[abstract] GAS-BLOOD O2, DIFFERENCE OF THE INSTRUMENTATION LABORATIRES MODEL 1304 BLOOD GAS ANALYZER AT LOW AND HIGH O2 PRESSURES AT 1.0 AND 2.0 ATA.

Abstract

BACKGROUND: A wide range of arterial O2 pressures is encountered in hypoxia and hyperoxia during investigation and HBOT. O2 electrodes in blood gas analyzers typically read lower when filled with blood than when filled with gas at the same PO2. This gas-blood PO2 difference is not generally known. It is determined here for the Instrumentation Laboratories (IL) 1304 analyzer over a wide range of O2 pressures at 1.0 ATA. PROCEDURES: The IL1304 was calibrated with 2 gases (FO2 = 0.00 +/- 0.01percent and 0.20 +/- 0.03percent). On 6 different days an IL237 tonometer was used to equilibrate at 37.0(C freshly drawn heparinized venous blood with gases of FO2 = 0.08, 0.16 and 0.95 +/- 0.01percent. The PO2 of the tonometer gas (B) and the tonometered blood (C) as measured by the IL1304, as well as the computed PO2 of the tonometer gas (A) are given below: RESULTS: A B C, Tonometer gas, Computed PO2, Gas PO2, Blood PO2, C - B, C - A, FO2, (Torr), (Torr), (Torr), 0.08, 57.5, 56.9, 57.0, 0.1, -0.5, 0.16, 115.0, 115.0, 115.6, 0.6, 0.6, 0.95, 682.5, 690.6, 682.5, -8.1, 0.0 Mean values, N = 6-10. =sig., p less than 0.05, Analysis of Variance. CONCLUSION: Comparing tonometered blood and tonometer gas as measured by the IL1304, the only observed PO2 difference (8.1 Torr, or 1.2percent of the gas value) is within instrumental measurement error range. There were no differences comparing blood and computed tonometer gas PO2. These results demonstrate that the IL1304 can be used over the full O2 pressure range at 1.0 ATA without correction for gas-blood differences. Following modifications of the IL1304 and 237 for use at elevated O2 pressures employed in investigation and therapy, preliminary results at 2.0 ATA are compatible with these findings. ACKNOWLEDGMENTS: Supported in part by USN NMRDC N0014-96-1-0776, NASA NAGW-4359 and NASA NAGW-3628.