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

Abstract

BackgroundThe 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.MethodsWe 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.ResultsA 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.ConclusionsFor obese and non-obese critically ill patients with mechanical ventilation, the impact of oxygen saturation on hospital mortality is different.