Hypoxemia is the main component of COVID-19 related acute respiratory distress syndrome, however, its mechanisms are disputed, especially in patients with low respiratory system elastance (Ers). About 60 critically ill patients were hospitalized and assessed in ICUs, specially equipped for those suffering from C-ARDS. Contrast transthoracic echocardiography was used to assess the “Patent Foramen Ovale” shunt and the “Transpulmonary Bubble Transit.” The median respiratory system elastance observed in the patients was 32 cmH2O/L. The PFO shunt was detected in 10% of the patients and TPBT in 20% of patients.  In conclusion, PFO and TPBT were not found to be the leading hypoxemia operators for C-ARDS, in patients with low Ers.

The present study aimed to assess the intracardiac or intrapulmonary shunt’s role in C-ARDS-related hypoxemia and their possible association with C-ARDS respiratory mechanics. Patients who had laboratory-confirmed Covid-19 infection, and admitted to the ICU between March 8th to April 14th, 2020 were studied. The prevalence of PFO shunt in C-ARDS (10%) is close to that described in other types of ARDS upon using TTE (7%) but lower than that detected upon using TEE (16–19%). SARS-COV-2 virus enters host cells via angiotensin-converting enzyme 2 receptors, widely expressed on endothelial cells, including those present in the lung vasculature. TPBT does not precisely depict the anatomical sites of the intrapulmonary shunt.

Ref:  https://annalsofintensivecare.springeropen.com/articles/10.1186/s13613-020-00726-z