To Observe Whether Isoflurane Can Treat COVID-19 Patients

This is a blood collection and retrospective data collection study. The investigators plan to assess whether the sedative drug, isoflurane, can treat COVID-19 patients relatively better compared to other sedative drugs given during routine treatment to patients on mechanical ventilation. The investigators will also use nanoneedle biosensors to quickly detect blood IgM/IgG ratio in those patients, and (3) to establish a pre-clinical system to determine the effects of inhalational anesthetics on amounts of SARS-CoV-2 and other viruses, and pneumoniae.