This chapter considers the possible origins of extraalveolar air in ventilated patients and then reviews the manifestations and most frequent clinical settings of its various forms. After a discussion of general principles of management and a review of reported therapeutic approaches, it presents logical steps for prevention in susceptible patients and points out important gaps in the existing evidence base pertaining to this important topic. Although all the clinical forms of barotrauma are touched upon, most attention is devoted to those that pose a threat to life.
Only overt extraalveolar air is covered in this chapter. The reader is referred to Chapter 42 for a discussion of lung damage at the tissue or subcellular level related to mechanical lung distension and the application of positive pressure to the airways. Because data from laboratory studies are covered extensively in that discussion, this chapter deals primarily with barotrauma as a complication in patients, referring mainly to the adult clinical literature. As will be apparent, although the latter is replete with anecdotes and observational reports, this focus primarily on human data means that the evidence base in terms of prospective studies and “hard data” available to the clinician is remarkably limited. Spontaneous pneumothorax and other forms of extraalveolar air encountered in patients who are not intubated or receiving mechanical ventilation are not dealt with extensively here, nor is decompression-related barotrauma or bronchopleural fistula complicating lung resection.
Pneumothorax, subcutaneous emphysema, and other clinical forms of extraalveolar air occurring in association with mechanical ventilation are commonly referred to as barotrauma. This term is doubly unfortunate, trauma connoting iatrogenic injury and baro implying that it is pressure, rather than volume, shear force, or some other factor that produces it. In fact, these implications of both roots of the word are probably incorrect, and the expression ventilator-associated extraalveolar air would be technically more appropriate. Similarly, the term bronchopleural air leak would be more accurate than bronchopleural fistula, because of the implications of inflammation and suppuration associated with the word fistula in surgical and other settings. Like barotrauma, however, the latter is so ingrained in clinical usage that change is unlikely, and the more familiar terms are used in this chapter, as elsewhere in this book.
Although extraalveolar air appearing during ventilator support may not be caused by the ventilator itself, the expression ventilator-induced lung injury would seem as applicable to clinical barotrauma as to parenchymal damage associated with mechanical stretch and overdistension. Again, however, owing more to convention than to logical etymology, the term ventilator-induced lung injury is generally reserved for the latter, in this book and in the broader literature.
Usually, barotrauma in mechanically ventilated patients is automatically assumed to be a complication of mechanical ventilation. As with nosocomial pneumonia, however, ventilatory muscle dysfunction, and most of the other adverse developments to which ventilated patients are prone, whether the ventilator per se is responsible is usually unclear, because patients ill enough ...