DOES POSITIVE END-EXPIRATORY PRESSURE SIGNIFICANTLY REDUCE AIRWAY BLOOD-FLOW

Nutritive (systemic arterial) airway blood flow (mL/min/100 grams tiss ue) was studied in various size airways at four randomized levels of p ositive end expiratory pressure (PEEP) in smoke injured and normal lun gs. Seven sheep were studied 24 hours after an isolated injury to the left lung using cotton smoke. Radioactive 15-mum microspheres were uti lized to measure this airway blood flow. These data demonstrated a mar ked increase in systemic arterial blood flow to the airways in the inj ured left lung. Increasing levels of PEEP significantly reduced this h yperemic response. PEEP did not significantly affect the uninjured rig ht lung. Systemic airway blood flow was never reduced to below normal control levels (uninjured) in either lung despite PEEP of up to 20 cm H2O. Severe reduction in airway nutritive flow, and the possibility of airway necrosis, does not appear to occur at PEEP levels of up to 20 cm H2O.