Cardiopulmonary effects of severe thoracic subcutaneous emphysema

Isolated subcutaneous emphysema appeared to cause significant pulmonary dysfunction in a traumatized child with no demonstrable intrinsic pulmonary injury or disease. We developed an animal model of severe thoracic subcutaneous emphysema to determine whether it alters pulmonary-thoracic compliance such that ventilation-perfusion relationships or cardiac performance are affected adversely. Twelve anesthetized, mechanically ventilated swine were studied. Baseline measurements and calculations included intrapulmonary shunt fraction (Qsp/Qt), total static pulmonary-thoracic compliance, thermodilution cardiac output, systemic and pulmonary arterial pressures, and mean pulmonary arterial occlusion pressure. Measurements and calculations were repeated after each of three consecutive injections of 400 cc of air into the tissue over the sternum. Comparison of the baseline values with those after the injections showed no increase in Qsp/Qt and no change in any other variable (p less than 0.05). We conclude that, in this model, isolated thoracic subcutaneous emphysema does not adversely affect cardiopulmonary function during positive pressure ventilation.