Equipment Testing and Validation ASSESSMENT OF FRACTIONAL EXPIRED GASES AND AIR FLOW BY AN AMBULATORY METABOLIC ANALYZER

ASSESSMENT OF FRACTIONAL EXPIRED GASES AND AIR FLOW BY AN AMBULATORY METABOLIC ANALYZER. PATRICK L. JACOBS, MARK S. NASH AND C. DAVID MINTZ. JEPONLINE, 1999, 2(4):2028. Fractional expired oxygen (FEO2) and carbon dioxide (FECO2), and air volume flow were compared using an ambulatory metabolic analyzer (KB1-C, Aerosport, Inc.) and a laboratory metabolic analyzer (Horizon MMC, Sensormedics, Inc.). Ten subjects with paraplegia exercised to exhaustion using their arms, and ten nondisabled subjects ran to exhaustion on a treadmill. Simultaneous FEO2 and FECO2 measurements were taken during exercise by inserting the KB1-C pneumotachometer in series with the MMC. Measurement accuracy of air flow was examined by sending known air volumes through the KB1-C at three pneumotachometer flow settings (low = 3 to 30 Lmin; medium = 3 to 120 Lmin; and high = 3 to 200 Lmin). Results showed a significant positive association for FEO2 (R 2 = 0.94) with minimal but statistically significant absolute differences (SEE = 0.26%, p<0.001)). The R 2 for FECO2 was 0.89, although average KB1-C measurements were slightly lower (SEE = 0.28%, p<0.001). Differences from the reference standard for the low flow pneumotachometer were 12.3 and 15.5% at 3 L/min and 6 L/min, respectively, but averaged between 2.5 and 4.0% at 9-45 L/min. For the medium flow setting, average differences from the reference standard ranged from 0.5% at 72 L/min to 4.6% at 117 L/min. For the high flow setting, measurements varied dramatically from the reference standard at flow rates up to nine L/min, and by 7.0 8.8% at 27 to 54 L/min. Otherwise, differences of less than 2% were observed at rates of 99-198 L/min. This study observed similar measurements for FEO2 and FECO2 when measured by an ambulatory metabolic analyzer and a laboratory standard, and found that accurate measurement of air flow depended upon careful matching of the pneumotachometer setting with the expected air volume ranges.