A patient with acute respiratory distress syndrome (ARDS)

Discussion in 'USMLE Step 2 CK' started by Neha Gupta, Apr 27, 2013.

  1. Neha Gupta

    Neha Gupta Active Member

    A patient with acute respiratory distress syndrome (ARDS) is being managed with the following ventilator settings:
    Assist-Control Ventilation
    Ventilator set rate = 10 breaths/minute
    Total respiratory rate = 24 breaths/minute
    Exhaled tidal volume 750 ml
    PEEP 5 cm H20
    FIO2 100%
    On these setting he has the following blood gases:
    pH 7.35
    PaCO2 35 mm Hg
    PaO2 65 mm Hg
    SaO2 92%
    Because of patient agitation and some breathing discoordination, it is decided to paralyze the patient. Without changing any ventilator settings, what is the most likely scenario after paralysis?
    a) Oxygenation and ventilation will improve
    b) Oxygenation will be unpreditable but ventilation will stay the same
    c) Oxygenation will be unpredictable but ventilation will worsen
    d) Oxygenation will worsen but ventilation will be unpreditable.
    e) Oxygenation and ventilation will worsen.

    The answer is ....(e) Oxygenation and ventilation will worsen.

    By paralyzing the patient you effectively change respiratory rate from 24 full ventilator breaths/minute to 10 full ventilator breaths/minute. Thus it would be expected that both ventilation and oxygenation will worsen, i.e., his PaCO2 will go up and PaO2 will go down.

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