Participants
This cohort study was conducted from January 11 to April 10, 2020, at Shenzhen Third People’s Hospital in Guangdong, China. The Shenzhen Third People’s Hospital was designated by the Shenzhen municipal government to be responsible for the treatment of COVID-19 patients in the city since January 2020. All patients included in this study had laboratory-confirmed COVID-19 and had received mechanical ventilation support. Participants were divided into two groups depending on whether they had been successfully weaned off the ventilator. Weaning failure was defined by failure of spontaneous breathing trials or a need for reintubation or non-invasive ventilation, or death within 48 h after extubation5. Patients in severe type should be consistent with any of the following items: (1) respiratory rate higher than 30 times / min; (2) fingertip blood oxygen saturation less than 93% in resting state; (3) partial arterial oxygen pressure/ fraction of inspiration oxygen(PaO2:FiO2) less than 300 mmHg. Patients with one of the three conditions are considered as critical type: Any of the following items: (1) respiratory failure, and requires mechanical ventilation; (2) shock; (3) multiple organ failure, which requires intensive care unit monitoring and treatment. The study was approved by the Ethics Committee of Shenzhen Third People’s Hospital (No.2020-157). Informed consent was obtained before retrospective data collection. A copy of the written consent is available for review by the Editor of this journal.