Objective The Sequential Organ Failure Assessment (SOFA) score is validated to measure severity of organ dysfunction in critically ill patients. However, in some practice settings, daily arterial blood gas (ABG) data required to calculate the respiratory component of the SOFA score are often unavailable. The objectives of this study were to derive SpO2/FiO2 (SF) ratio correlations with the PaO2/ FiO2 (PF) ratio to calculate the respiratory parameter of the SOFA score, and to validate the respiratory SOFA obtained using SF ratios against clinical outcomes. Patients and measurements We obtained matched measurements of SpO2 and PaO2 from two populations: Group 1- patients undergoing general anesthesia and Group 2- patients from the ARDS network -low versus high tidal volume for the Acute Respiratory Management of ARDS (ARMA) database. Using a linear regression model, we first determined SF ratios corresponding to PF ratios of 100, 200, 300 and 400. Second, we evaluated the contribution of positive end expiratory pressure (PEEP) on the relationship between SF and PF, for patients on PEEP in centimeters of water (cm H2O) of <8, 8–12 and >12. Third, we calculated the SOFA scores in a separate cohort of ICU patients using the derived SF ratios and validated them against clinical outcomes. Results The total SOFA scores calculated using SF ratios and PF ratios were highly correlated (Spearman's rho 0.85, p<0.001) in all patients and in the 3 stratified PEEP categories (<8 cm H20, Spearman's rho 0.87, p<0.001; PEEP 8–12 cm H20, Spearman's rho 0.85, p<0.001; PEEP>12 cm H20, Spearman's rho 0.85, p<0.001). The respiratory SOFA scores based on SF ratios and PF ratios correlated similarly with ICU length of stay and ventilator-free days, when validated in a cohort of critically ill patients. Conclusion The total and respiratory SOFA scores obtained with imputed SF values correlate with the corresponding SOFA score using PF ratios. Both the derived and original respiratory SOFA scores similarly predict outcomes.

Background: A surgical scoring system, akin to the obstetrician's Apgar score, has been developed to assess postoperative risk. To date, evaluation of this scoring system has been limited to general and vascular services. The authors attempt to externally validate and expand the Surgical Apgar Score across a wide breadth of surgical subspecialties. Methods: Intraoperative data for 123,864 procedures including all surgical subspecialties were collected and associated with Surgical Apgar Scores (created by the summation of point values associated with the lowest mean arterial pressure, lowest heart rate, and estimated blood loss). Patients' death records were matched to the corresponding score, and logistic regression models were created in which mortality within 7, 30, and 90 days was regressed on the Apgar score. Results: Lower Surgical Apgar Scores were associated with an increased risk of death. The magnitude of this association varied by subspecialty. Some subspecialties exhibited higher odds ratios, suggesting that the score is not as useful for them. For most of the subspecialties the association between the Apgar score and mortality decreased as the time since surgery increased, suggesting that predictive ability ceases to be helpful over time. After

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