Pulmonary Barotrauma

Barotrauma is a well-recognized complication of positive pressure ventilation. Excessive pressure applied to the lungs causes widespread disruption of alveoli. The gas escapes into the perivascular space to form pulmonary interstitial emphysema (PIE). The small bubbles coalesce and stream towards the mediastinum. The gas either accumulates there, or if the pressure is continued, it moves up into the neck and over the body to form subcutaneous emphysema, ruptures the mediastinal pleura to cause a pneumothorax, or moves down alongside the aorta and oesophagus to form pneumoretroperitoneum and with even higher pressures, pneumoperitoneum. The danger from extra-alveolar air (EAA) in the form of pneumothoraces, is well recognized. However, gas in the other sites can also cause complications. Lung disruption caused by PIE can cause hypoxia and hypercarbia, as well as more chronic respiratory impairment in the form of bronchopulmonary dysplasia (BPD). Cardiorespiratory embarrassment can result from mediastinal emphysema and upper airways obstruction from subcutaneous emphysema. Splinting of the diaphragms and cardiovascular impairment can be caused by raised intraabdominal pressure associated with pneumoretroperitoneum and pneumoperitoneum. Like many conditions in medicine, the best way of managing barotrauma is prevention. There are now alternative ways of artificially maintaining gas exchange apart from conventional ventilation and PEEP. Techniques such as CPAP, reversed inspiration: expiration (I: E) ratios, IMV, LFPPV with ECRCO₂ and hypoxic pulmonary vasoconstriction can often maintain gas exchange at lower airway pressures than IPPV and PEEP. As a result, there is less cardiovascular depression and a much lower incidence of lung disruption by barotrauma.