Positive end-expiratory pressure redistributes perfusion to dependent lung regions in supine but not in prone lambs

OBJECTIVETo examine the influence of positive end-expiratory pressure (PEEP) and posture on the distribution of pulmonary blood flow. DESIGNExperimental study. SETTINGUniversity animal laboratory. SUBJECTSSeven anesthetized and mechanically-ventilated lambs. INTERVENTIONSFour conditions were studied in random orderprone or supine position, with or without 5 cm H2 O PEEP. MEASUREMENTS AND MAIN RESULTSThe distribution of pulmonary blood flow was assessed using fluorescent-labeled microspheres (15 [micro sign]m) in small ([similar]1.7 cm) lung regions. Pulmonary blood flow heterogeneity was evaluated using the coefficient of variation of blood flow of the lung regions.The number of regions analyzed were 1290 +/-154 (SD) per animal. PEEP increased pulmonary blood flow heterogeneity in the supine position (47.0 +/- 7.7% to 54.1 +/- 7.3%, p