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

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 (Spo) during the first 24 h were recorded and analyzed between non-obese and obese patients. The main exposure included Spo, time-weighted mean Spo (TWM-Spo), and proportion of time spent in different Spo (PTS-Spo) levels. The primary outcome was hospital mortality. We used multivariable logistic regression models to assess the relationship between Spo and mortality, as well as the interaction between PTS-Spo 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-Spo of 94-98%, TWM-Spo of < =88% (OR 3.572; CI [2.343, 5.455]; < 0.001) and of 89-93% (OR 1.514; CI [1.343, 1.706]; < 0.001) were both associated with higher risk of mortality. PTS-Spo of 99-100% was associated with increased risk of mortality for obese patients (OR 1.028; 95% CI 1.010-1.046; = 0.002; P 0.001), while PTS-Spo of 89-93% was associated with increased risk of mortality (OR 1.089; 95% CI 1.051-1.128; < 0.001; P 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.