Acute Respiratory Distress Syndrome (ARDS)
Acute respiratory distress syndrome (ARDS) is a life-threatening condition caused by severe lung inflammation. This can happen after pneumonia, including pneumonia induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.
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It is common to develop ARDS after COVID-19 infection (Aslan et al., 2021) and 42% of patients presenting with COVID‐19 pneumonia develop ARDS. 61–81% of patient requiring intensive care also develop ARDS (Gibson et al., 2020). Recent studies indicate that the median age of ARDS patients is 56.5 years (Xu et al., 2021). The incidence of ARDS among non-survivors of COVID-19 is 90% and the mortality rate is 45% (Tzotzos et al., 2020).
Due to the damaged lungs, the main symptom of ARDS is shortness of breath which usually develops within few hours and the risk of death increases with age. Other symptoms may include labored and rapid breathing. The low oxygen levels in the blood may result in low blood pressure, confusion and extreme tiredness.
Tipically, treatments for ARDS aim to increase oxygen levels in the blood which include ventilation and medication. A number of aspecific drugs are currently used to modulate ARDS symptoms, these include chorticosteroids and inhaled vasodilators (Matera et al., 2020)
In some Covid-19 patients, the virus triggers a severe immune response in their lungs. This causes the production of cytokines (inflammatory molecules). This results in the so-called “cytokine storm.” ARDS causes diffuse alveolar damage in the lung resulting in fibroblast proliferation and scarring (Gibson et al., 2020) (Figure 4).
Galectin-3 plays an important role in amplifying the pro-inflammatory response and contribute to acute airway inflammation. A key domain in the spike protein of SARS-CoV2, has been shown to bind N-acetylneuraminic acid (Neu5Ac), this may help the infection of the host cells. Strikingly, Neu5Ac-binding domain shares structural-sequence and functional similarities with Galectin-3 (Caniglia et al., 2020).