Which of the following is not a role of PEEP

PEEP prevents total collapse of alveoli at end exhalation. The stinting open of the alveoli prior to the next breath helps increase the amount of lung mass paicipating in gas exchange. PEEP decreases V/Q mismatch by decreasing atelectasis and thereby improves both oxygenation and ventilation. PEEP increases intrathoracic pressure, which can be impedance to venous return and cardiac output. PEEP increases, not decreases, the risk of pneumothorax.