Statistical Analysis
To compare the demographic, anthropometric, biochemical, and pathological indices of the two groups by independent t-test and chi-square tests for quantitative and qualitative variables, respectively. The relationship between enteral nutrition and mortality was investigated using logistic regression. The confounding factors including age, gender, BMI, length of stay in the ICU, the Acute Physiology and Chronic Health Evaluation (APACHE II), the Glasgow Coma Scale (GCS), presence of chronic diseases, and smoking were adjusted in various regression models. SPSS 21 software was used for all statistical analyzes considering the significance level of P<0.05.

Results

The general characteristics of the COVID-19 patients included in this study are presented in Table 1. There was no significant difference between the two groups of patients (died versus recovered) for their age (55.24±15.46 vs. 58.49±15.08 years), BMI (26.69±3.86 vs. 27.46±4.46 kg/m2), and gender. However, the patient group that died had a significantly higher APACHII and lower GCS compared to the control group (both P<0.001). Also, the same group had significantly higher incidences of chronic disease and smoking compared to the control group (P<0.01).
The comparison of the volume and type of formula received among the case and control groups is presented in Table 2. The recovered patients received significantly more high protein (60.8% vs. 39.6%, P=0.004) and high volume (61.6% vs. vs. 42.3%, P=0.005) formula compared to the dead patients.
The association between mortality with the volume and type of formula is presented in Table 3. Mortality was inversely associated with high volume (OR:0.45 CI95%: 0.26-0.81, P=0.008) and high protein formula (OR:0.42 CI95%:0.23- 0.75, P=0.003). The results did not change after adjustments for age and sex (model 2), further adjustments for underlying diseases and smoking (Model 3), further adjustments for BMI (Model 4), and additional adjustments for APACHII (Model 5) (Figure 1).