危重病肺部并发症影像学表现.ppt

* Most pneumonia in the ICU are due to either mixed anaerobic or aerobic gram-negative organisms. They are commonly related to aspiration. Opportunistic infection should be considered if the patient is immunosuppressed. The incidence of pneumonia in the ICU is approximately 10%; however, in patients with ARDS, the incidence has been reported to range from 20% to 60%, with a 70% incidence at autopsy.[15] Although pneumonia is commonly present in patients with ARDS, the CXR radiograph is only 30% to 50% accurate.[15] The CXR typically shows patchy areas of consolidation or poorly defined opacities that are often multifocal (Figure 6). Air bronchograms are helpful in the diagnosis of pneumonia, but they may also occur in areas of atelectasis. When present, cavitation is a more specific finding of pneumonia. Radiographic changes in pneumonia typically occur more slowly than in atelectasis, aspiration, or pulmonary edema. * An estimated 4% to 15% of patients on ventilators develop barotrauma, Underlying lung disease, such as pneumonia and especially ARDS, raise the risk significantly. The major factors associated with development of barotrauma include a peak inspiratory pressure 40 cm H2O, the use of positive end-expiratory pressure (PEEP), and an inappropriately large tidal volume. * The initial abnormal air collection in barotrauma is pulmonary interstitial emphysema (PIE), most often identified in children. Streaky lucencies radiate from the hila, without branching or tapering as do air bronchograms. The gas collections can grow into bubbles, clefts, and cysts between 1 and 8 cm in size. Cysts may resolve or persist and can become superinfected. Patients with ARDS frequently develop cysts at the lung bases. Pulmonary interstitial emphysema carries a significant risk of pneumothorax (77%) from rupture of a cyst.[18] The risk of PIE spreading to the mediastinum is 37%. * Pneumothorax (PTX) is the most concerning sequela of barotrauma. It occurs in up to 25% of v