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What is the status of respiratory support for patients with COVID-19 related ARDS? - CARDS-Landing-Page-16-6-D-876-2021_GettyImages-1205199983.jpg

What is the status of respiratory support for patients with COVID-19 related ARDS?

Introduction

Even though there has never been a disease for which so much clinical data has been generated in such a short time as was done in the past year on COVID-19 and related ARDS (CARDS), to date there is still not much hard evidence regarding the question how CARDS is actually different to “classical” ARDS, and if these differences should result into different clinical strategies. 

The concept that CARDS and non-COVID-ARDS may present  with different clinical pictures requiring different treatment approaches has been discussed with the aim to prevent progression of the disease into more severe states with poor outcomes. This article will provide you with an overview of relevant literature and guidelines, as well as distinct clinical opinions. 

In the further course we will summarize current recommendations for respiratory support and mechanical ventilation in COVID-19 patients based on recent literature and published guidelines. More important studies are on the way, and we will update this article or add information as they provide further or new, relevant findings.

You'll find several references throughout the following text. Please download the PDFs to review all corresponding references.

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Some facts on CARDS

  • 30 to 40 percent of COVID-19 hospitalized patients develop acute respiratory distress syndrome (ARDS).1
  • COVID-ARDS (CARDS) is associated with a 30-70 percent fatality rate.1
  • Mild disease is observed in approx. 81% of patients, severe or critical forms in 14% and 5% respectively.
  • Major differences exist between COVID-19 associated ARDS and ARDS of different etiology with respect to the pathophysiology (Ary).
  • Severe, progressed CARDS presents with clinical characteristics that are in line with the Berlin criteria for ARDS. In the absence of specific hard evidence, the respiratory management of CARDS patients is largely based on the guidelines of ARDS patients.
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COVID-19 related ARDS – a new entity or just another cause of ARDS?

Very early on in the pandemic, opinions based on clinical observations and smaller case series were raised that COVID-19 related ARDS is different to “classical” ARDS. Gattinoni et al. reported that the lungs of some patients with COVID-19 related ARDS had good compliance but presented with severe hypoxemia and high shunt fraction2

This was somewhat different to ARDS as normally, severe hypoxemia was associated with low compliance. Furthermore, lung weight and gas volume appeared to be almost normal in this group of COVID-19 patients. However, this case series also reported COVID-19 patients with lung conditions fairly similar to non-COVID-ARDS (low compliance and increased weight). Based on this observation, Gattinoni hypothesised two different phenotypes, which will be well known to most of you.

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FULL WHITEPAPER: Is COVID-19 related ARDS just like any ARDS of any other origin? What’s the latest discussion on the role of phenotypes in clinical decision making?

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Excessive respiratory drive and effort: possible factors for disease progression

The mechanisms of severe COVID-related ARDS are heterogeneous and still not well understood.15 However, COVID-19 appears to be associated with a strong activation of respiratory drive and excessive inspiratory effort.16 Many COVID-19 patients exhibit a very strong respiratory drive – either as a consequence of their hypoxemia or – potentially – a direct influence of the virus on the respiratory control center. 

COVID-19 patients might therefore be particularly vulnerable to develop P-SILI and their respiratory drive should be monitored.16 Excessive respiratory drive and effort is believed to be an important factor for the disease progression in COVID-19 patients in several ways, potentially leading to a transition from phenotype L to H and further to F, as postulated by Tonelli et al.13

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FULL WHITEPAPER: Does respiratory drive and effort play a substantial role in the progression of COVID-19 related ARDS? 

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EIT, a bedside tool to support decision on ventilation strategy?

Lung imaging, specifically CT, is the gold standard to assess the status of the lung, i.e. extent of lung damage as well as ventilation and aeration in ARDS. However, transportation is unfavorable in these critically ill patients. Furthermore, CT is associated with radiation exposure and provides only static images.

EIT is a bedside technology providing dynamic insights into the aeration of the lung. It is used in ARDS patients to optimize mechanical ventilation settings and might help to evaluate lung recruitability and success of prone positioning. It therefore seems sensible to conclude that this technology may be of use in establishing individualized ventilation strategies in complex patients such as those suffering from CARDS.

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FULL WHITEPAPER: What does EIT play in the treatment of COVID-19 related ARDS? 

