COVID-19 – not your typical ARDS

Over the past few months of treating patients with COVID-19, one thing has develop into abundantly clear: we’re consistently learning learn how to treat this infection and its complications. While most individuals who contract COVID-19 have mild symptoms and get better, others need further intervention, including hospitalization. Patients with severe COVID-19 symptoms often develop acute hypoxemic respiratory failure and pneumonia, and 17 to 29% of those patients develop adult respiratory distress syndrome (ARDS) (Auwaerter, 2020). Critical care physicians have been treating ARDS for years; nonetheless, COVID-19 ARDS doesn’t behave like the everyday ARDS we all know, and we want to learn a brand new solution to treat it.

ARDS was originally defined in 1994 by the American-European Consensus Conference, but experts began to query the reliability and validity of this definition. In 2011, the European Society of Intensive Care Medicine, the American Thoracic Society, and the Society of Critical Care Medicine developed the Berlin definition of ARDS, which relies on the degree of hypoxemia and 4 other variables, including the severity of the chest radiograph, respiratory compliance, positive end-expiratory pressure (PEEP), and corrected expiratory volume per minute (ARDS Task Force, 2012).

Lung compliance may be very vital when comparing traditional ARDS to COVID-19 ARDS. The lungs expand during inspiration and retract during exhalation. The ability of the lungs to expand and retract is compliance. Compliance could be divided into two types:

• Static Compliance
  • Lung compliance when the lungs and lung muscles are at rest; the one variable is the pressure
  • Think of the “lungs that don’t move”

• Dynamic Compatibility
  • Lung compliance during respiratory
  • Imagine the “movement of the lungs”

In patients with traditional ARDS, lung compliance is reduced. Interventions are based on stopping barotrauma and optimizing oxygenation, ventilation, and perfusion with interventions reminiscent of low tidal volumes (6 ml/kg of predicted body weight), maintaining the plateau pressure below 30 mm H₂O, avoiding oscillatory ventilation, prone positioning, and use of upper PEEP levels in patients with moderate or severe ARDS.

COVID-19 patients often develop acute hypoxemic respiratory failure and develop ARDS, but their ARDS is different. In COVID-19 patients, lung compliance is high; it is just not what you see in a conventional ARDS patient (Gattinoni et al., 2020). So, although COVID-19 patients meet the Berlin criteria for ARDS based on the degree of hypoxemia, they don’t meet the compliance component.

In a recent anecdotal study from Italy involving 16 intubated and mechanically ventilated COVID-19 patients, the authors noted that these patients appeared to lose the flexibility to control lung perfusion and hypoxic vasoconstriction (Gattinoni et al., 2020). In ventilated COVID-19 patients, oxygenation increased with high PEEP and prone positioning, but this was not attributable to alveolar recruitment, which is frequently observed in traditional ARDS. In these patients, oxygenation increased with high PEEP and prone positioning due to redistribution of perfusion in response to pressure and gravity. Higher PEEP was sometimes related to hemodynamic instability. Furthermore, the development induced by prone positioning was modest and took longer to be appreciated. Their suggestion was to make use of gentler ventilation and the bottom possible PEEP (Gattinoni et al., 2020).

The results of Gattinoni et al. are somewhat inconsistent with other reports suggesting that COVID-19-induced ARDS with relatively high lung compliance profit from 10–15 cm H₂About PEEP in comparison with 5 cm H₂From (Annes, 2020).

COVID-19 patients may not tolerate traditional ventilation modes, reminiscent of volume-limited ventilation and low tidal volume ventilation. This is clear of their inability to attain a plateau pressure lower than or equal to 30 com H₂O or experience ventilator dyssynchrony. Pressure-limited modes or pressure-controlled ventilation with a goal volume could also be essential (Siegel & Hyzy, 2020). Physicians worldwide have recognized that weaning these patients off ventilatory support takes an extended time. The weaning process is slow, with small incremental changes in FiO2 and pressure support (PS), because reducing ventilatory support appears to speed up decompensation even in a patient who appears quite comfortable on PS settings. These patients remain on the ventilator for two weeks or longer and will require a tracheostomy.

As bedside clinicians, we must depend on the evidence and proposals made available to us. We must also accept that daily we are going to learn something recent about treating patients with COVID-19. Everyone can agree that the strength of evidence for a lot of COVID-19 treatment recommendations is either best practice statements or weak recommendations, and it’ll take time and research to find what really works for these patients.

The current suggestions and proposals from the Society of Intensive Care Medicine are presented below (Alhazzani et al., 2020):

• Start with supplemental oxygen if SpO₂ is lower than 90% and this ought to be taken under consideration if SpO₂ is lower than 92%.
• In case of acute respiratory failure with hypoxia, oxygen therapy ought to be used to keep up SpO2₂ not more than 96%.
• In cases of acute respiratory failure with hypoxemia, a high-flow nasal cannula (HFNC) ought to be used as an alternative of conventional oxygen therapy; if one is just not available and the patient doesn’t require intubation, a trial of non-invasive positive pressure ventilation (NIPPV) with close monitoring is beneficial.

For mechanically ventilated patients, the Society of Intensive Care Medicine recommends the next:

• Use a low tidal volume (Vt) ventilation strategy (Vt 4–8 ml/kg predicted body weight).
• Target plateau pressures lower than 30 cm H₂ABOUT.
• For patients with moderate or severe ARDS, a better PEEP strategy (above 10 cm H₂O) and monitor closely for barotrauma.
• In patients with hypoxia despite optimized ventilation, recruitment maneuvers ought to be considered but stepped/increased PEEP mustn’t be used.

COVID-19 provides us with a possibility to learn as we practice and explore the optimal approach to treating these patients. It is significant to acknowledge that the pathophysiology of COVID-19, highly concordant ARDS, is different from traditional ARDS. The query is, should we call what we see in clinical practice highly concordant ARDS or should we call it severe acute hypoxemic respiratory failure secondary to COVID-19? Regardless, understanding that what we see clinically is just not “typical ARDS” may help us refine our approach to mechanically ventilated patients to stop barotrauma and optimize oxygenation, ventilation, and perfusion.
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Alhazzani, W., Moller, M., Arabi, Y., Loeb, M., Gong, M., Fan, E.,â…¦Rhodes, A., (2020). Surviving Sepsis Campaign: Guidelines for the treatment of critically unwell adults with coronavirus disease 2019 (COVID-19). . doi: 10.1097/CCM.0000000000004363

Anesi, G., 2020. Coronavirus disease 2019: critical care issues. Updated March 2020. Â

ARDS Definition Group, Ranieri V., Rubenfeld G., Thompson B., Ferguson N., Caldwell E., Fan E., Camporota L., and Slutsky A. (2012). Acute respiratory distress syndrome: the Berlin definition. JAMA,.307(23). doi: 10.1001/jama.2012.5669.

Auwaerter, P. (2020). Coronavirus 2019: COVID-19. . Unbound Medicine. Updated April 2020.

Gattinoni, L., Coppola, S., Cressoni, M., Busana, M., and Chiumello, D. (2020). COVID-19 doesn’t result in a “typical” acute respiratory distress syndrome. doi: https://doi.org/10.1164/rccm.202003-0817LE

Siegel, M., & Hyzy, R. (2020). Ventilator management strategies for adults with acute respiratory distress syndrome. Updated March 2020.