Introduction
One of the main concerns of coronavirus disease 2019 (COVID-19)
infection is development of acute respiratory distress syndrome (ARDS).
Although the definition of ARDS has changed over the decades, its
clinical context remains the same: a rapidly progressive inflammatory
syndrome that impairs oxygen transport in the lungs.1–3 Historically, the most common viral cause of
adult ARDS prior to COVID-19 infection was influenza pneumonia, and the
complication of ARDS from influenza is known to be associated with an
increased mortality.4,5 The pulmonary injury in ARDS
due to COVID-19 has been shown to resemble other viral causes of ARDS,
and as expected, the severity of ARDS is associated with significantly
worsened mortality among COVID-19 patients.1,6,7
Due to the high mortality rate of ARDS due to COVID-19, there has been a
high demand for refractory treatment options in patients who do not
improve upon standard ventilation and treatment. Thus, extracorporeal
membrane oxygenation (ECMO) was used in select cases of COVID-19 with
refractory ARDS and severe hypoxemia.7–10 ECMO is a
temporary form of mechanical cardiopulmonary support, used in patients
with severe cardiac and/or respiratory shock. ECMO was first clinically
used in 1972 and has been increasingly incorporated into standard
practice in the past two decades.11–13 Despite
controversial and conflicting evidence on its overall efficacy, ECMO has
become a common treatment for patients with refractory
ARDS.13–16
In cases of influenza, ECMO can be used adjunctive support in cases
complicated by severe ARDS.17 With knowledge learned
from years of critical care and development of protocols, there is a
good understanding of how to properly care for patients with
influenza.18,19 It is known that in the setting of
influenza, immunosuppression with steroids increases the duration of
viral shedding and worsens mortality,20 so high dose
immunosuppression is usually avoided. If traditional therapies fail to
stabilize the patient, early initiation of ECMO in critically ill
patients with influenza can improve their chance of survival by
promoting lung protective ventilator strategies without compromising
required gas exchange. The amount of benefit provided by ECMO in
complement to anti-influenza agents is unclear, though outcomes have
been acceptable.17 In contrast, we have not identified
a specific, proven treatment protocol for COVID-19 infection despite the
widespread use of supportive measures such as remdesivir,
lung-protective ventilator strategies, anti-inflammatory agents, and
steroids.21 Despite initial support for some of these
agents, some subsequent research has been less
optimistic.21,22
While ARDS due to COVID-19 has been compared to ARDS caused by
influenza, severe cases of COVID-19 continue to demonstrate high
mortality rates, and the similarities and differences between the two
diseases are not well understood. Similarly, despite recent studies on
the use of ECMO in COVID-19 patients,23–25 there
remains a lack of evidence documenting the overall efficacy of ECMO in
treating ARDS due to COVID-19. This paper will compare the outcomes and
efficacy of ECMO in treating patients with ARDS due to COVID-19 or
influenza to better understand the prognosis of ARDS due to COVID-19 and
the use of ECMO in treating it.