Navajas D, Roca J, Farré R, Rotger M
Facultat de Medicina and Servei de Pneumologia i Al-lergia Respiratòria, Hospital Clinic i Provincial, Universitat de Barcelona, Spain.
Eur Respir J. 1997 Apr;10(4):901-4.
Mechanically-driven syringes used to test peak expiratory flow (PEF) meters must produce the American Thoracic Society (ATS) standard waveforms with PEF accuracy of 2%. However, gas compression within the syringe could result in significant PEF inaccuracy when testing high resistance meters. The gas compression artefact was investigated in a mechanical syringe (PWG; MH Custom Design & Mfg L.C., Midvale, Ut, USA) of 13.6 L connected to a standard range mini-Wright PEF meter (Clement Clarke International, Harlow, UK). Scaled versions of the ATS standard waveform No. 24, with peak flows of 750 and 450 L x min(-1), were discharged through the PEF meter from different starting piston positions to vary syringe volume (Vsyr). The PEF recorded by the meter decreased linearly with increasing Vsyr. PEF decreased by 0.31 and 0.27% per litre for the ATS standard waveforms with PEF of 750 and 450 L x min(-1), respectively. The target PEF computed from piston displacement overread the actual PEF delivered into the PEF meter by approximately 4% when Vsyr = 13.6 L. Overreading fell to approximately 1% when Vsyr was reduced to 3.62 L. Therefore, gas compression error in commercially available large mechanical syringes can exceed the 2% inaccuracy limit when testing high resistance portable PEF meters. Measurements can be corrected for gas compression by linearly extrapolating PEF recordings to zero volume.
用于测试呼气峰值流速（PEF）仪的机械驱动注射器必须产生符合美国胸科学会（ATS）标准的波形，且PEF精度为2%。然而，在测试高阻力仪时，注射器内的气体压缩可能会导致显著的PEF测量不准确。在连接到标准量程小型赖特PEF仪（英国哈洛的克莱门特·克拉克国际公司）的13.6升机械注射器（PWG；美国犹他州米德瓦尔的MH定制设计与制造公司）中研究了气体压缩伪像。通过改变注射器体积（Vsyr），从不同的起始活塞位置通过PEF仪排出ATS标准波形24的缩放版本，其峰值流速分别为750和450升/分钟。仪器记录的PEF随Vsyr增加呈线性下降。对于PEF分别为750和450升/分钟的ATS标准波形，PEF每升分别下降0.31%和0.27%。当Vsyr = 13.6升时，根据活塞位移计算的目标PEF比实际输送到PEF仪中的PEF大约高4%。当Vsyr降至3.62升时，高估降至约1%。因此，在测试高阻力便携式PEF仪时，市售大型机械注射器中的气体压缩误差可能超过2%的不准确限制。可以通过将PEF记录线性外推至零体积来校正气体压缩对测量结果的影响。
