Figure 1.

Summary of major therapeutic properties of inhaled nitric oxide gas (NO). From top left: inhaled NO gas is known to be a selective pulmonary vasodilator. NO can improve right heart function and decrease pulmonary vasoconstriction in subjects with acute and chronic pulmonary hypertension. Middle left vignette: breathing NO gas is shown to improve ventilation and provide bronchodilation in mild asthmatic subjects. Bottom left vignette: NO gas in the alveolar space improves oxygenation by increasing blood flow to ventilated lung units (i.e., improvement of ventilation perfusion matching). Top and middle right vignettes: in vitro and in vivo data showed that NO gas can act as an antiinflammatory and antithrombotic agent. Bottom right vignette: NO donors and NO gas showed antibacterial and antiviral properties in in vitro studies and early clinical investigations. The extent of benefits of these six therapeutic pathways of NO gas in coronavirus disease (COVID-19) infection are now under investigation. Some of those studies testing NO therapeutic properties are highlighted in Table 1.