The ongoing pandemic of the new coronavirus disease COVID-19 poses a serious threat to the world’s human population, particularly in countries with limited health care system efficacy (1). Severe bilateral pneumonia is the main symptom of COVID-19, so adequate ventilatory support is critical for patient survival. Although knowledge about COVID-19 continues to grow, it is still unclear what type of respiratory failure support is the most beneficial. Hypoxemia is crucial in the course of COVID-19, so improving oxygenation is the first and essential step in the treatment of patients with COVID-19 (2, 3). This becomes particularly important in situations of limited capacity for mechanical ventilation due to lack of equipment or medical staff. Oxygen delivery can be increased using non-invasive techniques which are more advanced than the reservoir face mask, such as non-invasive ventilation (NIV) using CPAP masks or helmets, high flow nasal ventilation (HFNC), and the abdominal position called the prone position (4-6).

The presence of hypoxemia itself should not be an indication for endotracheal intubation and mechanical ventilation, as hypoxemia in COVID-19 is often remarkably well tolerated. Exhaustion due to respiratory failure as well as consciousness disturbances and increasing hypercapnia argue for the implementation of invasive mechanical ventilation.

Nasal cannulas enable the administration of oxygen at the flow of up to 6 L/min (FiO₂ about 45%), various types of face masks allow the use of oxygen flows of 10-20 L/min (FiO₂ about 61-99%). However, it should be noted that an increase in oxygen flow increases the risk of contamination of personnel and the environment with pathogens (7). Aerosol dispersion during oxygen therapy using a face mask with a reservoir has been shown to range from 11.2 ± 0.7 to 27.2 ± 1.1 cm (8). The use of non invasive ventilation (NIV) methods results in a similar level of aerosol dispersion e.g. for HFNC 6.5 ± 1.5-17.2 ± 3.3 cm for a flow rate of 10-60 l/min respectively, allowing a much higher arterial blood oxygen saturation to be achieved. This enables their large-scale use in departments treating patients for COVID-19.

In hypoxaemic respiratory failure manifesting as decreased saturation, accelerated and shallow breathing, the essential element of therapy is to increase the oxygen concentration in the respiratory mixture of the patient by expanding the inflamed alveoli, improving ventilation and alveolar perfusion, mechanical, continuous positive airway pressure (CPAP) breathing support and ventilator therapy (9, 10). Most patients with COVID-19 should be ventilator-assisted with the lowest possible effective inspired oxygen concentration (FiO₂). The saturation of the patient on ventilatory support should be maintained between 92-96% (11-13).

Non-invasive ventilation allows the patient to be ventilated with positive inspiratory pressure without the need for endotracheal intubation, using face masks, nasal masks, or intranasal cannulas adapted to deliver High Flow Oxygen Therapy (HFOT). When evaluating a patient with a high probability of developing acute respiratory failure, a prompt decision to initiate NIV is crucial. Delaying the decision to use NIV increases the risk of treatment failure (14-16). This method is mainly used by emergency departments and intensive care units. Studies show beneficial effects of this type of ventilation also in internal medicine departments (17). The beneficial effect of non-invasive therapy is possible thanks to the care of the patient by adequately trained medical staff. Analysis of the procedure of NIV use by emergency medical teams in prehospital management indicates a reduction in mortality and a decrease in the risk of patient intubation. A trained member of the emergency medical team, can successfully use CPAP in patients with severe respiratory failure. This is associated with a 30% reduction in intubation rates, and a 21% reduction in mortality in appropriately qualified patients (18-21).

There are some technology solutions available to ensure proper bedside NIV in the emergency department or intensive care setting. CPAP is a therapy that allows the delivery of a breathing mixture under positive pressure that is maintained in the airway throughout the respiratory cycle. The patient independently initiates inspiration through a mask tightly placed on the face, which allows ventilation with oxygen or its mixture with air using positive pressure generated by the device. It leads to the creation of positive pressure in the airways protecting the alveoli from collapsing (22). The ventilator is controlled by setting the end-inspiratory pressure at which the inspiratory phase is terminated. The optimal baseline positive airway pressure (PEEP) should be 5 to 8 cm H₂O and FiO₂ which should be able to maintain saturation > 90%. PEEP can be increased to 20-25 cm H₂O, but special caution must be taken in such cases due to the higher than in other conditions risk of barotrauma.

Another non-invasive respiratory support technique that was widespread during the COVID-19 pandemic is high flow nasal cannula oxygen therapy (HFNC).