Acute Respiratory Distress Syndrome (ARDS) 

 

 

Considerations

 

  • Profound hypoxemic respiratory failure

  • Complications related to etiology of ARDS:

    • Sepsis/SIRS

    • Infection/aspiration

    • Trauma

    • Transfusions

    • Multi-organ system failure

  • Lung protective ventilation strategies:

    • Tidal volume: 6 mL/kg IBW (ideal body weight)

    • PEEP & FiO2 to avoid hypoxemia: goal PaO2 ~60 mmHg

    • Plateau pressure: goal < 30 cmH2O

    • Permissive hypercapnea

  • Therapies for refractory hypoxemia:

    • Optimize PEEP: esophageal pressure, PV curves, lung ultrasound

    • Consider paralysis

    • Advanced treatments: prone position, inhaled nitric oxide, high frequency oscillatory ventilation (HFOV), ECMO

 

 

Goals

 

  • Maintain oxygenation & end-organ perfusion

  • Avoid further lung injury by using lung protective ventilation strategy

 

 

Berlin Definition of ARDS (JAMA 2012): All criteria must be present

 

  • Respiratory symptoms must have begun within one week of a known clinical insult, or the patient must have new or worsening symptoms during the past week.

  • Bilateral opacities consistent with pulmonary edema present on a chest x-ray or CT scan. Opacities must not be fully explained by pleural effusions, lobar collapse, lung collapse, or pulmonary nodules.

  • The patient’s respiratory failure must not be fully explained by cardiac failure or fluid overload. An objective assessment (e.g., echocardiography) to exclude hydrostatic pulmonary edema is required if no risk factors for ARDS are present.

  • A moderate to severe impairment of oxygenation must be present, as defined by the ratio of arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2)

  • With ventilation & PEEP ≥5 cmH2O, the severity is defined as: 

    • Mild ARDS: PaO2/FiO2 is 200 - 300 mmHg

    • Moderate ARDS: PaO2/FiO2 is 100 - 200 mmHg

    • Severe ARDS: PaO2/FiO2 is  ≤100 mmHg