['Oxygen saturation to fraction of inspired oxygen ratio (SpO(2)/FiO(2)) has been validated as a surrogate marker for partial pressure of oxygen to fraction of inspired oxygen ratio among mechanically ventilated patients with acute respiratory distress syndrome (ARDS). The validity of SpO(2)/FiO(2) measurements in predicting ARDS has not been studied. Recently, a Lung Injury Prediction Score (LIPS) has been developed to help identify patients at risk of developing ARDS.', 'This was a secondary analysis of the LIPS-1 cohort. A multivariate logistic regression included all established variables for LIPS, Acute Physiology and Chronic Health Evaluation 2, age, and comorbid conditions that could affect SpO(2)/FiO(2). The primary outcome was development of ARDS in the hospital. The secondary outcomes included hospital mortality, hospital day of ARDS development, and hospital day of death.', 'Of the 5584 patients, we evaluated all 4646 with recorded SpO(2)/FiO(2) values. Median SpO(2)/FiO(2) in those who did and did not develop ARDS was 254 (100, 438) and 452 (329, 467), respectively. There was a significant association between SpO(2)/FiO(2) and ARDS (P ≤ .001). The SpO(2)/FiO(2) was found to be an independent predictor of ARDS in a "dose-dependent" manner; for SpO(2)/FiO(2) < 100--odds ratios (OR) 2.49 (1.69-3.64, P < .001), for SpO(2)/FiO(2) 100 < 200--OR 1.75 (1.16-2.58, P = .007), and for SpO(2)/FiO(2) 200 < 300--OR 1.62 (1.06-2.42, P = .025). The discriminatory characteristics of the multivariable model and SpO2/FiO2 as a single variable demonstrated area under the curve (AUC) of 0.81 and AUC of 0.74, respectively.'] Is spO2/FiO2 ratio on hospital admission an indicator of early acute respiratory distress syndrome development among patients at risk?