INCLUSION CRITERIA  Adults for assessment:  Male or female RT-PCR positive or negative for COVID-19 Aged 18-64 years, with severe pneumonia and hypoxemia (SpO2 < 90%). Willing and able to provide written informed consent.  Staff:  Staff (physicians and nurses) who are engaged in the medicine ward, HDU and COVID ward of Dhaka Hospital of icddr,b and Dhaka Medical College Hospital. Staff who agree to participate and give written informed consent.  EXCLUSION CRITERIA  Adults for assessment:  Patients will not be included in the study if they will not have adequate respiratory drive such as gasping respiration or requiring cardiopulmonary resuscitation or Known to have life threatening heart disease, Status asthmaticus Upper-airway obstruction Patients with pneumonia/respiratory tract illness but without hypoxaemia or SpO2< 80% in room air even on prone position and chest physiotherapy Pregnancy, nasal polyp and Patients who are not willing or able to provide written informed consent. Arterial blood gas analysis will be performed to check the exclusion criteria.  Staff:  • For Focus Group Discussions, physicians and nurses who do not provide written informed consent will be excluded.