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Study Objective: Part 1: To describe cases of emphysema (subcutaneous and/or mediastinal) and pneumothorax after percutaneous dilational tracheostomy (PDT) in a series of 326 patients, and to review the existing literature describing the incidence and possible mechanisms. Part 2: To analyze the potential mechanisms for the development of emphysema and pneumothorax in human cadaver models.Design: A retrospective analysis of PDTs, in combination with an anatomic study in human cadavers.Materials and Methods: Part 1: All ICU patients who underwent PDT between 1997 and 2002 were enrolled in the study. We analyzed the cases of emphysema and pneumothorax. Similar cases were retrieved from the literature and underwent a systematic review. Part 2: The relevant anatomic structures were studied. We simulated the clinical situation after PDT in a human pathologic study in order to induce subcutaneous emphysema and pneumothorax.Measurements and Results: Part 1: Five cases of subcutaneous emphysema (1.5%) and two cases of pneumothorax (0.6%) are described. In the literature search, we found 41 cases of emphysema (1.4%) and 25 cases of pneumothorax (0.8%) in a total of 3,012 patients. Part 2: Subcutaneous emphysema could easily be induced in a human cadaver model by inflating air in the pretracheal tissues and after posterior tracheal wall laceration. Air leakage was also possible through a fenestrated cannula via the space between the inner nonfenestrated cannula and outer cannula and then through the fenestration.Conclusions: We conclude that one mechanism for the development of emphysema is an imperfect positioning of the fenestrated cannula, whereby the fenestration is extraluminal. For this reason, fenestrated cannulas should not be used immediately after placement of a PDT. Posterior tracheal wall laceration is another mechanism responsible for emphysema after PDT. After perforation of the posterior tracheal wall, the pleural space can be reached easily. This may result in a pneumothorax. [ABSTRACT FROM AUTHOR]