The investigators never completed the IRB application due to decrease in need to conduct the study.

Our goal is to assess the effects of Tadalafil in the setting of confirmed COVID-19 pneumonia. In particular we plan to assess its effects on oxygen saturation, P:F ratio, and mixed central venous oxygen

We plan to recruit all hospitalized patients at Santa Barbara Cottage Hospital with a confirmed COVID19 pneumonia (positive PCR + clinical signs/symptoms of lower respiratory disease) who meet the Berlin definition of ARDS and have access to measure a mixed venous oxygen saturation. For the purposes of obtaining mixed central venous oxygen, all participating patients will already have an internal jugular central venous catheter in place for inclusion in this study. Since all patients will be intubated, their Legally Authorized Representative (LAR) will be approached to discuss the study and asked to participate in the study by an ICU physician, either the attending physician or a medical resident.

Informed consent will be obtained from the LAR by an ICU attending physician or resident involved in the study prior to participation. Patients who meet the above eligibility criteria will have baseline levels of mixed central venous oxygen, oxygen saturation, P:F ratio, blood pressure and PaO2 recorded.

Each patient will then receive Tadalafil 40mg once. The above listed parameters will be monitored again 30 minutes after drug administration and 4 hours after drug administration. No other medication or ventilator changes will be made during this time period outside of emergent changes in the setting of patient deterioration. We will continue to analyze the data in the event of emergent ventilator changes.

Inclusion Criteria:

• Hospitalized patients at SBCH with confirmed COVID19 pneumonia (PCR + clinical signs/symptoms of lower respiratory disease)
• Patients currently on a ventilator
• Patients who meet the Berlin definition of ARDS
• Patients who have access to measure a mixed venous oxygen saturation (i.e., patients with an internal jugular central venous catheter)
• Patient and/or Legally Authorized Representative is willing/able to provide informed consent

Exclusion Criteria:

• As tadalafil is currently a FDA Class B1 medication, indicating that little information is available, pregnant women along with women who are actively breastfeeding will be excluded from this series.
• All patients under 18
• Patients who are routinely taking nitrate medications
• All patients using Tadalafil daily for pulmonary arterial hypertension (Note: patients using Tadalafil intermittently for erectile dysfunction may still participate in the study)