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[Artigo] Acute respiratory distress syndrome in adults

Acute respiratory distress syndrome

TERMINOLOGY

CLINICAL CLARIFICATION

  • Acute respiratory distress syndrome is severe and often fatal acute respiratory failure; characterized by diffuse
    inflammatory lung injury rapidly progressing to increased pulmonary vascular permeability, increased lung weight, and
    hypoxemia
  • Preceded by a clinical insult—usually pneumonia, nonpulmonary sepsis, or trauma
  • Berlin definition of acute respiratory distress syndrome includes presence of all following criteria:
    ○ Timing of acute onset of symptoms (or worsening of nonacute symptoms) within 1 week of a known clinical insult
    ○ Hypoxemia as shown by the PaO₂ to FIO₂ ratio of 300 mm Hg or less with PEEP or CPAP of 5 cm H₂O or greater
    ○ Chest imaging showing bilateral opacities that are not explained by effusions, atelectasis, or nodules, and are not
    cardiogenic in nature
    ○ Respiratory failure or pulmonary edema not fully explained by cardiac failure or fluid overload

CLASSIFICATION

  • Under conventional mechanical ventilation, the following apply:
    ○ The 3 categories of acute respiratory distress syndrome are based on degree of hypoxemia, as follows:
    – Mild: 200 mm Hg < PaO₂/FIO₂ ≤ 300 mm Hg2
    – Moderate: 100 mm Hg < PaO₂/FIO₂ ≤ 200 mm Hg2
    – Severe: PaO₂/FIO₂ ≤ 100 mm Hg2
    ○ A minimum PEEP of 5 cm H₂O is required to make the severity classification; it may be delivered noninvasively with
    CPAP to classify mild cases

DIAGNOSIS

CLINICAL PRESENTATION

  • History
    ○ Recent known clinical insult (usually within 3 days and nearly always within 7 days) or new or worsening respiratory
    symptoms 
    ○ Symptoms may vary in severity, with some being mild initially; all worsen over a period of several hours
    – Dyspnea
    – Cough
    – Chest discomfort
    – Anxiety
    ○ With vaping-related lung injury, some patients report nonspecific gastrointestinal symptoms
    – Nausea, vomiting, diarrhea, and abdominal pain
  • Physical examination
    ○ Cyanosis may be evident
    ○ Tachypnea at rest
    ○ Tachycardia at rest
    ○ Hypotension is often present
    ○ Fever may or may not be present, depending on the presence of infection as an underlying cause
    ○ Use of accessory muscles of respiration (usually indicates moderate to severe disease)
    ○ Coarse crepitations of both lungs at presentation
    ○ Cold, mottled extremities with prolonged capillary refill time (longer than 2 seconds) indicates ineffective circulation

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