Evaluation of a new method for assessing arterial oxygen pressure, avoiding arterial blood collection

Arterial computed PO2 (PO2 com) was computed from SaO2 ear and finger capillary pH using equations of Severinghaus and Ellis, and compared with measured arterial PaO2 in 100 patients with chronic obstructive pulmonary disease (76 men, aged 42 to 82 yr). SaO2 ear ranged from 73 to 98%. There was no significant difference between SaO2 ear and SaO2 com (calculated from PaO2 and arterial pH), nor between arterial pH and pHc (capillary blood). Mean directly measured finger capillary oxygen tension, PcO2, was lower than PaO2 by 10.1 mm Hg +/- 5.4 SD. Mean bias of (PaO2-PO2 com) was -0.22 mm Hg +/- 2.6 SD. When subdivided by range, bias, and SD of mean bias of (PaO2-PO2 com) were -0.47 mm Hg +/- 2.5 with SaO2 ear less than 95% and 0.1 mm Hg +/- 2.9 with SaO2 ear greater than 95%. We conclude that PaO2 may be reliably computed from SaO2 ear and capillary pH when SaO2 ear is less than 98%.