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    Acute Respiratory Distress Syndrome (ARDS): Diagnosis & Initial Management

    Cardinal Presentations / Presenting Problems, Critical Care / Resuscitation, Respiratory

    Last Updated Aug 04, 2021
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    By Lee Graham, Conor Barrie, Matthew White

    Context

    • ARDS is a life-threatening inflammatory condition of the lungs.
    • Globally it affects 3 million patients annually and 10% of all ICU admissions.
    • Triad of hypoxia, bilateral CXR opacities, and reduced lung compliance.

    Pathophysiology

    • Three phases: exudative, proliferative and fibrotic.
    • Acute exudative phase = lungs initial response to injury and is characterized by the innate. inflammatory damage of alveolar endothelial and epithelial barriers allowing for the accumulation of fluid within the interstitium and alveolus.
    • Direct insults or indirect lung injury from systemic critical illness (Table 1).

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    Diagnostic Process

    • The Berlin Definition (Table 2) is the most widely used clinical criteria.
    • Consider common mimics of ARDS:
      • Congestive Heart Failure
      • Idiopathic pulmonary fibrosis
      • Diffuse alveolar hemorrhage
      • Drug-induced lung diseases
      • Cancer

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    Recommended Treatment

    • Supportive therapy is mainstay.
    • Identification and treatment of the underlying cause.
    • High flow nasal canula is preferential for management of mild ARDS. However, non-invasive positive pressure ventilation can also be used in some circumstances.
    • For more severe cases, ventilatory support with mechanical ventilation continues to be the hallmark of ARDS management.
    • Lung protective ventilation and the avoidance of ventilator-induced lung injury (VILI) are important principles in mechanical ventilation of patients with ARDS.
    • Initial ventilator settings:
      • Initial tidal volume (Vt): 6-8 mL/kg (ideal body weight)
      • Target Plateau Pressure ≤ 30 cmH2O
      • Permissive hypercapnia allowed to achieve above with goal pH ≥ 25
      • A PEEP of at least 5 cmH2O should be used, and in more severe cases a higher PEEP should be used
    • A more fluid restrictive resuscitation strategy is likely beneficial.
    • Steroid use remains controversial. However, steroids should be used for COVID-19 related ARDS.
    • For severe, refractory hypoxia related to ARDS:
      • Optimization of PEEP
      • Neuromuscular paralysis
      • Prone positioning
      • Institution of VV-ECMO

    Quality Of Evidence?

    Justification

    Lung protective mechanical ventilation continues to be the hallmark of management in ARDS and is one of the few critical care interventions with a proven mortality benefit (Brower et al.)

    High

    Prone positioning for cases of severe ARDS is also well established (Proseva, Guerin et al 2013).

    High

    The diagnosis of ARDS using the Berlin Criteria has some degree of subjectivity leading to under recognition and inter-clinician variability.

    Moderate

    Optimal methods for PEEP titration continues to be an evolving area in the literature, with no one standard accepted approach.

    Moderate

    High flow nasal canula vs non-invasive ventilation. Evolving body of evidence and current recommendations are based largely on expert opinion and practice patterns.

    Low

    Related Information

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