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Discussion Starter · #1 ·
A 79-year-old man, weighing 75 kg, with emphysema is intubated in the intensive care unit because of respiratory failure after developing adult respiratory distress syndrome secondary to an Escherichia coli bacteremia after an untreated urinary tract infection. His ventilator is set to a respiratory rate of 20/min, a tidal volume of 750 mL/breath, and a pO2 of 100%. If these settings are continued for the next 72 hours, the patient is at most increased risk for the development of which of the following complications?

A. Congestive heart failure
B. Jugular venous distention
C. Pulmonary embolus
D. Pumonary fibrosis
E. Tension pneumothorax
 

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Pulmonary fibrosis is a process that takes time, both for exposure and for development. Pulmonary fibrosis indicates, on pathophysiologic basis, a continuous process alternating of inflammation and repair, with fibroblasts & cytokines like EGF-1 & TGF-a playing a pivotal role. Free radicals undoubtedly have a contribution as initiating factors of this process, but the final damage is attributed to non-controlled repairing mechanisms rather than the inflammation itself.

The combination of emphysema & mechanical ventilation poses this pt at risk for developing tension pneumothorax, which is considered a subtype of barotrauma in this setting.
 

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Discussion Starter · #5 ·
The correct answer is Pulmonary Fibrosis

High concentrations of inspired oxygen delivered through a ventilator may lead to pulmonary fibrosis, which becomes irreversible. In the setting of adult respiratory distress syndrome (ARDS), if the inspired fraction of oxygen cannot be lowered without producing hypoxia, the addition of positive-end expiratory pressure (PEEP) is indicated. Although PEEP does increase the risk of both barotrauma and hypotension by impairing right-sided heart filling, it is indicated to prevent the development of oxygen toxicity, which may result in irreversible pulmonary fibrosis.

Tension pneumothorax would be more likely to occur if the tidal volume were significantly greater than 750 mL/breath (corresponding to the optimal flow rate of 10 mL/ kg).
 
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