The WHO2SAFE Score: A Predictive Tool for Postoperative Oxygen Requirement After PACU Recovery

Figures

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  Figure 1. Flow diagram.

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  Figure 2. The ROC curve of the WHO2SAFE scoring system.

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  Figure 3. The calibration curve of the WHO2SAFE score. Predicted probabilities were grouped and plotted against the corresponding observed proportions. The solid blue line represents the mean calibration curve, and the shaded area denotes the 95% confidence interval obtained via bootstrap resampling. The dashed diagonal line represents perfect calibration, where predicted probabilities would exactly match observed event rates.

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  Figure 4. Performance metrics across different thresholds. (a) Sensitivity, specificity, and accuracy plotted across WHO2SAFE thresholds with 95% confidence intervals. The optimal threshold score of 6, indicated by the red dashed line, was selected based on balancing sensitivity and specificity. (b) Tables detailing the values of each metric are provided alongside the performance metric plot.

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  Figure 5. WHO2SAFE score distribution by postoperative oxygen requirement. (a) Boxplot comparing WHO2SAFE scores between patients who did and did not require postoperative oxygen. (b) Stacked bar chart showing the proportion of oxygen-requiring patients across score levels.

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  Figure 6. QR code of web-based application program for individual risk calculation of postoperative oxygen requirement after PACU recovery.