PEEP and “Reverse Mismatch”: A Case Where Less PEEP is Best

A V ˙ / Q ˙ lung scan was obtained in a patient with LLL collapse who was receiving IPPV and PEEP. This revealed absent ventilation and hyperperfusion to the collapsed lobe. After a reduction in PEEP from 12 to 5 cm H 2 O, a repeat V ˙ / Q ˙ scan showed a more even distribution of pulmonary perfusion. Arterial hypoxemia improved.