The aim of this study is to evaluate the preliminary safety and performance of a low-cost locally-made Venturi-based Non-invasive Positive Pressure Ventilator (NIPPV) device for hypoxemic COVID-19 patients. The device administers Continuous Positive Airway Pressure (CPAP) therapy using the jet-mixing or Venturi effect to increase the volume flow rate of oxygenated air from a pressurized cylinder by entraining the atmospheric air. To provide CPAP therapy, this high flow of oxygenated air is delivered to the patient via a low-cost non-vented mask with a tight seal with a High-Efficiency Particulate Air (HEPA) filter connected to the exhalation limb. The tight seal and HEPA filter ensures a minimal risk of aerosol generation and thus the device can be used without a negative pressure room. The system consists of the developed Venturi-based flow-generator, a standard 22mm breathing tube, a standard Y-connector, a non-vented CPAP mask (e.g., snorkel mask, helmet), a HEPA filter, and a Positive End Expiratory Pressure (PEEP) valve. The bench-top testing of the device is done in the laboratories of BUET and was verified that the device performs within the CPAP guidelines provided by the Medicines and Healthcare products Regulatory Agency (MHRA), UK. This study aims to assess the safety of and efficacy of the device in three different steps: (1) design validation, (2) clinical feasibility and (3) pilot clinical trial for safety and efficacy evaluation. Only if the device successfully passes the parts 1 and 2, the investigators will proceed to the final clinical trial in step 3. In this final step, the investigators aim to conduct a randomized controlled trial (RCT) evaluating for non-inferiority of the CPAP intervention compared to standard HFNO treatment. The number of ventilator-free days will be used as the primary outcome for efficacy, while patient recovery, death, or need of intubation and other adverse events will be used as secondary outcomes.

Inclusion Criteria:

• Age ≥ 18 years
• Confirmed or suspected COVID-19 patient (by RT-PCR) having severe pneumonia and hypoxemia (SpO2 ≤90%) who did not respond to standard oxygen therapy (non-rebreather mask on 15L/min at 100% FiO2).

Exclusion Criteria:

• Severely hypoxemic patients (SpO2≤85%)
• Patients with low respiratory drive or requiring cardiopulmonary resuscitation
• Patients with contraindications for CPAP
• Pregnant status
• Age > 65 years