Compensation of Peak Expiratory Air Flow Rate Considering Initial Slope in Velocity Type Air Flow Transducer

속도계측형 호흡기류센서에서 상승시간을 고려한 최고호기유량의 교정 기법

  • 차은종 (충북대 의대 의학과) ;
  • 이인광 (충북대 의대 의용생체공학과) ;
  • 김성식 (충북대 의대 의용생체공학과) ;
  • 김완석 (충북대 의대 의용생체공학과) ;
  • 박경순 (충북대 의대 의용생체공학과) ;
  • 김원재 (충북대 의대 의학과) ;
  • 김경아 (충북대 의대 의학과)
  • Published : 2009.04.01

Abstract

Peak expiratory flow rate(PEF) is one of the most important diagnostic parameters in spirometry. PEF occurs in a very short duration during the forced expiratory maneuver, which could lead to measurement error due to non-ideal dynamic characteristic of the transducer. In such case the initial slope of the flow rate signal determines the accuracy of the measured PEF. The present study considered this initial slope as a parameter to compensate PEF. The 26 standard flow rate signals recommended by the American Thoracic Society(ATS) were flown through the air flow transducer followed by simultaneous measurements of PEF and maximum transducer output$(N_{PEF})$. $N_{PEF}$-PEF satisfied a quadratic equation in general, however, two signals (ATS #2 and #26) having large initial slopes deviated from the fitting equation to a significant degree. The relative error was found to be in a linear relationship with the initial slope, thus, $N_{PEF}$ was appropriately compensated to provide accurate PEF with mean relative error less than only 1%. The 99% confidence interval of the mean relative error was less than a half of the error limit of 5% recommended by ATS. Therefore, PEF can be very accurately determined by compensating the transducer output based on the initial slope, which should be a useful technique for air flow transducer calibration.

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