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Background The updated global criteria for diagnosing acute respiratory distress syndrome (ARDS) include SpO 2 /FiO 2 as a substitute for PaO 2 /FiO 2 to enhance practicality in settings with limited resources and reduce reliance on arterial blood gas testing. However, the applicability of these SpO 2 /FiO 2 thresholds in high-altitude regions remains unvalidated. This study investigated the relationship between the SpO 2 /FiO 2 and PaO 2 /FiO 2 in patients with ARDS in the Xining region of Qinghai and validated whether the critical values for hypoxemia severity classification based on SpO 2 /FiO 2 are applicable in this population. A retrospective analysis was conducted on the clinical data of 276 patients with ARDS admitted to the intensive care unit (ICU) of Qinghai Provincial People’s Hospital from October 2020 to October 2024. All patients who met the inclusion criteria were classified into mild, moderate, and severe ARDS as defined by the Berlin Definition. Spearman’s correlation analysis was used to assess the correlation between SpO 2 /FiO 2 (corrected) and PaO 2 /FiO 2 (corrected). Curve estimation was used to derive the linear and nonlinear relationships between SpO 2 /FiO 2 and PaO 2 /FiO 2 , as well as between SpO 2 /FiO 2 (corrected) and PaO 2 /FiO 2 (corrected). Receiver operating characteristic curve analysis was used to validate whether the cutoff values proposed by the new global definition for SpO 2 /FiO 2 -based hypoxemia severity stratification apply to Xining. Results A significant nonlinear relationship was observed between the SpO 2 /FiO 2 and PaO 2 /FiO 2 ratios. The optimal fitting model was a power function model: SpO 2 /FiO 2 (corrected) = 5.661 × PaO 2 /FiO 2 (corrected) 0 · 71 . The area under the curve (AUC) of the SpO 2 /FiO 2 (corrected) for predicting mild ARDS was 0.912, with an optimal diagnostic threshold cutoff value of 360.4. For moderate ARDS, the AUC was 0.487, with a cutoff value of 238.8. For severe ARDS, the AUC was 0.956, with an optimal cutoff value of 168. Conclusion This study revealed a nonlinear relationship between the SpO 2 /FiO 2 and PaO 2 /FiO 2 ratios in patients with ARDS in Xining, Qinghai Province, a characteristic that may better align with the pathophysiological features of high-altitude regions. The globally redefined hypoxemia grouping thresholds based on SpO 2 /FiO 2 may not apply to this area, suggesting that regional diagnostic criteria should be established according to altitude variations.
Sun et al. (Thu,) studied this question.