp-Ez” in 1989. It replaced the mercury strain gauge that had been the standard for many years with a small, convenient package that did not run the risk of mercury contamination if it broke. A piezo crystal is essentially a ceramic material that is capable of emitting a weak electrical signal when it is flexed. The little LED lights on children’s shoes are often powered by a small piezo crystal in the sole of the shoe that is stressed with each footstep. When the stress is removed the electrical output stops. The repeated stress and release transmitted by the rise and fall of a patient’s chest through an elastic band creates the familiar sine wave pattern on the recorder. The waveform is only an approximation of the movement of the chest and abdomen. In particular the output of the piezo is not linear. In other words the output created by a 1 inch change in chest or abdomen circumference is not twice the output
