Safety and efficacy of umbilical cord blood mononuclear cells in the treatment of severe and critically novel coronavirus pneumonia(COVID-19): a randomized controlled clinical trial

INTERVENTION: control group:Conventional treatment;experimental group:conventional treatment combined with umbilical cord blood mononuclear cells group; CONDITION: novel coronavirus pneumonia (COVID‐19) PRIMARY OUTCOME: PSI; SECONDARY OUTCOME: CT;X‐ray;Arterial blood gas analysis;Assisted breathing use time;mortality;Disease evolution;hospitalization day;Safety outcome index; INCLUSION CRITERIA: On January 27, 2020, the general office of the national health commission and the office of the state administration of traditional Chinese medicine issued the pneumonia diagnosis and treatment plan for new coronavirus infection (trial version 4). Only patients with severe and critical 2019‐ncov were included in this study. 1. Patients with severe 2019‐ncov according to the clinical stage met any of the following criteria: (1) Respiratory distress, RR >= 30 times/min; (2) In resting state, oxygen saturation is less than 93%; (3) Partial arterial oxygen pressure (PaO2)/oxygen absorption concentration (FiO2) <= 300mmHg (1mmHg= 0.133kpa); 2. According to the clinical stage of critical 2019‐ncov, one of the following conditions is met: (1) Respiratory failure occurs and mechanical ventilation is required; (2) Shock; (3) Combined with other organ failure, intensive care unit is required. 3. Other INCLUSION CRITERIA: good compl