A total of 86.1% of patients had at least 1 PaOdos/FiO2 ratio during the first 24 hours of ventilation (Supplemental Table 2 a ). 81, 95% CI = 0.81-0.82) than with the worst PaO2/FiO2 ratio (AUROC = 0.78, 95% CI = 0.78-0.79, p < 0.001). Results were similar when SF-TAR was compared with the single worst SpO2/FiO2 ratio in the first 24 hours (AUROC = 0.79; 95% CI = 0.79-0.80, p < 0.01). Even when SF-TAR data were limited to either the first 6 or 12 hours of mechanical ventilation, the AUCs for these models were both 0.80 (95% CI = 0.79-0.80 and 0.80-0.81, respectively). Each 10% increase in SF-TAR during the first 24 hours of ventilation was associated with a 24% increase in the odds of hospital mortality (adjusted odds ratio = 1.24, 95% CI = 1.23-1.26, p < 0.001).
Validation Investigation
The MIMIC cohort included 13,755 hospitalizations with mechanical ventilation. The patients’ mean age (SD) was 63.1 (16.0) years, and the median duration of ventilation was 22 hours (IQR = 9-75; Supplemental Table 1 a ). Correlation between SpO2/FiO2 and PaO2/FiO2 ratios was moderate at 0.49 when both values were available concurrently. The hospital mortality rate was 9.7% among patients with SF-TAR of 0% and was 53.0% among those with SF-TAR of 91% to 100% (Figure 2 and Supplemental Table 4 a ). Each 10% increase in SF-TAR was associated with an adjusted odds ratio of 1.26 for hospital mortality (95% CI = 1.23-1.30, p < 0.001).
The UCD cohort included 1088 hospital encounters involving mechanical ventilation where SpO2/FiO2 and PaO2/FiO2 ratios were available concurrently. The mean age (SD) was 54.9 (17.0) years; the median duration of mechanical ventilation was 35 hours (IQR = 12 to 126 hours; see Supplemental Table 1 a ).