A case of pneumomediastinum in a patient with acute respiratory distress syndrome on pressure support ventilation.

During mechanical ventilation for acute respiratory distress syndrome, tidal volume (V(T)) must be reduced. Once switched to pressure-support ventilation, there is a risk that uncontrolled large V(T) may be delivered. A 63-year-old man with community-acquired pneumonia required tracheal intubation and mechanical ventilation, with a V(T) of 6 mL/kg predicted body weight, PEEP of 10 cm H2O, a respiratory rate of 30 breaths/min, and F(IO2) of 0.60. Plateau pressure was 22 cm H2O. He improved and received pressure-support. Twelve days later a chest radiograph showed suspected air leaks, confirmed via computed tomogram (CT), which showed anterior pneumomediastinum. V(T) received over the previous 3 days had averaged 14 mL/kg predicted body weight. The patient was put back onto volume-controlled mode, and 2 days later there were no air leaks. In pressure-support ventilation, V(T) must be closely monitored to ensure lung-protective mechanical ventilation.