Figure 1.

Plot of oxygen reserve index (ORI) compared with arterial partial pressure of oxygen (Pao₂) obtained from 106 patients undergoing surgery in whom measured Pao₂ from 485 arterial blood gas analyses was between 62 and 534 mm Hg. Patients had >1 sensor applied, with analysis done using 1594 ORI values. A, Locally weighted regression analysis showed a nonlinear relationship overall with a more positive linear relationship for Pao₂ up to 240 mm Hg than >240 mm Hg. B, Linear regression analysis of ORI and Pao₂ up to 240 mm Hg showed a positive relationship (r² = 0.536); dashed lines indicate 95% confidence interval of regression line.