Postintubation Decline in Oxygen Saturation Index Predicts Mortality in COVID-19: A Retrospective Pilot Study

Abstract

Background. Acute respiratory failure from COVID-19 pneumonia is a major cause of death after SARS-COVID-19 infection. We investigated whether PaO2/FiO2, oxygenation index (OI), SpO2/FiO2, and oxygen saturation index (OSI), commonly used to assess the severity of acute respiratory distress syndrome (ARDS), can predict mortality in mechanically ventilated COVID-19 patients. Methods. In this single-centered retrospective pilot study, we enrolled 68 critically ill mechanically ventilated adult patients with confirmed COVID-19. Physiological variables were recorded on the day of intubation (day 0) and postintubation days 3 and 7. The association between physiological parameters, PaO2/FiO2, OI, SpO2/FiO2, and OSI with mortality was assessed using multiple variable logistic regression analysis. Receiver operating characteristic analysis was conducted to evaluate the performance of the predictive models. Results. The ARDS severity indices were not statistically different on the day of intubation, suggesting similar baseline conditions in nonsurviving and surviving patients. However, these indices were significantly worse in the nonsurviving as compared to surviving patients on postintubation days 3 and 7. On intubation day 3, PaO2/FiO2 was 101.0 (61.4) in nonsurviving patients vs. 140.2 (109.6) in surviving patients, p = 0.004 , and on day 7 106.3 (94.2) vs. 178.0 (69.3), p < 0.001 . OI was 135.0 (129.7) in nonsurviving vs. 84.8 (86.1) in surviving patients ( p = 0.003 ) on day 3 and 150.0 (118.4) vs. 61.5 (46.7) ( p < 0.001 ) on day 7. OSI was 12.0 (11.7) vs. 8.0 (10.0) ( p = 0.006 ) on day 3 and 14.7 (13.2) vs. 6.5 (5.4) ( p < 0.001 ) on day 7. Similarly, SpO2/FiO2 was 130 (90) vs. 210 (90) ( p = 0.003 ) on day 3 and 130 (90) vs. 230 (50) ( p < 0.001 ) on day 7, while OSI was 12.0 (11.7) vs. 8.0 (10.0) ( p = 0.006 ) on day 3 and 14.7 (13.2) vs. 6.5 (5.4) ( p < 0.001 ) on day 7 in the nonsurviving and surviving patients, respectively. All measures were independently associated with hospital mortality, with significantly greater odds ratios observed on day 7. The area under the receiver operating characteristic curve (AUC) for mortality prediction was greatest on intubation day 7 (AUC = 0.775, 0.808, and 0.828 for PaO2/FiO2, OI, SpO2/FiO2, and OSI, respectively). Conclusions. Decline in oxygenation indices after intubation is predictive of mortality in COVID-19 patients. This time window is critical to the outcome of these patients and a possible target for future interventions. Future large-scale studies to confirm the prognostic value of the indices in COVID-19 patients are warranted.

Novel Oxygenation and Saturation Indices for Mortality Prediction in COVID-19 ARDS Patients: The Impact of Driving Pressure and Mechanical Power

“… 41 In another analysis of C-ARDS patients, it was observed that P/F, SpO 2 /FiO 2 , OI-P mean , and OSI-P mean values were associated with hospital mortality on both the third and seventh days after intubation, with the odds ratio being higher on the seventh day compared to the third day. 42 High OI-P mean and OSI-P mean values were found to be correlated with negative outcomes in both C-ARDS and non-C-ARDS patients, reinforcing their significance in clinical assessments. 12 , 13 , 16 , 42 These studies have reaffirmed the value of conventional oxygenation indices as reliable predictors of outcomes for ARDS patients.…”

“… 42 High OI-P mean and OSI-P mean values were found to be correlated with negative outcomes in both C-ARDS and non-C-ARDS patients, reinforcing their significance in clinical assessments. 12 , 13 , 16 , 42 These studies have reaffirmed the value of conventional oxygenation indices as reliable predictors of outcomes for ARDS patients. Moreover, the new oxygenation indices, OI-ΔP insp , OSI-ΔP insp , and OSI-MP dyn , have demonstrated superior mortality predictive capabilities compared to the traditional indices in C-ARDS patients.…”

Effective prognostic and clinical risk stratification in COVID‐19 using multimodality biomarkers

“…Reduced peripheral oxygen saturation acts as both a risk factor for intubation [205][206][207] and a guide to the timing of assisted ventilation [208,209]. Moreover, after COVID-19 patients have been intubated, further declines in oxygenation continue to be predictive of mortality risk [210], and improvements in saturation readings can act as a guide to the effectiveness of prone ventilation therapy [211]. Indeed, monitoring of peripheral oxygen saturation is useful not only in prognosticating patients with severe COVID-19, but also in patients discharged from hospital to facilitate the early detection of acute deterioration [212].…”