Impact of Oxygen Saturation on Mortality in Obese and Non-obese Critically Ill Patients With Mechanical Ventilation: A Retrospective Observational Study

Abstract

Background: The main aim of this study was to evaluate the effect of oxygen saturation on mortality in critically ill patients with mechanical ventilation according to obesity status. Methods: We conducted an observational study in mechanically ventilated patients admitted to the ICU retrospectively. Demographic, arterial blood gas, ventilator setting, interventions, and peripheral oxygen saturation (Spo2) during the first 24 h were recorded and analyzed between non-obese and obese patients. The main exposure included Spo2, time-weighted mean Spo2 (TWM-Spo2), and proportion of time spent in different Spo2 (PTS-Spo2) levels. The primary outcome was hospital mortality. We used multivariable logistic regression models to assess the relationship between Spo2 and mortality, as well as the interaction between PTS-Spo2 and obesity status. Results: A total of 25,100 patients were included, of which 10,564 (42%) were obese patients. After adjusting for confounders, compared with TWM-Spo2 of 94–98%, TWM-Spo2 of < =88% (OR 3.572; CI [2.343, 5.455]; p < 0.001) and of 89–93% (OR 1.514; CI [1.343, 1.706]; p < 0.001) were both associated with higher risk of mortality. PTS-Spo2 of 99–100% was associated with increased risk of mortality for obese patients (OR 1.028; 95% CI 1.010–1.046; p = 0.002; Pinteraction = 0.001), while PTS-Spo2 of 89–93% was associated with increased risk of mortality (OR 1.089; 95% CI 1.051–1.128; p < 0.001; Pinteraction = 0.001) for non-obese patients. Conclusions: For obese and non-obese critically ill patients with mechanical ventilation, the impact of oxygen saturation on hospital mortality is different.