Performance Characteristics and Interanalyzer Variability of PO ₂ Measurements Using Tonometered Human Blood

Abstract

We performed a side-by-side comparison of the ability of four blood gas analyzers (IL-1312, Corning-178, AVL-995, and ABL-330) to measure PO2 across a wide range under controlled laboratory conditions. Samples of fresh whole human blood, tonometered with analytic quality gas, were prepared with partial pressures of oxygen from 0 to 283 mm Hg. Fifteen determinations were made at 16 levels of tonometric PO2 (tPO2) on each of the four blood gas analyzers. The bias, precision, and root mean squared error (RMSE) of the PO2 measurement relative to tPO2 were determined for each analyzer at each tPO2 level. Mean bias and precision across the range tested were 2.78 +/- 1.29 mm Hg (IL), -0.35 +/- 1.91 (Corning), 2.14 +/- 1.43 (AVL), and 3.00 +/- 1.47 (ABL). RMSE was 3.28, 2.61, 3.57, and 2.41 for IL, AVL, ABL, and Corning, respectively. Percent RMSE (RMSE/tPO2 x 100%), ranged from 0.9% (AVL at 75 mm Hg PO2 and IL at 283 mm Hg tPO2) to 9.1% (IL at 29 mm Hg tPO2). Three analyzers (AVL, ABL, and Corning) showed a statistically significant (p < 0.0001) correlation between RMSE and tPO2, and no correlation between percent RMSE and tPO2. This demonstrates that, for these instruments, accuracy is a function of the magnitude of the tPO2 value. IL did not show a significant correlation between RMSE and tPO2 but did demonstrate a significant negative correlation (r = -0.78, p > 0.001) between percent RMSE and tPO2, indicating that, for this analyzer, accuracy is not a function of tPO2. The differences in PO2 measurements between pairs of analyzers were also examined.(ABSTRACT TRUNCATED AT 250 WORDS)