The correct answer is D. 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.
Congestive heart failure (choice A) can occur as a complication of the patient's longstanding underlying pulmonary disease, but the incidence would not likely be increased because of his ventilator settings.
Jugular venous distension (choice B) can be a marker for either right heart congestive failure (see choice A discussion) or tension pneumothorax (see choice E discussion), but would not be a likely complication of a high pO2.
Pulmonary embolus (choice C) would more likely be related to prolonged bed rest with resultant venous thrombosis.
Tension pneumothorax (choice E) would be more likely to occur if the tidal volume were significantly greater than 450 mL/breath (corresponding to the optimal flow rate of 6 mL/ kg).
PEARL: High concentration of oxygen can be toxic to lung tissue and therefore the lowest possible fraction of inspired oxygen (FiO2) should be used to maintain adequate oxygenation. In high concentrations, oxygen can lead to absorptive atelectasis, accentuation hypercapnia, airway injury, and lung parenchymal injury. The oxygen toxicity is caused by inflammation which leads to cell death. It should be noted that there is NO threshold FiO2 or duration of oxygen supplementation below which oxygen toxicity cannot occur. Titration of FiO2 should be performed to maintain adequate oxygenation. A goal is to aim for a PaO2 greater than 60 mmHg and an oxygen saturation above 90%, but these recommendations are not as steadfast as patients with coronary artery disease or pulmonary hypertension will not tolerate hypoxemia very well. In most situations, physiologic PEEP is indicated for intubated patients to minimize risk of end-expiratory alveolar collapse and ventilator-associated pneumonia.
High concentrations of inspired oxygen delivered through a ventilator may lead to irreversible pulmonary fibrosis. In the setting of adult respiratory distress syndrome (ARDS), PEEP (positive end-expiratory pressure) is indicated to prevent the development of oxygen toxicity.
