There were no differences of age, sex, body mass index, and clinical frailty score between the two group, but significant differences were found between the HFNC-F and MV groups in terms of smoking status (never smoker: 60.8% in MV group vs. 74.8% in HFNC-F group, p = 0.008), diabetes mellitus (43.1% in MV group vs. 23.4% in HFNC-F group, p = 0.011), C-reactive protein level (12.3 mg/dL in MV group vs. 9.3 mg/dL in HFNC-F group, p = 0.020), and procalcitonin level (0.4 ng/mL in MV group vs. 0.1 ng/mL in HFNC-F group, p < 0.001). Here, CRP is linked to diabetes mellitus.