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4. 1 and 3
Lung biopsy is not indicated at this time and has risk in this patient who is profoundly hypoxic on 100% FiO2. It is unclear whether she has the adult respiratory distress syndrome (ARDS) from sepsis or diffuse viral pneumonia from influenza. Oseltamivir is indicated but otherwise the therapy is supportive. Something does need to be done about her high FiO2. 100% oxygen will eventually prove toxic to the lungs. The level that is safe is unclear but generally considered to be both concentration and time-dependent. Most consider an FiO2 of 60% to be a reasonable goal.
At times the pO2 seems little affected by the FiO2, i.e., lowering the FiO2 results in a pO2 little different from the pO2 on an FiO2 of 100%. The reason for this is that in ARDS there are two sets of alveoli, those that are ventilated and perfused and those that are not ventilated but perfused with the later causing the hypoxia. Lowering the FiO2 does not profoundly affect the alveoli that are both ventilated and perfused. Unfortunately, lowering the FiO2 in this patient resulted in rapid desaturation.
Which of the following might be considered to lower of the FiO2? (Click on the correct answer to proceed to the fourth of five panels)