Patients who met the inclusion criteria were included and signed an informed consent form, which complied with the requirements of the ethics committee of our unit. All subjects were inpatients. Subjects were randomized into two groups. patients in group A were first treated with HFNC on top of conventional treatment, and after 24 hours, patients were treated with non-invasive ventilator-assisted ventilation BiPAP mode until discharge. patients in group B were treated with a non-invasive ventilator on top of conventional treatment, and after 24 hours of treatment, patients were treated with HFNC until discharge. Patient information was collected during treatment.