Potential confounders
Potential confounders were identified literature review. Directed
acyclic graphs (DAG) were subsequently drawn to visualize causal
assumptions to identify confounders (Figure S1 in the online
supplement). Age, sex, body mass index (BMI), medical history of chronic
pulmonary disease, diabetes mellitus, active malignancy, hypertension,
obstructive coronary heart disease, myocardial infarction, nonischaemic
cardiomyopathy, heart failure, previous heart surgery, electronic heart
device, cerebrovascular accidents, and/or peripheral artery disease, use
of immunosuppressive medication, and no-ICU policy were identified as
confounders that were available in our database.