Operation Everest II: Comparison of Four Instruments for Measuring Blood O2 Saturation

The bias and precision of four different methods for determining O2 saturation So2 were evaluated during a study of hypobaric hypoxia conducted with seven male subjects exposed progressively over a 40-day period to simulated altitudes from sea level 760 Torr to 8,840 m 240 Torr. So2 of arterial and mixed venous blood samples were measured with the Instrumentation Laboratory 282 CO-oximeter CO-OX, the Radiometer ABL-300 ABL, and the Lex-O2-Con-K LEX. Noninvasive measurements of arterial So2 were made with a Hewlett-Packard 47201A ear oximeter EAR-OX. The CO-OX method was used as a secondary standard for comparison with the other methods because it has been validated against the classical Van Slyke method over a wide physiological range. The LEX results most closely approximated but consistently underestimated those of the CO-OXLEX 0. 93 CO-OX -0.86, standard error of the estimate SEE 5.17, r 0.98, n 670. The ABL method appeared to combine two linear trends for So275, ABL 0.84 CO-OX 14.4, SEE 1.77, r 0.97, n 36975, ABL 0.98 CO-OX 5.9, SEE 4. 44, r 0.97, n 486. The EAR-OX results were found to approximate those of the CO-OX at So2 values only 65 EAR-OX 1.07 CO-OX -6.12, SEE 7.71, r 0.98, n 326. Hypobaric hypoxia Tonometry Reprints Mixed venous saturation.