METHOD TO PRODUCE AMERICAN-THORACIC-SOCIETY FLOW-TIME WAVE-FORMS USING A MECHANICAL PUMP

The American Thoracic Society (ATS) recently adopted a new set of 26 s tandard flow-time waveforms for use in testing both diagnostic and mon itoring devices, Some of these waveforms have a higher frequency conte nt than present in the ATS-24 standard volume-time waveforms, which, w hen produced by a mechanical pump, may result in a pump flow output th at is less than the desired flow due to gas compression losses within the pump, To investigate the effects of gas compression, a mechanical pump was used to generate the necessary flows to test mini-Wright and Assess peak expiratory now (PEF) meters, Flow output from the pump was measured by two different independent methods, a pneumotachometer and a method based on piston displacement and pressure measured within th e pump, Measuring output flow based on piston displacement and pressur e has been validated using a pneumotachometer and mini-Wright PEF mete r, and found to accurately measure pump output, This method introduces less resistance (lower bark-pressure) and dead space volume than usin g a pneumotachometer in series with the meter under test. Pump output flow was found to be lower than the desired flow both with the mini-Wr ight and Assess meters (for waveform No, 26, PEFs 7.1 and 10.9% tower, respectively), To compensate for losses due to gas compression, we ha ve developed a method of deriving new input waveforms, which, when use d to drive a commercially available mechanical pump, accurately and re liably produces the 26 ATS flow-time waveforms, even those with the fa stest rise-times.