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Synopsis

In the very early stage of the disease, a differentiation between CARDS and ARDS seem to be reasonable. Otherwise, later stages of CARDS are similar to non-COVID-ARDS and should be treated as ARDS of a different presentation with regard to clinical care and diagnosis. Following the concept of P-SILI, respiratory drive may play an important role in spontaneously breathing patients or patients with assisted ventilation and may impact disease progression and risk for relapse.

Pre-Intubation (Prevent Phase)

Non-invasive respiratory support

There seem to be high hopes that non-invasive respiratory support would prevent the need for endotracheal intubation (ETI) and invasive ventilation. However, there is also the fear of missing the right point for ETI in the individual patient. There is not much evidence specifically for COVID-19 patients, therefore recommendations are not available on all aspects on non-invasive respiratory support and the question of when to decide for ETI. In the following we will take a practical approach: We compiled the recommendations of four different guidelines and complemented this with information from recent publications. This is not to be interpreted as a review reflecting all currently available data, but more as a practical approach to get at least some guidance.

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Reviewed Guidelines:

  • German S3 Guideline – Recommendations for the therapy of hospitalised patients with COVID-19, Version 4.1, February 2021 [referred to as GS3)34
  • Surviving Sepsis Guidelines on the Management of Adults with Coronavirus Disease 2019 (COVID-19) in the ICU: First Update; March 2021 [referred to as SSC)35
  • ERS Guideline for the Management of hospitalized adults with coronavirus disease 2019 (COVID-19): A European Respiratory Society living guideline, January 2021 [referred to as ERS]36
  • Australian guideline for clinical care of people with COVID-19, National COVID-19 Clinical Evidence Taskforce [referred to as NCCET]37
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FULL WHITEPAPER: Which approach to non-invasive respiratory support is more effective? High flow nasal Cannula? NIV with helmet or mask?

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ONE PAGE SYNOPSIS: COVID-19 related ARDS - Non-invasive respiratory support

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Timing of intubation

The timing of intubation is a contentious issue: It is clearly critical, as delayed intubation is associated with a worse prognosis; at the same time, controversy exists regarding the role of early intubation vs. use of non-invasive respiratory support (NRS) to avoid intuba­tion41. However, one current review of twelve studies on close to 9,000 patients came to the conclusion that the timing of intubation may actually have no effect on mortality and morbidity of critically ill COVID-19 patients (‘early’: intubation within 24h from ICU admission, ‘late’= intubation any time after 24h of ICU admission); the conclusion was that these findings might well justify a “wait and see” approach, which in turn could lead to fewer intubations42. But what's the guidance from the current guidelines we reviewed for this article?

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FULL WHITEPAPER: Is early intubation beneficial? Or is intubation to be avoided at all costs? Timing here seems to be more a matter of individuality. 

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Invasive Ventilation (Stabilize)

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Invasive mechanical ventilation of patients with COVID-19 related ARDS

Once intubated, the right ventilation regimen in COVID-19 patients has to be decided on. The earlier stated concept of the COVID-19 phenotypes led to the assumption that the L-Type representing an early stage of the disease is significantly different to “classic” ARDS with respect to a variety of lung characteristics, which was supposed to be found at least in a part of the COVID-19 cases.8,4

Subsequently, quite a few larger studies from various countries looking at a total number of about 7,000 patients, however, did not confirm these findings and postulated the compliance as more or less in the range of patients with non-COVID-ARDS. This challenged the idea of the “different” ARDS.

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FULL WHITEPAPER: Discussions about the different nature of COVID-19 have raised the question of whether mechanical ventilation needs to be different compared to non-COVID patients. 

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ONE PAGE SYNOPSIS: COVID-19 related ARDS - Invasive Mechanical Ventilation

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Assisted spontaneous breathing and weaning

As mentioned earlier, patients with COVID-19 associated ARDS exhibit high respiratory drive and intense effort. It is suspected that this is not only caused by a gas exchange disorder, but also by the direct invasion of respiratory centers due to SARS-CoV-2.

The role of inspiratory effort in promoting lung damage in COVID-19 may be critical13. This underlines the need to closely and continuously monitor the respiratory drive and effort during assisted spontaneous breathing.

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FULL WHITEPAPER: Are there any measures available that have been evaluated for COVID-19? Get an overview of these parameters and what to keep in mind when weaning patients with COVID-19 related ARDS.

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ONE PAGE SYNOPSIS: COVID-19 related ARDS - Assisted spontaneous breathing and weaning

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