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Methods: In a lavage-injured sheep acute respiratory distress syndrome model, the authors compared the effects of three approaches to determining PEEP level after a recruitment maneuver: (1) 2 cm H2O above the lower inflection point on the inflation pressure-volume curve, (2) at the point of maximum curvature on the deflation pressure-volume curve, and (3) at the PEEP level that maintained target arterial oxygen partial pressure at a fraction of inspired oxygen of 0.5.
Results: Positive end-expiratory pressure set 2 cm H2O above the lower inflection point resulted in the least injury over the course of the study. PEEP based on adequate arterial oxygen partial pressure/fraction of inspired oxygen ratios had to be increased over time and resulted in higher mRNA levels for interleukin-8 and interleukin-1[beta] and greater tissue inflammation when compared with the other approaches. PEEP at the point of maximum curvature could not maintain eucapneia even at an increased ventilatory rate. 相似文献
Methods: Six dogs were studied in four protocols: (1) control experiments (controls); (2) ETA blockade using ABT-627 (ETAB); (3) AT1 blockade using losartan (AT1B); and (4) combined AT1B and ETAB (AT1B + ETAB). After a 30-min awake period, isoflurane-nitrous oxide anesthesia was established (1.3 minimum anesthetic concentration). After 60 min of anesthesia, 20 ml blood/kg body weight was withdrawn within 5 min, and the dogs were observed for another hour. Thereafter, the blood was retransfused, and the dogs were observed for a final hour.
Results: Anesthesia: Cardiac output decreased in all protocols, whereas mean arterial pressure decreased more in AT1B and AT1B + ETAB than in controls and ETAB. Hemorrhage: After 60 min, cardiac output had decreased less in controls than in all other protocols. Mean arterial pressure decreased more during ETAB than in controls, but most severely during AT1B and AT1B + ETAB. Angiotensin II increased further only in controls and ETAB, whereas vasopressin and catecholamines increased similarly in all protocols. Retransfusion: Mean arterial pressure remained below controls in all protocols but was lowest when the AT1 receptor was blocked. Cardiac output fully recovered in all but the ETAB protocol. 相似文献