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

INTERVENTION: control group :Conventional treatment ;Experimental group :conventional treatment combined with umbilical cord mesenchymal stem cell conditioned medium 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). 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, meet one of the following conditions: (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 compliance, willingness to cooperate with the study, and informed consent signed by the patient